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

1. WHAT ARE PHYSICS AND CHEMISTRY?

Science is the knowledge of things through watching and reasoning. Experimental science is the one which is based on the experience. Physics and Chemistry, and Biology and Geology too, are experimental sciences.

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

Physics study physical changes and Chemistry, chemical changes. Quite clear, isn´t it? Let´s see what is a physical or chemical change.

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 that they may be 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 can

2. Melting ice

3. Throwing a ball

4. Boiling water

5. Mixing sugar and sand

6. Dissolving sugar and water

7. 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

2. Combustion of wood

3. Metabolism of food in the body

4. Cooking an egg

5. Digesting sugar with amylase in saliva

6. Mixing baking soda with vinegar to produce carbon dioxide

7. Baking a cake

8. Using a battery…

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

1. The falling of an apple

2. The echo

3. Evaporating water

4. Oxidation of a nail

5. Mixing bleach and ammonia

6. Mixing salt and water

7. The 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 a logical way to solve a problem. It is a process that is used to find answers about the world around us. The scientific method is used by researchers to prove or disprove a theory. Now we are going to see the steps of the scientific method.

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

Scientific Method

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. Observation

When 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. Research

We 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 statement

A hypothesis statement is a statement that expresses what we expect will be the answer to our problem. 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 statement

A 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 do 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 made. This is the variable we are trying to find out about. We do not know the value of that variable before we start the experiment.

· A constant variable is the one that does not change during the experiment. It stays the same.

5. Experimentation

An 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.

http://youtu.be/x2606GQmDqY This is the video´s URL we are going to see now…In case you desire to see it again.

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:

(What is the dependent variable in each experiment?What´s the independent variable in each experiment?What are the controlled variables in each experiment?)

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.

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…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.

ii) Repeat the steps i to v above.

By now, you should have data that will let 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 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.

ii) Repeat the steps I to v above.

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 the experiment? How did you solve them? Tell the class your results.

(General layout for an experimental desing diagramTitle: 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.VData obtained from the experiment for the D.V.Values for the controlled variables __________________________________________________)

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/x

Example

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 this formula corresponds to a scientific law (Ohm´s law, free fall law…).

· A set of hypothesis 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…)

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 unit. We can measure a physical magnitude using different instruments that are characterized by precision (The number of figures we can produce from our 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 flas

Beaker

Mass: the amount of matter a physical object contains

Balance: Is the apparatus to measure masses.

Analytical scale

Balance

Roman scale

The international system of units

In 1790 the French government appointed a committee of scientist to develop a universal measuring system. It was the international system of units (S.I)., 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 notation

In Physics and Chemistry we may find very long numbers, 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?

(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 108It 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)

Some examples:

Name

Number

How to read it

Meaning

Speed of light in vacuum

c= 3 108 m/s

Three times ten to the power of eight metres per second

It´s the speed of any 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 by 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 which studies of various 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 units

1. Earth radius: 6,37 Mm

2. Volume of a drop of water: 0,05 ml

3. Mass of an ant: 0,5 mg

4. Spain area: 504000 km2

5. Madrid area: 60800 ha

6. Liver cell: 200 μm

7. 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/h

12. 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 notation

1. Earth-Sun distance: 1496000000 m

2. Proton radius: 0,000000000000001 m

3. Electron charge: 0,00000000000000000016 C

4. Universe age: 13700000000 years

5. Earth mass: 5980000000000000000000000 kg

6) Try your own definitions of the following concepts

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

PROJECT.1

Remember how science works. The scientific method is a common way of working in different sciences. Let´s remember it:

· The first thing is to make and observation to come up with the facts.

· This observation provokes some questions in you: who, how, what, which, where, when, why…

· To trying to answer this questions you can do some background research, in order to find the way to do things. You can it on the internet or the library…

· Now you are on the way of constructing a hypothesis like: if I do …..then, ……….will happen.*

While constructing your hypothesis, you must try to guess relationships between variables.

Remember that variables can be independent (if you can select it and test it) or dependents (they are affected by the independent variable and you have to measure and control them in order to do a fair test).

· You have to test your hypothesis with an experiment that results in an amount of data.

· You can make a tables and graphic representations using the data to make clear the results (linear and non linear relationships between variables).

· After analyzing results you can draw a conclusion in the form of a law or even a theory if your hypothesis is true. If not…you must start again, I am sorry.

Key words: Hypothesis, Experiment, Variables, Data, Observation, Question, Research…

Some useful expressions in this topic: I can observe that…/ I realized…/ I think that…/ If I make….then, …..will happen/ If you change the …..then…../ the more ….the more…./ the more…. The less….

· Experiments in daily life: Lots of people like sugar in their coffee, but have you ever wondered…

· How much sugar will dissolve in a cup of coffee?

· Is it easier to dissolve sugar in cold or hot liquid?

· Is it easier to dissolve sugar in coffee? In water? In oil

· First we need scientific hypothesis. Use the words: amount, depends on, quantity, solvent…

Ex: The amount of sugar dissolved depends on the quantity of solvent.

In groups you are going to do a video about one of the questions above, using the scientific method, explaining what are your variables (the dependent and independent one), the materials you are going to use, how you have done your experiment and the conclusions you have obtained. It will be perfect if you propose another question related to our topic. (The best video will be upload to our web).

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