Physical and Chemical Change

Chemical change Definition

A chemical change or chemical reaction has occured whenever a new substance has formed.

Physical Change Definition

A physical change occurs when a substnace changes, but no new substance is formed.

Precipitation reaction

A solid is formed when two solutions are mixed together this is called a precipitate. It starts as a fine powder that then settles out into a layer of sediment at the bottom of a clear solution. Precipitates are insoluble.

The four basic types of chemical reactions

Combination reactions, decomposition reactions, precipitation reactions, combustion reactions

Ways the rate of reaction can be affected?

Concentration of reactants, temperature, surface area, catalysts and enzymes.

Decomposition reaction

One substance breaks up into a number of smaller ones.

Combination reaction

Reactants combine to form a single new substance.

products Definition

The substances you end up with.

Reactants definition

The substances you start off with.

Examples of substance changes

When a substance changes colour, a change in temperature, the production of light or bubbles. When a substance is cooked, burnt, exploded, ripening or rotting.

Examples of substance changes

When a substance changes of shape, is broken or crushed, is dissolved, is mixed with other substances, changes its state by melting, evaporating, freezing or condensing.

Combustion reaction

When you burn or explode something. A substance reacts with oxygen usually from the air around it.