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Matter and Measurements
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Chemistry 151: Computer presentations:
If it doesn’t work!!!
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What is Chemistry?
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What is matter?
Anything that has mass and occupies space.
MASS
vs.
WEIGHT
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vs.
MASS
WEIGHT
SCALE
BALANCE
GRAVITY INDEPENDENT
GRAVITY DEPENDENT
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STATES OF MATTER
SOLID
LIQUID
GAS
PLASMA
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MATTER
ELEMENTS
ONE TYPE OF ATOM
COMPOUNDS
TWO OR MORE ATOMS
CHEMICALLY COMBINED
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PURE SUBSTANCES vs. MIXTURES
Element
or compound
2 or more substances
not chemically combined
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Classifying Matter:
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Compounds follow the law of definite (or constant)
proportions.
All molecules of H2O
have 2 H’s and 1 O’s.
This is a fixed number
and not an average!
We also have the law of MULTIPLE PROPORTIONS
Carbon monoxide is CO and
Carbon dioxide is CO2.
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C4H10
C5H12
H2SO4
HNO3
C8H18
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PHYSICAL AND CHEMICAL CHANGES
Physical: changes that occur with no change
in the chemical composition.
Example: Ice melting. (You still have H2O)
Chemical: different chemical substances are formed.
Example: paper burning.
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Scientific Units (SI)
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These symbols all represent numbers, not units!
Go to vacation question presentation.
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Derived Units!
1 mL = 1 cm3 = 1cc
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Accuracy and Precision in Measurements
Accuracy: how close a measurement
is to the accepted value.
Precision: how close a series of
measurements are to one another or
how far out a measurement is taken.
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Significant Figures
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