Changes (t2-t3)

Solid

Is a substance, has fixed shape and volume

Liquid

A substance has fixed volume but flows to take the shape of the bottom of its container

Gas

A substance that has no fixed shape or volume but expands to fill the space in container

Sublimation

solid to gas

Deposition

Gas to solid

condensation

Gas to liquid

Evaporation

Liquid to gas

Solidification

Liquid to solid

Melting

Solid to liquid

Physical changes

Change size, shape, reversible, no new substance is created, can change state eg dissolving sugar in water if evaporate water sugar remain, same particles remain after change, particles move to new position may slow down or speed up

Heating particles

Atoms move faster and gain energy

Chemical changes

New substances formed, change in colour or temp, formed new substance produces sound or light or releases odour. Release or absorb heat it can’t be reversible and the disappearance or appearance of a solid

Mixing

Mixing 2 liquids don’t produce a new substance the particles remain the same. Substances can be separated again by evaporation etc

Solution

Dissolve one substance in another, molecules are still present and no new substance is produced

grinding cacao beans into a liquid

Physical change

Roasting cocoa beans in an oven

Chemical change

Souring milk

Chemical change

What happens to molecules when a chemical change occurs

The original molecules, collide break apart, new chemical bonds are made and rearrange

Wheat happens to molecules when a physical change occurs

The molecules remain exactly the same only spacing movement or arrangement changes

Sodium+ chlorine

Sodium chloride

copper + oxygen

Coper oxide

Iron + Sulfur

Iron sulfide

Exothermic

The reaction is hotter than surroundings

Endothermic

Something cool’s down because it takes heat out of environment