| A | B |
|---|
| calcium carbonate | limestone |
| sulphur dioxide | made by volcanoes and burning fossil fuels |
| oxides of nitrogen | contain oxygen and nitrogen |
| pollution | man made substances that damage the environment |
| air quality | the level of pollution in the gases we breathe |
| hydrocarbons | contain only carbon and hydrogen |
| carbon monoxide | toxic gas containing carbon and oxygen |
| ozone | gas produced by the action of sunlight on oxygen |
| pH | measure of acidity and alkalinity |
| acid rain | has pH less than 7 and destroys forests |
| sediment | rock particles that have been deposited by a river |
| vegetation | plant life |
| humus | animal and plant remains found in soil |
| greenhouse effect | the build up of heat in the earth's atmosphere |
| global warming | increase in average temperatures due to changes in the levels of gases in the atmosphere |
