Chapter 8: Matter and Changing of State

Materials come in three different forms-solid, liquid and gas.
Which state something is at a certain temperature depends on how strong the forces of attraction are between the particles of the material
How strong the forces are depends on three things * The material(the structure of the substance, and the type of bonds holding the particles together) * The temperature * The pressure

Particles theory:

Solids * In solids, there are strong forces of attraction between particles, which holds them close together in fixed positions to form a very regular lattice arrangement * The particles don’t move from their positions, so all solids keep a definite shape and volume and don’t flow like liquids * The particles vibrate about their positions, the hotter the solid becomes, the more they vibrate(causing solids to expand slightly when heated)
Liquids * In liquids, there’s a weak force of attraction between the particles * They’re randomly arranged and free to move * Definite volume but don’t keep a definite shape * Constantly moving with a random motion, hotter the liquid faster they move
Gases * In gases, the force of attraction is very weak * Free to move and far apart * Constantly moving with a random motion

Physical changes don’t change the particles-just their arrangement or their energy * When a solid is heated, its particles gain more energy * This makes the particles vibrate more, which weakens the forces that hold the solid together * At a certain temperature, called the melting point the particles have enough energy to break free from their positions, called melting and turns a solid to an liquid * When a liquid is heated, again the particles get even more energy * This energy makes the particles move faster, which weakens and breaks the bonds holding the liquid together * At a certain temperature, called the boiling point, the particles have enough to break their bonds * This is evaporating, and the liquid becomes a gas * As a gas cools, the particles no longer have enough energy to overcome the forces of attraction between them * Bonds form between the particles * At the boiling point, so many bonds have formed between the gas particles that the gas becomes a liquid, this is called condensing * When a liquid cools, the particles have less energy so move around less * There’s not enough energy to overcome the attraction between the particles, so more bonds form between them * At the melting point, so many bonds have formed between the particles that they’re held in place * The liquid becomes a solid and this is called freezing