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Bires, 2007Bires, 2010

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 4-61

All our science, measured against reality, is primitive and

childlike - and yet it is the most precious thing we have.

-Albert Einstein

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Bires, 2010 Slide 2

Inferences & ObservationsInferences & Observations• Observation

– Detected with one’s senses or lab equipment– No explanations

• Inference– Explains what is observed based on prior

knowledge.– Like a hypothesis.

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Bires, 2010 Slide 4

States of Matter and ChangesStates of Matter and Changes• Four primary states of matter…

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

• We observe 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, 2010 Slide 5

Changes of MatterChanges of Matter• Physical change

– Substance does not change, just the form.– Examples?

• Chemical change– Original substance is lost, and a new substance is

formed.– Examples?

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

opening a soda bottle, boiling, rusting?

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Bires, 2010 Slide 6

Chemical ReactionsChemical Reactions• “reactants” are placed on the left side of a

“chemical reaction equation”:

• “product”, is produced, placed on the right.

• Remember:

–“Reactants react to produce products”

• Law of the Conservation of Mass:–Mass is not created or destroyed in a

chemical reaction.

CchemicalBchemicalAchemical

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Bires, 2010 Slide 7

Energy TransferEnergy Transfer• The Law of Conservation of Energy

– energy cannot be created or destroyed.

• Energy can change form and be stored 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, 2010 Slide 8

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.– Compounds don’t change their properties.

• Two types of mixtures:

• Homogeneous (“homo” = “same”)…– Homogenous mixtures cannot be easily separated

• Heterogeneous (“hetero” = “different”)– Heterogeneous mixtures can be separated with

simple mechanical processes. These often have “phases.”

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Bires, 2010 Slide 9

A step closer to the micro…A step closer to the micro…• Compound

– substance made up of two or more pure elements.

• Water is a compound. Why?

• Table salt is a compound. Why?

• 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, 2010 Slide 10

The micro…The micro…• Elements

– simplest form of pure substances. – 112 known elements, found on the periodic table of

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.– different properties (due to different arrangements

of its atoms.)– Diamond and graphite are allotropes.

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The The very microvery micro……• Atom

– smallest thing with the properties of something in the macro.

– 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 ( + or - )– Atoms with a different number of electrons.

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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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The Periodic Table…The Periodic Table…• A model that groups elements with similar

properties.

• Vertical columns Groups of elements with similar properties.

• Horizontal rows Periods of elements with similar atomic mass.

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

• Metals, left side.– are malleable, ductile, and good conductors of heat

and electricity.

• Nonmetals, right side.– solids are brittle and poor conductors of e- and

heat.

Metalloids have some characteristics of both metals and

nonmetals

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He NeThe Noble GassesThe Noble Gasses

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

• …Mostly unreactive.• (*not entirely unreactive*)

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

End of chapter 1

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Theory vs. LawTheory vs. Law• TheoryTheory

– an explanation of observations of natural phenomena.

– explains whywhy things do what they do.– cannot be proven, but it has never been disproven.– If a theory is disproven, it must be modified or

rejected.

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

broken.End of chapter 1…

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Measuring…Standard UnitsMeasuring…Standard Units• Kilogram – mass (kg)

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

• Liter – volume (L)– in lab, we will usually measure in milliliters, (mL)

• Meter – length (m)

• Second – time (s)

• Kelvin – temperature (K)• AMU – atomic mass (amu) (more later)

• Mole – amount of substance (mol) (more later)

Table on 34

The Kelvin Scale:

0K = absolute zero

273.15K = water freezes

373.15K = water boils

Celsius Kelvin

oC + 273 = K

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Measuring…SI PrefixesMeasuring…SI PrefixesUse “EE” or “EXP” or ( # x 10 ^ # )

• 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

Not this nano … This one

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Derived UnitsDerived Units• Derived units - products of standard units.• Volume, VV

– The SI unit is the cubic meter m3. m3 is huge, so we use the L, or mL (cm3).

• Density, ρρ (rho) (rho)– The amount of mass that is crammed into a certain volume.

ρρ = m / V = m / V.– Each compound has a unique density.– ( g/ml, g/cm3, or kg/m3 )

• Temperature EffectsTemperature Effects?– How does temperature affect mass, volume, density?

See page 37

Osmium (#76) is the densest element on

the planet

volumemassdensity V

msmilliliter

grammLg

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Metric conversionsMetric conversions• Multiply / divide by powers 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

10-3

base unit

base unit

12 x 102 = 1200 cm

345 x 10-3 = 0.345 g

Alwaysshow units!

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Measuring…Scientific NotationMeasuring…Scientific Notation• Scientific Notation

– a form of shorthand very small or very large numbers.

• 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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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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Measuring…Significant FiguresMeasuring…Significant Figures• “Sig Figs”

– how many digits to include in measurements and calculations.

– It is a measure of how precise our equipment is.• Rules: (shortcut coming)

– 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

Text page 47 for help

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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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Sigfigs…more examplesSigfigs…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• 1010 has …?• 45.30 has …?• 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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Metric Conversions PracticeMetric Conversions Practice• Convert the following:

• 2.52 meters to millimeters

• 8.47 millimeters to meters

• .0250 micrometers to meters

• .995 kilometers to meters

• 51.2 m to km

• 5.24 x 10-2 m to mm

• 8.91 x 103 km to m

• 4.21 x 10-4 m to mm

• 1.23 x 10-2 µm to m

31052.2 x mm252031047.8 x m00847.

6100250. x310995. x

3102.51 x32 101024.5 xx

33 101091.8 xx 34 101021.4 xx

62 101023.1 xx

mx 81050.2

m995km0512.

mmx 11024.561091.8 x

11021.4 x81023.1 x

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Two types of measurements, dataTwo types of measurements, data• Qualitative

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

• Quantitative– data expressed with numbers and units.– “42.3 kilograms” “14 milliliters” “3.80 grams.”– Always include units (g, mL, etc)

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

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Accuracy and PrecisionAccuracy and Precision• Accuracy

– closeness to an accepted value.

• Precision– closeness of a set of measurements.– We demand precision. How?

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RelationshipsRelationships• Variable Relationship

– If one variable changes as another changes

• 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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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

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