Edexcel IGCSE Chemistry - Principles of Chemistry, States of Matter and Solubility

The three states of matter are solid, liquid, and gas.
- Solid: Least energy; particles vibrate and are arranged closely in a regular structure.
- Liquid: More energy than solids but less than gases; particles are close but randomly arranged and can move.
- Gas: Most energy; particles are far apart with random arrangement and move freely.

Interconversions occur through physical changes (not chemical).
- Melting: Solid to liquid at the melting point (gain kinetic energy, particles move more).
- Freezing: Liquid to solid at the melting point (lose kinetic energy, particles become more closely arranged).
- Boiling: Liquid to gas at the boiling point (gain kinetic energy, particles spread further apart).
- Condensing: Gas to liquid (lose kinetic energy, particles become closer and more regularly arranged).

Diffusion:
- Movement of particles from an area of high concentration to low concentration.
- Does not occur in solids because particles cannot move freely.
- Example: Coloured solutions diluted by adding water, allowing colour particles to diffuse and mix.

Solvent: Liquid in which a solute dissolves.
Solute: Substance that dissolves in a liquid.
Solution: Mixture formed from a solute dissolving in a solvent.
Saturated Solution: Solution where no more solute can dissolve in the solvent.

Solubility: Expressed in g per 100 g of solvent; indicates how much solute can dissolve.
Solubility Curves:
- Generally, solubility of solids increases with temperature.
- Solubility of gases increases with pressure.
- Any mass below the curve indicates an unsaturated solution.
- Any mass above the curve indicates a supersaturated and unstable solution.

Investigate the solubility of a solid in water at a specific temperature to understand the concepts better.