AP ChemistryAP ChemistryChapter IChapter ILesson 3Lesson 3

Significant NumbersSignificant Numbers

Giving the Cat BathGiving the Cat Bath

QuestionQuestion

A sample of carbon dioxide that undergoes A sample of carbon dioxide that undergoes a transformation from solid to liquid to gas a transformation from solid to liquid to gas would undergowould undergo

(A) a change in mass(A) a change in mass(B) a change in density(B) a change in density(C) a change in composition(C) a change in composition(D) no change in physical properties (D) no change in physical properties

Answer B

QuestionQuestion

A solution is a(n) A solution is a(n) (A) compound(A) compound

(B) pure substance(B) pure substance(C) homogeneous mixture of (C) homogeneous mixture of substancessubstances(D) heterogeneous mixture of (D) heterogeneous mixture of substances substances

Answer C

Chemical EquationChemical Equation

Symbolic representation of the Symbolic representation of the change or changes occurring.change or changes occurring.

sodium bicarbonate + hydrochloric acid Sodium chloride + water + carbon dioxide     

ReactantReactant

Substances reacting to produce Substances reacting to produce product.product.

ProductProduct

Substances that are produced.Substances that are produced.

iron + oxygen Iron III oxide     

ExampleExample

2 Na + Cl2 Na + Cl2 2 2 NaCl 2 NaCl

Reactants ProductReactants Product

AccuracyAccuracy

How close is How close is measurement to measurement to the true value.the true value.

PrecisionPrecision

Agreement Agreement between several between several measurements of measurements of some quantity.some quantity.

IonsIons

electrically charged atoms or groups electrically charged atoms or groups of atoms.of atoms.

Cations (+) Cations (+)

charged ionscharged ions

Anion (-) charged ions Anion (-) charged ions

ConvertConvert

7 in to cm7 in to cm

17.8 cm17.8 cm

ConvertConvert

179 m to cm179 m to cm

1.790 x 104 cm1.790 x 104 cm

ConvertConvert

15 km/L to mi/gal15 km/L to mi/gal

35 mi /gal35 mi /gal

Calculation of significant Calculation of significant figuresfigures

Preceding zeros do NOT count.Preceding zeros do NOT count. Ex: 0.00034 is 2 sig #’sEx: 0.00034 is 2 sig #’s

Zero between non zero digits count.Zero between non zero digits count. Ex: 8976.02 is 6 sig #’s Ex: 8976.02 is 6 sig #’s

Calculation of significant Calculation of significant figures cont.figures cont.

Trailing zeros do NOT count.Trailing zeros do NOT count. Ex: 100 is 1 sig #Ex: 100 is 1 sig #

Zeros behind the decimal after a non Zeros behind the decimal after a non zero digit DO count.zero digit DO count.

Ex: 1.00 x 10Ex: 1.00 x 1022 is 3 sig #’s is 3 sig #’s

AnswerAnswer

Significant # forSignificant # for A. 134.066A. 134.066

B. 100.000B. 100.000

6 sig #

6 sig #

AnswerAnswer

Significant # for:Significant # for: A. 23400A. 23400

B. 00.009B. 00.009

3 sig #

1 sig #

Rules for Significant figures in Rules for Significant figures in multiplying and dividing.multiplying and dividing.

Ex: 4.56 x 1.4 = 6.38 round to 6.4 Ex: 4.56 x 1.4 = 6.38 round to 6.4 use the number that has the least use the number that has the least number of significant figures.number of significant figures.

Due to the least precise number.Due to the least precise number.

Rule for significant figures and Rule for significant figures and addition and subtraction.addition and subtraction.

Ex: 12.11 + 18.0 + 1.013 + 31.123 Ex: 12.11 + 18.0 + 1.013 + 31.123 round to nearest tenth due to digit round to nearest tenth due to digit with least precise measurement.with least precise measurement.

So correct answer would be 31.1 due So correct answer would be 31.1 due to (18.0).to (18.0).

MassMass

Amount of matter in an object.Amount of matter in an object.

VolumeVolume

1 L = 1000ml = 1000 cm1 L = 1000ml = 1000 cm33 = 1 dm = 1 dm33

Temperature Temperature

property of matter that determines property of matter that determines whether heat energy can be whether heat energy can be transferred from one body to transferred from one body to another and the direction of that another and the direction of that transfer. transfer.

Formulas:Formulas:

a. Convert a. Convert ooF to F to oo C ( C (oo F - 32) x 5/9 = F - 32) x 5/9 = oo C C

b. Convert b. Convert oo C to C to oo F F oo C x 9/5 + 32 C x 9/5 + 32 = = oo F F

Fahrenheit

Celsius

Formulas:Formulas:

c. Convert c. Convert oo C to K C to K

oo C + 273.15 = K or C + 273.15 = K or

K - 273.15 = K - 273.15 = oo C C

Lord Kelvin

Absolute Zero Absolute Zero

lowest possible temperature. Where lowest possible temperature. Where all motion of molecules ceases.all motion of molecules ceases.