Gases are gases because their molecules are relatively far
apart from one another and they are moving at high speeds in a random motion. There is
very little attraction between the individual particles. If you could look at the
interface between air and water you would see some air molecules (gases) striking the
surface of the water while others at the same time are exiting from the surface of the
water. Water has a relatively high surface tension because of the hydrogen bonding
between the water molecules so the air molecules (gases) have to strike the surface with
enough energy to penetrate the surface layer and go into the bulk
water.
Once a gas molecule enters the water the only thing
holding it there are weak intermolecular forces between the gas molecule and the water
molecules and the surface tension of the water molecules at the
surface.
As the water heats up the water molecules heat up
- causing the hydrogen bonds to break and reform more rapidly - and the gas molecules
also heat up - gaining kinetic energy. The increased kinetic energy results in the gas
molecules moving more rapidly, allowing them to escape from the liquid more
easily.
For most solids, as the water warms it expands -
increasing in volume - producing a larger space between the water molecules for the
solid solutes.
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