Any substance with a pH lower than 7. Acid Rain

Any substance with a pH higher than 7. Atmosphere

A highly poisonous gas produced when fuel is burnt. It is mainly emitted from car exhausts. Catalytic Converters

Chemicals used in products like aerosols and fridge. Fossil Fuels

Pollution has increased the Greenhouse Effect by putting more gases that trap heat into the atmosphere. This makes the Earth's temperature go up, and is called Global Warming. Greenhouse Effect

Gases in the atmosphere, which can trap the heat escaping from the Earth, causing the temperature to go up. Industrial Revolution

Neither acidic nor alkaline, with a pH of 7. Nitrogen Oxides

A gas that has no colour or smell. There is a lot of it in the atmosphere and vital for life. Ozone

A layer of ozone high up in the atmosphere, which shields us from the harmful rays of the Sun. Particulate

The pH scale is used to measure the amount of acid in a substance. The lower the number, the higher the amount of acid. Rain below pH 5 is said to be "acid rain". Plankton