anchor overboard lab name: p artner: per:...anchor overboard lab name: _ _ _ p artner: _____...

Anchor Overboard Lab Name: ___ ___________ ___ P artner: ________________ Per: ____

As summer draws to a close, you and your best friend decide to go fishing. You go out on a boat; your friend decides to fish from shore. At one particularly promising spot, you throw the anchor overboard (unfortunately you forget to tie the anchor rope to the boat , so the un-tethered anchor just sinks to the bottom...DOH!). At the moment you do this, your friend happens to be looking at the water level on the shore. What does your friend see? Assume your friend has incredibly good vision and can see even the slightest change in water level! So… as the boat’s anchor is thrown overboard, does the water level on the shore go up, go down or remain the same? Make a prediction – AKA: “a hypothesis.” [Do this on your own – independent of your partner.] _______________

Why do you think the water level will do this? (Justify your hypothesis) ___________________________________

____________________________________________________________________________________________

Share your ideas with your partner. Does he/she have the same hypothesis? ____ …the same justification? ____ Now, go over to the central lab bench and look at the equipment you have available: graduated cylinders, water, lead weights, string, forceps, test tubes. Working together, design an experiment to determine whether or not your hypothesis is correct. Then take the needed equipment over to one of the available lab stations and try your experiment. The design must have quantitative results – that is, actual measurements – with numbers! Hints: * The change you are looking for might be very small and difficult to see. Try to design the experiment in a way that will accentuate this change. (“Accentuate” means to make more noticeable.) * Don’t worry about getting this right the first time. Try something, discuss it, think about it, then try again. THIS IS HOW SCIENCE WORKS! In the space below write down the final procedure you used – the best one you came up with. Use numbered steps and command form. Include approximate amounts or ranges for quantities used. In the right-hand space make neatly-drawn diagrams (at least two, with labels like “test tube”, “weight”) to illustrate the procedure. This procedure should be written in a way that anyone could follow and know exactly what to do and what to measure... Diagram(s): Procedure: Data Table: Show your data in a logical table format – like the one shown at right for a completely unrelated lab.

Volume of acetic acid (mL) 25.0 Mass of sugar used (g) 15.98 Initial temperature of oil (*C) 22.8 Final temperature of oil (*C) 34.2 Time required for reaction (s) 238

Example: 1) Place a small beaker on a scale and zero the scale. 2) Add 10-20 g of sugar to the beaker (See Fig 1)

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Follow-up questions: Some of these are quite thought-provoking, but do your best.

1. According to your experiment, did the water level go up, go down, or remain the same? ____________ Why do you think that happens? (If you’re not sure, make a good guess.) 2. Abby predicted the water level would rise because the sinking anchor would push water up out of its way. Binky thought the water level would remain the same because the lake was so big compared to the anchor. Carl assumed that the water level would go down because the anchor would splash some of the water out. Although none of them was completely correct, if you had to pick, who do you think was most correct among these three? _________ Explain your choice. 3. When the anchor was in the boat it was essentially floating along with the boat. When it was thrown overboard, it obviously sank. What does this tell you about the amount of water displaced (displaced means pushed aside) by a floating object compared to the amount displaced by a sunken object? 4. You probably already knew that a sunken object displaces its own volume’s worth of water (in other words a 2 L stone will displace 2 L of water). What you probably didn’t know is that a floating object displaces its weight’s worth of water (a 100 kg boat will displace 100 kg of water). So which is greater: the amount of water it takes to equal the weight of the anchor or the amount of water it takes to equal the volume of the anchor? Explain. 5. Which would weigh more: 1 L of water or 1 L of the material the anchor was made out of? _____________ What property of matter is it that compares the weights of equal volumes of substances? _______________ 6. Predict whether the water level would go Up or Down or Remain the same for each of the following transitions: __a) An anchor is thrown from shore into the water (this one should be easy!) __ b) An anchor is thrown from shore into the boat. __ c) An anchor is thrown from one small boat into a second, much bigger boat. __ d) A log (which floats) is thrown from shore into the water. __ e) A log is thrown from shore into the boat. __ f) A log is thrown from the boat into the water. __ g) A big, dry sponge is thrown from the boat into the water; it soaks up some water but remains floating. __ h) The boat, made of aluminum, springs a leak and sinks to the bottom. Pick any one of the last three transitions (f, g or h) and explain your prediction:

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SCIENTIFIC METHODS WS Name: _________________ 1. Science begins with questions: how, why, where, when, what... all kinds of questions can serve as starting points for scientific investigations. But these questions must be testable: that is they must be capable of being answered through experimentation and observation. Most questions are testable, even if the technology may not currently exist to test them. From the list below, check off the ones that you think are testable questions: __ How do birds know which direction to fly when they are migrating? __ What causes some people to snore? __ If a tree fell in the forest and no person or object were there to record it in any way, would it still make a noise? __ What are distant stars made of? __ When does life actually begin in a developing fetus? __ Can dogs see in color or just black and white? __ Which brand of soda tastes best? __ Is all that we experience real or just a dream? __ Why do some people tend to eat a lot of chocolate after they’ve broken up with someone? __ Where do our souls go after we die? 2. The next step usually associated with the scientific process is to take the question and turn it into a claim or hypothesis. This is essentially just an intelligent prediction or guess. For example, the first question above (hopefully you chose it as one that is testable) might be turned into the following claim: “Birds use the position of the sun in the sky to help them navigate.” Note that this can also be written as an if-then hypothesis statement: “If birds see what they perceive to be the sun in the sky, then they will navigate by it.” And an experiment to test this hypothesis might involve using a bright light indoors to simulate the sun and see if the light’s position influences the direction the birds fly. Another hypothesis is “If birds detect what they perceive to be the Earth’s magnetic field, then they will use it to help them navigate.” [Even though it may seem far-fetched, there is quite a bit of evidence that supports this hypothesis!] For each of the following testable questions from above, develop an hypothesis: Have at least two of them be in an if-then format __ What causes some people to snore? _____________________________________________________________ __ What are distant stars made of? _____________ ___________________________________________________ __ Can dogs see in color or just black and white? ______________________________________________________ __ Which kind of soda tastes best? ________________________________________________________________ __ Why do people tend to eat a lot of chocolate after they’ve broken up with someone? _____________________________________________________________ 3. Science may begin with a question, but it is misleading to think that science ends with an answer. Science is much more likely to end with a better understanding of the original question – an understanding that is likely to lead to even more questions. In other words, science never really ends! What’s more, science never proves anything – this is not a shortcoming of science: it’s just that proving things is not what the scientific method is designed to do. “Prove” is far too definitive a word. It implies that the question has been answered for good and cannot possibly be refuted or disproven at a later time. Instead of saying that an experiment proves a certain hypothesis is correct, it is better to say that the results of the experiment seem to support the conclusion that the hypothesis is correct. Although this is not as dramatic as saying that the hypothesis was proven, it is the way real scientists talk. Pantene shampoo claims that it is “scientifically proven to be better for your hair than Herbal Essence.” What’s wrong with this statement? _________________________________________________________________ Rewrite the statement so that it is more truthful:

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4. Years of research on human eyes have led to the current understanding that there are two types of cells in our retinas: cells called “rods” that allow us to see light and dark, and cells called “cones” which allow us to see color. [Note again: even though these statements are regarded as “truths” by just about everybody, they have not been “proven,” nor will they ever be. And just because they have not been proven, that is not to say that they are useless. In fact, together with a lot of other unproven concepts, they have lead to an understanding of the eye that has helped scientists develop drug and surgical techniques to enable people to see better and lead better lives.] Now take the claim: Dogs can see in color. One thing scientists might do to investigate this claim is to dissect the eye of a dog. If they find that the retina contains the same kind of rod and cell cones as human eyes, have they necessarily proven that the dogs can see in color? No, because what appears to be a cone cell on the outside may be very different on the inside. And if they analyze the cone cells and determine that they appear to be chemically identical to those of humans, it adds credibility to the claim that dogs can see in color, but it still hasn’t proven it.

Why not? ____________________________________________________________________________________ And if a scientist takes two identical objects and paints one blue and the other red, and a dog can be trained to always pick up the red one and never the blue one, this also adds credibility to the claim that dogs can see in color, but it still hasn’t proven it. Why not? ____________________________________________________________________________________ And if a scientist hooks electrodes up to a dog’s brain and measures brain waves as the dog is shown a variety of blue objects and a variety of red objects, and finds that the waves are distinctly different for the red objects than they are for the blue ones, this also adds credibility to the claim that dogs can see in color, but it still hasn’t proven it. Why not? ____________________________________________________________________________________ 5. From the reading of the text book and/or class notes, define in your own words the following terms: Observations – Hypothesis – Experiments – Theory – 6. Label each of the following as: “O” for observation, “H” for hypothesis, “E” for experiment or “T” for theory: __ Talking on cell phones while driving causes accidents. __ Yesterday, a man talking on a cell phone while driving nearly crashed into me on highway 44. __ Police reports from several hundred accidents were reviewed by a team of insurance adjusters. __ 76% of people who used cell phones while driving were in accidents during the past year. __ After reviewing the evidence and comparing it to the result of nearly fifty other studies, it is concluded that cell phone use in cars does indeed correspond to a higher risk of car accidents. __ Many moths are seen flying around a front porch light. __ Moths are attracted by bright lights. __ Twenty randomly selected moths are observed in a large cage with a light at one end. __ Nine of the twenty fly toward the light source, nine fly away from it, and two do neither. __ The bulb is replaced with a brighter one (200 Watt) and the same moths are observed again. __ Again, nine of the twenty fly toward the light source, nine fly away from it, and two do neither. __ The bigger an adult is, the more alcohol it takes to make him/her drunk. __ 95 adults were given repeated drinks and asked to say when they felt too drunk to drive a car. __ The information gathered is shown at right: __ Many of the subjects were staggering or talking funny before they declared themselves drunk.

# of drinks to feel drunk: 1 2 3 4 5 6 average weight (lbs) 105 123 151 148 178 180

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7. What does the term “anecdotal evidence” mean? ____________________________________________________ Put a star next to statement in #6 above that could be considered anecdotal evidence.

8. What does the term “data” mean? ________________________________________________________________ Circle all the statements in #6 above that could be considered data. (Hint: there are only 4-5)

9. Looking at the first set of statements in #6 above, what would you want to compare the 76% to before drawing any conclusions about the dangers of driving while talking on a cell phone? _________________________________________________________________

10. Looking at the second set of statements in #6 above, it does not appear that moths on average really are attracted by light. Why do you think most people believe they are? ______________________________________________________________________

11. Looking at the third set of statements in #6 above, what would be a better way of doing the experiment?

_________________________________________________________________________________________________

12. Define “Law” as it applies to science: ________________________________________________________________ 13. The terms “hypothesis,” “theory” and “law” form a sort of progression. Explain: __________________________

________________________________________________________________________________________________

14. Define the following terms:

Independent variable: ______________________________________________________________________________

Dependent variable: ______________________________________________________________________________

Controlled variable: ______________________________________________________________________________

15. Consider each of the following experiments. For each, identify the independent variable, the dependent variable and the controlled variable(s). Also for each, write the hypothesis that the experiment is designed to be testing. At least two of the hypotheses should be in if-then format. a) Joey called up fifteen different girls and asked them out on dates. Each call lasted precisely two minutes and ended with the question: “so, you want to go the movies Saturday night?” In five of the calls, Joey mentioned his love of chemistry class once, in five of the calls he mentioned his love of chemistry class twice, and in the remaining calls he didn’t mention chemistry at all. For each group, he made note of the number of girls who said “yes.”

IV: _________________________ DV: __________________________ CV(s) _________________________________

Hypothesis: _______________________________________________________________________________________

b) Kyrie did an experiment and collected the following data

IV: ______________________________________

DV: _____________________________________

CV(s) ____________________________________________

Hypothesis: _______________________________________

_________________________________________________

c) Tanya burped the alphabet up to “J” after drinking a whole can of Coke. Using Pepsi, she can get to “Q” or “R.” IV: _________________________ DV: __________________________ CV(s) _________________________________

Hypothesis: _______________________________________________________________________________________

d) Ryan got an 83% on his Chem test after studying for two hours and listening to “Lil Wayne.” On the next test, he got a 67% after studying the same amount of time to “T-Pain.” IV: _________________________ DV: __________________________ CV(s) _________________________________

Hypothesis: _______________________________________________________________________________________

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Some Definitions & Distinctions You Need to Know WS Name: _____________________________

1. Accuracy vs. Precision (and Validity & Reliability)

Accuracy: How close a measurement (or answer) is to the correct answer. This is also known as “validity.”

Precision: How specific or consistent a measurement (or answer) is, regardless of its accuracy.

Reliability: (like precision) How reproducible/consistent results of an experiment are

Fill in the following blanks with G for good, P for poor or ? for impossible to answer.

a) Sam estimated the mass of the brick to be 750 g. It turned out to be 748.17 g.

His estimation showed ___ accuracy and ___ precision.

b) The meteorologist predicted tomorrow’s high temperature would be 28.583*C.

This shows ___ accuracy and ___ precision.

c) When asked how old she was, Sarah correctly responded 15.72 years old.

Her answer has ___ accuracy and ___ precision.

d) The dart board shown at right indicates ___ accuracy and ___ precision.

e) In a lab to determine ice’s heat of fusion, Shalonda got 72 cal/g, 75 cal/g and 96 cal/g for her three trials, which gave

her an average of 81 cal/g. The actual value is 80.0 cal/g. Her results have ___ accuracy and ___ precision.

f) As a prank, Joey taped a quarter to the underside of a very expensive electronic balance pan. This balance would have

___ accuracy and ___ precision.

g) All the fine increments had worn off of the graduated cylinder, so it just read 10 mL, 20 mL... with nothing in between.

This graduated cylinder has ___ accuracy and ___ precision.

h) Although he took very careful measurements, Tony forgot that the “0” on the ruler was indented a bit from the end.

The measurements he made had ___ accuracy and ___ precision.

i) The witness said the man was wearing a light blue Izod polo shirt, tan corduroy pants and drove a burgundy red

Datsun 280ZX. Her testimony had ___ accuracy and ___ precision

2. Quantitative vs Qualitative Data

Quantitative: information that has numbers (quantities) associated with it.

Qualitative: information that has descriptions (qualities) associated with it.

Label the following as either quaNtitative or quaLitative:

The flask was round on the bottom __, it contained 78.4 mL ___ of dark green ___ liquid, slightly warmer than room

temperature___. 6.93 g ___ of fine ___ white ___ powder were added. 23.7 sec ___ later, the flask began to

bubble___.

3. Systematic vs Random Error Sources:

Systematic: Error sources that always affect the results in the same direction

Random: Error sources that throw the results off in varying directions

Label the following error sources as Systematic or Random:

___ a) There was a constant draft in the room pushing down on the electronic balance.

___ b) In reading the scale, Tom would often do number inversions: “561” instead of “651”

___ c) There was a small gap in the mercury column in the thermometer

___ d) Ann thought she was supposed to read from the top of the meniscus instead of the bottom.

___ e) The rulers tended to warp somewhat over time.

___ f) The weighing paper was so big, it hung over the edge of the pan, slightly touching the top of the scale.

___ g) Andre’s reaction time caused him to press the stop watch button 0.5-0.8 seconds late.

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4. Extensive vs Intensive Properties

Extensive: properties that changes from sample to sample (such as mass)

Intensive: properties that are constant and depend only on the substance, not on the size, shape, etc.

Label the following properties as Extensive or Intensive:

The aluminum rod had a length of 23.7 cm __ a mass of 86.78 g __ and a density of 2.70 g/mL __

The sample of water had a volume of 56 L __ and a temperature of 24.7*C __

The tin foil is a solid at room temperature __ and has a melting point of 232*C __

The naphthalene nugget was white __, about the size of a pea __ and gave off a strong odor __

The gold wire was very thin __ shiny__ and flexible __ and conducted electricity very well __

The platinum ring resisted corrosion __ was worth about $3000 __ and came from Spain __

The ethanol boiled at 82*C __ and the vapors were clear __ colorless__ and quite flammable __

The sodium bar was soft enough to cut with a knife __ and it reacted violently with water __

Potassium nitrate is very soluble in water __ but it will not dissolve in oil __

Trinitrotoluene (TNT) tends to explode under certain conditions __

5. Physical vs Chemical Properties

Physical: Properties that describe the look or feel of a substance

Chemical: Properties that describe how a substance reacts with other substances or by itself.

Look back over the properties listed in #4 above. 4-5 of them are chemical properties, the rest are all physical. List all

those that are chemical properties:

________________________ __________________________ _____________________________

________________________ ___________________________

6. Physical vs Chemical Changes

Physical: a change in a substance’s physical property (shape, phase,etc) but NOT its chemical composition

Chemical: a change in a substance’s chemical composition (a rearrangement in how the atoms are bonded) which may

or may not be accompanied by a change in physical appearance

Label the following changes as either Physical or Chemical:

__ a candle burns

__ the wax melts

__ the wick turns black

__ a puddle of water evaporates

__ water is broken up into hydrogen and oxygen

__ copper sulfate dissolves in water

__ a dollar bill is torn in half

__ an iron pipe rusts over the years

__ the potassium cyanide poisoned the man

__ the baking soda gave off carbon dioxide when it was heated

__ the tungsten filament glowed white hot inside the light bulb

__ mixing certain cleansers produces toxic chlorine gas

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The Cat’s Meow Lab – an investigation into cause and effect Name: __________ Partner: ____________ Although there is no one correct, cut-and-dry process used by all scientists in all investigations, there is something called the “scientific method” which involves specific components useful to scientists. The activity you are about to perform should help introduce some of these components to you and familiarize you with some of the vocabulary. Let’s start off with the following two observations: 1) Anyone who has ever tried to clean grease, oil or fatty residue off their hands with just water (no soap) knows that soap really does make the job easier. 2) There is fat in milk; in fact, that’s what the 2%, 1%, etc refers to in milk categories. Now let’s add a few more observations: ones you will make on your own. At your lab station, find a small plastic petri dish. Fill it half way with water and then add 10-20 drops of vegetable oil. What do you observe? Now use a toothpick to take a tiny droplet of dish detergent and place it right in the center. Hold the tip of the toothpick just below the liquid surface. Record your observations: Wipe the tooth pick off with a paper towel and return it to the container. Now let’s make a prediction: what effect do you think soap would have on milk? If you add a small drop of soap to a

dish of milk, then…. (What do you predict will happen?) _____________________________________________.

[This prediction is considered a “hypothesis” – an educated guess, often in the form of an if-then statement.] Here is the simple experimental procedure you will use: 1) Take the large empty plastic cup and fill it about half-way with milk (from one of the containers at central lab station). Pour this milk into the large glass petri dish. Wait about 30 seconds for the milk to come to rest, then add four drops of food coloring, a different color in each “corner” of the dish as shown in the figure at right: 2) As before, use a toothpick to take a tiny droplet of dish detergent and place it right in the center. Record detailed observations: Clean-up: Again, wipe the tooth pick off with a paper towel and return it to the container. Thoroughly rinse out and wipe dry the two petri dishes. Always leave a lab station the way you found it! Now answer the following follow-up questions: 1) Most experiments involve an independent variable (I-N-D-E-P-E-N-D-E-N-T, DO YOU KNOW WHAT THAT MEANS?) and a dependent variable. The independent variable is the thing you (the experimenter) does or changes in the experiment, and the dependent variable is the change that occurs as a result of the independent variable. If you put your super ball in the freezer, for example, to see if it will bounce higher, then the temperature of the ball would be the independent variable and the height to which it bounces would be the dependent variable. It is a sort of cause and effect. In the experiment you just did, which of the following might you consider the independent variable: a) the adding of the food coloring b) the adding of the soap c) the use of the toothpick d) the movement of the milk e) the size of the petri dish (circle your choice).

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2) What is the dependent variable? (Again, think cause and effect.) __________________________ Explain your choice: 3) What purpose do you think the food coloring served? 4) A good experiment (which this really wasn’t) would have had a control: an exact repeat of the procedure with the independent variable either changed or removed. This control would test whether it was in fact the adding of the soap (and not something else) that caused the milk to move the way it did. Describe what a control for this experiment would require you to do. 5) Also, a good experiment would not just rely on just one trial; it would involve multiple trials of the exact same procedure with nothing changed at all. Even though this might seem like a waste of time, the performing of multiple trials is considered very important in scientific research. Why? 6) In scientific research, for every question that gets answered, twenty more questions present themselves. For example: Would 2%, 1% or skim milk work just as well? Does the shape of the container matter? How would the temperature of the milk impact the outcome of the experiment? Do all soaps work equally well? What would happen if the drops of food coloring were placed in different spots? What if the drop of soap were added somewhere other than the middle? For the first question, one hypothesis might be: “If milk with a lower fat content were used, then the soap would still cause the same motion of the milk’s surface, but it would not last as long.” Pick one of the other questions (or make up your own) and write a simple if-then hypothesis for it. 7) Now write a step by step procedure for testing that hypothesis. Include figures or diagrams if they are useful. Make sure your procedure includes a control and multiple trials. 8) For extra credit, perform the experiment at home to the best of your ability. Write up what you observed, and e-mail it along with digital photos to your instructor at ([email protected]).

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Naked Penny Lab! Name: _________________ Part I: Removing the zinc from the inside of a penny:

1. Obtain a new penny (post’82). This new penny is actually made of zinc, with a thin coating

of copper plated on. Use the flat side of a file to file away the copper coating from 3-4 spots

around the perimeter of a post’82 penny, then place the penny in some dilute HCl solution.

Part II: Removing the copper from the outside of another penny

1. Obtain a second new penny (post ’82) and examine it. Date: _____ Make a guess as to

what percent (by weight) of the penny is actually copper: _______

2. The unit we use in science for mass is the gram. A gram is roughly the mass of a dollar bill.

So just by hefting it in your hand, estimate the mass of the penny in grams: ___________.

Now weigh it. Actual mass: ___________

3. Now take this penny over to “the hood” where the instructor will help you remove the copper coating with nitric acid. This is a little tricky since nitric acid reacts with both copper and zinc. In fact it reacts much more vigorously with zinc than it does with copper. The trick is to take it out as soon as the bubbling reaction goes from mild to wild! After it has been rinsed with water to remove any extra acid, wipe it dry with t paper towel and then use a piece of steel wool to buff off the black coating that formed on the zinc. Buff both front and back until the penny looks shiny.

4. Predict the mass of the “naked” penny in grams: ___________ Now weigh it. Actual mass: ___________

5. Calculate how much the copper coating weighed: _______ Calculate the percent copper in the original penny: _____

Follow up questions: 1. In an attempt to see how thick the copper coating was, Ben used a ruler to measure the thickness of the penny before and after the reaction. Why would this probably not tell him much? 2. Can you think of a better way Ben could determine the thickness of the copper coating using one hundred pennies and a ruler? 3. Why would using one hundred pennies provide better a better estimate of the copper’s thickness? 4. Can you think of a completely different way Ben could determine the thickness of the copper coating using just one penny, the mass measurements you made above, a metric ruler and being given the density of copper as 8.96 g/mL? 5. For bonus, see if you can determine the thickness of the copper coating using the process in #4 above: _________ Show your calculations below. (This is REALLY tricky, so don’t be upset if you can’t figure it out right away.) 10

EXPERIMENTAL DESIGN WS Name: _________________________ Sometimes scientific experiments can be flawed. That is, they are poorly designed, and so their results are not very convincing. Below are five common experimental errors -- things you want to avoid in designing an experiment. A) Too small a sample size: Joe’s hypothesis is that a certain penny he found lands on heads more often than tails when it is flipped. He flips it five times, and it comes up heads four out of five times, which he believes proves him right. (A better experiment would be to flip it five hundred times. If it came up heads 400 out of 500 times, that is much more convincing.)

B) Nonrandom sampling: Sara’s hypothesis is that reggae music is more popular than rap at her high school. So she calls up 100 friends, and finds that 93 of them do in fact prefer reggae over rap. She considers this proof of reggae’s popularity. (Since they were her friends, they are more likely to have her same taste in music. A better experiment would involve Sara calling 100 randomly chosen students from the buzz book).

C) Experimental bias: Kendra’s hypothesis is that she can taste the difference between Sam’s Club skim milk and Shop & Save skim milk. She pours out a small cup of each and tastes them, and she is able to taste a difference. She repeats the experiment ten more times and each time she can taste the difference. She says “Ha! I told you I could taste the difference!” (Since she poured the cups herself, Kendra already knows which is which before she tastes them. A better experiment would be to have Kendra wearing a blindfold and someone else pouring out the twenty cups of milk -- ten of each brand -- and handing them to her in random order.)

D) Too many variables: Waylon’s hypothesis is that plants grow faster in sunshine than in shade. He plants 25 beans in one large pot and places it outside in a sunny spot in his back yard. He plants another 25 beans in an identical pot and places them in a corner of his garage. He measures them all after three weeks to see if there is a difference. The ones grown outside are significantly taller. (In addition to sunshine, there were other variables that might have affected the plant growth: temperature differences, rainfall, wind, car exhaust... A better experiment would have had the pots side by side in the back yard, one under a clear plastic overhang, the other under an opaque plastic overhang, as shown at right.)

E) No experimental control: Lisa’s hypothesis is that people are happier after they have watched a funny show on TV. She has 50 randomly selected people watch a funny episode of Seinfeld, and she asks them after the show to rate their mood on a scale from 1(very unhappy) to 10 (very happy). The average score was a 6.8, which she considers to confirm her hypothesis. (Where’s the comparison? A better experiment would be to ask another 50 people to rate their happiness without having watched any show at all. You might think that a more controlled experiment would involve the control group sitting in the same room staring at the same TV for half an hour but with the TV turned off. Why would this not be a fair control?) For each of the following experiments, find the design flaw (A, B, C, D or E from the list above). Some may have more than one. Others may not have any design flaws. Also, list some of the good features of the experiment, and describe possible improvements you could make. The first is done for you. _______ 1. Cam hypothesizes that birthday candles kept in the freezer will burn for longer than ones that are at room temperature. He takes two candles, a yellow one which he puts in the freezer over night and a green one which he leaves out in the room. The next day he burns them: the yellow took 6.5 minutes to burn, the green one took 5.9 minutes.

What is a good feature of the experiment? He does use a control: the candle that was not in the freezer. Describe a better way of doing this experiment: He could have used 20 candles in the freezer, and 20 left out, and stuck with just one color (changing colors introduces an extra variable...)

A

,

D

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_______ 2. Cody’s hypothesis is that Clorox bleach makes her clothes look cleaner than Oxy-Clean. She washes a load of her clothes in Clorox and a load of her brother’s clothes in Oxy-Clean. Later, she examines the clothes and finds that her clothes are much cleaner. What is a good feature of the experiment? Describe a better way of doing this experiment: _______ 3. Lisa thinks she does better on tests after she has had coffee in the morning. One morning she drinks a cup of coffee and then does very well (A-) on her chemistry test. She does it again before her next chemistry test and again does very well (B+). Now she is convinced her hypothesis is right. What is a good feature of the experiment? Describe a better way of doing this experiment: _______ 4. Jason believes that Tylenol is effective at reducing a fever quickly. He is a nurse, and of 500 patients with fevers, he randomly divides them into two groups: he gives 250 Tylenol and the other 250 get a placebo (a pill with no medicine in it). He monitors their temperatures over the next three hours and finds that the Tylenol patients temperatures went down at an average rate of 1.28*C/hour, and for the placebo patients it was 1.26*C/hour. He considered this difference to be insignificant. What is a good feature of the experiment? Describe a better way of doing this experiment: _______ 5. Tessa hypothesizes that the longer you hold a glow-in-the-dark superball up to a light, the longer it will glow. She holds it 5 cm away from a 100 Watt light bulb for 5 minutes, and notices that it appears to glow in the dark for 85 seconds. She then holds it 5 cm away from the same 100 Watt light bulb, this time for 6 minutes, and this time it appears to glow for 92 seconds. She feels pretty confident that this supports her hypothesis, but she found it difficult to tell exactly when the superball stopped glowing. What is a good feature of the experiment? Describe a better way of doing this experiment: OK, now see if you can develop a good experiment for each of the following hypotheses: Be as specific as you can about how you would conduct the experiment: how many subjects or trials, how you would control for all the variables, and how you would avoid researcher bias. (Use a separate sheet of paper if you need more space.) For #8, YOU come up with an original hypothesis, and then describe the experiment you would perform to test it.

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6. Hypothesis: If you talk to your house plants, they will grow more quickly. Experiment: 7. Hypothesis: Pennies get lighter over time as they are used and get worn down. Experiment: 8. Hypothesis: (make up your own!) __________________________________________________ Experiment: One more thing to consider about scientific studies is the credibility of the researcher. Credibility is essentially the believability of the study, and it is determined by both the trustworthiness and expertise of the researcher. 9. Recently, concerns have arisen over Nalgene drinking bottles and the chemicals they may be releasing into the water. Two scientists publish their findings. One who works for a major Nalgene producing company, the other does not. Which is more credible and why? ____________________________________________________________________ 10. A scientist who has published twelve studies about alcohol’s effect on the brain claims that a BAC of 0.08 should be considered legally drunk. Britney Spears claims that BAC of 0.08 is perfectly normal and does not impair a person’s judgment at all. Which is more credible and why? _______________________________________________ 11. One scientist publishes an article on the effect of lithium carbonate on manic depressive disorder in teens. In it she cites 32 other related studies from well-respected journals. A second scientist publishes a similar article, but only cites two related articles. Which is more credible and why? _______________________________________________ 12. An article is published in Science Digest which discusses the discovery of water on Mars and the likelihood that living organisms may once have evolved there. A second article on the same topic is published in National Enquirer. Which is more credible and why? _______________________________________________ 13

METRIC WS Name: __________________________ 1. Fill in each of the blanks with an appropriate unit: mm, cm, m, km, mg, g, kg, mL, L, kL

a) Judy weighed her pen before and after class and found that she had used 23.6 ____ of ink.

b) The empty fish tank weighed about 7 ___ , and it had a capacity of 43 ___.

c) The anchored hot air balloon was 35 ___ tall and held about 7200 ___ of air.

d) The steak I had was huge: it was about 3 ___ thick and must have weighed at least 800 ___.

e) The slot was just 2-3 ___ too short for the dime to pass through.

f) A standard archery arrow is 0.85 ___ in diameter, 0.72 ___ long and 0.045 ___ in mass.

g) It only takes 4 to 5 ___of cayenne on your tongue to make your mouth feel like it’s on fire.

h) The 65 ___ man was so thirsty after running 13 ___ that he drank 1500 ___ of water.

Convert each of the following by simply moving the decimal point or changing the power of ten:

#2 and #20 have been done for you.

2) 25.2 cm = 0.252 m 3) 25.2 cg = ______ g 4) 25.2 km = ______ m

5) 25.2 mL = ______ L 6) 25.2 cm = ______ mm 7) 25.2 g = ______ g

8) 0.023 mL = ______ dL 9) 0.023 ng = ______ g 10) 0.023 m = ______ cm

11) 0.023 L = ______ cL 12) 0.023 kg = ______ cg 13) 0.023 nm = ______ m

14) 4500 dm = ______ m 15) 4500 mg = ______ kg 16) 4500 mm = ______ m

17) 4500 m = ______ Mm 18) 4500 dL = ______ L 19) 4500 dg = ______ kg

20) 6 x 109 mm = 6 x 106 m 21) 6 x 109 m = ______ cm 22) 6 x 109 kg = ______ g

23) 6 x 109 dL = ______ L 24) 6 x 109 Mm = ______ dm 25) 6 x 109 g = ______ kg

26) 4 x 103 cm = ______ m 27) 4 x 103 mg = ______ kg 28) 4 x 103 km = ______ m

29) 4 x 103 dL = ______ L 30) 4 x 103 L = ______ mL 31) 4 x 103 g = ______ Gg

32) 7 x 10-6 mL = ______ L 33) 7 x 10-6 kg = ______ g 34) 7 x 10-6 m = ______ cm

35) 7 x 10-6 mg = ______ cg 36) 7 x 10-6 cL = ______ L 37) 7 x 10-6 g = ______ mg

Ans: (IRO+7*) mg mg g g kg kg kg mm cm cm m m km mL L kL 0.0252 0.252 0.252 2.52 252 25,200 25,200,000 0.000000000023 0.0000023 0.00023 2.3 23 2300 2300 0.0000000045 0.0045 0.45 4.5 450 450 450,000,000 6 x 100 6 x 104 6 x 106 6 x 1011 6 x 1012 6 x 1014 6 x 1016 4 x 10-6 4 x 10-3 4 x 101 4 x 102 4 x 106 4 x 106 4 x 108 7 x 10-9 7 x 10-7 7 x 10-5 7 x 10-4 7 x 10-3 7 x 10-2 7 x 103 * “IRO + 7” means the answers are In Random Order with seven extra answers

Cross off the answers as you find them. Then circle the seven extra answers.

You must memorize this prefix number line and know how to use it.

- m- k- M- c- d- n- G-

14

Measurement Tutorial Notesheet Name: __________________ Per: ___ A. ___________ B. ___________ C. ___________ D. ___________ E. ___________ F. ___________ G. ___________ H. ___________ I. ___________ J. ___________ 1. ___________ 2. ___________ 3. ___________ 4. ___________ 5. ___________

6. ___________ 7. ___________ 8. ___________ 9. ___________ 10. ___________ 11. ___________ 12. ___________ 13. ___________ 14. ___________ 15. ___________ 16. ___________ 17. ___________ 18. ___________ 19. ___________ 20. ___________ 21. _______ 22. _______ 23. ________ 24. _________ 25. ________ 26. ________ 27. ________ 33. 28. _______ 29. _______ 30. _______ 31. _______ 32. _______ 34. 35. 36. 37.

172 mm 170 mm 8m 23.0 mL

4.8 cm

15

Sig Fig tutorial Note sheet Name: _____________________________ 1. How many significant figures does 3190 mm have? __ 2. How many significant figures does 0.00273 m have? __ After you have mastered the fifty sample problems, write your own rules for significant figures:

Sig Fig Rounding tutorial Note sheet

3. What would 763.48 cm be rounded to four significant figures? __________

4. What would 763.48 cm be rounded to three significant figures? __________

5. What would 763.48 cm be rounded to two significant figures? __________

6. And what would 763.48 cm be rounded to just one significant figure? __________

7) Now, try rounding 3.8719 g off to…

… four significant figures: __________

… three significant figures: __________

… two significant figures: __________

… one significant figure: __________

.

BONUS. If time permits, go to the game “SIG FIG BLASTER”: http://scratch.mit.edu/projects/beckerr/1834194 (or google “scratch.mit” click on the first site, then search for “sig fig blaster.”). Practice at home. Bonus points will for the top ten scores by this Friday (e-mail a legible screen shot of your best score to: [email protected] )

10) Try rounding 0.081479 km off to…

…four significant figures: __________

…three significant figures: __________

…two significant figures: __________

…one significant figure: __________

11) Try rounding 0.0029964 kg off to…





12) Try rounding 5189.2 mm off to…





13) Try rounding 2699.4 s off to…





14) Round 5999.8 mL off to…





15) Try enhancing 15 cm up to…



…five significant figures: __________

16) Try enhancing 0.38 m up to…




17) Try enhancing 7200 g up to…




7) Now, try rounding 3.8719 g off to…

… four significant figures: __________

… three significant figures: __________

… two significant figures: __________

… one significant figure: __________

8) Now, try rounding 6.9837 L off to…





9) Try rounding 54.298 s off to…





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http://scratch.mit.edu/projects/beckerr/1834194

mailto:[email protected]

MEASUREMENT WS Name: ______________________ For each of the following drawings/photos, make an appropriate measurement. In each length measurement, assume that the other end of the object is aligned with the “0 cm mark.” Note: your answers should be consistent with the answers below. “Consistent” means that there is agreement on all digits except perhaps for the last (guessed) digit. “5.46 cm” and “5.48 cm” are consistent with each other. “5.46 cm” and “5.26 cm” are not. Neither are “5.46 cm” and “5.461 cm.” Don’t forget to include the correct units on EVERY measurement you make.

2000 3000 m

13. Length = _____________

2000 3000 m

14. Length = _____________

2000 3000 m

15. Length = _____________

2000 3000 m

16. Length = _____________

23 24 mm

17. Length = _____________

18.

600 700 cm

19. Length = _____________

600 700 cm

20. Length = _____________

600 700 cm

21. Length = _____________

230 240 cm

22. Length = _____________

230 240 cm

23. Length = _____________

230 240 cm

24. Length = _____________

38 39 cm

1. Length = _____________

38 39 cm

2. Length = _____________

38 39 cm

3. Length = _____________

38 39 cm

4. Length = _____________

200 300 mm

5. Length = _____________

200 300 cm

6. Length = _____________

20 21 cm

7. Length = _____________

20 21 cm

8. Length = _____________

20 21 cm

9. Length = _____________

100 200 cm

10. Length = _____________

100 110 cm

11. Length = _____________

100 101 cm

12. Length = _____________

23 24 mm

Length = _____________

50

40

25. Volume = _____________

50

40

26. Volume = _____________

mL

mL

mL

mL

mL

mL

mL

mL

12

11

27. Volume = _____________

32

33

28. Volume = _____________

32

33

29. Volume = _____________

600

500

30. Volume = _____________

600

500

31. Volume = _____________

600

500

32. Volume = _____________

For 33-36 below, draw a diagram (like those in 1-32) that would have the measurement given:

33. 43.6 cm

34. 43.60 cm

35. 2800 mm

36. 2804 mm

Ans for 1-32 (IAO+1): 11.22 19.99 20.02 20.42 23.537 23.543 32.63 32.80 38.7 38.70 38.71 38.72 45.0 45.6 100.60 107.5 147 208 234.7 236.0 237.6 247 50Ō 517 53Ō 548 60Ō 602 643 2700 27Ō0 2800 2820 Units: cm(17) mm(3)

m(4) mL(8)

17

37. For the following photographs, record what you think is a correct measurement for the length (in cm). Length = ______________ Length = ______________ Length = ______________ 38. For the following photographs, record what you think is a correct measurement for the length (in cm). Length = ______________ Length = ______________ Length = ______________

39. How did your three answers for #46 above compare to your three answers for #45? You may or may not have realized it, but the lower images are just close-up shots of the exact same measurements as the upper images, so your three answers should have been identical. If they were not, which do you feel more confident about? ___________ Why? __________________________________________________________________________________________ 40. In general, is it better to make measurements up close, or from a greater distance? _________________________ 41. Here are some more close-up images to make measurements of a) b) c) d) e)

Length = ___________ Length = ___________ Length = ___________ Length = ___________ Length = ___________

42. Were your answers similar for d and e? _____ They should have been exactly the same, since they are duplicate images!

43. Now try some photographs of graduated cylinders. Record the volume (in mL) for each of the following.

a) b) c) d) volume = ___________ volume = ___________ volume = ___________ volume = ___________

44. Believe it or not, the four images above are all taken of the exact same graduated cylinder with the same volume of water inside it. (a) was done the way most students would read a graduated cylinder. In (b), a black stripe was brought up behind the cylinder, this helps accentuate where the precise bottom of the meniscus is (you should have read it as “7.58 mL” or “7.59 mL”), and that is the correct way to read the cylinder. Can you tell what mistake was made in reading the measurement in (c) and (d)? ______________________________________________________

45. So, there are actually five things to keep in mind when reading a graduated cylinder: 1) Make sure the cylinder is on a level surface, 2) always read from the bottom of the meniscus, 3) use a dark stripe behind the cylinder to help accentuate the meniscus, 4) get as close as you can (as you did for the rulers), and 5) __________________________________________________________ 46. Here are two more graduated cylinders to read: volume = ___________ volume = _____________

Ans (IAO + 1): 7.58 7.60 7.62 7.64 9.50 9.50 18.94 18.97 19.97 20.00 20.01 21.86 21.86 21.87 55.9 256 Units: cm (11) mL(6)

18

METRIC MAYHEM Name: ____________________ Per: _____

The purpose of this game is to help you hone your estimation skills and to become more familiar with the relative magnitude of

some common metric units.

M/V/L/T

M/V/L/T

M/V/L/T

M/V/L/T

M/V/L/T

M/V/L/T

M/V/L/T

M/V/L/T

M/V/L/T

M/V/L/T

M/V/L/T

M/V/L/T

M/V/L/T

How to play: students will be divided up into two teams. Three students from each side will come up at a time, and they will be given an approximation task: (What is the length of this rod? What is the mass of this plate? What is the volume of this box? What is the temperature of this cup of water?) Without conferring with one another, these six students must quickly write down their predictions. The numbers they write down must be between 1 and 1000. For something very heavy for example, rather than guess 45,600 g, an appropriate guess would be 45.6 kg. Guesses must have appropriate units and three significant figures – with the last sig fig not being a zero. Good guesses: 78.1 g, 1.95 km, 201 mL Bad guesses: 15 g, 12.35 *C, 83.0 cm, 0.465 L, 6.28 oz, 19.4 Once all six participants have written down their guesses, they reveal them to the instructor. Any missing units = -2 pts, any inappropriate unit or inappropriate number = -1 pt. The middle value in each case will count for that side’s guess. The object will then be measured and whichever team is closest earns 5 points. Also note: For any given turn, if the winning team’s guess is within 10% of the actual value (20% for mass), then that side wins an extra three points. After three turns, a new group of three students come up from each side. Just to give you some reference points: Length: A dollar bill is 15.5 cm long and 6.5 cm tall. A standard door is a little over 2 m tall. Mass: a new penny weighs about 2.5 g. Your chemistry textbook weighs about 2 kg. Volume: a typical grape is 5-6 mL. A 2 L soda bottle is… hmmm 2 L! Temperature: water freezes at 0*C and boils at 100*C. Normal body temperature is 37*C.

object Your estimate Actual

measurement Error

(estimate-actual) % Error

(error÷actual x 100)

Total |% error|

Mean |% error| (total ÷ # trials)

%

%

Median |% error| (average of the two

middle values)

%

%

%

%

%

%

%

%

%

%

%

%

%

%

%

%

19

Follow up Questions: 1. Take the absolute value of all of your percent errors and add them together, write this in the appropriate space on the front side. Then divide by 14 (the # of trials) and write down your average (mean) |% error| in the appropriate space. Also, determine the median |% error|. Since there are an even number of trials, take the two values in the middle and average them. Write this value in the appropriate space on the front side. 2. Consider these two students, each doing just two trials. Their % errors are Joe: +3.4%, +5.7% Sarah: -49.3%, +51.7%. Just by eyeballing these results (no calculations) which student was more accurate with their estimations? ________ Calculate their mean percent errors without using absolute values: Joe: _______ Sarah: ________ Based on these averages, who looks like they had better estimating skills? ________ Why? _______________________ Now use absolute values and calculate their mean percent errors: Joe: _______ Sarah: ________ So why did we use absolute percent errors? 3. Consider these students each with five trials. Their |% error| are Brenna: 9.6%, 11.2%, 13.4%, 21.5%, 795.3% Will: 56.4%, 78.6%, 84.1%, 98.3%, 116.4%. Just by eyeballing these results (no calculations) which student was more accurate with their estimations? ________ Calculate their mean |% error| Brenna: _____ Will: _____ and their median |% error| Brenna: _____ Will: _____ Which seems to be a better measure of their performance, mean or median? __________ Why? 3. Consider these students each with five trials. Their |% error| are Julia: 1.3%, 2.2%, 2.8%, 56.9%, 78.5% Sam: 1.4%, 2.1%, 3.8%, 4.7%, 5.8%. Just by eyeballing these results (no calculations) which student was more accurate with their estimations? ________ Calculate their mean |% error| Brenna: _____ Will: _____ and their median |% error| Brenna: _____ Will: _____ Which seems to be a better measure of their performance, mean or median? __________ Why? 4. So, overall, which do you think is a more reliable way of picking the best estimator: mean or median? ______ Why? 5. One the graphs below, plot your absolute percent error as a function of the trial number. You’ll have to scale the y-axes yourselves based on your results. Draw best fit straight lines for the values. (example ) What does a negative slope to the best fit line imply? _______________________ How about a positive slope? ______________________ Which of these applies to you!? _______________________

20

Length: Mass: Volume: Temperature:

t1 t2 t3 t5 t4 t1 t2 t3 t4 t1 t2 t3 t1 t2

HOME LAB Candle observation Name: ________________ This lab is designed to be done at home together with a parent or guardian. It should take about 25 minutes. Once it is completed, have that parent/ guardian sign and date below to confirm that they worked on it with you from beginning to end: Signature of Parent/ Guardian: ___________ ________________________________ Date: _________ How is it that two people can both witness the exact same event and observe very different things? Observations are an important part of science, and as good as you may think your observation skills are, they could always be better. This lab is all about observations, and that means more than just seeing. Observations involve all the senses. In this activity, you will essentially be competing with your parent/guardian to see who is more observant! Good luck to you both. Tear off the attached sheet and hand it to your “opponent.” You will fill out your observation sheet and they will fill out theirs – independently, without looking at one another’s. Only when you are completely done should you compare your lists. Use a small piece of clay or playdough (or a cupcake!) to hold the candle upright on a plate. Without saying anything, spend 3-5 minutes quickly writing down all the observations you can under the column “Before Burning,” (Meanwhile your opponent is doing the same on his/her observation sheet!). When the time is up, go ahead and light the candle, and let it burn for about 5-7 minutes, writing down all the observations you can under the column “During Burning.” Then blow it out and spend another 3-5 minutes writing down all the observations you can under the column “After Burning.” When that time is done, stop and compare. Read through your list of observations. Give yourself a point for each observation that you made. Your opponent should do the same:

Before Burning During Burning After Burning

Continue your observation list on the back side of this sheet if you need more room!

21

Parent/ Guardian Observation Sheet: You should record your observations below while your child does the same on his/her sheet. Follow-up Questions: 1. So…what was the final score? Student: ____ Parent/Guardian: _____ 2. Did you notice any patterns in your list of observations? If so what were they? How about your opponent? 3. Did you see (and hear, smell, taste(?), feel) things that your opponent did not? ____ Why do you think that was? 4. So why do you think two people can look at the exact same event and observe such different things? 5. The “score” above is based only on the number of observations. Are there other things that you think should be included into how this “game” is scored?

Before Burning During Burning After Burning

Continue your observation list on the back side of this sheet if you need more room!

23

SIGNIFICANT FIGURES WS Do this: http://scratch.mit.edu/projects/beckerr/1834194 Name: _________________________

For each of the following, indicate how many significant digits (AKA: significant figures, sig figs, sf’s) there are, circle them, and then underline the uncertain (guessed) digit. (#1 and #6 are done for you)

1) 34 g 2 2) 564 L ___ 3) 19.3 mm ___ 4) 23.45 mg ___ 5) 101 km ___

6) 13400 g 3 7) 5040 L ___ 8) 19,000 mm ___ 9) 20 mg ___ 10) 160 km ___

11) 0.00034 g ___ 12) 0.564 L ___ 13) 0.0019 mm ___ 14) 0.5 mg ___ 15) 0.12 km ___

16) 34.0 g ___ 17) 56.40 L ___ 18) 19.00 mm ___ 19) 20.0 mg ___ 20) 8.200 m ___

21) 30.020 g ___ 22) 50.04 L ___ 23) 0.230 mm ___ 24) 0.0040 mg ___ 25) 1.060 kg ___

26) 3.4 x 103 g ___ 27) 5.64 x108L ___ 28) 7 x 10-5 mm ___ 29) 2.4 x 104 g ___ 30) 3.61x102 m ___

31) 3.0 x 103 g ___ 32) 5.60 x108L ___ 33) 2.04 x 104 g ___ 34) 6.00x102 m ___ 35) 2.0 x 100 m ___

36) 340ō g ___ 37) 2ō00 L ___ 38) 14ō mm ___ 39) 190ō0 mg ___ 40) 650ō km ___

41) 800 g ___ 42) 50.4 L ___ 43) 10,900 mm ___ 44) 1.0090 mg ___ 45) 803 km ___

46) 4.2 x 104 g ___ 47) 0.004 L ___ 48) 0.0040 L ___ 49) 60 mg ___ 50) 6ō mg ___

51) 1,000,000 g ___ 52) 1,000,001 g ___ 53) 0.05060m ___ 54) 56 mg ___ 55) 0 m ___

Convert between scientific notation and expanded notation (without changing the number of sf’s)

56) 5700 g = 5.7 x 103 g 66) 3.6 x 105 m = 360,000 m

57) 14,000,000 m = _______________m 67) 3.6 x 10-5 m = _________________m

58) 104,000 kg = ______________kg 68) 3.60 x 10-5 m = _________________m

59) 2,000 cm = ______________cm 69) 3.60 x 105 m = _________________m

60) 2,ō00 cm = ______________cm 70) 6.00 x 101 kg = _________________kg

61) 0.000043 kg = ______________kg 71) 6.00 x 102 kg = _________________kg

62) 0.001036 m = ______________m 72) 6.00 x 103 kg = _________________kg

63) 0.00023 mg = ______________mg 73) 8 x 1017 mg = ____________________mg

64) 0.000230 mg = _____________mg 74) 3.25 x 103 L = _________________L

65) 0.0002300 mg = ______________mg 75) 3.25 x 100 L = _________________L

Round each of the following off to the specified number of significant figures:

76) Round 78.241 g to... 4 sf: 78.24_ 3 sf: _78.2__ 2 sf: __78__ 1 sf: ___80__

77) Round 4.2983 g to... 4 sf: __________ 3 sf: __________ 2 sf: __________ 1 sf: __________



80) Round 50,001 g to... 4 sf: __________ 3 sf: __________ 2 sf: __________ 1 sf: __________

81) 7625 g is a fine measurement; so is 0.0456 g. Why is 7625.0456 g not very likely? __________________________________

________________________________________________________________________________________________________

Ans (1-55, IRO+1): 0 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 5 5 7

(56-80 even, IRO): 0.0000360 2.30 x 10-4

1.036 x 10-3 60.0 78.24 78.2 78 80 374.0 374 370 400 2.0 x 103 3250 5.7 x

103 60ō0 50,000

50,ō00 50,0ō0 5ō,000 1.04 x 105 360,000

25

http://scratch.mit.edu/projects/beckerr/1834194

Note sheet: Calculations involving significant figures – rules for rounding Name: _________________ Equations:

Area = L x W

Ratio = W ÷ L

Sum = L + W

Difference = L - W

Using Ruler A: Your estimates: L = _________ W = _______ A = ________ R = __________ S = _________ D = _______

Other estimates: L = _________ W = _______ A = ________ R = __________ S = _________ D = _______


Rounded: A = ________ R = _________ S = _________ D = _______ Using Ruler B: Your estimates: L = _________ W = _______ A = ________ R = __________ S = _________ D = _______



Rounded: A = ________ R = _________ S = _________ D = _______ Using Ruler C: Your estimates: L = _________ W = _______ A = ________ R = __________ S = _________ D = _______



Rounded: A = ________ R = _________ S = _________ D = _______ Rounding rule when multiplying and dividing: _________________________________________________________________________ Rounding rule when Adding and subtracting: __________________________________________________________________________

L

W

0 10

cm A

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

cm B

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

cm C

Cut along dotted line; then cut into separate strips.

SIG FIG CALCULATIONS WS Name: ____________________

1) Review: Indicate how many significant figures are in each of the following measurements:

a) 34.0 cm ___ b) 61400 g ___ c) 0.002030 s ___ d) 6.35 x 104 L ___ e) 4.0 x 10-5 kg ___

2) Sig-Fig-Rule for x and ÷ : ____________________________________________________ Perform all calculations & express your answers with the appropriate sig figs & units:

a) 67 cm x 55 cm = ________ b) 4.29 m x 9.83 m = ________ c) 870 mm x 430 mm = ________ d) 0.034 g/L x 8.8 L = ________ e) 5.79 m/hr x 2.34 hr = ________ f) 1.405 m x 639.2 m = ________ g) 5.00 cm x 6.00 cm = ________ h) 5.6 m2 x 6.23 m = ________ i) 5.471 g/mL x 24.0 mL = _______ j) 45.9 mi ÷ 1.50 hr = ________ k) 320 m ÷ 160 s = ________ l) 234.6 g ÷ 67.4 mL = ________ m) 36.2 cm ÷ 4 min = ________ n) 3.45 L ÷ 19 s = ________ o) 8.90 lb ÷ 1730 days = ________ p) 3.56 cm x 2.45 cm x 0.83 cm = ________ q) 3.56 g ÷ (2.6 cm x 4.3 cm x 7.8 cm) = ________

3) Sig-Fig-Rule for + and - : ____________________________________________________ Perform all calculations & express your answers with the appropriate sig figs & units:

a) 67 cm + 45 cm = ________ b) 4.29 m + 9.83 m = ________ c) 170 mm + 250 mm = ________ d) 6.74 g + 2.1 g = ________ e) 1200 kg + 286 kg = ________ f) 13.531 s + 4.1 s = ________ g) 7800 cm - 2 cm = ________ h) 784.326 m - 2 m = ________ i) 2.54 g - 0.000034 g = ________ j) 720 kg - 34.2 kg = ________ k) 45230 mL - 230 mL = ________ l) 3.567 m - 0.067 m = ________

4) A box is 235.8 cm by 45.2 cm by 7.9 cm. Its volume (V = l x w x h) is : ________ 5) A 934 g cat ate an 82.4 g rat, and then coughed up a 3.672 g hair ball. The cat now weighs: ________ 6) A 5627 g brick measures 5.60 cm x 4.51 cm x 24.71 cm. Its density (D = m/V) is : ________ 7) A car travels a distance of 450 km in a time of 3.42 hrs. Its average velocity (v= d/t) is : ________ 8) A 45.67 g stone is placed in a graduated cylinder, and the liquid level rises from 25.7 mL to 32.6 mL. Determine the stone’s density. ________ 9) A 65 kg man is losing weight at the rate of 0.3612 kg/week. After 7.24 weeks he will weigh: ________ Ans (IRO+1): 0.00514 0.041 0.18 0.30 2 2.0 2.54 3 3 3 3.48 3.500 4 5 6.6 7.2 8.8 9 9.02 13.5 14.12

17.6 30.0 30.6 35 42.2 62 112 130 131 420 686 782 898.1 1013 1500 3700 7800 450ō0 84000 370000 Units (IRO+1):g g g g g kg kg kg m m m m cm cm mm mm m2 m2 cm2 cm2 mm2 m3 cm3 cm3 g/cm3 g/cm3 g/mL g/mL L/s cm/min km/hr s mL m/s mi/hr lb/day

26

(continued) Perfect numbers Sometimes in calculations we come across what are called “perfect numbers.” These are almost always small counted numbers that have no uncertainty in them at all, that is to say, they are exact and should be considered to have an infinite number of sig figs. The number of inches in a foot, for example, is 12. But this 12 is a perfect 12. The “2” is not a guess. It is not 12, maybe 13 or 14. It is exactly 12. Using 12.0 would be better, but still 12.0 means 12.0 maybe 12.1 or 12.2. What we really mean is that this 12 is 12.0000000000000... on forever. And if this number 12 were being used in a calculation, it should not be thought of as having just two sig figs. Instead, it should be thought of as having an infinite number of sig figs. Say, for example, you found that a foot of ribbon weighed 65.93 mg and you needed to determine how much one inch of the ribbon weighed. 65.93 mg *12 = 5.494167 mg. But how many sig figs should your answer have. The 65.93 mg has four sig figs, and if you count the 12 as having two, then, according to the rules for sig figs, your answer should only have two sig figs (5.5 mg). But this is not correct. The 12 has an infinite number of sig figs, and so you should be comparing 4 sig figs with * sig figs, and 4 is smaller than *, so the answer should just have 4 sig figs (5.494 mg). Try the following problems, but be aware that many of them involve perfect numbers. Keep this in mind when rounding your answers off: 10) A circle’s radius is 7.84 cm. What is its diameter? Ans: _________ 11) The perimeter of a standard stop sign is 128.9 cm. What is the length of one edge of the stop sign? Ans: _________ 12) The edge of a perfect cube is 4.63 cm. a) What is the area of one face of that cube? b) What is the cube’s total surface area -- all faces combined? c) What is the cube’s volume? a: ________ b: _______ c: _______ 13) It takes Sandy 298.25 s to run a mile. How long would it take her to run a foot? Ans: _________ 14) It takes Tom 174.92 s to run a kilometer. How long would it take him to run a meter? Ans: _________ 15) Assuming everyone consumes three meals a day, how many individual meals are consumed in one week by America’s entire population (304,000,000) Ans: _________ 16) You measured the mass of three pennies and got: 2.54 g, 2.57 g and 2.52 g. What is the average mass? Ans: _________ 17) You measured the mass of six pennies and got: 2.53 g, 2.58 g, 2.56 g, 2.54 g, 2.50 g and 2.52 g. What is the average mass? Ans: _________ Ans 10-17(IRO +1) 0.056487 0.17492 2.538 2.54 15.7 16.11 21.4 85.7 99.3 129 6,380,000,000 units: g g cm cm cm2 cm2 cm3 s s

27

Factor Label (AKA Dimensional Analysis) WS Name: ________________________

Factor label is an incredibly useful mathematical technique which (like calculators) allow you to get the right answer without having to do much thinking – not that you shouldn’t be doing much thinking, it’s just that sometimes your brain cells are better spent on more challenging tasks. Factor label takes care of the drudge work like converting units or solving simple equations so that you can save your brain power for loftier pursuits!

Here’s how it works: just multiply what you are given by a fraction (or a series of fractions) so that the units cancel out.

The teacher will go over a few of the following and then you should be able to take it from there! 1. Convert 4.3 km into mi Ans: _________ 2. Convert 78.9 cm into in Ans: _________ 3. Convert 29.53 g into oz Ans: _________ 4. Convert 3.50 x 108 in into km Ans: _________ 5. Convert 17.5 m/s into m/min Ans: _________ 6. Convert 2500 mi/hr into ft/s Ans: _________ 7. Convert 8.576 g/mL into lb/gal Ans: _________ 8. Convert 3.67 in2 into cm2

Ans: _________ 9. Convert 1750 m2 into ft2

Ans: _________ 10. Convert 45 ft3 into cm3

Ans: _________ 11. Aluminum has a density of 2.70 g/mL. What would be the mass in g of 34.8 mL of aluminum? Ans: _________ 12. Aluminum has a density of 2.70 g/mL. What would be the volume in mL of 930 g of aluminum? Ans: _________ 13. Copper has a density of 8.96 g/mL. A pound (lb) of copper costs $2.76. How much would 1.00 ft3 of solid copper cost? Ans: _________

1 m = 100 cm 1 km = 1000 m 1 kg = 1000 g 1 L = 1000 mL 1 in = 2.54 cm 1 L = 1.0567 qt 1 mi = 1.6093 km 1 kg = 2.2046 lbs 1 lb = 453.59 g 1 mi = 5280 ft 1 ft = 12 in 1 gal = 4 qt 1 lb = 16 oz

Ans (IAO+1): 1.042 2.7 23.7 31.1 71.57 94.0 340 1050 1540 3700 5230 8890 18,800 1.3e6 Units (IRO+1) in $ lb/gal cm2 ft/s blocks ft2 oz mL km g mi km cm3 m/min

28

14. Copper has a density of 8.96 g/mL. How many blocks (each with a volume of 58 mL) could be made from 3.2 kg of copper? Ans: _________ 15. In movies, you often see gold bricks or bags filled with gold being thrown around as though they weighed nothing. Gold has a density of 19.3 g/mL. What would be the weight in lb of a 1.0 gal bag filled with solid gold? Ans: _________ 16. In Norway right now the cost of gasoline is 10.99 NOK/L. What would that translate into in $/gal? (one Norwegian Krøner (NOK) = 16.125 cents) Ans: _________ 17. Mr Becker’s Civic hybrid gets 48.5 mi/gal. He drives for 3.57 hr averaging 65.4 mi/hr. Gas costs $2.53/ gal. a) How much gasoline did he burn? b) How much did it cost? c) How far did he go? a: _________ b: __________ c: __________ 18. Sodium fluoride has a molar mass of 42.0 g/mol. What mass of sodium fluoride would be needed to make up 5.0 L of a solution containing 2.35 mol/L? Ans: _________ 19. A mol of propane weighs 44.0 g. A mol of any compound contains 6.022 x 1023 molecules of that compound. Each molecule of propane is made up of 3 carbon atoms and 8 hydrogen atoms. a) How many carbon atoms would there be in 25.0 g of propane? b) What would be the weight (in g) of 3.56 x 1022 molecules of propane? a: _________ b: __________ 20. Bla bla bla bla bla 31.4 fd/k. Bla bla bla bla bla one k = 7.38 N bla bla bla bla bla bla 567 N. Bla bla bla fd? Ans: _________

Ans (IAO+1): 2.60 4.81 6.2 6.71 12.20 160 233 490 2410 1.03e24 Units (IRO+1): g $ lb mi $/gal fd gal

29

DENSITY WS (SHOW ALL WORK) Name: _________________ __1. The first figure below shows the atoms in an object under certain conditions. Which subsequent figure (A-E) would represent a change that would cause that object’s density to increase? 2. Consider two solid spheres of gold, both under the same conditions: sphere X weighs 20.0 g, sphere Y weighs 10.0 g. Label the following as True or False __ X has twice as many atoms as Y __ X has twice the volume of Y __ X and Y have the same mass __ X and Y have the same density __ The individual atoms in X and Y have the same average mass __ The individual atoms in X are twice as large as the individual atoms in Y __ The atoms in X are spaced out twice as far apart as the atoms in Y 3. A 13.2 mL rock weighs 47.6 g. Determine its density. Ans: ______ 4. 138.42 g of salt water has a volume of 117.0 mL. Determine its density. Ans: ______ 5. 0.446 g of hydrogen gas fills a 5.0 L bag. Determine hydrogen's density. Ans: ______ 6. 25.2 mL of water are placed in a graduated cylinder. A 22.6 g stone is dropped in, and the water level rises to 32.4 mL. Find the stone's density. Ans: ______ 7. A graduated cylinder is placed on an electronic balance, and the scale reads 78.32 g. 10.0 mL of glycerine are added, and the scale reads 91.78 g. What is the density of glycerine? Ans: ______ 8. A 3.0 cm thick, 4.5 cm wide 6.7 cm long brick has a mass of 985 g. a) What is its density, and b) from what material is it most likely made? a)_______ b)________ 9. A graduated cylinder is weighed empty: 56.30 g and then tiny copper bee-bees are dropped in until they reach the 13.7 mL mark. The graduated cylinder and bee-bees together weigh 144.92 g. What value does this give for the density of the copper bee-bees? Ans: ______ Why is this value so far from the correct answer for the density of copper (8.96 g/mL)? Include a diagram with your answer.

A B C D E

Substance: Density: osmium 22.6 g/mL gold 19.3 g/mL mercury 13.6 g/mL lead 11.4 g/mL copper 8.96 g/mL aluminum 2.70 g/mL water 1.00 g/mL alcohol 0.781 g/mL Styrofoam 0.145 g/mL SF6 gas 5.96 g/L air 1.18 g/L helium 0.163 g/L Volume equations: block: V = l x w x h

cylinder: V = r2h

sphere: V = r3

continued on next page

Ans: (IAO + 1) B F F F T T T T 0.089 1.183 1.35 3.1 3.61 6.47 8.72 11 Units: (IRO +1) g g/mL g/mL g/mL g/mL g/mL g/mL g/L

30

10. A cylinder has a mass of 528.6 g, a length of 14.2 cm and a diameter of 2.30 cm. Of what is the cylinder most likely made? Ans: ______ 11. A ball has a mass of 753 g and a radius of 5.62 cm. a) Will the ball float or sink in water? b) Will it float or sink in salt water solution described in #4 above? a)_______ b)________ 12. a) How much would a 15.2 mL chunk of Styrofoam weigh? b) How much would the same size chunk of osmium weigh? a)_______ b)________ 13. How much would a 15.9 cm long, 11.6 cm wide, 7.3 cm thick block of aluminum weigh? Ans: ______ 14. What volume would 62.4 g of mercury have? Ans: ______ 15. How large would a balloon be when filled a) with 17.8 g of air? b) With 17.8 g of helium? Ans: a)_____ b)_____ 16. An empty graduated cylinder weighs 78.63 g. What volume of alcohol must be added to bring the total mass up to precisely 100.00 g? Ans: _______ 17. Make up your own density question so that its answer and unit match the left over answer and unit from the answer box!: Ans: _______

Ans (IAO+1): 2.20 4.59 15.1 27.4 32.4 109 344 3600 copper sink float Units: (IRO + 1): g g g mL mL mL L L

continued on next page 31

Density Challenge Problems: These are tricky – do your best! 18. What would be the diameter of a copper sphere weighing 297.6 g? Ans: ______ 19. At a cost of $350/oz, how much would you have to pay for 1.00 cubic foot of solid gold? (1 oz = 28.4 g; 1 in = 2.54 cm) Ans: ______ 20. A rectangular piece of aluminum foil measures 13.72 cm by 8.63 cm and has a mass of 3.1 g. Find how thick it is. Ans: ______ 21. A 15.40 cm x 8.32 cm x 6.44 cm box with a mass of 146.8 g is floating in a swimming pool filled with water. a) How many marbles (each weighing 12.6 g) can be placed inside the box before it sinks? b) How many marbles could it carry if it were floating on a pool of alcohol? a: ______ b: ______ 22. A thin gold wire has a diameter of 0.175 cm. How much would one kilometer of the wire weigh in kilograms? Ans: ______ 23. A 10.0 mL piece of lead is fastened to a 150.0 mL piece of Styrofoam. Will the resulting object float or sink in water? Ans: ______ 24. A hollow lead pipe is 25.0 cm long and has an OD (outer diameter) of 3.25 cm. It weighs 562 g. What is its ID (inner diameter)? Ans: ______ 25. A 25.0 L helium balloon floats up to the ceiling. At 12:00 noon, it springs a slow leak that lets 1.00 L of helium leak out each hour. At what time will it begin to descend to the floor? (The rubber of the balloon weighs 8.20 g). Ans: ______ 26. A coin is made of gold plated on copper. The coin’s density is precisely 10.0 g/mL. What is the percent by mass of copper in the coin? Ans: ______

Ans (IAO+1): 9.7e-3 3.99 2.84 4:56:13 25 39 46.4 53 80.5 6.7e6 float Units: (IRO + 1): am cm cm cm $ g marbles % marbles kg

32

DENSITY LAB: Identification of solids, liquids & gases Name: ________________ Partner: ________________

As you will discover, density is more than just mass divided by volume, it is a very important concept in chemistry. Density is an intensive property of matter; that means, for instance, that a small piece of gold will have the same density as a big piece; a solid block made of gold will have the same density as a long, thin wire made of gold; a thousand gold coins will have the same density as just one gold coin; a nugget of gold found in the US will have the same density as a nugget of gold found in Africa. This means that if we can determine as precisely as possible the exact density of an unknown substance, it may help us identify what that substance is, be it gold, fool’s gold, silver or platinum. In this lab, you will determine the density of two different solids, two different liquids and two different gases. Make your measurements and calculations as precisely and accurately as possible, so that you can identify what the samples are. Substance A: Procedure: 1. Obtain sample A-1. 2. Very carefully measure its length, width and height (in cm) and record them in the table below. (Make sure your readings are precise.) 3. Zero a balance, then place the sample gently on the pan, Record this mass in the table. 4. Repeat steps 1-3 for samples A-2, A-3, A-4, A-5 and A-6.

Sample A-1 A-2 A-3 A-4 A-5 A-6

length (cm)

width (cm)

height (cm)

mass (g)

Calculations: For a rectangular block, Volume = length X width X height. Calculate the volume of each of the samples and write them in the table below (round them to the appropriate number of sig figs.). Then calculate densities by taking the masses recorded above and dividing them by the calculated volumes. Record these in the table below.

Sample A-1 A-2 A-3 A-4 A-5 A-6

Volume (cm3)

Density (g/cm3)

Look at your calculated densities. Rule out any obvious outliers, and take an average of the remaining ones. Average density of A: ___________ Based on its density, of what substance is A most likely made? ______ Substance B: Procedure: 1. Obtain a small cup full of the pebbles labeled substance B. (Dry them with a paper towel if they appear wet). 2. Fill a 100 mL graduated cylinder about half-way with water and place it on the scale (record this mass in the Data Table below). Also, take a careful measurement of the water level in the cylinder (Record this below as well). 3. Transfer a small portion (about one sixth) of the pebbles from the cup into the cylinder of water – be careful not to splash any water out. Also, tap the side of the cylinder repeatedly to shake loose any trapped bubbles. 4. Place the cylinder containing the water and sample on the scale. Record this mass in the table below – the second box beneath B-1. 5. Now take a measurement of the new water level in the cylinder (Record this in the bottom box beneath B-1). 6. Now simply repeat steps 3-5 five more times, to get a total of six progressively larger sample sizes.

Standard Densities (g/mL) solids liquids

balsa wood poplar pine white oak red oak iron wood magnesium aluminum marble limestone iron gold

0.12 0.51 0.57 0.68 0.73 1.03 1.74 2.70 2.71 3.35 7.87 19.3

ethanol oil water urine 20% salt soln mercury helium CH4 air butane SF6

0.789 0.922 1.00 1.03 1.15 13.6 0.00016 0.00066 0.00118 0.00238 0.00596

gases

Volume = length x width x height

length

height

width

33

Sample B-1 B-2 B-3 B-4 B-5 B-6

mass of cylinder & water (g) " " " " "

mass cyl, water & sample (g)

water level w/o sample (mL) " " " " "

water level with sample (mL)

Calculations: To determine the mass of each sample, simply subtract the mass of the cylinder and water from the mass of the cylinder, water and sample. For example, using the figure at right: mass of sample = 92.32 g - 64.51 g = 27.81 g Calculate the masses for each of your six samples and record them in the table below. To determine the volume of each sample in the graduated cylinder, simply subtract the water level w/o the sample from the water level with the sample. For example, using the figure at right: volume of sample = 61.7 mL - 48.3 mL = 13.4 mL Calculate the masses for each of your six samples and record them in the table below. Once again, to determine the density of each sample, simply divide the mass by the volume. Calculate the density for each of your six samples and record them in the table below.

Sample B-1 B-2 B-3 B-4 B-5 B-6

mass of sample (g)

volume of sample (mL)

density of sample (g/mL)

Look at your calculated densities. Rule out any obvious outliers, and take an average of the remaining ones.

Average density of B: ___________ Based on its density, of what substance is B most likely made? ______ Substance C: Procedure: Liquids are easy. 1. Fill a 250 mL beaker about half way with liquid C. 2. Obtain an empty graduated cylinder; if there are droplets of liquid inside it from a previous experiment, shake them out, weigh it and record this mass below. 3. Pour a small sample (10-20 mL) of liquid C into the graduated cylinder. 4. Record the precise mass of the cylinder and sample (C-1) in the table below. 5. Make a careful measurement of the precise volume of sample C-1 and record it in the table below. 6. Repeat steps 3-5 five more times using progressively larger and larger samples: C-2 = 30-40 mL, C-3 = 45-55 mL, C-4 = 60-70 mL, C-5 = 75-85 mL, and C-6 = 90-100 mL. (Time saving hint: don’t empty out the liquid each time, simply add more and more of liquid C to get the desired total amounts.) 7. Pour liquid C from the beaker back into the bottle from which it came.

Sample C-1 C-2 C-3 C-4 C-5 C-6

mass of empty cylinder (g) " " " " " mass of cylinder w/sample (g)


64.51 g 92.32 g

48.3 mL

61.7 mL

32.52 g 104.52 g

68.7 mL

34

Calculations: To determine the mass of each sample, simply subtract the mass of the empty cylinder from the mass of the cylinder and sample. For example, using the figure above: mass of sample = 104.52 g - 32.52 g = 72.00 g Calculate the masses for each of your six samples and record them in the table below.

Once again, to determine the density of each sample, simply divide the mass by the volume. For example, using the figure above: Density = 72.00 g / 68.7 mL = 1.05 g/mL Calculate the density for each of your six samples and record them in the table below.

Sample C-1 C-2 C-3 C-4 C-5 C-6

mass of sample (g)



Average density of C: ___________ Based on its density, of what substance is C most likely made? ______

Substance D: Shake out the graduated cylinder, then repeat the procedures for sample C and fill out the tables below:

Sample D-1 D-2 D-3 D-4 D-5 D-6

mass of empty cylinder (g) " " " " " mass of cylinder w/sample (g)


Sample D-1 D-2 D-3 D-4 D-5 D-6

mass of sample (g)



Average density of D: ___________ Based on its density, of what substance is D most likely made? ______

Substance E : Weighing an “empty” syringe: gases are rather tricky. Because they are so low density, we will need to use the super-sensitive electronic balance; get the teacher to help you. You must first weigh an empty syringe (“empty” means there is nothing inside, not even air). Procedure1. 1. Obtain a syringe labeled “1” and push the plunger all the way in, cap the syringe tightly, then pull the plunger out and have your partner stick the nail through the hole to hold the plunger in that position, as shown below. 2. Weigh the syringe, making sure it is completely on the balance and not touching the glass case (Record this mass in the table below). Then pull the plunger back a bit so you can take the nail out (the plunger should spring all the way back in to a volume of zero, if it does not, it means that air leaked in and you need to repeat this step). Weighing the syringe filled with gas E. 3. Remove the cap, fill the syringe to the full 35 mL volume with the gas from the bag container labeled E; it helps to have your partner open the pinch clamp while you pull on the plunger. 4. Disconnect the syringe from the bag, insert the nail in the hole and push the plunger back in to its previous position (where the nail stops it from moving in any further), then cap the syringe securely. Record the precise volume in the table. 5. Weigh the syringe with the gas inside. Record the mass in the table. 6. Remove the cap and the nail and push all the gas E sample out of the syringe. 7. Repeat steps 3-6 above using gas sample F.

Read volume here

35

8. Repeat steps 1-8 above using a syringe labeled “2”

Sample E-1 F-1 E-2 F-2

mass of empty syringe (g) " "

Mass of syringe w/sample (g)

Volume of sample (mL) " "

Calculations: To determine the mass of each sample, simply subtract the mass of the empty syringe from the mass of the syringe and sample. Calculate the masses for each of your six samples and record them in the table below. Once again, to determine the density of each sample, simply divide the mass by the volume. Calculate the density for each of your six samples and record them in the table below.

Sample E-1 F-1 E-2 F-2

mass of sample (g)

Density of sample (g/mL)


Average density of E: ___________ Based on its density, of what substance is E most likely made? ______ Average density of F: ___________ Based on its density, of what substance is F most likely made? ______

Density Lab Follow-Up Questions: 1. Did you remember to put units on each and every density you determined in this lab: for A, B, C, D, E and F? Y/ N (Advice: if you didn’t, you had best go back and add them in!)

2. Did you remember to express your all those densities to the correct number of significant figures? Y / N (Advice: if you didn’t, you had best go back and modify them appropriately!)

3. Use a metric ruler (cut out the one below if you do not have One available) to measure the dimensions of the block at right. Calculate its volume: ___________ (show work:) Use the mass shown at right (in g) to calculate its density: __________ Of what material is the block probably made? ____________

top view

side view

36

4. Use the figures at right to calculate the mass of the sample in the cylinder: _________ Use the figures below to calculate the sample’s volume: ______ What is the density of this sample? __________ Of what material is the sample probably made? ________ 5. What is the mass of the liquid sample shown at right? ___________ What is its volume? ___________ What is its density? ____________ What liquid is probably in the cylinder? _________ 6. The syringe shown below was weighed empty (27.435 g) and then weighed with an unknown gas (27.502 g).

What is the gas’s volume? _________ What is the gas’s density? _________ What gas is probably in the syringe? _________

7. a) In the lab you did, why was it important to dry off sample B before you used it? b) If you hadn’t dried it, would that make your density value for B come out too high or too low? _____ Explain.

54.52 g 112.81 g

60

50 mL

90

80 mL

32.52 g 104.43 g

80

70 mL

80

70

mL

37

8. a) Why was it important not to splash any water out when adding sample B to the half-filled cylinder? b) If water had splashed out, would that make your density value for B too high or too low? _______ Explain.

9. a) Why was it important to dry the graduated cylinder before adding liquid C?

b) If you hadn’t dried it, would that make your density value for C come out too high or too low? ______

Explain.

c) Why did you not have to dry the graduated cylinder for B?

10. a) What did “empty” mean when it was used for C & D? ________________________________

b) What did “empty” mean when it was used for E & F? __________________________________

c) Why was it important to change the definition?

11. Consider each of the following potential error sources in the lab you just did. Answer: "H" if it would have caused your calculated density value to come out too high, "L" if it would have caused it to come out too low or "N" if it would have had no effect at all on your value. ___ You measured the block in inches, thinking they were centimeters.

___ You forgot to subtract out the weight of the empty graduated cylinder for the density of the liquid.

___ When you weighed the empty graduated cylinder, it actually had some liquid drops on the inside.

___ When you weighed the empty graduated cylinder, it actually had some liquid drops on the outside.

___ When making the vacuum in the syringe, a little air leaked back in before it was weighed

___ You read the volume of the gas in the syringe from the bottom of the plunger rather than the top.

12. If a gas like helium were put into an evacuated syringe, would the mass go up, down, or stay the same?

______________ Explain:

13. Instead of creating the vacuum inside the syringe, why could you not just weigh the syringe with the plunger pushed all the way in, as shown at right? 14. Look at iron wood in the Table of Standard Densities (page 1). What behavior would a piece of this substance exhibit which would be unusual for a wooden material?

38

IV / DV/ Graphing Review WS: Name: __________________________________

1. Define the following terms:

Independent variable: ______________________________________________________________________________

Dependent variable: ______________________________________________________________________________

Controlled variable: ______________________________________________________________________________

Hypothesis: ______________________________________________________________________________________

Consider each of the following experiments. For each, identify the independent variable, the dependent variable and the controlled variable(s). Also for each, write the hypothesis that the experiment is designed to be testing. At least two of the hypotheses should be in if-then format. 2. Joey called up fifteen different girls and asked them out on dates. Each call lasted precisely two minutes and ended with the question: “so, you want to go the movies Saturday night?” In five of the calls, Joey mentioned his love of chemistry class once, in five of the calls he mentioned his love of chemistry class twice, and in the remaining calls, he did not mention chemistry at all. For each group, he made note of the number of girls who said “yes.” IV: _________________________ DV: __________________________ CV(s) _________________________________

Hypothesis: _______________________________________________________________________________________

List two additional variables that should be kept constant: ________________________ ______________________

3. Kyrie did an experiment and collected the following data

IV: ______________________________________

DV: _____________________________________

CV(s) ____________________________________________

Hypothesis: _______________________________________

_________________________________________________


4. Tanya burped the alphabet up to “J” after drinking a whole can of Coke. Using a whole can of Pepsi, she can get to “Q” or “R.” With Mountain Dew, she only got to “F.” IV: _________________________ DV: __________________________ CV(s) _________________________________

Hypothesis: _______________________________________________________________________________________


5. Ryan got an 83% on his Chem test after studying for two hours and listening to “Lil Wayne.” On the next test, he got a 67% after studying in the same room for the same amount of time to “T-Pain.” IV: _________________________ DV: __________________________ CV(s) _________________________________

Hypothesis: _______________________________________________________________________________________

List two additional variables that should be kept constant: ________________________ ______________________ 6. Lydia had to ask her Dad’s permission to take the car out on Saturday night. She found that the day she made the request had a big effect on how her Dad responded. Even though she asked the exact same question in the exact same tone of voice each time, she found her Dad gave her permission only 11% of the time on Monday, 31% on Wednesday, and 87% on Friday. IV: _________________________ DV: __________________________ CV(s) _________________________________

Hypothesis: _______________________________________________________________________________________


Volume of water sample (mL)

Initial temp of water sample(*C)

Time required to freeze (min)

Temp of Freezer (*C)

25.0 20.0 36 -9.6

25.0 40.0 35 -9.6

25.0 60.0 31 -9.6

25.0 80.0 28 -9.6

39

7. Colin mixed various amounts of water (100 mL, 120 mL,…) together with 3.50 g of baking soda/citric acid mixture and measured how far the reaction would cause a baby bottle to travel down a 20 ft water-filled trough. IV: _________________________ DV: __________________________ CV(s) _________________________________

Hypothesis: _______________________________________________________________________________________


8. A deranged chemistry teacher did an experiment and collected the following data: IV: _________________________ DV: __________________________

CV(s) _________________________________

Hypothesis: _______________________________________________________________________________________


9. Jenni loved texting her friends during class, and she was always looking for new ways to maximize her texting speed. Check out the data she collected: IV: _________________________

DV: __________________________

CV(s) _________________________________

Hypothesis: _______________________________________________________________________________________


10. Jared found that he could get his dog to chew up his homework if he dripped meat juice on it. 10 mL of beef juice worked best, with about 95% of the paper being destroyed. 10 mL of pork juice was second at 72%; then 10 mL of chicken juice at 54%. With fish juice, the dog barely chewed it at all (less than 3%) – not enough for him to use the excuse that his dog ate his homework.

IV: _________________________ DV: __________________________ CV(s) _________________________________

Hypothesis: _______________________________________________________________________________________

List two additional variables that should be kept constant: ________________________ ______________________ 11. Drew’s ’79 Mustang took a long time to start up on some days, and it started up pretty quickly on other days. He decided to see if the time it took to start up was at all Related to how cold it was outside. IV: _________________________ DV: __________________________

CV(s) _________________________________

Hypothesis: _______________________________________________________________________________________


Room temp (*C)

24.1 24.1 24.1 24.1 24.1

Mass of sugar/KClO3 ignited in classroom

(g)

1.00 2.00 3.00 4.00 5.00

Time it takes for fire alarm to go off

(sec)

* 36.9 31.4 20.0 15.6

Day Of the week

M T W Th F

Texting speed during Spanish class (1

st hr)

(words/min)

26 34 24 41 39

Texting Speed during Chemistry class (6

th hr)

(words/min)

23 21 20 21 *

Amount of coffee consumed before school

(cups)

1.5 2.0 1.0 3.0 2.5

* data not available: teacher confiscated cell phone

Date March:

4 5 6 9

10 11 12

Time of day (AM)

7:25 7:28 7:22 7:22 7:24 7:28 7:32

Time required to start car

(min)

3.4 1.8 0.1 2.7 1.9 0.2 1.3

Outside temperature

(*F)

25 31 47 28 37 51 41

40

Graphing Experimental Data WS Due: __________ Name: _______________________________________ Generally when graphing experimental data, the independent variable goes on the x-axis (horizontal) and the dependent variable goes on the y axis (vertical). Just like when you are given the task in math class of graphing the function y = x2 – 7, you try different x values and see what the y-values come out to be. That is, what you change (the IV) is the x, and what changes as a result of that (the DV) is the y. At right is a possible graph for the experiment described in #2 above. Note how The IV (number of times Joey mentioned Chemistry) is on the x-axis), and the DV (number of girls who agreed to go out with Joey) is on the y-axis. Also notice how the graph has a title, which is pretty much in the format: “(DV) as a function of (IV)” So for each of the experiments described above (3 – 11), construct a graph of the results. If actual data are given, use them. If no data are given, just make up some numbers as was done for the example at right. Some of the graphs will be line graphs; others will be bar graphs. Also, give an appropriate title for each graph.

0 1 2 0

1

2

3

4

5

3 4

5 6

Title: number of girls saying “yes” as a function of the number of

times Joey mentioned Chemistry

41

7 8

9 10

11 extra

42

BEVERAGE DENSITY LAB: Sugar content analysis Name: _______________ Partner: _______________ So, how well do you know the beverages you drink? Try to rank the following four from lowest sugar content to highest: Coke, Welch’s 100% Grape Juice, Gatorade, Orange Soda ______________________ ______________________ ______________________ ______________________ (lowest sugar content) (highest sugar content) Along with adding Calories to a beverage, dissolved sugar also increases the density of the solution. In this lab, you will first determine the density of five known (standardized) sugar solutions: 0% (which is just plain water, not colored), 5% (colored yellow), 10% (colored green), 15% (colored blue), and 20% (colored purple). You will then plot these densities on graph of density as a function of sugar content. Finally, you will determine the densities of the four beverages, then use the graph to approximate their sugar contents. Procedure: The instructor will demonstrate the proper technique for using a volumetric pipet. 1. Place the beaker on the balance and hit the “tare” (re-zero) button. The scale should read “0.00 g.” Draw up a precisely measured 10.00 mL of 0% sugar solution into the pipet. Then empty it into the beaker, touching the tip of the pipet to the inside wall of the beaker to help get out most of the liquid in the tip. Do not try to shake out any liquid that remains there. The pipets are designed “TD” (“to deliver”) 10.00 mL and that remaining drop should not be squeezed out. Since the beaker has already been zeroed out, the mass is that of the liquid alone. Record this mass reading in the data table at right, then push the “tare” button to re-zero the scale for the next reading. 2. Touch the pipet to a paper towel to get rid of the excess liquid in the tip. Then repeat step 1 with each of the remaining sugar solutions, and then with each of the four beverages. Do not put any of the solutions back into the cups from which they came, just leave them in the beaker. When the beaker gets full, simply empty it into the sink, set it back on the scale and push the “tare” button. Calculations: Calculate the density of each solution. Enter these values in the boxes alongside the data table. (Hint: Since the volume is always 10.00 mL, this should be easy; you don’t even need a calculator!) Graph: On the last page, carefully plot a graph of the calculated densities of the five known sugar solutions as a function of their sugar content (%). Then use a ruler to draw a best fit straight line through the point (DO NOT PLAY CONNECT-THE-DOTS!!!). Then use the densities of the four beverages to approximate their sugar contents (%). To do this, start on the y-axis at a density of one of the beverages, then follow the line over to where it hits the best fit line you drew, then go straight down to the x-axis to determine the corresponding sugar content value. As with measurements, read your graph one place past the scale. Results: Below, list the sugar content values (%) you approximated from your graph. Also, list the values obtained by some other

lab group (their names: ________________ ________________)

your values: Coke _________ Grape Juice _________ Gatorade _________ Orange Soda _________

their values: : Coke _________ Grape Juice _________ Gatorade _________ Orange Soda _________

Sample Mass(g) Density (g/mL)

0% sugar

5% sugar

10% sugar

15% sugar

20% sugar

Coke

Grp Juice

Gatorade

Or. soda

43

Follow-up Questions: 1. How well did you do in guessing the sugar-content rank of the four beverages? 2. Water has a density of 1.00 g/mL at 4*C. Was your room-temperature value for the density of water (0% sugar) higher or lower than 1.00? Why do think it was off in that direction?

3. Why were you told not to put solutions back into the cups from which they came? 4. Why was it OK to leave liquid in the beaker from one trial to the next? 5. In this lab, you discarded all of the solutions into the sink. Can you think of situations where this would not be appropriate? 6. List three liquids found around your house that should not be discarded into the sink. 7. This lab focuses on sugar content. What assumption does the lab make concerning all the other ingredients in each of the beverages? 8. When plotting data such as these, why is it not appropriate to connect the dots in the graph you draw? If you were to redo the lab, do you think you would get the same results? 9. How precisely would you go about making up some 12% (by mass) sugar solution? Precisely how much sugar would you use, and how much water? [This is an easy question: just think what you would do if you were told to make up a group of people that was 12% male.] 10. Draw a sketch of the volumetric pipet. What makes it so precise? Why do you think it bulges in the middle?

44

0 5 10 15 20 25 0.980

0.990

1.000

1.010

1.020

1.030

1.040

1.050

1.060

1.070

1.080

1.090

1.100

Sugar Content (%)

D e n s i t y

(g/mL)

45

MYSTERY LIQUID DENSITY LAB Names:_________________ ___________________ Per:___ In this lab, you’re going to have some fun with density! You will collect data for the mass and volumes a liquid, and graph the results. You will then learn how that graph can help you make accurate predictions. But be very careful with your data collecting and your graph analysis: your grade is riding on it!

Procedure: Important: Use the same graduated cylinder throughout and the same scale.

1. Pour 15-20 mL of liquid X (red) into the small cup (between the lines). Then transfer this liquid into the graduated cylinder; record the precise volume in the table at right.

2. Weigh the cylinder and liquid on one of the scales at the front of the room. Record this mass in the table at right.

3. Repeat steps 1 and 2 four more times, for a total of five volume & mass readings – each time adding more and more liquid to the cylinder.

4. When you have finished five trials, pour liquid X back into the bottle from which it came.

5. Recopy your data onto the spreadsheet on the computer, and save it to your own H:drive. It is set up to graph the data points for you. Then print out your graph (two copies, one for you, one for your partner) and use a ruler to carefully draw a best fit straight line for the five points. (Ignore any obvious outliers.) Extend this line across the entire graph grid as shown at right and label it “liquid X”. Then use your best fit line to make the following predictions:

A. Predict how much the empty graduated cylinder weighs: Be as precise and accurate as you can. Your grade is based on how close your prediction is to the actual mass. (See scoring table at right.)

Once you have written down your prediction in the space above, dry out your graduated cylinder, and hand it (and this sheet) to your instructor, He/she will weigh it (on the same scale you have been using) and tell you your score.

B. Predict how much the cylinder will weigh with 50.0 mL of liq X in it: Once you have written down your prediction in the space above, pour precisely 50.0 mL of liquid X into the cylinder – use a dropper if you want to make this very precise – and hand it (along with this sheet) to your instructor, He/she will weigh it and tell you your score. C. Predict what volume of liq X must be added to the cylinder to give a total mass of 125.00g: Add precisely this much liquid X to the cylinder – again using a dropper if you want – then hand it to your instructor, He/she will weigh it and tell you your score.

6. Rinse out and dry out your cylinder, and now repeat steps 1-4 above, but this time use liquid Y (blue) instead of X. Record your data in the table at right. Plot these points (by hand) on the same graph you used for liquid X. Draw a separate best fit line for these data. Then answer the follow up questions below for homework. Follow-up Questions: 1) How do the y-intercepts of the two lines compare? ____________________________

2) Should the y-intercepts be the same? ______ Explain: ________________________

______________________________________________________________________

3) How do the slopes of the two lines compare? ____________________________________________________

4) Based on their slope comparison, which liquid is more dense? _____ How can you tell? __________________

_________________________________________________________________ (continued on the next page)

liquid X

volume mass (mL) (g)

Within score 0.5 g = 5.0 pts 1.0 g = 4.5 pts 2.0 g = 4.0 pts 3.0 g = 3.5 pts 5.0 g = 3.0 pts 10 g = 2.0 pts You tried 1.0 pt

liquid Y

volume mass (mL) (g)

liquid X

46

5) Now use your best fit lines to determine the precise densities of the two liquids. To do this, you must understand the mathematical definition of “slope.” Slope is defined as how much a line goes up divided by how far it goes over. This is sometimes called “rise over run,” and for a graph it is defined as the change in y-value divided by the change in x-value. Since our graph has mass plotted on the y-axis and volume plotted on the x-axis, the slope will be the change in mass divided by the change in volume. Mass divided by volume is density, so once you found the slope, you’ve found the density! And finding the slope of a line is actually very easy. Let’s start with the line for liquid X: a) Pick any two points on the line for liquid X. Don’t use data points; just use any points on the best-fit line. Try to use points that are pretty far apart and which are easy to read. b) Read the volume and mass for the higher point: Vhigher = _________ mhigher = _________ c) Read the volume and mass for the lower point: Vlower = _________ mlower = _________

d) Subtract the volumes (Vhigher - Vlower) = to get the change in volume: V = __________

e) Subtract the masses (mhigher - mlower) = to get the change in mass: m = __________

f) Divide: This is the slope of the line, and it is also the density of liquid X. m/V =

Repeat this calculation for liquid Y: a) Pick any two points on the line for liquid Y. Don’t use your data points; just use any points on the best-fit line. Try to use points that are pretty far apart and which are easy to read. b) Read the volume and mass for the higher point: Vhigher = _________ mhigher = _________ c) Read the volume and mass for the lower point: Vlower = _________ mlower = _________

d) Subtract the volumes (Vhigher - Vlower) = to get the change in volume: V = __________

e) Subtract the masses (mhigher - mlower) = to get the change in mass: m = __________

f) Divide: This is the slope of the line, and it is also the density of liquid Y. m/V =

Note: If you go back and open the spreadsheet file you saved on your H-drive, you can right click on one of the plotted data points, then click on “Add Trendline,” then click on “Options,” then check the box next to “Display Equation on Chart,” then click “OK.” This will give you the equation for the best fit line that the computer calculated. It is in the format y = mx + b. The “m” is the slope (the density) and the “b” is the y-intercept (the mass of the empty graduated cylinder). How do these two values compare to the ones you determined above? Joey repeated the experiment using two other liquids, P & Q, and plotted the data at right: P = Q = Draw in best- fit lines (ignoring outliers) for the two data sets. Then answer the following questions: 6) What would be the mass of 43.0 mL of liquid P

(together with the cylinder)? ________

7) What volume of liquid Q would (together with the

cylinder) have a mass of 44.0g? _________

8) The data indicate that Joey didn’t quite follow all the directions. Can you figure out what mistake Joey made? 9) In spite of his mistake, the data Joey collected will still give accurate results for the densities of P and Q. Even still, Joey is a little distraught, so can you please help by doing these calculations for him?

Density of P = =

Density of Q = = Joey thanks you! (continued on the next page)

Mass as a function of volume for liquids P & Q

70

60

50

40

30

20

10

0 0 10 20 30 40 50 60

volume (mL)

mass (g)

47

Plot the following data on the graph below; you will need to increment and label the axes yourself. Then draw a best fit line (ignoring any outliers) and use it to answer the questions below: 10) First give a title to your graph.

11) Which data line at right must have been read incorrectly? (Circle it).

12) Using the best fit line, what is the mass of the empty cylinder? __________

13) What volume of liquid Z must be added to the cylinder to give a total mass of 85.0 g? ___________ 14) What is the density of liquid Z? __________ Show work: 15) Liquid J is precisely half as dense as liquid Z. Draw in (and label) a line for liquid J on the graph below (assume the same cylinder was used).

Volume of mass of liquid Z Liquid Z (mL) & cylinder (g) 17.5 52.73 33.7 74.60 52.1 99.43 71.1 116.72 86.4 145.78

48

Archimedes Principle WS: Name: ________________________ 1) Do objects appear to gain or lose weight when they are submerged in a fluid? ________ Why? (Use diagrams in your answer, and include the concept of pressure.) 2) State Archimedes Principle: 3) A metal block has a mass of 75.34 g and a volume of 14.2 mL. The block is submerged in water (D = 1.00 g/mL).

What volume of water would the block displace? ________ How much would this volume of water weigh? ________

What buoyant force would be pushing upward on the block (This is the same thing as the weight lost)? ________ How much would

the block appear to weigh when submerged in water? __________

4) The same block described in # 3 above is submerged in salt water (D = 1.15 g/mL) What volume of salt water would the block displace? _____ How much would this volume of salt water weigh? ______

What is the buoyant (weight lost by the block)? ________ How much would the block appear to weigh? __________

5) The same block described in # 3 above is submerged in ethanol (D = 0.789 g/mL) What volume of ethanol would the block displace? _____ How much would this volume of ethanol weigh? ______

What buoyant force (weight lost by the block)? ________ How much would the block appear to weigh? __________

6) The same block described in # 3 above is submerged in air (D = 0.00118 g/mL or 1.18 g/L) What volume of air would the block displace? _____ How much would this volume of air weigh? ______

What buoyant force would be pushing upward on the block? ________ How much would the block appear to weigh? __________

7) If you want to determine the true mass of an object, how must it be weighed? ______________________________

Why? ____________________________________________________________________________________________

8) That means that you weigh more than you think you do! Why? ___________________________________________

So assuming your bathroom scale says you weigh 159.2 lbs. Convert that into kg: ___________ ( 1 kg = 2.2046 lbs)

Assuming you have pretty much the same density as water, what is your volume in L (recall that for water 1 mL = 1 g and therefore 1 L = 1 kg)? ____________ So what weight of air do you displace (in g)? __________ (in kg)? _________ (in lbs)?__________ So, how much do you actually weigh in lbs? ___________

ANS: 0.0107 0.0167 0.0167 0.0852 0.188 11.2 11.2 14.2 14.2 14.2 14.2 14.2 14.2 16.3 16.3 59.0 61.1 64.1 72.21 72.21 75.32 85.2 114.3 159.4 72,210 units: g g g g g g g g g g g g g mL mL mL mL mL lb lb kg kg

49

9. How much would a 6.80 cm x 3.47 cm x 2.10 cm block of aluminum (D = 2.70g/mL) weigh in a vacuum? ___________

How much would the block appear to weigh when submerged in water? _______ when submerged in ethanol? ______ when submerged in liquid mercury (D = 13.6 g/mL)? _______ What does this last answer imply? __________________

10. A helium balloon has a volume of 13.9 L and a mass of 8.59 g. How much would it weigh when submerged in hydrogen gas (D = 0.0826 g/L). _________ How much would it appear to weigh submerged in air? _______ How many 1.35 gram paper clips could this balloon lift into the air _____

11. A ring weighs 28.43 g in a vacuum and appears to weigh 26.82 g submerged in water. What is its density? ______ The ring appears to be made of gold (D = 19.3 g/mL). Is it pure gold? _____

12. A metal rod weighs 139.78 g in a vacuum and 121.98 g submerged in ethanol. What is the rod’s density? ________

That same rod weighs 104.13 g submerged in a container of carbon tetrachloride. What is carbon tetrachloride’s density? _______

13. A boat weighs 75.0 kg and it contains a 1.5 L anchor that weighs 12.0 kg . Combined weight = _______. When the boat is floating with the anchor inside it they collectively appear to weigh nothing. How much weight (in kg) did they appear to lose? _______ How many liters of water does the boat and anchor displace? _________ Now the anchor is thrown overboard with no rope attached (sound familiar?), and the anchor sinks to the bottom. Now only the boat is floating. How much water do the boat and anchor displace now? ______ Is there now more or less water being displaced than there was before? _______ So, will the water level on the shore go up or down? ______

14. A submerged object always displaces its ___________ worth of fluid, but a floating object always displaces its __________ worth of fluid.

ANS: -541 -7.81 1.58 5 6.20 7.44 17.7 31.8 76.5 84 87.0 87.0 87.0 95 134 weight’s volume’s g g g g g g kg kg L L g/mL g/mL g/mL No

50

Archimedes Principle Part II: for Floating Objects Name: _______________________

So far you have learned that when an object is submerged in a fluid, that fluid exerts a buoyant force upward on that object and makes that object appear to weigh less. But what about objects that float? Floating objects are usually only partly submerged, and yet since they are floating, they are essentially weightless: that is, they appear to have lost all of their weight. In other words, whereas sunken objects always displace their volume’s worth of the fluid they are submerged in, floating objects always displace their weight’s worth of the fluid they are floating in.

1. A 3.00 cm by 10.00 cm x 10.00 cm block of wood weighs 216 g.

a) What is its volume? _______

b) What is its density? _______

c) Will it float or sink in water (D = 1.00 g/mL)? _______

d) How much does it appear to weigh when floating in water? _______

e) What volume of water is it displacing? _______

f) Would it be floating like diagram A or B at right (dotted line shows liquid level)? ____

g) How far down (in cm) will it be submerged (x in fig C)? _______

h) How much does it appear to weigh submerged in salt water (D = 1.15 g/mL)? _______

i) What volume of salt water is it displacing? _______

j) How far down (in cm) will it be submerged in salt water? _______

k) What is the product of the depth (x) and fluid density (D) for the block when it was floating in water? _______

l) What is the product of the depth (x) and fluid density (D) for the block when it was floating in salt water? _______

m) What do you notice about these two products? ____________

n) Some object is floating in liquid a (density = Da) and is submerged to a depth of xa. It is then floated in liquid b (density

= Db) where it sinks to a depth xb. What general equation relates Da, xa, Db and xb? ___________

2. A block of oak wood 5.00 cm high, 5.00 cm wide, and 10.0 cm long is placed into a tub of water. The density of wood is 720.0 kg/m3. The density of pure water is 1000 kg/m3. Will it float or sink? If it floats, how far in cm will the block of wood be submerged?

3. Repeat the above problem for a block of iron of the same dimensions. The Diron = 7860 kg/m3.

A B

C

x

0.720 1.88 2.16 2.16 2.16 3.60 6.96 188 216 274 300. g/mL cmg/mL cmg/mL mL mL cm cm cm cm cm3 cm3 they’re equal sink float float Daxa = Dbxb

51

4. A block of wood floats submerged to a depth of 8.00 cm in pure water. How far will it be submerged when floating in salt water (D = 1150 kg/m3)? 5. A block of plastic floats submerged to a depth of 4.50 cm in salt water and a depth of 6.25 cm in oil. What is the density of the oil? 6. An iron (D = 7860 kg/m3) block 5.00 cm high, 5.00 cm wide, and 10.0 cm long is placed into a tub of mercury (D = 13,600 kg/m3). Will the iron block sink or float? If the iron block floats, to what depth does it sink before it floats? 7. A styrofoam block floats submerged to a depth of 1.50 cm in water. How far will it be submerged when floating in mercury? 8. A large rectangular raft (D = 650 kg/m3) is floating on a lake. The surface area of the top of the raft is 8.2 m2 and its volume is 1.80 m3. The density of the lake water is 1000 kg/m3.

a. Calculate the height of the portion of the raft that is above the surrounding water.

b. Calculate the magnitude of the buoyant force and state its direction.

c. If the average mass of a person is 75 kg, calculate the maximum number of people that can be on the raft without the

top of the raft sinking below the surface of the water. (Assume the people are evenly distributed on the raft.)

0.07 0.110 0.21 0.878 2.89 8 70 1170 g/mL float g/mL cm cm cm cm m m kg people upward

52

CHEMINAR WORKSHEET UNIT 1 15 pts for original + 5 pts for copy Name: _________________________ Per____ 1. Tom learned from a friend that when Mentos candies are dropped into a bottle of Diet Coke, it causes a huge eruption of soda foam that shoots several meters into the air. He conducts the following experiment: He drops four Mentos into a 2-L bottle of Diet coke and measures the height of the eruption: 3.6 m. Then he drops eight Mentos into a new 2-L bottle of Diet Coke and again measures the height of the eruption: 5.7 m. __ The dependent variable in Tom’s experiment is… a) the size of the soda bottle used b) the number of Mentos used c) the height of the eruption d) the type of soda used e) the newness of the soda __ The independent variable is… a) the size of the soda bottle used b) the number of Mentos used c) the height of the eruption d) the type of soda used e) the newness of the soda __ One controlled variable in this experiment is … a) the size of the soda bottle used b) the number of Mentos used c) the height of the eruption d) the type of soda used e) the newness of the soda __ An appropriate hypothesis for this experiment would be… a) If Mentos are dropped into a bottle of soda, it will erupt to a greater height if you use diet soda than if you use regular b) The more Mentos you drop into a diet Coke, the higher the eruption will be. c) Mentos work better than any other candy to make Diet Coke erupt out of its bottle. d) If you measure the height of the Diet Coke eruption, you will be more likely to drop in more Mentos the next time. __ To test the reliability of this experiment, Tom would have to… a) Change more than just one variable at a time and see how that affects his results b) Repeat the experiment several times to see if his results are consistent c) Search the internet to see if similar experiments have been performed d) Publish the results and see what other researchers have to say about them e) Look up the answer in a book somewhere to see if the results were correct __The information Tom collected could be considered… a) anecdotal evidence b) qualitative findings c) quantitative findings d) a theory e) a law __ If Tom had used a measuring tape that read to the thousandth of a meter, his results would be… a) more accurate b) more precise c) more reliable d) more valid e) more scientific __ The measuring scale Tom used was placed behind the bottle and so as Tom looked up at the eruption, it caused it to appear taller than it actually was. This would cause a ________ error and impact the ________ of his results a) random, precision b) random, accuracy c) systematic, precision d) systematic, accuracy 2. Connor remembers reading somewhere that scrambled eggs taste fluffier if you add a little baking soda before you cook them. So he decides to find out if this is true. He cooks up a batch of scrambled eggs (batch A) using no baking soda and then batch B using 1 mL of baking soda, and then a batch C using 2 mL of baking soda. Then he sits down to eat them, one bite from each batch and rate them on a fluffiness scale from 1 to 10. Based on what you just read, what would be a stated hypothesis for Connor’s experiment? What was the independent variable in this experiment? ___________________________________ What was the dependent variable? _________________________________ List three things that Connor should have as controlled variables in his experiment.

53

Why is it important that these variables be controlled? When Connor sits down to sample the different batches, he suddenly remembers that he is allergic to eggs! So he decides to ask his sister to judge for him. She has no knowledge of what the experiment was all about, but she’s happy to help her brother. Does using his sister as the fluffiness judge make Connor’s experiment better or worse? Why? Before drawing any conclusions, Connor decides to try the same experiment on several other relatives. Does this make Connor’s experiment better or worse? Why? 3. Consider the object drawn at right:

List two examples of quantitative data about the object: ______________ ______________

List two examples of qualitative data about the object: ______________ ______________ __ Tony designs an experiment to test whether soaking a brass rod in 50 mL of 90*C water for 10 minutes will make it grow noticeably longer. He would probably need each of the following scientific tools except … a) an electronic balance b) a thermometer c) a metric ruler d) a graduated cylinder e) a stopwatch “If batteries are stored in the refrigerator, they will stay charged longer than those stored at room temperature.” Design an experiment to test this hypothesis. Write the procedure in numbered steps below. Be very specific in your procedure to make it obvious that your experiment is well-controlled.

54

4. Assuming the zero marks are properly aligned with the left-hand edges of the blocks below, record appropriate measurements for their lengths: Obtain a metric ruler and measure the lengths of these three lines: (Your answers may not be consistent with those below due to copy machine variables…) Make appropriate readings for the liquid levels in the following two containers: 5. Perform the following calculations. Make sure you answers have been rounded appropriately and assigned the correct units: 8.24 m x 23.77 m = __________ 2.4179 m ÷ 940 s = ______________ 29.93 mL – 28.53 mL = __________ 7.47 g + 9.1 g = ___________ The actual mass of a wooden block is 67.92 g. In the lab, the mass of the block was measured with three different devices. The following values were obtained: a) 68 g b) 62.372 g c) 69.11 g Which measurement was least precise? __ Which measurement was least accurate? __ Consider the following four centimeter rulers (all drawn to scale)

A) B) C)

D)

Which of the rulers is least precise? ____ Which of the rulers is least accurate? ____

6. __ For the measurement “23500 cm,” which is/are the estimated digits? a) only the “2” b) only the “3” c) only the “5” d) the “2,” “3” & “5” e) the two “0”’s __ Which of the following would be an appropriate volume for a large cup of soda? a) 8 mL b) 800 mL c) 80,000 mL d) 8 L e) 800 L f) 80,000 L __ Which of the following would be an appropriate height for a typical locker? a) 1.5 mm b) 150 mm c) 15,000 mm d) 1.5 m e) 1500 m f) 150,000 m A metal block has a length of 12.45 cm, a width of 8.42 cm and a thickness of 2.97 cm. If the block is made of aluminum (D = 2.70 g/mL), how much would the block weigh? Ans: ________

3 4

a) b)

60 70 cm mm

0 cm

10

0 1 2 3 4 cm 5

20

30

15

14

mL mL

0 1 2 3 4 5 cm

0 1 2 3 4 cm

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7. The syringe at right was weighed empty (27.465 g) and then weighed with an unknown gas(27.502 g). What is the gas’s volume? _________ What is the gas’s density? _________ Based on the diagram at right, what is the mass of the sample of gravel? _________ What is their density? ____________ What purpose does it serve to find a substance’s density? _______________________________________________ 8. 34.6 mL of salt water (D = 1.15 g/mL) is placed in a cylinder and the total mass is 134.63 g. Some copper pellets are added until the total mass is 198.45 g. (Copper’s density is 8.96 g/mL). a) What is the new liquid level in the cylinder? b) How much does the empty cylinder weigh? a: _________ b: ________

9. Metric conversions: 3.48 L = __________ mL 5.7 x 1018 g = ___________ dg 47.5 m = __________ cm Copper’s density is 8.96 g/mL. a) What would be the volume of a 298.6 g block of copper b) How much would it appear to weigh submerged in ethanol (D = 0.789 g/mL)? a: _________ b: ________ 10. Hannah can bike at 16.7 mi/hr, and while she does so, she is burning 487 Cal/hr. It takes 3904 Cal to burn off one pound of fat. She is biking to raise money for the humane society, and her family and friends have pledged a total of $24.75 for every mile that she rides. If she bikes for 168 minutes, a) how much money did she raise? b) how many pounds did she lose? Show your work in factor label form. a: _________ b: ________ Gold has a density of 19.3 g/mL . What would this be in lb/ft3? Ans: __________ Show your work in factor label form. You may need to consult other worksheets for useful conversion factors.

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11. How many significant figures (sf) are in each of the following measurements? a) 23.00 cm __ b) 700 g __ c) 30.04 m __ d) 0.0710 s __ e) 1.28 x 102 mm __ f) 130000 kg __ g) 0.003040 L __ Round 7168.1 g off to 4 sf: ___________ to 3 sf: ___________ to 2 sf: ___________ to 1 sf: ___________ Amanda buys two rings that are the exact same size and shape; they both are made of pure gold. Will the rings have the same volume? __ Will the rings have the same mass? __ Will the rings have the same density? __ She cuts off a small piece of one of the rings. Will it have the same mass as the original? __ same volume? __ same density? __ Label the following as E (extensive) or I (intensive): density __ weight __ color __ age __ flammability __ Label the following properties as C (chemical) or P (physical): hard to break ___ bursts into flames ___ boils at 467°C __ dissolves in water __ turns green in air __ 12. Put a check mark next to each statement that was mentioned in the lab safety contract (see if you do this one from memory… you did read it, didn’t you?) ___ Never leave a lit burner or any hot object unattended. ___ Wash your hands with soap and water after handling chemicals ___ Do not cool off a hot beaker or test tube by running cold water over it ___ Never use a plastic pipet when transferring solutions of concentrated nitric acid or sodium hydroxide ___ Do not pick up broken glass with your bare hands. Peter heated up some samples of water over a hot plate to see if salt would dissolve faster when the temperature of the water was higher. IV: _________________________ DV: __________________________ CV(s) _________________________________

Hypothesis: _______________________________________________________________________________________


At right, graph the data he might have collected (just make stuff up!) make sure to label your axes and have a title for the graph.

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anchor overboard lab name: p artner: per:...anchor overboard lab name: ___ _____ ___ p artner: _____...

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anchor overboard lab name: p artner: per:...anchor overboard lab name: _ _ _ p artner: _____...