Unit 1 – Measuring Matter and Energy

Learning Objectives

By the end of this unit, you should be able to:• Describe what matter is and apply the law of

conservation of mass• Make careful qualitative and quantitative

measurements of matter using accurate units and vocabulary

• Calculate the density of an object and determine if it will sink or float

Chemistry• The study of the structure,

properties and composition of matter, and the changes that substances undergo

Organic Inorganic

Analytical Chemistry Physical

Biochemical

Matter•Anything that has mass and takes up space

Mass•The amount of matter an object contains

Volume

•The amount of space an object takes up

Density

• The ratio of the mass of an object to its volume

Law of Conservation of Matter

•Matter cannot be created nor destroyed

• Matter can change

Energy

• Is required for changes in matter• Does not have

mass or volume

The Composition of Air

Measuring Matter

Quantitative Measurements

• Use numbers (“quantity”)

• Considered more objective

Qualitative Measurements

• Use words (“quality”)

• Considered more subjective

Both are valid means of describing matter

Classify the following as quantitative or qualitative properties

• Mass• Volume• Color• Density• Texture• Smell• Length• Temperature• Phase

Quantitative• Mass• Volume• Density• Length• Temperature

Qualitative• Color• Texture• Smell• Phase

Q: Which of the following is an example of a quantitative measurement?

a. “It is really hot in here!”b. “There are too many people in this

room!”c. “The temperature is 102o F!”d. All of the above

QUALITATIVE MEASUREMENTS

Physical properties

• Can be observed or measured without changing the substance’s composition

• Ex: Height, weight, color, phase

Chemical properties

• can only be observed through chemical change

• Ex: Flammability, reactivity, acidity

Physical Changes

• A physical change alters a substance without changing its composition

• Can be reversed

Chemical changes

• Require the breaking and forming of bonds between atoms.

• New substances are formed from the original substances

How to tell?

• Signs of a chemical change:– Color change– Temperature change

(colder or warmer)– Release of a gas or

solid– Release of light– New/different odors

Fancy terms

• Effervescence is bubbling that occurs as an example of a chemical change

• A Precipitate is an insoluble solid that forms as a result of a chemical change

How is this different from boiling?

States of Matter(phases)

Properties of States of MatterPhysical State Definite

Shape?Definite Volume?

Readily compressible?

Solid

Yes Yes No

Liquid No Yes No

Gas No No Yes

Plasma: The Fourth State

•Charged particles in gas-like clouds

Yes, a plasma TV is really plasma.

So are stars

And lightning!

Freezing water into ice is an example of…

a) A physical change because ice and water are both H2O

b) A chemical change because a new substance, ice, is formed

c) A chemical change because ice is a solid while water is a liquid

d) None of the above

QUANTITATIVE MEASUREMENTS

S.I. Units (Metric System)Property Units Symbol

Mass Grams gVolume Liters* L

Length Meters m

Temperature Celsius/Kelvin

oC, K

PrefixesPrefix Symbol Number value

kilo k 1000 times Greater than

centi c 100 times Less than

milli m 1000 times Less than

micro μ 1 000 000 times Less than

nano n 1 000 000 000 times Less than

Unit Metric equivalent

Examples

Meter 1m A little more than a yard

Kilometer 1,000m About 2/3 of a mile

centimeter 0.01m Radius of a penny

millimeter 0.001m Width of a pencil tip

liter 1L ½ a pop bottle

milliliter 0.001L About 15 drops of water

Accuracy and Precision

• Often mistakenly treated as the same thing

• Accuracy = how close to accepted value you are

• Precision = how consistent you are

Accuracy vs. Precision

Making Accurate & Precise Measurements

• When recording measurements, estimate 1 place past the known measurement

• For the example on the right, we know that it is greater than 52 but less than 53.

• We would record this as 52.8 mL. (+/- .2)

Calculating Precision

• % Error: |Trial Value – Average Value| x 100Average Value

• Ex: You make 3 measurements of 20, 22, and 24 mL

• Avg = 20+22+24 = 22 mL. 3

• % error of trial 1 (20 mL) = (20-22)/22 = 9.09%

Calculating Accuracy

• % Error: |Trial Value – Accepted Value| x 100Accepted Value

• Ex: You record a measurement as 16g, but the teacher records 20g and is always right.

• % error = (16-20)/20 = 20%

Density

• The ratio of the mass of an object to its volume

• D = M / V

• Density = Mass Volume

Practice

• Mass = 30g

• Volume = 5cm3

• Density = 6g/cm3

Try again• Mass = 6g

• Volume = 2cm3

• Density = 3g/cm3

Now solve for Mass...• Mass = 40g

• Volume = 4cm3

• Density = 10g/cm3

Now solve for Volume…

• Mass = 100g

• Volume = 10cm3

• Density = 10g/cm3

Specific Gravity (relative density)• Is a measure of a

substance’s density vs. a reference (usually water)

• Tells you whether a substance will sink or float

• Any substance will float in a more dense substance than itself

Specific gravity of water = 1g/mL

Formula

• Specific Gravity = density of substance density

of reference• If the SG is less than 1, the object will float• If the SG is less than 1, the object will sink

Which items will sink in water? Float?

Hydrometer

• is used for measuring specific gravity

• Used to measure the progress of yeast in wine/beer making

• Also used to check oil & acid in your car battery

Hydrometers are very useful!

Predict

• How could measuring the specific gravity of liquids be useful?

• If the gravity of a substance changes, what can be inferred?

1st Law of Thermodynamics:

the total energy of a system is constant• In other words,

energy can be neither created nor destroyed (conservation of energy)

Chemistry Cat takes a different approach.

2nd Law of Thermodynamics:

• Energy always flows from a high energy object to a low energy object

• Heat always flows from hot objects to cool objects until they reach equilibrium

Temperature

• Is the degree of hotness or coldness of an object

• Is a measurement of energy

• Expressed in Degrees Centigrade (Celsius) or Kelvin

The Kelvin Scale

• is a measurement of the absolute amount of energy in a system

• Cannot be negative

• No degrees

The Scale was developed by Lord Kelvin, a British noble and scientist

Absolute Zero

• 0K (-273o C) = Absolute Zero

• Represents a complete absence of energy

• Lowest theoretically possible temperature

• Not naturally occurring; scientists have gotten extremely close

Temperature EquivalenceoC oF Kelvin Description

-273 -459.4 0 Absolute Zero0 32 273 Water freezes

10 50 283 Cool fall day20 68 293 Room

temperature30 86 303 Normal

Summer day40 104 313 Hot summer

day100 212 373 Water Boils

Temperature Conversions

K = oC + 273oC = K – 273

oC = 5/9(oF – 32)oF = 9/5oC + 32

Ex: 20o C = 20 + 273 = 293 K250 K = 250 – 273 = -23 oC60o F = 5/9(60-32) = 15.5o C

Practice Problems

1. 25o C = ____K2. 186o C = ___K3. -30o C = ___K4. 100 K = ___oC5. 300 K = ___oC6. 456 K = ___oC7. 58o F = ____oC8. 18o C = ____oF

298 459243

-173

2718314.464.4

Extra Practice

1. 230 oC = ___K2. 23K = _____oC3. -150 oC = ___K4. 120 K = ____oC5. 513 oC = ____K