8.1-States of Matter

The three states of matter-solid, liquid and gas

• 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

State symbols tell you the state of a substance in an equation

• Solid-s

• Liquid-l

• Gas-g

• Aqueous(means dissolved in water)-aq

8.2-Changing State

Substances can change from one state to another

• 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