Chemistry: The Study of Change

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Chemistry is the study of matter and the changes
it undergoes

• Matter is anything that occupies space and has
  mass.
• A substance is a form of matter that has a
  definite composition and distinct properties.

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Classifications of Matter
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The Three States of Matter
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Physical or Chemical?
A physical change does not alter the composition
or identity of a substance.
A chemical change alters the composition or
identity of the substance(s) involved.
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Extensive and Intensive Properties
An extensive property of a material depends upon
how much matter is is being considered.

• mass
• length
• volume

An intensive property of a material does not
depend upon how much matter is is being
considered.

• density
• temperature
• melting point, boiling point

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(No Transcript)
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Density SI derived unit for density is kg/m3
1 g/cm3 1 g/mL 1000 kg/m3
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K 0C 273.15
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Scientific Notation
6.022 x 1023
1.99 x 10-23
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Significant Figures

• Any digit that is not zero is significant
• 1.234 kg 4 significant figures
• Zeros between nonzero digits are significant
• 606 m 3 significant figures
• Zeros to the left of the first nonzero digit are
  not significant
• 0.08 L 1 significant figure
• If a number is greater than 1, then all zeros to
  the right of the decimal point are significant
• 2.0 mg 2 significant figures
• If a number is less than 1, then only the zeros
  that are at the end and in the middle of the
  number are significant
• 0.00420 g 3 significant figures

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More Significant Figures

• How many significant figures do each of the
  following have?
• 1. 7.2100 x 10-3 g
• 2. 0.036653 m
• 3. 72,100 km
• 4. 25.03
• 5. 18 students
• 6. 76.600 kg
• 7. 4.50200 x 103 g
• 8. 3000 nm
• 9. 0.00300 mL

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Significant Figures
Addition or Subtraction
The answer cannot have more digits to the right
of the decimal point than any of the original
numbers.
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Significant Figures
Multiplication or 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
16.5
6.8 112.04 0.0606926
0.061
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Significant Figures
Exact Numbers
Numbers from definitions or numbers of objects
are considered to have an infinite number of
significant figures
The average of three measured lengths 6.64, 6.68
and 6.70?
Because 3 is an exact number
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Chapter 1 In Class Problems

• 1. A pencil is 7.0 inches long. What is its
  length in cm?
• -conversion factor 2.54 cm 1 inch
• 2. A student has entered a 10 km run. How many
  miles is that?
• -conversion factors 1 m 1.094 yds, 1760 yds
  1 mile
• 3. A car is advertised to have a gas mileage of
  15 km/L. Convert to miles/gal.
• -conversion factors 4 qts 1 gal, 1L 1.06
  qts

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More Practice Problems

• 1. Express the following quantities in scientific
  notation
• a. The diameter of a sodium atom, 0.000 000 000
  372 m
• b. The distance from the earth to the sun,
  150,000,000,000 m
• 2. What units do the following abbreviations
  represent?
• a. mg b. ps c. mmol
• 3. Carry out the indicated conversions.
• a. How many grams of meat are in a quarter pound
  hamburger?
• b. How tall (in meters) is the Sears Tower in
  Chicago (1454 ft)?
• c. How large (in square meters) is the land area
  of Australia (2,941,526 mi2)?
• 4. Aspirin has a density of 1.40 g/cm3. What is
  the volume (in cubic centimeters) of an aspirin
  tablet weighing 250 mg? Of a tablet weighing 500
  lbs?
• Some useful conversion factors
• 1 kg 2.2046 lbs 2.54 cm 1 inch 1 km
  0.62137 m

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Answers to Problems

• (a) 3.72 x 10-10 m (b) 1.5 x 1011 m
• (a) micrograms (b) picoseconds (c) millimoles
• (a) 113.4 g (b) 443.1 m (c) 7.61 x 1012 m2
• (a) 0.178 cm3 (b) 1.62 x 105 cm3