Chapter 1 Introduction to Chemistry

Chemistry

Matter

Mass

Weight

Matter

Scientific Methods

Qualitative data

Quantitative data

How do scientists study matter?

Independent Variable

Dependent Variable

Control

Variables and Control

Theory

Law

Scientific Theories and Laws

Measurements and data

SI units

SI Base Units There are seven SI base units. Time:

Length:

Mass:

Temperature:

SI Prefixes

Derived SI Units

◦ Volume

◦ Density

460,000,000,000,000,000,000,000

Scientific Notation

Other Examples The diameter of the sun is 1,392,00 km

Addition and Subtraction In order to add and

subtract numbers in scientific notation, the exponents must be the same.

2.840 x 1018 3.146 x 1018 3.60 x 1017 1.50 x 1017 6.9 x 1016

6.565 x 1018

Multiplication and Division For multiplication, multiply the numbers and then add

the exponents. (2 x 103) x (3 x 102) 2 x 3 = 6 3 + 2 = 5 6 x 105

For division, divided the numbers and then subtract the exponent of the divisor from the exponent of the dividend.

(9 x 108) ÷ (3 x 10-4) 9 ÷ 3 = 3 8 – (-4) = 8 +4 = 12 3 x 1012

Conversions Dimensional Analysis

How many pizzas do you need to order if 32 people will attend a party, each person eats 3 slices of pizza, and each pizza has 8 slices?

We can do the same types of conversions with SI units.

We just need to know the relationship between the units we want to convert.

Examples: We know that there are 1000 m in 1 km. We can rewrite this as: 1000m/1km or 1km/1000m Then if we are given and number of meters

or kilometers we can convert. Convert 48 km into meters.

Uncertainty in Data Uncertainty

Accuracy

Precision

Using tools to make measurements

Significant Figures

Sig. Fig. Rules 1. Zeros between nonzero digits are always

significant.◦ 1005 kg – Has 4 significant figures

2. Zeros at the beginning of a number are never significant. ◦ 0.02 g – Has one sig. fig.◦ 0.0025 - Has two sig. figs.

3. Zeros at the end of a number are significant only if there is a decimal in the number.◦ 0.0200 g – Has three sig. figs.◦ 3.0 cm – Has two sig. figs. ◦ 100 cm – Has only one sig. fig.

Sig. Figs. in Calculations When we use measured quantities to do calculations, the

least certain measurement limits the certainty of our calculation.

Therefore the number of significant figures in our answer is determined by the number of sig figs in the least certain number.

Rules:◦ For addition and subtraction: The answer has the same number

of decimal places as the number with the least amount of decimal places.

◦ 20.42 + 1.322 + 83.1 = 104.842, we round to 104.8◦ For multiplication and division: The answer has the same number

of sig figs as the number with the smallest number of sig figs. ◦ 6.221 x 5.2 = 32.3492, we round to 32