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HONORS CHEMISTRY SUMMER ASSIGNMENT

Name: Date: Period:

Precision is a measure of how close a series of measurements are to one another. Estimating error is a way of quantifying the precision of your measurements.

Percent Error = measured value- actual value x 100

actual value

Average mean = sum of all measurements / # of measurements T

Ex: 5.50 cm, 5.49 cm, 5.53 cm, 5.48 cm, and 5.52 cm

https://www.youtube.com/ Average = 27.52 / 5 = 5.50 cm watch?v=loduc50moIQ

Deviation = |Experimental value – Average mean| T

Ex: |5.50 – 5.50| = 0

|5.49 – 5.50| = 0.01 |5.53 – 5.50| = 0.03 |5.48 – 5.50| = 0.02 |5.52 – 5.50|= 0.02

Degree of uncertainty = average of deviation

(0+0.01+0.03+0.02+0.02) / 5 = cm = 0.016 cm

5.50 cm ± 0.016 cm

Consider the following: The accepted data for the density of lead is 11.3g/mL. Five groups attempt to measure the density and got the following data.

Group # Mass (g) Volume (mL) Density (g/mL)

1 25.0 2.19

2 42.7 3.71

3 34.2 3.03

4 15.3 1.30

5 46.8 4.22

1. Complete the table by calculating the density of lead for each group. D =M/V

2. Calculate the error for each group (Ea)

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3. Calculate the average mean of the data

4. Calculate the deviation for each group

5. Calculate the percent error for each group

6. Calculate the degree of uncertainty for the lab data

Accuracy is a measure of how close a measurement comes to the actual or true value of whatever is measured.

A measurement can only be as accurate and precise as the instrument that produced it. A scientist must be able to express the accuracy of a number, not just its numerical value. We can determine the accuracy of a number by the number of significant figures it contains. Significant figures The last digit of a measurement expression is uncertain. That is because the last digit is an estimation.

Significant figures in a measurement expression comprise all digits that known with certainty, plus one digit that is uncertain. PLACEHOLDERS ARE NOT SIGNFICANT.

Rules for determining the number of significant figures in a given value:

1. All non-zero digits are significant.

2. All zeros between two nonzero digits are significant. (aka: sandwich rule)

https://www.youtube.com/ watch?v=eCJ76hz7jPM

PRACTICE: Determine the number of significant figures in each of the measurements below.

1. 43.8 L

2. 43.08L

3. 4567.98g

4. 5678.09807 g

5. 3,400,008 mL

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3. Trailing zeros are significant only if there is a decimal point or a bar drawn over the zero PRACTICE: determine the number of significant figures in each of the measurements below:

1. 345,00 g

2. 345,000,000 mL

3. 345, 000 cm

4. 345, 000 L

5. 345.000 mg

4. Zeros in the beginning of a number whose only function is to place the decimal point are not significant.

Ex: 0.0025 has 2 significant figures.

5. Zeros following a decimal significant figure are significant Ex: 0.00470 has 3 significant figures PRACTICE: determine the number of significant figures in each of the measurements below:

1. 0.00876 mL 2. 20.0005 kg 3. 0.0008076 g

4. 0.080906L 5. 0.080006g 6. 987.00cm

Significant figures - Determine the number of significant figures in the following measurements

1. 876 mL 13. 0.0098 L

2.

00.345 L

14. 987,876,643.00 mm

3.

0.09045 g

15. 98,008 g

4.

987,000 cm

16. 2000.00 g

5.

907,000 cm

17. 2020202 cm

6.

900,000 mL

18. 4 cm

7.

98.08 g

19. 40 cm

8.

907,008 mL

20. 40 cm

9.

40.000 L

21. 4.7 x 10-8 10.

40,000 g

22. 2.000 x 102 11.

_ 40,000.0 g

23. 3.01 x 1021

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Calculating using significant figures

Rule for Multiplying and Dividing

Limit and round to the least number of significant figures of any of the factors.

Example: 23.0 cm x 432 cm x 19 cm = 188,784 cm3 = 190,000 cm3 since 19 cm has only two significant figures

Rule for Adding and Subtracting

Limit and round your answer to the least number of decimal places

Example: 123.25 mL + 46.0 mL + 86.257 mL = 255.507 mL = 255.5 mL

since 46.0 mL has only one decimal place

Perform the following operations expressing the answer in the correct number of significant figures.

1. 1.35 m x 2.467 m =

https://www.youtube.com /watch?v=iorZdz4dsBU

https://www.youtube.com/ watch?v=xHgPtFUbAeU

2. 1,035 m2 / 42 m =

3. 12.01 mL + 35.2 Ml + 6 mL =

4. 55.46 g – 28.9 g =

5. 0.021 cm x 3.2 cm x 100.1 cm =

6. 0.15 cm + 1.15 cm + 2.051 cm =

7. 150 L3 / 4 L =

8. 505 Kg – 450.25 Kg = _

9. 1.252 mm x 0.115 mm x 0.012 mm =

10. 1.278 x 103 m2 / 1.4267 m =

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1. 1.5 x 103 = 6. 3.35 x 10-1 =

2. 1.5 x 10-3 =

7.

1.2 x 10-4 =

3. 3.785 x 10-2 =

8.

1 x 104 =

4. 3.75 x 102 =

9.

1 x 10-1=

5. 2.2 x 105 =

10.

4 x 100=

Scientific Notation

Scientist very often deal with very small and very large numbers, which can lead to confusion when counting zeros. We have learned to express these numbers as powers.

Scientific notation takes the form of M x 10n where 1 ≤ M < 10 and n represents the number of decimal places to be moved. Positive n indicates the standard form is a large number. Negative n indicates a number between zero and one.

Example: Convert 1,400,000 to scientific notation.

We move the decimal point so that there is only one digit to its left, a total of 6 places.

https://www.youtube. com/watch?v=i6lfVU p5RW8

1.4 x 106

Example: Convert 0.000025 to scientific notation. For this we move the decimal place 5 places to the right. 0.000025 = 2.5 x 10-5

Convert the following to scientific notation:

1. 0.005 =

6. 0.25 =

2. 5,050 = 7. 0.025 =

3. 0.008 = 8. 0.0025 =

4. 1,000 = 9. 500 =

5. 1,000,000 = 10. 5,000 =

Convert the following to standard notation:

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Temperature and its measurement

Temperature (which means the average kinetic energy of the molecule) can be measured using: Celsius and Kelvin. We use the following formulas to convert form one scale to another. Celsius is the scale most desirable for laboratory work. Kelvin represents the absolute scale.

°C = K – 273 K = ° C + 273

Complete the following chart. All measurements are good to 1° C or better.

° C K

1

0° C

2

25 °C

3

450 K

4

210 K

5

-273° C

6

294 K

7

100 °C

8

225 K

9

-40 ° C

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Manipulating Equations: Many problems in chemistry require the use of formulas for their solution. Formulas are simply equations that express a relationship between more than one variable or letter. Examples E = mc2 Einstein’s Equation PV=nRT The Ideal Gas Law 1/l = R(1/nf

2-1/ni2) The Rydberg Equation

It is vitally important that you can manipulate equations to solve for specific variables in a formula so here are some basic formulae that you need to solve for the variable indicated.

1. V = Bh for h

2. P =RB for B

3. C =2r for r

4. E= mc2 for m

5. V= LWH for H

6. I=PrT for T

7. V=r2h for h

8. S=2rh for r

9. PV = nRT for R

10. E = hc/ for

Organizing Data Graphing is another fundamental skill that you need to master. The ability to generate a graph and interpret data from a graph is at the foundation of all science not just chemistry. Scientists rely on data to describe nature and uncover relationships. The raw data, measurements taken in the lab, are most useful when they are organized in a way that makes the relationships clear. Graphing data enables us to organize data in a meaningful way that easily displays the relationships present. When scientists design an experiment they are usually looking for a cause-and-effect relationship between the independent variable X axis (the variable the scientist controls) and the dependent variable Y Axis (the variable that depends on the independent variable) . Therefore, organizing the data by the independent variable is the easiest way to reveal a relationship. When the data is not organized, the relationships are not apparent.

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Below is a data table obtained from a lab. The student measured 5 different volumes of an unknown substance and then massed the substances.

Determining Density through graphing

Volume (mL) Mass (g)

5 56.5

15 169.5

24 271.2

52 587.6

64 723.2

1. Create a plot of mass versus volume, Volume is the independent variable, Mass is the dependent. Label both the x and y axis and title the graph.

Title:________________________________________________________

2. Calculate the slope of this graph.

3. What is the equation for density and how does it relate to the slope of this graph?

4. Using the data table below identify which substance was involved in this experiment?

Substance Density (g/mL)

Copper 8.92

Lead 11.3

Gold 19.3

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Objective: How does study time effect CJ’s grades?

Background: CJ kept track of her study time for science class. She also recorded her test scores. The data is provided below.

Data: In the first week, she studied daily for 15 minutes and her end of the week test scores were 60%. During the second week, she studied daily for 30 minutes and her end of the week test scores were 70%. During the third week, she studied for 45 minutes and her end of the week test scores were 80%. Finally, during the fourth week, she studied for 60 minutes and her end of the week test scores were 90%.

Your task:

1. On the bottom of this page make a table that represents the data listed above. (Make sure your independent variable is listed in the left column.)

2. Manually graph this data

a. Label the x axis and y axis with the proper label and unit b. Choose a logical scale for each axis c. Number the divisions consecutively on your graph d. Title your graph

Title:________________________________________________________

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History of Atomic Theory Part 1: https://www.youtube.com/watch?v=5Ni9RK7Jex4 Part2: https://www.youtube.com/watch?v=1ik6lKegkjY Directions: Fill in the blanks on the answer form (after the story) with the words below atoms conservation of matter cathode ray tube Plum Pudding Democritus atomic sub atomic particle Aristotle (3) Electrons protons neutrons Gold Foil Dalton Solar System JJ Thomson Albert Einstein Alpha multiple proportions definite proportions nucleus energy levels Ernest Rutherford Brownian Motion Lavoisier empty negative

The Story of the Atom More than 2,400 years ago, the Greek philosopher __(1)__ proposed the existence of very small, indivisible

particles, each of which was called __(2)__. Unfortunately the prominent philosopher __(3)__ argued that

these particles did not exist and the idea was largely forgotten for nearly 2000 years. The first evidence that

these particles existed was found in 1778 when the French scientist __(4)__ found that the mass of the

products of a reaction always equaled the mass of the reactants or starting material in a chemical reaction. He

proposed that matter was not created nor destroyed in a reaction but simply rearranged. This statement

became known as the law of __(5)__, Shortly after the first __(6)__ theory was developed by __(7)__ who

compiled all the evidence for the existence of these particles. Two new laws were revealed in this Atomic

theory. The law of __(8)__ states that the ratio of elements in any given compound is always the same. Thus

every water molecule has 2 hydrogen atoms and 1 oxygen atom. The law of __(9)__ states that elements can

combine in different ratios to form different compounds. An example of this law is found in the existence of

both carbon monoxide, CO and carbon dioxide, CO2. The atomic theory stated that these particles were

indestructible and that different elements consisted of different particles that differ in size and shape.

Despite all of the evidence for the existence of these particles their existence was still up for debate. Still

evidence continued to mount in their favor. In 1898 __(10)__ discovered the first __(11)__ when he

performed his historic __(12)__ experiment pictured below.

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In this experiment he sent an electrical charge through a Crookes Tube and found that the beam of light that

appeared deflected toward the positive plate thus indicating that beam of light was made up of __(13)__

charged particles. He called the particles __(14)__ and through careful calculations was able to determine that

their mass was 1/1000th the mass of Hydrogen atom. In order to account for the negatively charged particles

he proposed the __(15)__ model of the atom in which electrons were embedded in the positively charged

cloud that was the atom.

Still there was debate over the existence of atoms. Then in 1905 a German scientist named __(16)__

proved the existence of the atom with his __(17)__ experiment. In the mid 1800’s Dr. Robert Brown had

discovered that pollen grains when dropped in water were jostled about almost as if they were dancing.

Einstein realized in 1906 that the movement of the pollen grains was caused by atoms hitting the grains.

By carefully measuring the movement of the pollen grains Einstein was able to calculate the size of an

atom which it turns out is extremely small. The width of a single human hair is 1,000,000 atoms thick. The

atom is so small that there are more atoms in a single glass of water than there are glasses of water in all

the world’s oceans combined.

Then in 1909 __(18)__ performed his famous __(19)__ experiment shown below.

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In this experiment Rutherford fired __(20)__ particles which are two proton, two neutron helium nuclei at

a very thin sheet of gold foil. He expected to see the particles rip right through the foil like shooting a gun

at a sheet of tissue paper. What he found astonished him. Roughly two percent of the particles were

deflected in some way and 1 in 8000 actually bounced off the foil and came back at him. He concluded

that at the center of the atom was a dense positively charged __(21)__ that deflected the positively

charged alpha particles. The rest of the particles passed straight through the atom because the rest of the

atom is mostly __(22)__ space. This lead Rutherford to propose his __(23)__ model of the atom in which

the electrons orbit the nucleus like planets orbiting the sun.

Of course the atom we know today is a lot different than Rutherford’s atom. Our atom has a nucleus with

both positively charged __(24)__ and neutral __(25)__ as well as electrons existing in __(26)__ instead of

orbits. Still the Rutherford model serves as nice approximation of an atom and represented the first time

that we realized that the atom had a nucleus, was mostly empty space and had electrons on the outside

of the atom.

ANSWERS

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. ____________________

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ATOMS AND ISOTOPES The atomic number tells you the number of protons an element has. Notice how no two elements have the same atomic number. As a result, you can identify an element’s identity based upon the number of protons it contains. If an element is neutral, meaning it has no charge, then the atomic number can tell you the number of electrons as well if the atom is neutral (no charge). The atomic mass is the weighted average of the mass numbers of all isotopes (isotopes have the same number of protons, but a different number of neutrons) of an element found in nature. The unit for atomic mass is amu (Model 1). This number is the decimal number seen on the periodic table. 1. The 3 particles of the atoms are: Their respective charges are: a. _________________________ a. ________________________ b. _________________________ b. ________________________ https://www.youtube.com/ watch?v=8C8BN-5HChM c. _________________________ c. ________________________ 2. Complete the diagrams below, by filling in the appropriate number of protons and neutrons for the following

isotopes.

___P

___N

___P

___N

___P

___N

Magnesium -24 Carbon - 14 Neon - 10

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Isotope Notation

https://www.youtube.com/watch?v=BYiu0kIWd30 Mass number is not represented on the periodic table. However, it tells us the number of protons plus neutrons for a particular isotope of an element. Ions are atoms that have lost or gained electrons. If an atom loses an electron, it forms an ion with a positive charge (cation). For example, when sodium loses an electron it becomes Na+1. When an atom gains electrons, it becomes an ion with a negative charge (anion). For example, when oxygen gains 2 electrons it become https://www.youtube.com/ watch?v=WWc3k2723IM

1. What does A stand for and how do you calculate A? Give an algebraic formula.

2. What does Z stand for? Which subatomic particle does Z represent?

3. When can the atomic number tell you the number of electrons?

4. If an atom gains 2 electrons, what charge will it form?

5. If an atom loses 2 electrons, what charge will it form

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Directions: Locate each element on the periodic table and write down the atomic number and atomic mass. Use that information to determine the number of protons, electrons, and neutrons in an atom of that element.

Element Name

Nuclear symbol

Atomic # Mass # # of protons

# of electrons

# of neutrons

Charge

Calcium

41 20Ca2+

20

41

20

18

21

2+

54 Fe

26

28

Sulfur

34

2-

54

130

54

58

27

2+