Foundations of

Chemistry

Prefixes Tera- T 1,000,000,000,000 1012

giga- G 1,000,000,000 109

mega - M 1,000,000 106

kilo - k 1,000 103

deci- d 0.1 10-1

centi- c 0.01 10-2

milli- m 0.001 10-3

micro- 0.000001 10-6

nano-n 0.000000001 10-9

pico- p 0.000000000001 10-12

Prefixes Tera- T 1,000,000,000,000 1012

giga- G 1,000,000,000 109

mega - M 1,000,000 106

kilo - k 1,000 103

deci- d 0.1 10-1

centi- c 0.01 10-2

milli- m 0.001 10-3

micro- 0.000001 10-6

nano-n 0.000000001 10-9

pico- p 0.000000000001 10-12

Mass is the amount of matter in an

object. Tool - balance scale Standard SI unit – kilogram Base unit - gram Common units = g,mg, g, kg Weight – pull of gravity on matter

LengthThe distance between two

pointsTool – metric rulerStandard unit - meterCommon units – mm, cm, m,

km

Derived UnitsMany SI units are combinations

of base units called derived units

Examples we will use at this time are volume and density

Volume The amount of space an object

occupies V = L x W x H Tools – metric ruler, graduated cylinder,

buret, volumetric flask SI unit - m3

1 Liter = 1 dm3 1 mL = 1 cm3 = 1 cc

Using Scientific Measurements

All measurements have a certain degree of uncertainty

Uncertainty can result in limitations that depend on the instrument or the experimenter

Scientists use two word to describe how good the measurements are

How good are the measurements?

Accuracy- how close the measurement is to the actual value

Precision- how closely the numerical values of a set of measurements agree with each other

Random error - equal chance of being high or low- addressed by averaging several measurements

Systematic error- same direction each time, they can be compensated for

Percent ErrorAccuracy is judged using percent error.

The formula is:

Actual Value – Experimental Value x 100

Actual Value

Significant figures (sig figs)

Scientists record measurements in significant figures.

Sig figs consist of all the digits known with certainty plus a final digit that is estimated.

Rules for Determining Sig FigsAll nonzero digits are significant

Exact numbers (from counting or definitions) do not limit sig figs

All zeros between nonzero digits are significant

Atlantic/Pacific Rule for Determining Sig Figs

If a decimal point is Present, count from the Pacific side

If a decimal point is Absent, count from the Atlantic Side

Begin counting with the first nonzero digit you come to and then keep counting

Adding and subtracting with sig figs

Round the answer so that the estimated digit is in the same place value as the least precise measurement

For example

27.93 6.4+ First line up the decimal places

27.936.4+

Then do the adding

34.33Find the estimated numbers in the problem

27.93 6.4

This answer must be rounded to the tenths place

Multiplication and Division The answer should have the same

number of significant figures as the measurement with the least number of sig figs

3.6 x 653 2350.8 3.6 has 2 s.f. 653 has 3 s.f. answer can only have 2 s.f. 2400

Dimensional AnalysisA problem solving method that treats units in calculations as algebraic factorsUnits common to both numerators and denominators are cancelled and removed from the expressionsA conversion factors is used to convert from one unit to the otherExact conversions do not limit significant figures

Density D = M / V An intensive property (it is

unaffected by the size of the sample)

Density is often used to identify substances.

Common units - g/ cm3, g/mL, g/L Tools? -

Density As the mass of the substance

increases the volume increases proportionately and the ratio of mass to volume (density) is constant

This is a direct proportion therefore the graph is a straight line that passes through the origin.

Density Because most substances expand

with an increase in temperature (increasing the volume), density usually decreases with increasing volume.

Density varies with temperature

Density of water1 g of water is 1 mL of water.density of water is 1 g/mL (at

4ºC)Specific gravity - the density of

an object compared to the density of water

Specific gravity of water is 1.0

Chem II Quick Lab Use the accepted density to determine the

thickness of aluminum foil.

Compare your data and calculations with other students to concur and determine an average.Write a short lab report in your composition book that includes a data table.

D = m/V D = m/ LWH H = m/DWH

Temperature A measure of the average kinetic

energy Different temperature scales based

on the same expansion of mercury. So why are they different?

273K 100 º C 373K

0ºC

K = C + 273.15

C = K - 273.15

Converting

Between Celsius and

Kelvin

100ºC 212ºF0ºC 32ºF

ConvertingBetween Celsius and Fahrenheit

1ºC = 9/5ºF

F= 9/5ºC +32C = 5/9 (ºF – 32)