Matter and Measurements

1
Chapter 1

• Matter and Measurements

2
Chemistry

• the study of the composition, structure, and
  properties of substances and the changes they
  undergo

3
Matter

• Matter has mass and takes up space
• Mass quantity of matter
• States of Matter
• Solid definite shape and volume
• Liquid definite volume, takes shape of
  container
• Gas takes shape and volume of container
• Plasma charged particles in gaseous state

4
Classifying Matter

• Pure substance single substance (every particle
  of the substance is the same)
• Element cant be broken down by ordinary
  chemical reaction
• smallest particle atom
• Ex. - copper
• Compound atoms of more than one element held
  together by chemical bonds, can be broken down by
  chemical reaction
• smallest particle molecule or formula unit
• Ex. - water
• Mixture combination of two or more substances
• Homogeneous also known as solution, uniform
  throughout
• Ex. apple juice
• Heterogeneous composition varies, looks
  different throughout sample
• Ex. vegetable soup

5
Metric Prefixes You Should Know

• nano 1/1000000000 or 10-9
• micro 1/1000000 or 10-6
• milli 1/1000 or 10-3
• centi 1/100 or 10-2
• kilo 1000 or 103

6
Temperature Conversions - C and F

• Fahrenheit to Celsius
• C (F - 32)(5/9)
• Ex. Convert 95F to Celsius.
• C (95 32)(5/9) Remember order of
  operations!
• C (63)(5/9) 35C
• Celsius to Fahrenheit
• F (9/5)C 32
• Ex. Convert 46C to Fahrenheit.
• F (9/5)46 32 Remember order of operations!
• F 82.8 32 114.8F

7
Temperature Conversions - C and K

• Kelvin to Celsius
• C K 273.15
• Ex. Convert 330.55 K to Celsius.
• C 330.55 273.15
• C 57.40C
• Celsius to Kelvin
• K C 273.15
• Ex. Convert 22.00C to Kelvin.
• K 22.00 273.15
• K 295.15 K

8
Temperature Conversions - F and K

• Always use Celsius as an intermediate for these
  conversions.
• Fahrenheit to Kelvin
• Convert Fahrenheit to Celsius
• Convert Celsius to Kelvin
• Kelvin to Fahrenheit
• Convert Kelvin to Celsius
• Convert Celsius to Fahrenheit

9
Taking Measurements

• There is uncertainty in every measurement. You
  should record all significant figures as follows
• When using a digital apparatus, record all digits
  displayed.
• When using a graduated apparatus (a ruler, etc.),
  record all digits that are known for sure and the
  first estimated digit.

10
Determining the Number of Significant Figures in
a Measurement

• Nonzero digits are significant.
• 178 (3 significant figures)
• Zeros between nonzero digits are significant.
• 3045 (4 sigfigs)
• Leading zeros are not significant.
• 0.0373 (3 sigfigs)
• Trailing zeros with a decimal are significant.
• 50.00 (4 sigfigs)
• Trailing zeros without a decimal are not
  significant.
• 7000 (1 sigfig)

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How many sigfigs?

• 85.00
• 0.00637
• 80,003
• 6,200,000
• 30.0
• 0.03100

Answer 4
Answer 3
Answer 5
Answer 2
Answer 3
Answer 4
12
Addition/Subtraction

• Calculations based on measurements must reflect
  the uncertainty in those measurements.
• Answer should have the same number of decimal
  places as the measurement with the fewest decimal
  places.
• 38.1
• -17.43
• 20.67

Fewest decimal places (1)
So round answer to 1 decimal place 20.7
13
Sample Problems

• 21.89 17.3 5.432
• 74 2.1
• 34.71 23.9 52.33
• 913.46 8.222 417

Answer 44.6
Answer 72
Answer 6.3
Answer 1339
14
Multiplication/Division

• Answer should have the same number of sigfigs as
  the measurement with the fewest sigfigs.
• 154.9
• x 6.21
• 961.929

Fewest sigfigs (3)
So round answer to 3 sigfigs 962
15
Sample Problems

• 3.4 x 22.1
• 8000/4.22
• 37.0 x 8.90 x 0.030
• 98.0/5.547

Answer 75
Answer 2000
Answer 9.9
Answer 17.7
16
Dimensional Analysis (Conversion of Units)

• Conversion factor -- ratio of two different
  things that are equal to each other
• 9 players 1 team
• Possible conversion factors 9 players/1 team
• or 1 team/9 players
• Use the conversion factor to convert from one
  unit to another. Cancel units just like you
  would xs or ys in algebra. The units that
  dont cancel are the units of the final answer.
• (18 players)(1 team/9 players) 2 teams
• 18 players and 2 teams are the same thing

17
Sample Problems

• Use the following equalities to make conversion
  factors to solve the problems
• 3 violet 2 red 4 red 1 green 5 violet
  2 brown
• How many green are equal to 4.45 red?
• (4.45 red)(1 green/4 red) 1.11 green
• Notice that the conversion factor is chosen so
  that the unit in the numerator on the left is the
  same as the unit in the denominator on the right.
  The numbers in the conversion factor must stay
  with the appropriate units from the equality.
• How many brown are equal to 3.9 red?
• (3.9 red)(3 violet/2 red)(2 brown/5 violet)
  2.34 brown
• Since there is no equality directly relating
  brown and red, two conversion factors must be
  used.

18
Sample Problems

• Use the same process for familiar units
• 1 m 1000 mm
• How many millimeters in 5.7 m?
• (5.7 m)(1000 mm/1 m) 5700 mm
• How many meters in 834 mm?
• (834 mm)(1 m/1000 mm) 0.834 m
• DONT JUST MULTIPLY OR DIVIDE! YOU ARE MUCH MORE
  LIKELY TO GET IT WRONG! SET IT UP FIRST!!

19
Properties of Substances

• Based on Quantity
• Intensive properties dont matter how much of
  substance is present
• Boiling point
• Density
• Extensive properties depend on how much is
  present
• Mass
• Length

20
Properties of Substances

• Based on Change
• Physical Properties can be observed without
  changing substance
• Ex. the length of a piece of paper can be
  measured without changing the piece of paper
• Chemical Properties substance must be changed
  to observe property
• Ex. to determine whether the paper is
  flammable, the paper must be burned it is
  changed to something else when it is burned

21
Physical Change

• Physical change a change that does not change
  substances identity
• Its still the same stuff.
• Examples
• Mowing lawn
• Tearing paper
• Breaking glass

22
Chemical Change

• Chemical change changes identity of substance
• Indications of chemical change
• Heat and/or light
• Color change
• Formation of Gas or Precipitate
• Examples
• Burning wood
• Rusting metal

23
Density

• Mass per unit volume
• density mass/volume
• (g/mL or g/cm3)
• Slope of mass vs. volume curve is equal to
  density

24
Sample Problems

• A solution has a mass of 12.56 g and a volume of
  9.8 mL. What is the density?
• Density mass/volume 12.56 g/9.8 mL 1.3
  g/mL
• A sample of metal has a density of 11.35 g/mL.
  If its mass is 4.78 g, find its volume.
• Volume mass/density (4.78 g)/(11.35 g/mL)
  0.421 mL
• Get used to setting things up now! On the AP
  exam, you will not get credit for correct answers
  if you do not show how you got them. You will
  also lose points for missing units in some
  cases, you will not receive any credit for an
  answer with missing units!

25
Solubility

• Measure of the amount of solute that can dissolve
  in a given amount (usually 100 g) of solvent
• Saturated maximum amount of solute dissolved in
  given amount of solvent at given temperature
• Unsaturated less than maximum amount of solute
  dissolved in given amount of solvent at given
  temperature
• Supersaturated more than maximum amount of
  solute dissolved in given amount of solvent at
  given temperature
• Doesnt sound possible, but the solution is
  heated to allow more solute to dissolve. It is
  then cooled to the desired temperature. It now
  contains more solute than it could have if you
  had just tried to dissolve solute at the desired
  temperature and had not heated it.

26
Color

• Copper solutions are blue.
• Iron solutions are yellow.