Chapter 1

Chemical Foundations

Chemistry

• the study of matter and the changes it undergoes

sodiumchlorine sodium chloride

Scientific Method

1. Make observations2. Formulate hypotheses3. Perform experiments

Benz

ene

Ring

Units of Measurements in SI UnitsPhysical Quantity Name of Unit Abbreviation

Mass kilogram kg

Length meter m

Time second s

Amount of Substance

Mole mol

Temperature kelvin K

PrefixesPrefix Symbol Value

giga G 109

mega M 106

kilo k 103

- - 1

deci d 10-1

centi c 10-2

milli m 10-3

micro μ 10-6

nano n 10-9

pico p 10-12

How to use prefixes

• Convert 500.0 mg to grams.

How to use prefixes

• Convert 700. nm to meters.

How to use prefixes

• Convert 8905 grams to kilograms.

Uncertainty in Measurement

1) 20.15 mL2) 20.14 mL3) 20.16 mL4) 20.17 mL5) 20.16 mL

uncertain digit

certain digits

Significant figures automatically indicate the uncertainty in a measurement.

20.15 mL 4 significant figures

The last digit is usually assumes to be 1

Another way to write uncertainty

mL 0.01 15.20

All measurements have some degree of uncertainty!

• In analyzing a soil sample, a soil scientist measures 15.00 g sample. Later the scientist uses a scale which measures 15 g.

• What is the difference between the measurements 15.00 g and 15 g?

QUESTION

• 15.00 g – Means – Measurement is between 14.99 g and 15.01 g.

• 15 g– Means – Measurement is between 14 g and 16 g

ANSWER

g 01.0 00.15

1g 15

Precision & Accuracy

• Not precise• Not accurate

Precision & Accuracy

• Precise• Not accurate

Precision & Accuracy

• Precise & accurate!

1) 20.15 mL2) 20.14 mL3) 20.16 mL4) 20.17 mL5) 20.16 mL

Precise Measurements

Accuracy

• The agreement of a particular value with the true value.

Precision

• The degree of agreement among several measurements of the same quantity

Significant Figure Review

1. Nonzero integers always count as sig figs.

146589321

Sig Fig Review

2. Leading ZerosZeros that precede nonzero digits do not count as sig figs.

0.00340.89

0.00255

Sig Fig Review

3. Captive ZerosZeros that are between nonzero digits always count as sig figs

1.005409

2004

Sig Fig Review

4. Trailing ZerosZeros at the right end of a number are significant if there is a decimal present.

100.020

40001.00 x 102

Atlantic Pacific Rule

Pac ifi c OceanDec imal i s Present

Count s ig fi gs f rom left

At lanti c OceanDec imal i s Absent

Count s ig fi gs f rom r ight

1.000.50050

10050050

Sig Fig Review

5. Exact NumbersIf a measuring device was not used, then the number is an exact number.

Counting: 10 apples

Defined Quantities: 1 inch = 2.54 cm

Numbers in Formulas: 2πr (The 2)

Sig Figs & Calculations

1. Multiplication & Division

Round to the least precise measurement used in the calculation.

4.88 x 1.5 = 7.32 7.3

Sig Figs & Calculations

2. Addition & Subtraction

The result has the same number of decimal places as the least precise measuremnt.

12. 00 + 6.001 = 18.001 18.00

Rules for Rounding

1. In a series of calculations, carry the extra digits through to the final result, then round.

Rules for Rounding

2. When you round, – if the digit to the right of the final sig fig is

less than 5, then the preceding digit stays the same.

6.22 6.2– If the digits is equal to or greater than 5,

then the preceding digit should be increased by 1. 4.57 4.6

Dimensional Analysisor

Units Rock

Unit Conversions

A glass rod is 6.00 inches long. What is the length in centimeters?

Unit Factor

inch 1

cm 2.54 and

cm 2.54

inch 1

Temperature

ºC to K K = ºC + 273

K to ºC ºC = K – 273

ºC to ºF ºF = 1.8 ºC + 32

ºF to ºC ºC =

Density – a derived unit

volume

mass Density

V

m

Units for Density

g/cm3

g cm-3

g/L

Classification of Matter Matter

Heterogeneous Mixtures

Homogeneous Mixtures

Pure substances

Compounds Elements

Atoms

Nucleus Electrons

protons neutrons

quarksquarks

States of Matter

Solid• Definite shape &

volume• particles vibrate

around fixed positions

Liquid

• Take the shape of the container

• Definite volume• Particles are free to move

Gas

• No definite shape• No definite volume