A mixture contains different substances that are not chemically joined to each other. For example, a packet of sweets may contain a mixture of different coloured sweets. The sweets are not joined to each other, so they can be picked out and put into separate piles.
A mixture of iron filings and sulfur powder can easily be separated using a magnet. The iron filings are attracted to the magnet but the sulfur powder is not.
Dissolving is one way to make a mixture. For example, when salt is stirred into water, the salt dissolves in the water to make salt solution. In a solution:
In salt solution, salt is the solute and water is the solvent. The particles of solute and solvent are completely mixed together.
Diffusion is another way to make a mixture. Particles of different substances mix together during diffusion. This happens:
Diffusion explains why the smell of cooking spreads through the house, and why a drop of paint spreads on its own through a jar of water.
You can find out more about diffusion in this Physics study guide.