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Figure 8
Because the density of ice
is lower than the density of water,
icebergs float on the ocean.
Consider the properties of water, for example. You might think of water as a liquid
(physical property) which is not particularly chemically reactive (chemical property).
You might also find that water has a density of 1.00 g/cm
3
(physical property). These
properties, however, apply only to water at standard temperature and pressure. At
temperatures greater than 100°C, water is a gas (physical property) with a density of
about 0.0006 g/cm
3
(physical property) that reacts rapidly with many different sub-
stances (chemical property). Below 0°C, water is a solid (physical property) with a
density of about 0.92 g/cm
3
(physical property). The lower density of ice accounts for
the fact that icebergs float on the ocean, as shown in
Figure 8
. Clearly, the properties of
water are dramatically different under different conditions.
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Summary
• Four states of matter are solid,
liquid, gas, and plasma.
• Physical properties can be
observed without altering a
substance’s composition.
• Chemical properties describe a
substance’s ability to combine
with or change into one or
more new substances.
• External conditions can affect
both physical and chemical
properties.
Demonstrate Understanding
1.
Create
a table that describes four states of matter in
terms of their properties.
2.
Describe
the characteristics that identify a sample of
matter as a substance.
3.
Classify
each of the following as a physical or a
chemical property.
a.
Iron and oxygen form rust.
b.
Iron is more dense than aluminum.
c. Magnesium burns brightly when ignited.
d. Oil and water do not mix.
e. Mercury melts at
−
39°C.
4.
Organize
Create a chart that compares physical and
chemical properties. Give two examples for each type
of property.
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Module 2 • Matter—Properties and Changes