lapalmafq.weebly.comlapalmafq.weebly.com/.../5/3/37532953/unit1.def4.docx · web viewseven base...

UNIT ONE: INTRODUCTION TO PHYSICS AND CHEMISTRY

Contents:

What are Physics and Chemistry? Scientific method; tables of values, graphs and formulas Magnitudes and units Conversion of units Significant figures Scientific notation Errors Exercises

1. WHAT ARE PHYSICS AND CHEMISTRY?

Science is the knowledge of things through watching and reasoning. Experimental science is based on experiments. Physics, chemistry, biology and geology, are experimental sciences.

Our subject is called Physics and Chemistry but…What do physics and Chemistry mean?

Physics is the study of physical changes and Chemistry, the study of chemical changes. Quite clear, isn´t it? Let´s see what the differences are between physical and chemical changes .

Physical changes involve states of matter and energy. No new substance is created during a physical change, although the matter takes a different form. The size, shape, and color of matter may change. Also, physical changes occur when substances are mixed, but don't chemically react. One way to identify a physical change is to see if it is reversible, especially phase changes. For example, if you freeze an ice cube, you can melt it into water again. This is a list of some examples of physical changes.

1. Crushing a can2. Melting ice3. Throwing a ball4. Boiling water5. Mixing sugar and sand6. Dissolving sugar and water7. Shredding a paper…

Chemical changes involve chemical reactions and the creation of new products. Typically, a chemical change is irreversible. This is a list of some examples of chemical changes.

1. Rusting of iron

IES La Palma Página 1

2. Combustion of wood3. Metabolism of food in the body4. Cooking an egg5. Digesting sugar with amylase in saliva6. Mixing baking soda with vinegar to produce carbon dioxide7. Baking a cake8. Using a battery…

Exercise: a) Classify the following phenomena in physical or chemical

1. The falling of an apple2. An echo3. Evaporating water4. Oxidation of a nail5. Mixing bleach and ammonia6. Mixing salt and water7. A rainbow

b) Try to give at least five examples of physical and other five of chemical changes.

2. THE SCIENTIFIC METHOD

The scientific method is normally described as the way scientists follow examining the physical world around them. In fact, no one uses just one scientific method every time, but the one we will learn describes most of the critical steps scientists go through sooner or later. The scientific method is a circular process that goes from observations to hypotheses to experiments and back to observations. These steps may lead in some cases to the creation of laws and theories.

To begin the scientific method, scientists make observations and note facts regarding something in the physical universe. These observations may raise a question or problem that the researcher wants to solve. He or she comes up with a hypothesis, a tentative explanation that´s consistent with the observations (in other words, an educated guess). The researcher then designs an experiment to test the hypothesis. With the experiment, the researcher collects data that well analyzed, conduct the researcher to verify the initial hypothesis or to change it. If the last takes place, the loop starts again.

Good experiments, may lead the researcher to propose a law or theory. A law is a generalization of the conclusion of the experiment, and sometimes it implies to get a formula. Scientific laws sometimes have to be modified based on new facts. A theory or model attempts to explain why something happens. The power of a theory is prediction of new facts that may be tested with more experiments that can lead to refine or modify the theory or model. Again, as mankind develops more advanced instrumentation and ways of examining nature, scientist may find necessary to modify our theories or models.

Now we are going to listen to a song: http://youtu.be/wlb7tLJy5AI

Scientific Method


http://youtu.be/wlb7tLJy5AI

Scientific Method (x 7)

First you make an observation of the world around

Take notes and record all the things that you found

Then you ask a simple question, something that you want to learn

Then you form a hypothesis to explain what you observed

Then you make a prediction about how it´s gonna go

Do a test with a control and a variable

Then you analyze the data and draw a conclusion

Do the scientific Method to avoid all confusion.

(Make an observation, ask a question, form a hypothesis and make a prediction, do a test or experimentation, analyze data and draw a conclusion) (x4)

Scientific Method (x 7)


1. ObservationWhen we make observations we use our senses to gather information about the world around us. A good scientist notices what is happening and became curious about what´s happening.

Qualitative observations are observations about quality and are usually made with our senses: color, shape, taste, sound, feel…

Quantitative observations are observations about quantity (how many). There will always be a number based on any kind of measurement, followed by a unit.

2. ResearchWe do not want to rely on prior knowledge alone when doing a experiment. Research is also important.

Find information about your topic Learn about theories related to your topic A theory is an explanation based on many observations

during repeated experiments that has consistent results, makes predictions that can be tested, and is the simplest explanation.

Theories can never be completely proven, only disproven. When new evidence comes along, we must change our theory or get rid of it and start over.

3. Make a hypothesis statementA hypothesis statement is a statement that expresses what we expect will be the answer to our question. This is what you think the results of the experiments will show.

A hypothesis is an educated guess It is a prediction Use an if…then format in a hypothesis statement. For example: I predict

that if I drop a ball from a higher height, then it will bounce higher.

4. Make a problem statementA problem statement is a question that compares variables. Careful observations lead to these questions. This is when scientist raise questions based on what they have observed.

When writing the problem statement think about you want to know or explain. Use observations you have made to create questions about the problem or topic you want to investigate.


A variable is something that changes. An independent variable is what we change or manipulate on purpose. We

know the value of the variable before we start the experiment. A dependent variable is what changes depending on some other factor. It

depends on the change you make. This is the variable we are trying to find. We do not know the value of that variable before we start the experiment.

A constant variable does not change during the experiment. It stays the same.

5. ExperimentationAn experiment is a planned way to test your hypothesis and find out the answer to the problem statement. To conduct an experiment a scientist develops and follows a procedure (steps to the experiment). The procedure also includes a detailed list of the materials needed.

When conducting an experiment, change one factor and keep everything else the same.

Remember that the factor you change is the independent variable (you can give it the value you want) and the factor you keep the same is a control.

An experiment is a way to collect data and help to determine the value of a dependent variable.

An experiment compares the independent variable to the dependent variable.

An experiment can only test one dependent variable at a time.

6.Collect data and analyze results

Data is the information you get when you test the variable. Confirm the results by retesting. Modify the procedure if needed. Did you get the same results each time you

retested? If not, why? Is there any change you can make that would make your results more consistent?

Include tables, graphs, and photographs that show your data.

7. Conclusion A conclusion statement is a statement that presents the

findings of an experiment, what the data shows, and states if the hypothesis was correct (supported) or incorrect (negated).

Conclusion statements also make recommendations for further study and possible improvements to the procedure.


This is the video´s URL we are going to see now…In case you desire to see it again. http://youtu.be/nzfDvfoBv_g

THE PENDULUM EXPERIMENT (a swing experiment)A pendulum is any mass which swings back and forth on a rope, string or chain. Pendulums can be found in old clocks and other machinery. A playground swing is a pendulum too. The length of time it takes the mass to swing once all its way over and back to the same place, is called the period of the pendulum.

Three questions:

Does the amount of mass at the end of the pendulum affect the period?

Does the angle at which you start the swing affect the period?

Does the length of the string affect the period?

We will develop three experiments in order to answer the three questions, changing the mass, changing the angle and changing the length of the rope.

First of all, we have to discuss:

Materials: A piece of string at least one metre long. 3 or 4 weights, all the same. A support for the pendulum. A watch that counts seconds (a timer). Pencil and paper to record the results.

Work in groups.

Experiment 1: Changing the mass

In this experiment, the angle and the length of the string stay the same (controlled variables).Change the amount of mass at the end of the pendulum and measure the period.

Procedure:

1. Decide what angle you will use to set the pendulum swinging. Mark it on the table (with a pencil) behind the release point in order to use the same angle each time.


What is the dependent variable in each experiment?

What´s the independent variable in each experiment?

What are the controlled variables in each experiment?

http://youtu.be/nzfDvfoBv_g

2. Set up the pendulum with a fixed length of string, and tie one weight to the end. Leave extra string bellow the tie point so that you can attach more weights later without changing the length of the string above the weights.

Trial 1:

i) Draw the weight back to the release point and allow it to swing for ten full periods (over and back 10 times).

ii) Time how long it takes to do this.iii) Then divide your answer by ten to get the time for one full period.iv) Repeat twice. Don´t forget to divide by ten each time because we want

the time for one period.v) Now average your three results.

Trial 2:

i) Add a weight, so that two are tied to the string. Don´t change the length of the string above the weights.

ii) Repeat the steps i to v above.

Trial 3:

i) Add another weight, so that three are tied to the string. Don´t change the length of the string above the weights.


By now, you should have data that will lead you to a conclusion.

When you change the mass at the end of the pendulum the period…………………………………………

Experiment 2: Changing the angle.

In this experiment you are going to keep the mass and the string length the same. You will change the angle of the swinging and you´ll measure the period.

Procedure: Set up a length of the string with a weight on the end.

Trial 1:

i) Draw the weight back to a sharp angle (eg: 90º) and allow it to swing for ten full periods (over and back ten times).

ii) Time how long it takes to do this.iii) Divide your answer by ten to get the time for one period.iv) Repeat twice. Don´t forget to divide by ten each time. We want the time

for one period.v) Now average your three results.

Trial 2:

i) Reduce the angle (45º) and allow the weight to swing for ten full periods (over and back ten times).

ii) Repeat the steps I to v above.

Trial 3:

i) Reduce the angle again (20º) and allow the weight to swing for ten full periods.

ii) Repeat the steps I to v above.


By now you should have data that will lead you to a conclusion.

When you change the angle of release of a pendulum, the period…………………………..

Experiment 3: Changing the length

In this experiment you are going to keep the mass and the angle the same. You will change the length of the pendulum and you will measure the period.

Procedure:

1. Decide what angle you are going to use to set the pendulum swinging. Mark it with pencil over the table in order to use the same angle each time.

2. Tie one weight on the end of your piece of string.

Trial 1:

i) Draw the weight back to the marked angle and allow it to swing for ten full periods (back and forth ten times).

ii) Time how long it takes to do this.iii) Divide your answer by ten to get the time for one period.iv) Repeat twice. Don´t forget to divide by ten each time…we want the time

for one period.v) Now average your three results.

Trial 2:

i) Retie the string at the top so it is about a third shorter.ii) Repeat the steps i to v above.

Trial 3:

i) Retie the string at the top so it is half as long as it was in the previous trial.


By now you will have data that will lead you to a conclusion:

When you change the length of the string of the pendulum, the period………………. The shorter the string, the………………………. The period.

Report back your results to the rest of the class. Did you have any problems with your experiments? How did you solve them? Tell the class your results.


General layout for an experimental design diagram

Title:

The effect of______________________________________(Independent variable) (I.V) on_______________________________________________(dependent variable) (D.V.)

Hypothesis:

If_______________________________________________(planning change in the I.V.) then___________________________________________(predicted change in the D.V).

Data from the experiment:

Values for the I.V Data obtained from the experiment for the D.V.

Table of values, graphs and formulas:

You will obtain a set of values directly from your measurements. To analyze them more easily you must organize them in a table of values as the table above.

You can try to represent the values in a graph. There are a lot of different representations, but we are going to study only three ways of graphical representations:

Name Straight line Parabola Hiperbola

Graph

Equation Y=ax+b Y=ax2 Y=a/xExample Y=3+2x Y=5x2 Y=3/x

If you get a straight line, passing for the point (0,0), your variables are proportionals. You can say: y is proportional to x.If you get a hiperbola the two variables are unproportionals. Y is unproportional to x.

To present the conclusions, you must try to get a formula. In this case the formula corresponds to a scientific law (Ohm´s law, free fall law…).

A set of hypotheses and laws forms a theory (theory of relativity, theory of general gravitation…)

3. DOING MEASUREMENTS; MAGNITUDES AND UNITS

A magnitude is anything you can measure. Examples (length, time, temperature…, etc).Measurement is the process of determining the quantity of a physical magnitude by comparing it with a certain quantity (this quantity is chosen by consensus) called a unit. We can measure a physical magnitude using different instruments that are characterized by precision (the number of figures we can produce from our


General layout for an experimental design diagram

Title:

The effect of______________________________________(Independent variable) (I.V) on_______________________________________________(dependent variable) (D.V.)

Hypothesis:

If_______________________________________________(planning change in the I.V.) then___________________________________________(predicted change in the D.V).

Data from the experiment:

Values for the I.V Data obtained from the experiment for the D.V.

measurement) and accuracy (ability of a measurement apparatus to give responses close to a true value).

We must express a magnitude with a number (quantity) + unit.The magnitude and its unit must not be confused

Apparatus for measuring different physical magnitudes

Volume: how much space a body occupies, or capacity: the maximum amount that can be contained in this body.

Pipettes Burette Graduated cylinders Volumetric flasks

Erlenmeyer flask BeakerMass: the amount of matter a physical object containsBalance: the apparatus which measures masses.

Analytical scale BalanceRoman scale

The international system of units


In 1790 the French government appointed a committee of scientists to develop a universal measuring system. It was the international system of units (S.I).,it consists of a set of units together with a set of prefixes. The units of the S.I. can be divided in two subsets:Seven base units: Each of these seven units represents different kinds of physical quantities.

Derived units: From these seven units, many more derived units are derived.

The S.I. units must not be suitable to measure great magnitudes or very tiny magnitudes. In these cases, the set of accepted prefixes for the units are:


In addition to this S.I. units, there is a set of non S.I. units accepted. These non S.I. units are more suitable to use in determined measurements such as astronomical unit, mile, yard, pound, litre…

Scientific notationIn physics and chemistry we may find very long numbers, such as the velocity of light which is 299792458 meters per second and very small numbers as the proton’s mass, which is 0,00000000000000000000000000167 kg.To write that type of numbers we use the scientific notation, which uses powers of ten to rewrite the numbers in a shorter way.

How to write numbers in scientific notation?

Some examples:

Name Number How to read it MeaningSpeed of light c= 3 108 m/s three times ten to the power It´s the speed of any


You should leave only one number,( it cannot be a zero), before the coma.

If the number is bigger than one: Multiply by ten powered to the number of places you move the coma.Ex: 299292458=2,99 108

It is not correct to write 29,9 107

Remember: only one number before the coma. If the number is smaller than one: Multiply by ten

powered to minus the number of places you have moved the coma.Ex: 0,000 000 000 3457=3,45 10-10

in vacuum of eight metres per second electromagnetic radiation. Nothing can travel faster than c

Avogadro´s number

6,02 1023 six point (o)two times ten to the power of 23

It´s the number of atoms you can find in 12 grams of carbon (a mole)

Mass of the electron

9,1 10-31 Kg nine point one ten to the power of minus 31 kilograms

The electron is the lightest particle in an atom

Mass of the sun 2 1030 kg two times ten to the power of 30

It´s mass is about 330.000 times the Earth´s mass

Exercises

1. Fill in the blanks with the words below

science, disciplines, synonymous, distinguish, modern-day, force, revolution, understanding, time ,weapons, appliances, however, behaves

Physics is a natural …........................... that involves the study of matter and its motion through space and …..........................., as well as all related concepts, including energy and…........................... More broadly, it is the general analysis of nature, conducted in order to understand how the universe …...........................Physics is one of the oldest academic …..........................., perhaps the oldest through its inclusion of astronomy. Over the last two millennia, physics had been considered…........................... with philosophy, chemistry, and certain branches of mathematics and biology, but during the Scientific …........................... in the 16th century, it emerged to become a unique, modern science in its own right. …..........................., in some subject areas as in mathematical physics and quantum chemistry, the boundaries of physics remain difficult to …...........................Physics is both significant and influential, in part because advances in its …........................... have often translated into new technologies, but also because new ideas in physics often resonate with other sciences, mathematics, and philosophy. For example, advances in the understanding of electromagnetism or nuclear physics led directly to the development of new products which have dramatically transformed …........................... society, such as television, computers, domestic…..........................., and nuclear …...........................; advances in thermodynamics led to the development of motorized transport; and advances in mechanics inspired the development of calculus.

2) THE RIGHT OPTION

Chemistry is the science of matter and the changes it undergoes / suffers. The science of matter is also known / addressed as physics, but while physics takes a


more general and fundamental approach / approximation, chemistry is more specialized, being set / concerned with the composition, behavior, structure, and properties of energy / matter, as well as the changes it undergoes during chemistry / chemical reactions. It is a physical science about atoms, molecules, crystals and other aggregated / aggregates of matter whether in isolation or combination, which incorporates the concepts of energy and entropy in relation to the spontaneity of chemical processes.The branches of Chemistry are: analytical chemistry (the study of material samples / matter portions to obtain their compositions), organic chemistry (carbon / silicon based compounds), inorganic chemistry (noncarbon based compounds), biochemistry (the study of substances found in biological animals / organisms), physical chemistry (the study of atoms and chemical systems from a physical point of watching / view) and industrial chemistry (the manufacturing of chemicals in a big scale). Many more specialized disciplines / studies have emerged in recent years, e.g. neurochemistry, the chemical study of the nervous system.

3) PHRASE ORDER

Arrange these sentences:a) tries and Science make predictions explanations. to give…..................................................................................................................b) a rearrange. reaction, atoms chemical In…..................................................................................................................c) and are Einstein's mass related Energy through equation.…..................................................................................................................d) devices. to research leads technological scientific The…..................................................................................................................e) don't and Earth fall on Satellites they high because quickly. the orbit…..................................................................................................................

4) Express these quantities in SI units1. Earth radius: 6,37 Mm 2. Volume of a drop of water: 0,05 ml3. Mass of an ant: 0,5 mg 4. Spain area: 504000 km2

5. Madrid area: 60800 ha 6. Liver cell: 200 μm7. Radius of Hydrogen atom: 5 nm


8. Energy of LHC collisions: 4,5 Tev 9. Internet connection: 180 Gbytes/h (bytes/s)10. Density of aluminium: 2,7 g/cm3

11. Speed of light: 1080 Gm/h12. Formula 1 speed record: 413 km/h 13. Speed limit UK: 70 miles/h 14. Madrid annual rainfall: 420 l/m2 (m)

5) Express these quantities with scientific notation1. Earth-Sun distance: 1496000000 m2. Proton radius: 0,000000000000001 m3. Electron charge: 0,00000000000000000016 C4. Universe age: 13700000000 years5. Earth mass: 5980000000000000000000000 kg

6) Try your own definitions of the following concepts

Magnitude, unit, hypothesis, variable, physical change (give some examples), International System of Units.

Writing Hypotheses: a student lesson

Purpose: to learn when and how to write hypotheses.

Most students believe that they are going to be experimenting anytime they are given a laboratory assignment in science. However, more often than not, students are doing something other than experiments. This is not necessarily bad. A good deal of science is observational and descriptive. For example, the study of bio-


diversity usually involves looking at wide variety of specimens and maybe sketching and recording their unique characteristics. However, there are other times when we science teachers are trying to teach students how scientists work and how we can verify things which others may say or believe is so without any proof.

To learn about what is not known or to verify a notion, the so-called "scientific method" might be carried out and an actual experiment may be conducted. It does not matter that your experiment has been done a thousand times before or that your teacher already knows the results. What matters is that you don't know the results and that you can independently find a verifiable answer. In real experiments, real hypotheses should be written before the actual experiment.

What Is a Real Hypothesis?

A hypothesis is a tentative statement that proposes a possible explanation to some phenomenon or event. A useful hypothesis is a testable statement which may include a prediction. A hypotheses should not be confused with a theory. Theories are general explanations based on a large amount of data. For example, the theory of evolution applies to all living things and is based on wide range of observations. However, there are many things about evolution that are not fully understood such as gaps in the fossil record. Many hypotheses have been proposed and tested.

When Are Hypotheses Used?

The key word is testable. That is, you will perform a test of how two variables might be related. This is when you are doing a real experiment. You are testing variables. Usually, a hypothesis is based on some previous observation such as noticing that in November many trees undergo

Any laboratory procedure you follow without a hypothesis is really not an experiment. It is just an exercise or demonstration of what is already known.

How Are Hypotheses Written?

1. Chocolate may cause pimples.2. Salt in soil may affect plant growth.3. Plant growth may be affected by the color of the light.4. Bacterial growth may be affected by temperature.5. Ultra violet light may cause skin cancer.6. Temperature may cause leaves to change color.

All of these are examples of hypotheses because they use the tentative word "may.". However, their form is not particularly useful. Using the word may does not suggest how you would go about proving it. If these statements had not been written carefully, they may not have even been hypotheses at all. For example, if we say "Trees will change color when it gets cold." we are making a prediction. Or if we write, "Ultraviolet light causes skin cancer." could be a conclusion. One way to prevent making such easy mistakes is to formalize the form of the hypothesis.

Formalized Hypotheses example: If skin cancer is related to ultraviolet light , then people with a high exposure to uv light will have a higher frequency of skin cancer.

If leaf color change is related to temperature , then exposing plants to low temperatures will result in changes in leaf color.


Notice that these statements contain the words , if and then. They are necessary in a formalized hypothesis. But not all if-then statements are hypotheses. For example, "If I play the lottery, then I will get rich." This is a simple prediction. In a formalized hypothesis, a tentative relationship is stated. For example, if the frequency of winning is related to frequency of buying lottery tickets. "Then" is followed by a prediction of what will happen if you increase or decrease the frequency of buying lottery tickets. If you always ask yourself that if one thing is related to another, then you should be able to test it.

Formalized hypotheses contain two variables. One is "independent" and the other is "dependent." The independent variable is the one you, the "scientist" control and the dependent variable is the one that you observe and/or measure the results. In the statements above the dependent variable is blue and the independent variable is red.

The ultimate value of a formalized hypothesis is it forces us to think about what results we should look for in an experiment.

Rewrite the first four hypotheses using the formalized style shown above. Single underline the dependent variable and double underline the independent variable in the If clause of each hypothesis. When you are done, write one more original hypothesis of your own using this form. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________

Try with the following:

If temperature of a cup of water is related to the amount of sugar that can be dissolved.

If the size of the molecules is related to the rate of diffusion as they pass through a membrane.

If the wave length of light is related to the photosynthesis rate.

If temperature is related to the rate of metabolism in animals.

If melting point is related to pressure.

If the amount of hours of light is related to people´s mood.

Exercise: Try to give the relations between variables and get a formula.


lapalmafq.weebly.comlapalmafq.weebly.com/.../5/3/37532953/unit1.def4.docx · web viewseven base...

Documents