A solution is formed when a solid DISSOLVES in a liquid. The solid that has been dissolved is called the solute. The liquid used to make the solution is called the solvent.
Example: When salt is dissolved in water then salty water is made
The solute is salt. The solvent is water.
SALT + WATER = SALTY WATER
(SOLUTE) + (SOLVENT) = (SALT
SOLUTION)
Not all solids dissolve by the same amount:
Salt dissolves easily so is said to be soluble in cold
water.
Lime (calcium hydroxide) is difficult to dissolve so is slightly soluble
in cold water.
A substance like sand does not dissolve so is insoluble
in water.
Factors (variables) which effect the amount of solid which
dissolves:
The quantity of solid being used.
The volume of water
The rate of stirring
The size of the particles in the solid
The temperature of the water.
How to speed up the time taken to dissolve a solid:
Use warm water
Stir the solution quicker
Grind the solid to make the
particles smaller.
How to tell if a liquid is pure or contains a solute:
Place one or two drops of the filtrate on to a clean watch glass (or
microscope slide)
Let the water evaporate and see if there is any residue.
If there is it means that some of the solid did dissolve.
Useful terms to know
Mixture:
Something that can be SEPARATED into two (or more) different substances. eg air,
sea water, earth, orange juice. Something that can be SEPARATED into two (or
more) different substances. eg air, sea water, earth, orange juice.
Pure:
A material is pure
if it contains only one chemical substance and so cannot be separated further A
material is pure if it contains only one chemical substance and so cannot be
separated further.
Filtrate:
The clear liquid that has
been filtered. The clear liquid that has been filtered.
Residue:
The solid left behind after an experiment (eg the solid left in the filter
paper). The solid left behind after an experiment (eg the solid left in the
filter paper).
Filtration:
The process used to separate
a solid (or suspension) from a liquid. The process used to separate a solid (or
suspension) from a liquid.
Suspension:
Very fine particles of solid mixed with a liquid. If the solid is in suspension
the water will often look cloudy. eg flour and water shaken together. Very fine
particles of solid mixed with a liquid. If the solid is in suspension the water
will often look cloudy. eg flour and water shaken together.
NOTE: in a suspension the solid has not dissolved but in a
solution it has.
Soluble:
Can dissolve eg Salt is
soluble in water
Insoluble:
Cannot dissolve eg sand is
insoluble
in water
Solvent:
The liquid that is
used to make a solution. Water and alcohol are both examples of good solvents
Solute:
A substance that has been dissolved
in a solution
Eg Salt can be dissolved in water to make salty
Salt is the solute and water is the solvent
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A solution is formed when a solid DISSOLVES in a liquid.