States of matter

Solid, liquid or gas?

​Matter can exist in one of three fundamental states: Solid, Liquid or Gas

Here we consider the way in which these three states behave

We see how matter can be converted from one state into another and we introduce the terms used for these changes. 

Evaporation, condensation, melting, freezing , sublimation and deposition.

It is important to be able to  recall and explain the properties and behaviour of solids liquids and gases.

We also look at the way in which some substances dissolve in others and consider the terms :

Solute, solution, dissolve, soluble, saturated solution

Students Should:

1.1 understand the three states of matter in terms of the arrangement, movement and
energy of the particles
1.2 understand the interconversions between the three states of matter in terms of:
the names of the interconversions, how they are achieved, the changes in arrangement, movement and energy of the particles.
1.3 understand how the results of experiments involving the dilution of coloured solutions
and diffusion of gases can be explained
1.4 know what is meant by the terms:
solventsolutesolutionsaturated solution.
1.5C know what is meant by the term solubility in the units g per 100 g of solvent
1.6C understand how to plot and interpret solubility curves
1.7C practical: investigate the solubility of a solid in water at a specific

Three fundamental states of matter 

The three primary states of matter

Properties of the three states

All matter is made up of particles. In solids, liquids and gases, the particles might be ions, molecules or atoms

  • In a solid the particles vibrate but the solid remains in a fixed shape. The solid has a fixed density and cannot be compressed
  • In a liquid the particles have enough energy to move freely and the liquid can therefore flow. A liquid will take up the shape of the container in which it is placed. The liquid cannot easily be compressed.
  • In a gas the particles are widely spaced and move freely. The gas will fill the container in which it is placed. Gases can be compressed.

Heating a material will give energy to its particles and cause them to move more rapidly. Cooling does the opposite. Heating or cooling can therefore cause a material to undergo a change of state.

Naming changes of state.. 

With three principal states of matter there are six possible changes depending on whether we are heating or cooling the substances. These are shown in the table below.

​Heating ​Cooling
​solid/liquid ​melting ​freezing
Can you name processes 1, 2, 3 and 4?
Four changes of state. Which two terms are missing?

Solubility curves 

This chart shows how the solubility of copper sulfate changes with temperature. The trend shows that higher temperatures mean a higher solubility.