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For more on Mixtures (Solutions, Suspensions, Emulsions,
Colloids ) A
solution is a mixture of one substance dissolved in another so the properties
are the same throughout. A solution is composed of a solute and the solvent. The
solute is the substance being dissolved and the solvent is the part of the solution
that does the dissolving. The solute is of molecular size. Examples
of Solutions:
| | | | Gas | Liquid | Solid |
| | Gas | Oxygen
and other gases in nitrogen (air) |
Water
vapor in air (humidity) | The
odor of a solid -- molecules of that solid being dissolved in the air |
| Liquid | Carbon
dioxide in water (carbonated water) | Ethanol
(common alcohol) in water; various hydrocarbons in each other (petroleum) * | Sucrose
(table sugar) in water; sodium chloride (table salt) in water |
| Solid | Hydrogen
dissolved to palladium | Water
in activated charcoal | Steel,
Brass, other metal alloys | * Two
liquids that are soluble are said to be miscible in one another. Strength
of Solutions The
solubility is the amount of solute that be be dissolved in a given amount of solvent
at any one temperature. A solution is said to be unsaturated as long as more solute
can be dissolved. Dilute
or Weak Solution - only a small amount of solute compared to solvent. Concentrated
Solution - A relatively large amount of solute to solvent. Saturated
Solution --At this point, the concentration of the solute in solution is the
maximum possible under the existing conditions (temperature and pressure). A solution
is saturated when no more solute can be dissolved at the current temperature.
A saturated solution is one in which the dissolved and undissolved solutes are
in equilibrium. Supersaturated
Solution -- a solution that contains more dissolved substance than does a
saturated solution; the solution is not in equilibrium with the pure substance.
Examples of supersaturated solutions are carbonated water, Water
is the Universal Solvent Although
water is sometimes called the universal solvent, there are many things it cannot
dissolve. For example water and oil do not mix. We say oil is immiscible
in water. What
makes water such a good solvent? Water
is a good solvent due to its polarity. The solvent properties of water are vital
in biology, because many biochemical reactions take place only within aqueous
solutions When
an ionic or polar compound enters water, it is surrounded by water molecules.
The relatively small size of water molecules typically allows many water molecules
to surround one molecule of solute. The partially negative dipoles of the water
are attracted to positively charged components of the solute, and vice versa for
the positive dipoles. For more on this topic see: Why
is water such a good solvent?
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