Notes Chemistry, Matter, Units, Densit, Temperature

7/31/2019 Notes Chemistry, Matter, Units, Densit, Temperature

http://slidepdf.com/reader/full/notes-chemistry-matter-units-densit-temperature 1/18

Notes: Chemistry, Matter, Scientific Method, Units,

Energy, Temp, Density, Phases

Reading for this set of notes: All of Chapter 1, Appendix I and IISuggested extra problems for text: 1 - 79

Chemistry:What is Chemistry? The study of properties of matter and electron’s actions.Chemistry is called the central science. This is because it links all other areas of science.All actions in the universe are controlled by physics: on a large scale - an auto accident; on a small scale -the formation of a salt when water evaporates from the ocean.Technically, all biological processes are run by physics, the processes are simply following laws of physics.Physics and biology are at far ends of the science spectrum. Chemistry bridges that gap. You can usechemistry to link any of the other sciences. Geology to physics, pharmacy to biology, oceanography toanthropology, mechanical engineering to physiology.

Electrons are the key to chemistry; they are the portions of the atom doing all the reacting. Chemistry dealswith the exterior of the atom, the electrons, not the nucleus. The nucleus is the interior of atoms. Thenucleus, as far as chemistry goes, is unaffected by chemical reactions.

Matter:The definition of matter is, anything that has mass and occupies space. So, there are two parts to matter. Itmust occupy space and it must have mass. Volume is the unit used to measure the amount of space anobject occupies. You can think of the volume unit in terms of how big something is, like a hot air balloonoccupies a lot of space.

The other half of the definition deals with the term mass. Mass is a measure of the amount of matter. This

differs from the size of the matter, the volume. The unit for mass is grams. Mass differs from weight, eventhough we, incorrectly, use them interchangeably.

Matter has mass and. I if it is near a large celestial body, i.e. Earth orf the moon, it will have weight. Matter always has mass, it does not always have weight, i.e. you are in space. A chunk of matter’s weight willchange based on its location, but its mass will not.

For example, a Frisbee with a mass of 175 grams will have 175 grams of mass on the moon and on Earth.But, on Earth it will weigh about 6 ounces, on the moon it will weigh about 1 ounce.

Pure substances and mixtures:

Matter is divided up into two broad categories.Pure substances:

have fixed properties.are composed of a constant composition.cannot be broken apart physically.

Mixtures:are properties vary with composition.have proportions of the components vary throughout mixture.can be physically separated into two or more pure substances.



Elements and Compounds:Pure substances are divided up into two categories.

Elements:are composed of one type of atom.cannot be broken apart chemically.

Compounds:are composed of more than one type of atom chemically bonded, called a molecule.can be broken apart chemically,sometimes this is VERY difficult to do, sometimes not.have the pieces that are either individual atoms or smaller molecules.can not be broken by physical means.you can not hit the molecule and break the bonds or pull them apart or filter them apart.

Heterogeneous and homogeneous mixtures:Mixtures can be separated by physical means like filtration or evaporation.Mixtures are divided up into two categories.Heterogeneous properties are not the same throughout the mixtureHomogeneous properties are the same throughout the mixture

Elements:Element: A pure substance composed of only one type of atomElemental Symbol: A 1 or 2 letter symbol assigned to each type of atom.

Only 11 have non-English origins.

1. Ag-argentum2. Au-aurum3. Cu-cuprum4. Fe-ferrum5. Hg-hydrargyrum6. K-kalium

7. Na-natruim8. Pb-plumbum9. Sb-antimony10. Sn-stannum11. W-wolfram

IUPAC – International Union of Pure and Applied Chemistry, the governing body for chemicalnomenclature. When new elements are made they go by Greek numbers, example, Uun, un un nil, 110, untila name is accepted.

Molecular Formula:

The molecular formula identifies which atoms and how many of these atoms will be found in eachmolecule. The atomic symbols, identify the atoms and a subscript will identifiesy the number of that atom.H2O is the molecular formula for water. Water is composed of hydrogen and oxygen. Each water moleculeis composed of 2 hydrogen atoms and 1 oxygen atom. SThe since there is only 1 oxygen atom, a 1 will not be written;, it is assumed that there is at least one oxygen, otherwise the O would not have been included inthe formula.

Sulfuric acid has a molecular formula of H2SO4. Each molecule is composed of 2 hydrogen atoms, 1 sulfur atom and 4 oxygen atoms. Again, since there is only 1 sulfur, the a number 1 is not needed as it is assumed.



oxygen carbon dioxide paper Kool-Aid™

Matter

Pure Substance Mixture

Element Compound Heterogeneous Homogeneous



silver baking soda sand bleach

Chemical and Physical Changes:All matter may undergo changes, either physical or chemical.

Physical changes to matter do not change the matter’s composition.Chemical changes to matter do change the matter’s composition.

Examples:o If you dump rubbing alcohol, isopropyl alcohol, on your bathroom counter what happens?

• It will disappear or evaporate; it will change from a liquid to a gas.

• Is this a physical or chemical change?

• Physical, even though it is now a gas, it is still isopropyl alcohol; it is still C3H8O.o What about burning the isopropyl alcohol?

• Chemical, as new substances are formed from the alcohol, which is no longer

present, you now have water and carbon dioxide, the gas you exhale.The Big 3: Indicators of a Chemical Change.

1. Color cChange2. Presence of a gas – bBubbles3. Formation of a pPrecipiate (ppt) – a solid appears in a liquid



The Scientific Method:The method basically lays out an organized plan to solve a problem.

This method is employed by more than simply scientists. It can be applied to most any situation.

Step 1:State the Problem

You cannot solve a problem until you know exactly what it is.

Problem - A pitcher needs to get a batter out.Step 2:Research andBackground

What will it take to solve my problem?Research prior to game for all batters on other team, watching team play live or on video.

What do I need to know, about my problem?I need to know what pitches each batter has trouble with.

What do I know, about my problem, examine the possibilities?Eliminate poor choicesConsider likely choices

Step 3:Form a Hypothesis

A possible solution to my problem. (The simplest solution is often the bestsolution!)Batter hits the fastball well; throw curveballs, sliders and change-ups. .Batter hits the away pitches.

Step 4:Test the Hypothesis

Perform an experiment to see if your hypothesis works.Throw offspeed pitches on the inside of the plate.

Step 5:Draw Conclusions fromDataReform Hypothesis

Data are the results of an experiment.In its simplest form, there are only two possible conclusions:Conclusion 1: If your hypothesis was correct, the batter is out.

PROBLEM SOLVED!

Conclusion 2: If your hypothesis was incorrect, the experiment failed.DON'T GIVE UP!

DO MORE RESEARCH!- What was wrong with your original hypothesis?- Did you make a poor selection?- Was your experiment flawed?- Form another hypothesis based on additional research.- Test the new hypothesis.



Units:

• All measurements have 2 parts, a number and a unit. Measurements are useless without both pieces.

• A unit is a standard of measurement:

• I in the past units were based on political leaders body parts.

• uUnits must be agreed upon by the users.

• M metric system/ SI system, “Systeme International d’Unites” 1960.• Why are we not using the SI system? $$$$$$

parameter SI English

Length meter foot

Volume liters gallons

Mass grams slugs/stones

Energy Joule or Cal BTU

Time sec sec

Pressure Pascal psi

Force Newton Pound

List other units of length: m, cm, mm, km, Mm, µm, pm, ft, in, mile

Which is easier to relate? SI uses factors of 10

G giga 109 billion100000000

0 1

1000000000

M mega 106 million 10000001

1000000

k kilo 103 thousand 10001

1000

c centi 10-2 hundredth .01100

1

m mill 10-3 thousandth

.0011000

1

µ micro 10-6 millionth .0000011000000

1

n nano 10-9 billionth .0000000011000000000

1



Base Unit vs. Derived Unit:There are two classes of Units: Base and Derived

• For the first class, the International System chose seven well-defined units which, by convention, areregarded as dimensionally independent: the meter, the kilogram, the second, the ampere, the Kelvin, themole and the candela. These SI units are called base units.

• The second class of SI units is that of derived units. These are units that are formed as products of the base units according to algebraic relations linking the quantities concerned. The names and symbolsof some units thus formed in terms of base units may be replaced by special names and symbols whichcan themselves be used to form expressions and symbols for other derived units.

1. The meter is the length of the path traveled by light in a vacuum during a time interval of 1/299792458 of a second.2. The kilogram is the unit of mass; it is equal to the mass of the international prototype of thekilogram.3. The second is the duration of 9,192,631,770 disintegrations for a Ce-133 atom.4. The ampere is that thea constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2 x 10-7 Newton per meter of length.5. The Kelvin, unit of thermodynamic temperature, is the fraction 1/ 273.16 of the thermodynamictemperature of the triple point of water.6. The mole is the amount of substance of a system, which contains as many elementary entities asthere are atoms in 0.012 kilogram of carbon 12; its symbol is “mol”.

• When the mole is used, the elementary entities must be specified and may be atoms, molecules,ions, electrons, other particles, or specified groups of such particles.

7. The candela is the luminous intensity, in a given direction, of a source that emits monochromaticradiation of frequency 540.1012 hertz and that has a radiant intensity in that direction of 1/ 683 watt per steradian.

1 milliliter = 1 centimeter cubed1mL = 1cc = 1cm3





Exponents:k means 1000 or 103 so 1 km means 1000 meter.m means 1/1000 or 10-3 so 1 mm means one thousandth of a meter.Eexponents mean how many times you multiple that number to itself.Iif there is a negative sign, it is the same thing but it is in the denominator of a fraction.Example:

23 = 2 ⋅ 2 ⋅ 2

222

12 3

⋅⋅=−

Scientific Notation:• U used to condense very large or very small numbers

• F format is:o one number

o a decimal

o reminder of numbers

o timeso 10 to some exponent.

o Example:

1.25 x 105 = 125000

5.82 x 103 = 5820

8.34 x 10-4 =.000834

6.02 x 1023 = 602000000000000000000000

• T to type the following number into your calculator press these buttons: 1.25 x 105

Example:

⋅ 1

⋅ .⋅ 2

⋅ 5

⋅ E or EE or Exp (whichever button your calculator has!)

⋅ 5

Significant Figures:Rule 1: non-zero numbers are always significant.Rule 2: Any zeros between two numbers are significant.Rule 3: Trailing zeros have two rules:

A – if the trailing zero in the value is to the right of the decimal, the zero is significant.

B – if the trailing zero in the value is to the left of the decimal, the zero is only significant if it isfollowed by a decimal point.

How many significant figures are in the following values?

a) 547 3 b) 6084 4 c) 23.590 5 d) 670 2



e) 93780. 5

When you add or subtract numbers, the number whos significant figure falls farthest to the left controls thesignificant figures for your answer.

56.78

1239.034

451.1

+ 56.0144

1802.9284

You may only report 1802.9

For multipication or division answers, you may only report the number of significant figures equal to thefewest number of significant figures from any one of the values in the calculation.

So, your answer may be reported as 5400 or 5.4 x 101 Either is correct, but the scientific notation answer would be considered formated more correctly.



Unit Conversion Methods: Railroad or Dimensional Analysis or Factor Label:This is the most effective means of handling mathematical calculations when the variables have unitsconverting units.

Example 1: miles →kilometers

9.8 mi 5280 ft 12 in 2.54 cm 1 m 1 km

1 mi 1 ft 1 in 100 cm 1000 m

9.8 x 5280 x 12 x 2.54 x 1 x 1 = 15.77 km

1 x 1 x 1 x 100 x 1000

Example 2: miles per hour →feet per second

22 mi 5280 ft 1 hr 1 min

hr 1 mi 60 min 60 sec

22 x 5280 x 1 x 1 = 32.3 ft

1 x 60 x 60 sec

Characteristics of PhasesDensity Shape Thermal Expansion Compressible

Solid High fixed Very Little Very LittleLiquid Medium takes shape of the container Very Little Very Little

Gas VERY Low takes shape of the container Lots Very Easily

=

=



Density:• Density is a measure of the ratio of a matter’s mass to its volume. How many grams fit into a cm3 or mL.

• The concept is easy if you think about 2 objects;, 19 grams of gold would fit in a cube with sides1cm x 1cm x 1cm

• If you were to measure the volume of a helium balloon that had a mass of 19 grams, it would fillapproximately 106 cubes with sides 1cm x 1cm x 1cm.

• The equation for density is d = m/vo d = density

o m = mass

o v = volume

• What are the units for mass and volume?

• So what must the units for density be? grams/liter or grams/ml or grams/cm3

• Gold has a density of 19.3 g/ml. Write this out:

o Nineteen point three grams per milliliter.o Per refers to the division sign.

o So, for gold you are able to put 19.3 grams of gold in a cube that is 1cm x 1cm x 1cm (as

shown above).

• The symbol most scientists use for density is not a ‘d’ but it is the Greek letter ‘roe’ (, ‘ρ).’ Iit iskind of a lower case p looking character.

• Matter with lower densities floats on matter with higher densities. Air floats on water and land, oilfloats on water, water floats on land, wood floats on water.

• Ships float on water, even though the density of steel is much greater than water, 7.7g/ml versus1g/ml, because the ship takes up a lot of space. And most of that space is filled with air. If you take themass of the steel, air, people and everything else on the ship and divide that by how much space it takesup you will get a number smaller than 1 g/ml. Water has a density of 1 g/ml; therefore, the ship floats.

Example1:

What is the density of a piece of wood with a mass of 2200 grams and a volume of 2400 cm3?

33917.

2400

2200

cm

g

cm

g d

v

md

==

=

Will this piece of wood float in water? Yes, its density is less than 1g/cm3



Example 2: Calculating mass given density and volumeThe equation to calculate density is D=m/v, but if you know the units of each variable you don’t need toknow the equation.

The reasoning:, you know the units for mass are grams or kilograms, so your answer must be in units of grams.

Set up the railroad to eliminate all units except the mass unit and make sure the mass unit is in thenumerator.D = 7.2 g/cm3

v = 35 cm3

7.2 x 35 = 252 g

Specific Gravity:This for of measurement is another way to, for all practical purposes, another way to measure density. Thismethod is a relativistic method, meaning you relate the density of your sample to the density of water.

This method is used a lot in the medical, wine and brewing fields. In the medical field, blood and urinesamples are frequently measured in terms of their specific gravity. The alcoholic beverage industries usesspecific gravity to determine the amount of alcohol in the beer or wine.

Specific gravity is easy to calculate. You divide the density of your sample by the density of water. Well thedensity of water is 1 g/cm3 so the calculation is kind of silly. You simple remove the units.

For example:If density of normal urine is 1.03 g/cm3 and the density of water is 1 g/cm3

03.1/00.1

/03.13

3

=cm g

cm g

So, what did we do here? We removed the unit.

Energy:

7.2 g 35 cm3

cm3

=



We will talk about two definitions for energy, potential and kinetic.

What is KE? A definition is the energy of motion of a substance. This is energy being used right now.The equation would be:

2mv

2

1KE =

Where m is the substance’s mass and v is the substance’s velocity.So, KE depends on two things, how big the object is and how fast it is going. This is common sense. Adump truck traveling at 50mph has more energy than a VW bug going 50mph and a BMW moving at 110mph has a lot more energy than a BMW moving at 55 mph, see the story in USAToday’s sports sectiondated 1/15/03 about a Dallas Cowboy’s cornerback.

So, if KE is the energy of use, potential energy, PE, is stored energy. This energy has the potential to dosomething, but right now it is being stored.

Look back at that dump truck. Let’s say it is parked on a hill. It has more potential energy sitting up therethan if it was parked at the bottom of the hill. On the hill it has the potential to turn that PE into KE andcome racing down the hill through someone’s home.

PE is not only found in position, chemicals have stored energy. The gasoline in the tank of the BMW that isdriving 110 mph is not involved in making the car move;, it has the potential to, and when it is pumpedfrom the tank to the engine, its potential energy will be converted to kinetic energy. The octane in thegasoline will be converted into carbon dioxide, carbon monoxide, water and energy.

You will see the following units used to describe energy, calories and joules. A Ccalories is the Englishunit, with joules being the SI unit. The abbreviations are cal and J. A calorie is defined as that amount of energy needed to raise the temperature of one gram of water one degree Celsius. So, this is not muchenergy. A calorie is equal to 4.184 J, so a joule is even less energy.

There is a law that applies to this topic, the Law of the Conservation of Energy. This law states thatenergy is neither created nor destroyed; it only changes forms. So, PE is converted to KE and vicse versae, but the energy is never really lost. This law took some heat in from Einstein’s theory of relativity which issurmised by the equation E = mc2. E is energy, m is mass and c is the speed of light. Well from thisequation energy can be lost, it could be converted into mass. So, is the law untrue? No, Einstein said thatthe law still applies as written because the scientific community holds that matter is just a form of energy, soas written we have only changed its form since it can be converted back from matter to energy.



Temperature:Temperature is defined as a measure of the average kinetic energy of a substance. The symbol for average

kinetic energy is, KE .

So, if we make an object move faster its temperature goes up. This is also kind of common sense., Tthewater molecules in ice are moving slower than the water molecules in liquid water or much slower than insteam.

Another example is a cold basketball. If you have ever pulled your ball out of the trunk of your car inDecember and went to bounce it, you know it does not bounce back up to you. But if you keep trying, after many bounces, the ball is behavesing normally. Why?, Yyou slammed the air molecules in the ball aroundso now they are moving faster,, their temperature has actually gone up.

Lord Kelvin is honored with having the absolute temperature scale named after him. What this scale reallydeals with is the speed of molecules. Basically, the Zero of Absolute Zero, is the point at which themolecules stop moving. The reason you measure temperature is to find out what speed the molecules of asubstance are moving.

• A a measure of the average kinetic energy of matter.

• KE = ½ mv2 or KE = ½ mass x velocity2

• When we are measuring changes in matter’s temperature, we are really measuring the speed atwhich its atoms are moving.

• All atoms in a matter move;, the higher the temperature, the faster they are moving.

• For a given molecule, when its atoms are a gas it is moving faster than when it is a liquid or solid;, therefore, it has a higher temperature.

• There are three primary temperature scales used in the world.

• What are they?

English Fahrenheit

Metric CelsiusMetric Kelvin

• Here are the equations to convert between the temperatures.

( )

273

273

32

5

9

9

532

+=−=

+

×=

×−=

C K

K C

C F

F C

T T

T T

T T

T T



• Example:o Lets say your Celsius thermometer reads 45˚.

o What is this in Fahrenheit?

o What is this in Kelvin?

K C T

F C

T

o

K

oo

F

31827345

113325

945

=+=

=+

×=

Notice Kelvin does not get the little degree circle!

These three thermometers are at thesame level, meaning the average KE(temperature) of each is the same.But each thermometer is scaled

differently. This is the temperature atwhich water freezes but each isreading a different number.

F = 32°

C = 0°K = 273



Specific Heat:Heat is simply a form of energy,. Sspecific heat is a unit used to describe how much heat is needed tochange the temperature of an object.

We use this principle every time you cook. The pan is made of metal, but the handle is coated in plastic,why? Metal’s temperature changes with small amounts of heat, each so, it transfers heat well while, plastic’s temperature does not change unless a large amount of heat is added to it, it does not transfer heat

well.

Another example would be the paper sleeves you get with your coffee. The cup is really hot, but if you puton the sleeve you are not burned by the cup becauseas the sleeve is made of a material that does not transfer heat.

Specific heat is defined as that amount of heat needed to changed the temperature of onea gram of asubstance one degree Celsius. That sounds like the definition of a calorie, a calorie is defined as thatamount of energy needed to raise the temperature of one gram of water one degree Celsius.

Here is the equation to calculate a substance specific heat capacity.

celciusT

C C g

cal c

kg g m

or caloriesQ

T mcQ

o

→⋅⋅

→

→→

⋅⋅=∆=

og

Jor

or

joules

: bleeach variafor units Acceptable

turein temperachangeheatspecificmassHeat

Here are some examples of substances specific heat capacities:



Example:

The specific heat of stone is .19 cal/g⋅°C. For a 600 -gram sample of stone with an initial temperature of

20°C and a final temperature of 90°C, how much heat was added to the stone?

Q = 600 g .19 cal 70 °C = 7980 cal

g ⋅°C

An interesting point involves the calorie unit. You no doubt have heard the word calorie in terms of food.The funny little fact is that the food calorie and the science calorie are different. The science calorie isabbreviated cal the food calorie is Cal. The food calorie’s value is actually 1000 cal. So, these colas, whichclaim they are one calorie, are actually 1 Calorie, a thousand times more than the calorie. Read a food label,the word Calorie is capitalized.

f)

Documents

Notes Chemistry, Matter, Units, Densit, Temperature