1a) States of Matter

Solids:

• Have strong forces of attraction between particles which holds them close together in fixed positions to form a very regular lattice arrangement
• Particles vibrate

Liquids:

• Have weak forces of attraction between particles and are randomly arranged so they don't have a definite structure/shape
• They are constantly moving in a random motion

Gases:

• Are free to move because the forces of attraction are very weak
• The particles travel in a straight line
• Random motion
• Don't have a definite shape   

Changes to the arrangement or energy of particles 

Movement of particles 
Diffusion: molecules move and spread randomly due to bumping into each other
Lighter particles travel faster