Solutions & Solubility

This lesson covers:

  1. What the terms solution, solute, solvent and saturated solution mean
  2. How temperature affects solubility
  3. Solubility curves 

Key terms:

1Solute - the substance that dissolves in a solvent

2Solvent - the liquid that the solute dissolves in

3Solution - the mixture of the dissolved solute and the solvent it is dissolved in

4Saturated solution - a solution in which the maximum amount of solute has been dissolved, so no more solute will dissolve

Solubility and temperature

Solubility is defined as the maximum amount of a substance that will dissolve in a given amount of solvent at a certain temperature.


For example, the maximum amount of NaCl that can dissolve in 100g of water (at 25°C) is 35g, therefore the solubility of NaCl is 35g per 100g of water (at 25°C).

The temperature is important because most substances become more soluble at higher temperatures. We can see this on solubility curves which show how the solubility of a substance changes with temperature. The graph below shows the solubility curve for potassium nitrate (KNO3).

Graph showing solubility curves for potassium nitrate and sodium chloride with temperature.

Some sodium chloride is dissolved in water.

What do we call the sodium chloride?

Saturated solution 

Solution

Solvent

Solute 

0

/

1

Some potassium nitrate is dissolved in ethanol.

What do we call the ethanol?

Solute 

Saturated solution 

Solution

Solvent

0

/

1

Illustration of a beaker with water and undissolved magnesium chloride.

A student keeps adding magnesium chloride to a beaker of water until no more dissolves. At this point we can say that they have a solution.

saturated

0

/

1

Which units do we usually use to measure solubility?

g/dm3

mol/dm3

g/100g

mol/100g

0

/

1

increases / decreases


As the temperature increases, the solubility of most solutes .

increases

0

/

1