Chapter 1: The Scientific Method

Chemistry = The science that seeks to understand what matter does by studying what atoms and molecules do.

Observation = A way of acquiring information about nature.

• Simple descriptions (qualitative observation)• Number (quantitative observation)

Hypothesis = A tentative explanation of your observations• Falsifiable: a test may invalidate your hypothesis

Experiments = Tests of hypotheses, laws or theories• Results either Validate (confirm) or Invalidate (deny) your ideas

Law = A statement that combines all past observations• Predict future observations• You cannot choose to violate a scientific law

Theory = An explanation that extends beyond individual observations to an understanding of the underlying causes for the way nature is or behaves

• Models of nature

This is what the scientific method is made of

Observation: anything wrong with this picture?

Observations

Hypothesis

Law

Theory

Experiments

Experiments

Experiments

This is how the scientific method works

http://www.youtube.com/watch?v=5Owji16tge0

The (meaningful) beauty of the scientific method

Source: http://www.meaningfulbeauty.com/theStory.php

Measurement = Quantitative observation• Comparison to an agreed upon standard• Every measurement has a number and a unit

Scientists have measured the average global temperature rise over the past century to be

0.6 °C The number tells you

1. what multiple of the standard the object measures

2. the uncertainty in the measurement

The unit tells you what standard you are

comparing your object to

Chapter 2: Measurements and Problem Solving

Scientific Notation is a way of writing large and small numbers

The sun’s diameter is1,392,000,000 m

An atom’s average diameter is0.000 000 000 3 m

The sun’s diameter is1.392 x 109 m

An atom’s average diameter is3 x 10-10 m

Large Number = Positive Exponent

1.392 x 109 m

Small Number = Negative Exponent

3 x 10-10 m

Writing a number in scientific notation

1,392,000,000 m

1. Locate the decimal point2. Move the decimal point until a number

between 1 and 10 is obtained 3. Multiply the new number by 10n

4. n is the number of places you moved the decimal point

5. Large number? n is positiveSmall number? n is negative

1,392,000,000. m

1.392,000,000. m

1.392 x 10 ? 9 m

1.392 x 10 9 m

Significant Figures Writing Numbers to Reflect Precision

Exact Values• Can be obtained by counting or by definition• Exact values have “unlimited significant figures”

Measurements• Are obtained from instruments• The number of significant figures reflects the instrument precision. All the digits written are known with certainty except the last one, which is an estimate

1.2 gramsCertain

Estimated

Counting Significant Figures

0.003004500 m1. Non-zero digits are significant2. Zeroes in between non-zero digits are significant 3. Zeroes on the right of the last non-zero digit are significant4. Zeroes on the left of the first non-zero digit are not significant

Important exception 1: Exact numbers.Numbers that come from1. Counting2. FormulasAre not measurements and have an infinite amount of sig. fig.

Important exception 2: Ambiguous numbers.A number has an ambiguous amount of sig. fig. if:1. It is bigger or equal to 102. It has no decimals3. It ends with a zero

10 Fingers >

100 Miles

How many significant figures are in each of the following numbers?

0.0035

1.080

2371

2.97 × 105

12 items (In a dozen)

100,000

Counting Significant Figures. Examples.

Multiplication and Division with Significant Figures

When multiplying or dividing measurements with significant figures, the result has the same number of significant figures as the measurement with the fewest number of significant figures

5.02 × 89,665 × 0.10 = 45.0118 = 45 3 sig. figs. 5 sig. figs. 2 sig. figs. 2 sig. figs.

5.892 ÷ 6.10 = 0.96590 = 0.966 4 sig. figs. 3 sig. figs. 3 sig. figs.

Addition and Subtraction with Significant Figures

When adding or subtracting measurements with significant figures, the result has the same number of decimal places as the measurement with the fewest number of decimal places

5.74 + 0.823 + 2.651 = 9.214 = 9.21 2 dec. pl. 3 dec. pl. 3 dec. pl. 2 dec. pl.

4.8 - 3.965 = 0.835 = 0.8 1 dec. pl 3 dec. pl. 1 dec. pl.

The Standard Units

Scientists have agreed on a set of international standard units for comparing all our measurements called the SI units

Système International = International System

Quantity Unit Symbol

length meter m

mass kilogram kg

time second s

temperature kelvin K