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Elements, Compounds and Mixtures
Solid, Liquid and Gas.
Any substance may exist as solid, liquid or gas.
If a solid is heated, it
will melt to become a liquid.
The temperature at which it
melts is called its melting point.
If the liquid is then cooled, it will freeze to become a solid again.
The temperature at which it
freezes is called its freezing point.
The melting point and the freezing point is the same for the same
substance.
Similarly, if a liquid is heated it
will boil to become a gas.
The temperature at which it
boils is called its boiling point.
If the gas is then cooled, it will condense to become a liquid again.
A gas will condense at its boiling
point.
Sometimes a heated solid will
turn into a gas without becoming a
liquid.
This is called sublimation.
Examples of solids which sublime are iodine and carbon dioxide.
The figure below shows
interconverting
from
one state
to another by heating or cooling.
Red arrows involve heating, blue arrows
involve cooling.
The state of a substance
(whether it is solid, liquid or gas)
depends on its temperature, the
RFM of the
particles
and the forces of attraction
between the particles.
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Copyright © 2008 Dr. Colin France. All Rights Reserved.
