1. Welcome to AP Chemistry

2. Scientific method A logical way of solving problems Three steps
Making observations
Formulate hypothesis
Perform experiments
Hypothesis is an educated guess (possible explanation)
Experiment is designed to test hypothesis and leads to new observations

3. Scientific method
After many cycles, a broad, generalized explanation is developed for why things behave the way they do (Theory explains why)
Also regular patterns of how things behave the same in different systems emerges (Law explains how)
Laws are summaries of observations

4. Law Observations Theory (Model) Hypothesis Modify Experiment
Prediction
Law
Experiment

5. Metric System Every measurement has two parts Number Unit
SI system (le Systeme International) is based on the metric system
Prefix + base unit (Prefixes found on p. 10)
Prefixes are based on powers of 10

6. Mass and Weight Mass is measure of resistance to change in motion
Weight is force of gravity
Sometimes used interchangeably
Mass can’t change, weight can

7. Uncertainty of Measurement
Basis for significant figures
All measurements are uncertain to some degree
Precision is how repeatable the measurement is
Accuracy is how close to true value.
Random error - equal chance of being high or low- addressed by averaging measurements (It is expected)

8. Uncertainty of Measurement
Systematic error- same direction each time
Better precision implies better accuracy
Precision can occur without accuracy
Accuracy cannot occur without precision

9. Significant figures All measurements have some degree of uncertainty
Exact numbers are counted, have unlimited significant figures
If it is measured or estimated, it has sig figs.
All numbers except zero are significant.
Some zeros are significant, some aren’t

10. Which zeroes count? In between other sig figs, zeros count
Before the first non-zero, zeros don’t count
After the last number, zeros count if
it is after the decimal point
sig figs
sig figs

11. Sig fig math
In multiplication and division, the answer must have the same number of sig figs as the number with the least sig figs in the problem.
In addition and subtraction, same number of decimal places must be used in the answer as the number with the fewest sig figs.

12. Dimensional Analysis Use conversion factors to change units
Conversion factors = 1 (ALWAYS!)
1 foot = 12 inches (equivalence statement)
12 in = = 1 ft ft in
2 conversion factors
multiply by the one that will give you the correct units in your answer.

13. Examples 11 yards = 2 rod 40 rods = 1 furlong 8 furlongs = 1 mile
The Kentucky Derby race is 1.25 miles. How long is the race in rods, furlongs, meters, and kilometers?
A marathon race is 26 miles, 385 yards. What is this distance in rods, furlongs, meters, and kilometers?
The speed of light is 3.00 x 108 m/s. How far will a beam of light travel in 1.00 ns?

14. Temperature A measure of the average kinetic energy
Use three different temperature scales, but all are talking about the same height of mercury. (Celsius, Kelvin, Fahrenheit)

15. 0ºC = 32ºF
32ºF
0ºC

16. 100ºC = 212ºF
0ºC = 32ºF
0ºC
100ºC
212ºF
32ºF

17. 100ºC = 212ºF
0ºC = 32ºF
100ºC = 180ºF
0ºC
100ºC
212ºF
32ºF

18. 100ºC = 212ºF
0ºC = 32ºF
100ºC = 180ºF
1ºC = (180/100)ºF
1ºC = 9/5ºF
0ºC
100ºC
212ºF
32ºF

19. Density Ratio of mass to volume D = m/V
Useful for identifying a compound
Useful for predicting weight
An intrinsic property- does not depend on the amount of the material

20. Density Problem
An empty container weighs g. Filled with carbon tetrachloride (density 1.53 g/cm3 ) the container weighs g. What is the volume of the container?

21. Classification of Matter
Pure substances have constant composition
Elements cannot be broken into simpler substances
Compounds have constant composition and can be broken down
Separation
Filtration removes a solid from a liquid
Distillation uses heat to separate gases
Chromatography uses the mobile phase (liquid or gas) to remove from a stationary phase (solid) substance