Solutions

  • 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:

  1. Use warm water 
  2. Stir the solution quicker 
  3. Grind the solid to make the particles smaller.

How to tell if a liquid is pure or contains a solute:

  1. Place one or two drops of the filtrate on to a clean watch glass (or microscope slide)
  2. Let the water evaporate and see if there is any residue.
  3. 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 water
Salt + water = salt solution
Salt is the solute and water is the solvent
Salt is soluble in water