Solutions are formed when two or more substances are mixed on
an atomic or molecular scale to form one state only. A solution
can be composed of liquids, gases or solids, but the resulting
solution must be one state.
Sea water is a typical solution. It is formed when solid salt
is dissolved in liquid water to form the liquid "salt water"
Muddy water is not a solution; it is a simple mixture. Solid
dirt and liquid water have been mixed, but the two have not mixed
on a molecular scale to form one state. The dirt remains as relatively
large clumps in the mixture.
Clean air is a solution of many different gases, but polluted
air is not a solution. It is a mixture of larger bits of solids
and liquids in the air gases.
Test for solutions
The simple test for a liquid or gas solution is to look at it. If light
passes through, even if it is coloured, then the particles are very small
and it is a solution. If you cannot see through it clearly and it looks
cloudy or dirty, then at least some of the particles are relatively
large clumps and it is a mixture, not a solution.
Solutions are physical mixtures of two or more substances, the parts
of which are not chemically combined and can be separated relatively
easily. For example, the salt can be separated from the water in sea
water by warming the solution and evaporating off the water, leaving
the solid salt behind. The salt and the water themselves are chemicals
and cannot be further separated without applying chemical means.
Types of solutions
Solutions fall into different categories depending on what states are
mixed and the state of the resulting solution. Some common examples
- Gas + gas to give a gas solution air
- Gas + liquid to give a liquid solution soda water
- Liquid + liquid to give a liquid solution alcoholic drinks
- Solid + liquid to give a liquid solution salt water
- Solid + solid to give a solid solution metal alloys
Solutes and solvents
The components of solutions are divided into two types, solutes and
solvents. Generally, the solute is the substance in the lesser quantity
in the solution and the solvent is the substance in the greater quantity.
In sea water there is a lot more water than salt, so the water is the
solvent and the salt is the solute. The solute is said to dissolve in
the solvent to form the solution.