Back ©Bires, 2002Bires, 2004 Chapter 1 and 2: Matter and Change Measurements and Calculations How do we do what we do? What do we measure? How do we measure?

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©Bires, 2002Bires, 2004

Chapter 1 and 2:Chapter 1 and 2:Matter and ChangeMatter and Change

Measurements and CalculationsMeasurements and Calculations

Chapter 1 and 2:Chapter 1 and 2:Matter and ChangeMatter and Change

Measurements and CalculationsMeasurements and Calculations

How do we do what we do?

What do we measure?

How do we measure?

How do we do what we do?

What do we measure?

How do we measure?

Read Text pages 4- This unit: text p4-61

All our science, measured against reality, is primitive and childlike - and yet it is the most precious thing

we have.-Albert Einstein

This is thebasics of *DOING*

Chemistry

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Bires, 2004 Slide 2

Matter’s propertiesMatter’s properties• When observing matter, we observe many of its properties.

• Extensive Property - depends upon how large your sample of matter is.– What are some extensive properties?

• Mass and volume are extensive properties.

• Intensive Property - unique to that type of matter, and does not depend on sample size.– What are some intensive properties?

• Density, and melting point are intensive properties.

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Bires, 2004 Slide 3

States of Matter and ChangesStates of Matter and Changes• The four primary states of matter are: (?)

• solid, liquid, gas, and high energy plasma.

• When we observe properties, these can be physical or chemical properties:

• Physical property - can be observed without changing the substance.

• (color, mass, others?)

• Chemical property - requires that the substance be changed to be observed.

• (flammability, others?)

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Bires, 2004 Slide 4

Changes of MatterChanges of Matter• Physical change - substance does not change,

just the form.– (It can also revert back to its original state…ie:

melting and vaporization)

• Chemical change - original substance is lost, and a new substance is formed.– (The original substance cannot be returned without

additional chemical changes.)

• Which kinds of changes are these?:– Burning, freezing, vinegar + baking soda, and

opening a soda bottle,

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Bires, 2004 Slide 5

Chemical ReactionsChemical Reactions• When chemicals react, we call them “reactants”

and they are placed on the left side of a “chemical reaction equation”:

• The chemical(s) that is produced is called a “product”, placed on the right.

• Remember:

“Reactants react to produce products”

CchemicalBchemicalAchemical

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Bires, 2004 Slide 6

Energy TransferEnergy Transfer• The law of conservation of energy states that

energy cannot be created or destroyed.• We can force energy to change form and store

energy in various forms.– How is a flashlight battery like gasoline in a car?

• Exothermic process – releases energy.– (think exit energy)

• Endothermic process – takes energy from surroundings.– (think into energy)

• Can you think of an exothermic reaction?• Can you think of an endothermic reaction?

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Bires, 2004 Slide 7

From the macro to the micro…From the macro to the micro…• We can classify matter in terms of its complexity:• Mixture - collection of two or more physically different

compounds.– The compounds in a mixture can be separated out without

the need to chemically change either of the compounds.

• Two types of mixtures are Homogeneous (homo) meaning “same”)…– Homogenous mixtures cannot be easily separated

• And Heterogeneous (“hetero” meaning “different”)– Heterogeneous mixtures can be separated with simple

mechanical processes. These often have “phases.”

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Bires, 2004 Slide 8

A step closer to the micro…A step closer to the micro…• A compound - substance made up of two or

more pure elements.

• Water is a compound because it is composed of the elements H and O.

• Table salt is a compound because it is composed of the elements Na and Cl.

• A compound cannot be separated from its elemental makeup– (without destroying the compound)

• Compounds have very different properties than their elements.

OH 2

NaCl

Mixtures and Compounds-FeS.mov

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Bires, 2004 Slide 9

The micro…The micro…• Elements - simplest form of pure substances.

– There are approximately 110 elements, and they can be found on the periodic table.

• Elements consist of a single type of atom.

• Water is NOT an element. Pure diamond IS an element. Why?

• Allotropes – different forms of a single element.

• Each allotrope has different properties due to different arrangements of its atoms.– Diamond and graphite are allotropes.

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Bires, 2004 Slide 10

The The very microvery micro……• Atom - smallest thing with the properties of something

in the macro.– (a single helium atom will function just like a the helium in a party

balloon.

• Atoms = protons and neutrons in the nucleus + electrons in electron orbits.

• Properties of atoms depends upon the number of protons, neutrons, and electrons in the atom– (we’ll get into atomic and sub-atomic theory later.)

• Isotopes - Two atoms with same number of protons (are the same element) but a different number of neutrons

• Ions - Atoms with a different number of electrons

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Bires, 2004 Slide 11

Similar to table on Similar to table on page 15page 15

Using this flowchart, what is our water?

Is milk really homogenous?

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Bires, 2004 Slide 12

The Periodic TableThe Periodic Table• The periodic table is a collection of all the

known elements into a model that groups elements with similar properties.

• Vertical columns are Groups of elements with similar properties.

• Horizontal Periods represent elements with similar atomic mass

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Bires, 2004 Slide 13

Three Main Areas of the Periodic TableThree Main Areas of the Periodic Table

• Metals are found on the left.– Metals tend to be malleable, ductile, and good

conductors of heat and electricity.

• Nonmetals are found on the right.– Nonmetals tend to be brittle, and poor conductors of

e- and heat.

The elements between metals and nonmetals

are called Metalloids and have some

characteristics of both metals and nonmetals

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Bires, 2004 Slide 14

He NeThe Noble GassesThe Noble Gasses

• The Noble gasses are found on the far right of the P-table. The Nobles are:

• …Very unreactive.– (*not entirely unreactive*)

• …Gasses at room temperature.• …Mined from gas pockets in the ocean• …Produce bright emissions when electrified• …Have filled octets. (more later)

End of chapter 1

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Bires, 2004 Slide 15

The Scientific Method The Scientific Method (p29 in text)(p29 in text)• The scientific method - process of solving problems by asking and testing

questions.• Observation

– Observation of a natural phenomena.• Question

– Create a question to test your observations.• Hypothesis

– A reasonable explanation of your observations. A possible answer to your question. This is NOT a guess. Your text: A Testable statement

• Experiment/Test– A controlled observation (a test of your hypothesis).

• Collect and Analyze Data– Experimental results must be collected and interpreted. A

valid experiment must be reproducible.• Conclusions

– Data is explained and compared to the hypothesis. The final step… What next? How can I this new information?

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Bires, 2004 Slide 16

A more complex model of the S.M.A more complex model of the S.M.

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Bires, 2004 Slide 17

Theory vs. LawTheory vs. Law• Theory - an explanation of observations of

natural phenomena.– A theory cannot be proven, but it has never been

disproven.– If a theory is disproven, it must be modified or

rejected.– A theory explains whywhy things do what they do.

• Law - a description of fact.– A law describes whatwhat willwill happenhappen.– Because a law is a description of fact, it cannot be

broken.

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Bires, 2004 Slide 18

Lab Work and Lab ReportsLab Work and Lab Reports• The main sections of a lab report are:• Title (with name, class, instructor, date)• Purpose / Problem (why are you doing this lab)• Variable (when present)• Hypothesis (when applicable)• Equation (chemical, balanced A+BC)• Procedure, with Materials List• Data (create table), with Graph (when applicable)• Calculations (includes equations used and a sample

calculation (word equation))• Conclusion (includes error analysis of calculations, as

well as answers to lab questions and “what next”)

Lab Report Format

Title, Student Names, Date, Class, Instructor

Purpose/Problem

Variables (be specific)

Hypothesis (when applicable)

Equation (balanced)

Procedure, Materials List

Data (create table), Graph (if applicable)

Calculations (includes sample calculation)

Conclusion (includes error analysis)

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Bires, 2004 Slide 19

Measuring…Standard UnitsMeasuring…Standard Units• Standard units we use in the sciences:

• Meter – length (m)

• Kilogram* – mass (kg)

• Second – time (s)

• Kelvin – temperature (K)

• Liter** – volume (L)• Mole – amount of substance (mol) (more later)

• AMU – atomic mass (amu) (more later)

– * in lab, we will usually measure in grams, (g)– ** in lab, we will usually measure in milliliters, (mL)

Table on 34

The Kelvin Scale:

0K = absolute zero

273.15K = water freezes

373.15K = water boils

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Bires, 2004 Slide 20

Measuring…SI PrefixesMeasuring…SI Prefixes• Prefixes are added to the standard units to express

measurements that are very large or very small. Common prefixes are:

• kilo – (k) x103 (x 1,000)– kilogram = 1000 grams

• milli – (m) x10-3 (x 1/1,000)– milliliter = 0.001 liters

• micro – (μ) x10-6 (x 1/1,000,000)• Mega – (M) x106 (x 1,000,000)• centi – (c) x10-2 (x 1/100)

– centimeter = 0.01 meters

• nano – (n) x10-9 (x 1/1,000,000,000)

1.0ml = 1.0cc

cc = cm3

About 35 ml

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Bires, 2004 Slide 22

Metric conversionsMetric conversions• To convert one metric prefix to another, multiply

by a power of ten.• Example:

• To convert 12 meters to centimeters…

• Or to convert 345 milligrams to grams…

• REMEMBER: If the unit gets bigger, the number gets smaller! (and vice versa)

10-2

x 10-3

base unit

base unit

12 x 102 = 1200 cm

345 x 10-3 = 0.345 g

Alwaysshow units!

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Bires, 2004 Slide 23

Measuring…Scientific NotationMeasuring…Scientific Notation• Scientific notation - a form of shorthand used to

express numbers that are very large or very small.• SciNot - real decimal number, multiplied by a base-ten

exponent.– The number is expressed with one digit to the left of

the decimal– and the base-ten exponent is always an integer.

• For instance, 135000 becomes 1.35 x105.

• Can you figure what 4500 is?• How about moving the decimal the other way…try

0.00056.

We moved the decimal five places

6.02 x1023

6.02x1023

3105.4 x

4106.5 x

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Bires, 2004 Slide 24

Scientific Notation PracticeScientific Notation Practice• Convert the following to scientific notation:

• Convert the following to floating point notation:

56.4 0291.0 8956 50.583 000,36001056.4 x 21091.2 x 310956.8 x 2108350.5 x 5106.3 x

41052.8 x 3101.1 x 21091.3 x 0105.6 x 231002.6 x

000852. 1100 0391. 5.6

000,000,000,000,000,000,000,602

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Bires, 2004 Slide 25

Measuring…Significant DigitsMeasuring…Significant Digits• Significant Digits tells us how many digits to

include in our measurements, calculations, and answers.– It is a measure of how accurate our equipment is.

• Rules:– All non-zero numbers are significant.

• 1, 2, 256, 952456

– Zeros between significant numbers are significant.• 303, 50034, 1001

– Zeros to the RIGHT of a decimal are significant.• 3.000, 24.0, 31.0000, 35.520

– Zeroes to the LEFT of a decimal are NOT.• 4000, 256000, 10, 2400, 1 000 000 000

Open books to page 47 for help

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Bires, 2004 Slide 26

Pacific or Atlantic?Pacific or Atlantic?• Decimal Present?• Count from the Pacific

• Decimal Absent?• Count from the Atlantic

A little trick for “sig figs”

31.80

564300.0020

10000

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Bires, 2004 Slide 27

SigDigs…more examplesSigDigs…more examples• 2450 has 3 sig figs.• 245.0 has 4 sig figs• 0.082 has 2 sig figs• 0.0820 has 3 sig figs• Exceptions to the rules:

– Fractions– Counting– When the teacher tells you to ignore them

Figure the number of sigfigs for the following:

• 6.781 0.0563 1200 63003 1.42x10-2

• 4 3 2 5 3

Can you see why significant digits are

important?

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Bires, 2004 Slide 28

Why Use Significant Digits?Why Use Significant Digits?• We use Significant Digits to express

accuracy.• When you measure something, your

measurement is only as accurate as your weakest instrument.

• When you add figures, round your answer to the least number of digits after the decimal.

• When you multiply, express your result with the least significant digits.

• What is the volume of a box 2.34m wide, 3.1m deep, and 3.56m long?

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Bires, 2004 Slide 29

Qualitative vs. Quantitative Qualitative vs. Quantitative MeasurementsMeasurements

• Qualitative measurement – a description of an object.– “blue” “sticky” “smelly.”

• Quantitative measurement – data expressed with numbers and units.– “42.3 kilograms” “14 kilometers per hour” “3.80

grams.”

• To accurately describe a compound or solution in chemistry:– use color, transparency, and texture/state.– “A colorless, clear, liquid.” ?

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Bires, 2004 Slide 30

Accuracy and PrecisionAccuracy and Precision• Accuracy - closeness to an accepted

value.• Precision - closeness of a set of

measurements.– we strive for accuracy and demand

precision!– All equipment has a level of precision that

you should record in lab. (ie: +/- 0.001gram)

• We use a percent error calculations when working with data.

uldhavegotwhatyousho

whatyougotuldhavegotwhatyoushoerrorPercent

The ideal value The exp value

The ideal value

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Bires, 2004 Slide 31

RelationshipsRelationships• If one variable changes as another

changes, we say they have a relationship.

• Direct relationship:– If A increases as B increases– If their quotient is a constant (y/x = k),

we say they are directly proportional.

• Inverse relationship:– If A decreases as B increases– If their product is a constant (yx=k),

we say they are inversely proportional.

Page 55

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Bires, 2004 Slide 32

Factor Label Analysis (T-chart)Factor Label Analysis (T-chart)• Factor label analysis is a way of converting

between a number of units.

• Convert 32,000 inches into miles, knowing that there are 1609 meters in a mile and 39.4 inches in a meter.

• Using factor analysis helps keep us from making costly mistakes by using the units (labels) as a check.

• Convert 1.5 days into seconds

• Convert 36 pounds into grams

• Convert 44 ounces (fluid) into mL.

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Bires, 2004 Slide 33

A Little MoleA Little Mole• The mole is an amount, much like a

dozen.

• Referred to as Avogadro's number,

the mole is equal to 6.02x1023 things.

• We’ll find this number to be very handy later. For now, just know that when you see one mole, that equals

6.02x1023 things.

End of chapter 2