Students use syringes to make samples of sedimentary rock from sand both with and without cementing agents.

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:

  • Selecting and planning the most appropriate ways to answer science questions, recognising and controlling variables where necessary, including:
    • Observing changes over different periods of time.
  • Asking their own questions about scientific phenomena.
  • 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.
  • Describe in simple terms how fossils are formed when things that have lived are trapped within rock.

Concepts supported

Children will learn:

  • What fossils are and why they are only found in sedimentary rocks.
  • That the different types of rocks have different properties often due to the way they are formed.
  • How sedimentary rocks are formed.

Suggested activity use

This activity can be used with younger children as the basis of a whole-class demonstration of how rocks are formed.

With older children, this can be carried out as an investigation into the formation of sedimentary rocks.

Practical considerations

When using this activity care needs to be taken not to introduce or embed several misconceptions, including:

  • that all types of rocks are formed the way being modelled;
  • that all sedimentary rocks are made from the same particles; and
  • that sugar and salt are cementing agents in the natural world.

Also, please be aware that it will take approximately 2 days for the homemade rocks to ‘set’.

To understand what is being modelled, children may need prior knowledge of the weathering process, as well as sedimentation in water. What’s more, it may be difficult to understand cementation.

The plaster of Paris will need careful handling with younger children, and a thorough risk assessment and other health and safety considerations will need to be carried out with this activity.

You should note that the curriculum links at the beginning of the document are now out of date.

Websites