General Chemistry

1. 1
Welcome to
AP Chemistrypp

2. 2
Ch. 1 Significant figures
Meaningful digits in a MEASUREMENT
Exact numbers are counted, have
unlimited significant figures
If it is measured or estimated, it has sig
figs.
If not it is exact . . .
All numbers except zero are significant.
Some zeros are, some aren’t

3. 3
Which zeroes count? pp
In between other sig figs does
Before the first number doesn’t
After the last number counts if
it is after the decimal point
the decimal point is written in
3200 2 sig figs
3200. 4 sig figs

4. 4
Which zeroes count?
Atlantic Pacific Rule
Decimal point Present, use Pacific
Ocean
E.g., 0.002540
Decimal point Absent, use Atlantic
Ocean
E.g., 2540

5. 5
Doing the math pp
Multiplication and division, same
number of sig figs in answer as the
least in the problem
Addition and subtraction, same number
of decimal places (vs. sig figs) in
answer as least in problem.

6. 6
More Preliminaries
Scientific Method
Metric System
Uncertainty

7. 7
Scientific method.
A way of solving problems
Observation - what is seen or measured
Hypothesis - educated guess of why
things behave the way they do.
(possible explanation)
Experiment - designed to test hypothesis
leads to new observations,
and the cycle goes on

8. 8
Scientific method.
After many cycles, a broad,
generalizable explanation is developed
for why things behave the way they do.
This is a Theory
Also, a regular pattern of how things
behave the same in different systems
emerges.
This is a Law
Laws are summaries of observations

9. 9
Scientific method.
Theories have predictive value.
The true test of a theory is if it can
predict new behaviors.
If the prediction is wrong, the theory
must be changed.
Theory is the why
Law is the how

10. 10
Observations
Hypothesis
Experiment
Law
Theory
(Model)
Prediction
Experiment
Modify

11. 11
Metric System
Every measurement has two parts:
Number
Scale (unit)
SI system (le Systeme International) is based
on the metric system.
Prefix + base unit
Prefix tells you the power of 10 to multiply by -
decimal system - easy conversions

12. 12
Metric System
Base Units
Mass - kilogram (kg)
Length - meter (m)
Time - second (s)
Temperature - Kelvin (K)
Electric current- ampere (amp, A)
Amount of substance - mole (mol)

13. 13
Prefixespp
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 - m 0.000001 10-6
nano - n 0.000000001 10-9

14. 14
Deriving the Liter
Liter is defined as the volume of 1 dm3
gram is the mass of 1 cm3
1 ml = 1 cm3

15. 15
Figure 1.3
Measurement
of Volume

16. 16
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

17. 17
Uncertainty
Basis for significant figures
All measurements are uncertain to
some degree
Precision - how repeatable
Accuracy - how correct - closeness to
true value.
Random error - equal chance of being
high or low - addressed by averaging
measurements - expected

18. 18
Figure 1.4
Common Types of Laboratory
Equipment Used to Measure
Liquid Volume

19. 19
Figure 1.6
Measurement
of Volume
Using a Buret
The volume is
read at the
bottom of the
liquid curve
(called the
meniscus).

20. 20
Uncertainty
Systematic error - same direction each
time
Want to avoid this
Better precision implies better accuracy
you can have precision without
accuracy
You can’t have accuracy without
precision

21. 21
Figure 1.7
The
Difference
between
Precision and
Accuracy

22. 22
Dimensional Analysis
Using the units to solve problems

23. 23
Dimensional Analysis
Use conversion factors to change the units
Conversion factors = 1
1 foot = 12 inches (equivalence statement)
12 in = 1 = 1 ft.
1 ft.
12 in
2 conversion factors
multiply by the one that will give you the
correct units in your answer.

24. 24
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?

25. 25
Examples
Science fiction often uses nautical
analogies to describe space travel. If the
starship U.S.S. Enterprise is traveling at
warp factor 1.71, what is its speed in
knots?
Warp 1.71 = 5.00 times the speed of light
speed of light = 3.00 x 108
m/s
1 knot = 2000 yd/h exactly

26. 26
Apothecaries (druggists) use the
following set of measures in the English
system:
20 grains ap = 1 scruple (exact)
3 scruples = 1 dram ap (exact)
8 dram ap = 1 oz. ap (exact)
1 dram ap = 3.888 g
1 oz. ap = ? oz. troy
What is the mass of 1 scruple in
grams?
Examples

27. 27
Examples
The speed of light is 3.00 x 108
m/s.
How far will a beam of light travel in
1.00 ns?

28. 28
Temperature and Density

29. 29
Temperature
A measure of the average kinetic
energy
Different temperature scales, all are
talking about the same height of
mercury.
Derive a equation for converting ºF toºC

30. 30 0ºC 32ºF
0ºC = 32ºF

31. 31 100ºC 212ºF
100ºC = 212ºF
0ºC 32ºF
0ºC = 32ºF

32. 32 100ºC 212ºF0ºC 32ºF
100ºC = 212ºF
0ºC = 32ºF
100ºC = 180ºF

33. 33 100ºC 212ºF0ºC 32ºF
100ºC = 212ºF
0ºC = 32ºF
100ºC = 180ºF
1ºC = (180/100)ºF
1ºC = 9/5ºF

34. 34 ºC
ºF

35. 35
ºC
ºF
(0,32)= (C1,F1)

36. 36
ºC
ºF
(0,32) = (C1,F1)
(120,212) = (C2,F2)

37. 37
Celsius/Fahrenheit Conversions
Y - intercept is at 32 degrees F
Tc = 5/9(Tf - 32)
Tf = (9/5 x Tc) + 32

38. 38
Figure 1.8
The Three
Major
Temperature
Scales

39. 39
Figure 1.9
Normal Body Temperature on the Fahrenheit,
Celsius, and Kelvin Scales

40. 40
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 what the material is

41. 41
Density Problem
An empty container weighs 121.3 g. Filled
with carbon tetrachloride (density 1.53
g/cm3
) the container weighs 283.2 g.
What is the volume of the container?

42. 42
Density Problem
A 55.0 gal drum weighs 75.0 lbs. when
empty. What will the total mass be
when filled with ethanol?
density 0.789 g/cm3
1 gal = 3.78 L
1 lb = 454 g

43. 43
Matter:Matter:
Anything occupyingAnything occupying
space and havingspace and having
mass.mass.

44. 44
Classification of Matter
Three States of Matter:Three States of Matter:
– Solid: rigid - fixed volume andSolid: rigid - fixed volume and
shapeshape
– Liquid: definite volume butLiquid: definite volume but
assumes theassumes the shape of itsshape of its
containercontainer
– Gas: no fixed volume or shape -Gas: no fixed volume or shape -
assumesassumes the shape of itsthe shape of its
containercontainer

45. 45
Types of Mixtures
Mixtures have variable composition.Mixtures have variable composition.
AA homogeneous mixturehomogeneous mixture is ais a
solution (for example, vinegar)solution (for example, vinegar)
AA heterogeneous mixtureheterogeneous mixture is, to theis, to the
naked eye, clearly not uniform (fornaked eye, clearly not uniform (for
example, a bottle of ranch dressing)example, a bottle of ranch dressing)

46. 46
Pure Substances
Can be isolated by separationCan be isolated by separation
methods:methods:
ChromatographyChromatography
FiltrationFiltration
DistillationDistillation

47. 47
Figure 1.10
Simple Laboratory Distillation Apparatus

48. 48
Element:Element: A substance thatA substance that
cannot be decomposed intocannot be decomposed into
simpler substances by chemicalsimpler substances by chemical
means.means.
Compound:Compound: A substance with aA substance with a
constant composition that can beconstant composition that can be
broken down into elements bybroken down into elements by
chemical processes.chemical processes.

49. 49
Figure
1.13
The
Organization
of Matter