This activity is designed for students aged 11-14. It can be used to reinforce work on the reactions of carbonates with acids as well as the chemical weathering of rock.

The chemical attack on limestone by rain that is naturally acidic (containing dissolved carbon dioxide) and ‘acid rain’ (rain that is more acidic because of dissolved pollutants such as sulfur dioxide and nitrogen oxides).

If you teach primary science, see the headings below to find out how to use this resource:

Skill development

Children will develop their working scientifically skills by:

  • Drawing conclusions and raising further questions that could be investigated, based on their data and observations.
  • Using appropriate scientific language and ideas to explain, evaluate and communicate their methods and findings.

Learning outcomes

Children will:

  • Compare and group together different kinds of rocks on the basis of their appearance and simple physical properties.

Concepts supported

Children will learn:

  • That rocks have different properties, often as a result of the type of rock they are and how they are formed.
  • That rocks are natural materials whereas bricks are man-made (also referred to as manufactured).

Suggested activity use

This activity can be used as a whole-class investigation into the properties of rocks, in particular limestone. This leads on to children being able to make suggestions about the properties and possible uses of rocks, based on their findings from this experiment. The activity can lead onto subsequent investigations into testing other properties of rocks, such as hardness, permeability and reaction with acids.

Practical considerations

Equipment for the activity will need to be sourced prior to the lesson, including universal indicator and limestone. Also, if you are progressing on to the properties of different types of rocks, a selection of other rocks will be needed.

In order for children to understand what is happening, prior knowledge of the colours of universal indicator in the presence of acidic, alkaline and neutral solutions is needed. Also, children require knowledge of gases, in particular carbon dioxide and oxygen, as well as understanding what we breathe in and breathe out.

If not carefully managed, you may introduce or reinforce the misconception that carbon dioxide is an ‘acidic gas’, whereas in fact it produces an acidic solution when dissolved in water.

As with all experiments, a thorough risk assessment should be carried out along with other health and safety considerations. It must be stressed to children that they need to blow out through the straws and not suck in.

You should note that the national curriculum links at the beginning of the document are now out of date.