Year 9 Chemistry Revision

A single atom

A pure substance made of one type of atom

Two or more atoms held together by chemical bonds

A mixture of different substances

Change in color

Formation of a gas

Change in shape only

Production of heat

Liquid

Solid

Gas

Plasma

Boiling water

Burning wood

Folding paper

Rusting iron

They remain the same but move to new positions

They change into different particles

They disappear

They combine to form a new substance

The composition of the iron changes

The shape of the iron changes but it remains iron

A new substance is formed

The iron melts

Change in colour

Change in temperature

Change in shape

Production of light

Products

Reactants

Solvents

Mixtures

Matter can be created or destroyed in a closed system.

Matter can only be transformed, not created or destroyed, in a closed system.

The mass of products is always greater than the mass of reactants.

The total mass of a system can change during a chemical reaction.

The total mass of the substances

The number of atoms of each element

The volume of the substances

The color of the substances

1

2

3

6

1

2

5

10

1

3

6

18

Coefficient

Subscript

Synthesis

Decomposition

Displacement

Synthesis

Decomposition

Displacement

Synthesis

Decomposition

Displacement

Absorbed from the surroundings

Released to the surroundings

Stored in bonds of products

Destroyed

Energy is released and the temperature of surroundings increases.

Energy is absorbed and the temperature of surroundings decreases.

The reaction is endothermic.

The reaction is exothermic.

Red

Blue

The maximum energy particles can have

The energy needed to break bonds and start the reaction

The energy released when bonds form

The total energy of the products

Energy must always be absorbed

The temperature must be very high

Particles only need to touch each other

Particles must collide with enough energy and the correct orientation

Particles move slower and collide less often

Particles have more energy, so more collisions are successful

Activation energy increases

The particles are larger

It lowers the activation energy

It reduces the surface area for collisions

It increases the surface area for collisions

It cools the particles

It increases the number of collisions

It lowers the activation energy needed

It is used up during the reaction

Decreasing the concentration of reactants

Decreasing the surface area of a solid reactant

Increasing the concentration of reactants

Lowering the temperature