Chemistry: The Study of Change

1
Chemistry The Study of Change

• Chapter 1

 
2
CHEMISTRY

• The study of matter and the changes it undergoes.

3
UNITS
Table 1.2 SI Base Units Table 1.2 SI Base Units Table 1.2 SI Base Units
Base Quantity Name of Unit Symbol
Length meter m
Mass kilogram kg
Time second s
Temperature kelvin K
Amount of substance mole mol
4
PREFIXES
Prefix Symbol Meaning
Tera- T 1012
Giga- G 109
Mega- M 106
Kilo- k 103
Hecto- h 102
Deca- da 101
Deci- d 10-1
Centi- c 10-2
Milli- m 10-3
Micro- m 10-6
Nano- n 10-9
Pico- p 10-12
5
SCIENTIFIC NOTATION
N is a number between 1 and 10
n is a positive or negative integer
N x 10n
6.022 x 1023
1.99 x 10-23
6
SCIENTIFIC NOTATION
568.762
0.00000772
n gt 0
n lt 0
568.762 5.68762 x 102
0.00000772 7.72 x 10-6
7
Making Measurements
8
SIGNIFICANT FIGURES
9
Once you start the counting dont stop!
10
SIGNIFICANT FIGURES

• Rule 1
• Every nonzero digit in a measurement is
  significant.
• Examples 24.7 0.22 569
• Rule 2
• Zeros appearing between nonzero digits are
  significant.
• Examples 7003 60.8 0.502
• Rule 3
• A ZERO is NOT significant when it is a
  placeholder. A placeholder is used to show the
  location of the decimal point.
• Examples .00099 5280 700

11
SIG FIGS CONT.

• Rule 4
• Zeros at the end of a number and to the right of
  a decimal point are always significant.
• Examples 86.0 46.00 1.010
• Rule 5
• When a number is counted or defined within a
  system of measurement, there is an infinite
  amount of significant digits.
• Examples 11 students 100 cm 1 m

12
COUNT THE SIG FIGS
24 mL
3001 g
0.0320 m3
6.4 x 104 molecules
560 kg
13
SIG FIGS Addition and Subtraction
The answer cannot have more digits to the right
of the decimal point than any of the original
numbers.
14
SIG FIGS Multiplication and Division
The number of significant figures in the result
is set by the original number that has the
smallest number of significant figures
4.51 x 3.6666 16.536366
_______
6.8 112.04 0.0606926
_______
15
FACTOR LABEL METHOD

1. Determine which unit conversion factor(s) are
   needed
2. Carry units through calculation
3. If all units cancel except for the desired
   unit(s), then the problem was solved correctly.

How many mL are in 1.63 L?
1 L 1000 mL
16
The speed of sound in air is about 343 m/s.
What is this speed in miles per hour?
1 mi 1609 m
meters to miles
seconds to hours
1 min 60 s
1 hour 60 min
17
Important things to consider when solving
problems and performing experiments.
18
Volume SI derived unit for volume is cubic
meter (m3)
1 L 1000 mL 1000 cm3 1 dm3
1 mL 1 cm3
19
Matter - anything that occupies space and has
mass.
mass measure of the quantity of matter SI unit
of mass is the kilogram (kg)
weight force that gravity exerts on an object
20
Density SI derived unit for density is kg/m3
1 g/cm3 1 g/mL 1000 kg/m3
For Water 1g/mL
m d x V
21.5 g/cm3 x 4.49 cm3 96.5 g
21
K 0C 273.15
273 K 0 0C 373 K 100 0C
32 0F 0 0C 212 0F 100 0C
22
Convert 172.9 0F to degrees Celsius.
23
Graphing
Distance vs. Time
Line of Best Fit
Dependent Variable
Independent Variable
24
Accuracy how close a measurement is to the true
value Precision how close a set of measurements
are to each other
25
Percents and Percent Error

• Percent Error

Measured Value
- Accepted Value
X 100
Accepted Value
Example The mass of a compound measured in a lab
was 25.0 grams. The accepted value for this
compound is 24.5 grams. Calculate the percent
error.
- 24.5 g
25.0 g
X 100
2.04
24.5 g
26
Scientific Method
27
SCIENTIFIC METHOD

• logical approach to solving problems
• Observation
• Problem
• Hypothesis
• Experiment
• Data
• Analysis
• Conclusion

28
You have 15 seconds to count how many letter Fs
you see in the following statement.
29
FEATURE FILMS ARE THE RESULT OF YEARS OF
SCIENTIFIC STUDY COMBINED WITH THE EXPERIENCES OF
YEARS.
30
Observations

• Qualitative quality, non-numeric terms
• Quantitative quantity, numerical description

31
How observant are you?!?
32
MATTER

• Matter anything that occupies space and has mass

33
State of Matter Volume Shape Density Compressibility Motion of Molecules
Gas
Liquid
Solid
34
Three States of Matter
Plasma
35
Phase Changes
liquid
gas
solid
36
phase diagram summarizes the conditions at which
a substance exists as a solid, liquid, or gas.
Phase Diagram of Water
37
Phase Diagram Points

• critical point
• above this point a substance becomes a
  supercritical fluid
• critical temperature (Tc) temperature above
  which the gas cannot be made to liquefy, no
  matter how great the applied pressure.
• critical pressure (Pc) minimum pressure that
  must be applied to bring about liquefaction at
  the critical temperature.
• triple point
• point at which all three phases coexist

38
(No Transcript)
39
Classification of Matter

• Pure Substance form of matter that has a
  definite composition and distinct properties
• 2. Mixture combination of two or more substances
  in which the substances retain their own
  identities.

water, ammonia, sucrose, gold, oxygen

• mixed together physically
• can usually be separated

40
Types of Mixtures

1. Homogenous mixture composition of the mixture
   is the same throughout.

1. Heterogeneous mixture composition is not
   uniform throughout.

1.4
41
Mixture Pictures
42
Types of Mixtures

• solution mixture that remains uniformly mixed
• solute part of the mixture that gets dissolved
• solvent part of the mixture that does the
  dissolving
• suspension mixture where visible particles
  settle
• colloid mixture where particles are unevenly
  distributed but do not separate, positive Tyndall
  Effect

43
Hom/Het? Soln/Susp/Coll?

• Fog ____________ ___________
• Paint ____________ ___________
• Syrup ____________ ___________

44
Physical means can be used to separate a mixture
into its pure components.
1.4
45
Methods of Separation
PASTA/WATER
SAND/IRON FILINGS

• Strainer
• Filtration
• Physical

• Evaporation
• Centrifuge
• Distillation

SALT /WATER
SAND/WATER
BLOOD
FOOD COLORING/WATER
46

• Element
• all atoms are the same
• cannot be broken down by physical or chemical
  means
• 114 elements named on the Periodic Table
• 83 elements occur naturally on Earth
• gold, aluminum, lead, oxygen, carbon
• many elements have been created by scientists
• technetium, americium, seaborgium

47

• Compound
• 2 or more elements combined
• Cannot be broken down by physical means
• Can be broken down by chemical means
• Appears different from original elements
• Fixed ratios in definite proportions

48
(No Transcript)
49
PHYSICAL AND CHEMICAL CHANGES
50
Physical Properties and Physical Changes

• physical property characteristic that can be
  observed or measured without changing the
  identity of the substance.
• melting point, boiling point, density
• physical change change in a substance that does
  not involve a change in the identity of the
  substance.
• grinding, cutting, melting, and boiling

51
Physical Properties

• Intensive INDEPENDENT of amount of matter
  present (sample size)
• Example density, color, melting point
• Extensive DEPENDENT on the amount of matter
  present (sample size)
• Example mass, length, volume

52
Chemical Properties and Chemical Changes

• chemical property a substances ability to
  undergo changes that transform it into different
  substances
• Example combustibility, reactivity
• chemical change change in which one or more
  substances are converted into different
  substances
• Example rusting, cooking food

53
Evidence of a Chemical Change

• Color change
• Temperature change
• Production of a gas
• Change in odor
• Formation of a precipitate
• Precipitate insoluble solid that separates out
  of solution

54
Physical or Chemical?
hydrogen gas burns in oxygen gas to form water
Remember
physical change does not alter the composition or
identity of a substance.
chemical change alters the composition or
identity of the substance(s) involved.