Kitchen chemistry: Should beans be cooked with the lid on or off?


An investigation into whether having the lid on or off affects the colour of green vegetables.


A short investigation to determine whether the lid should be on or off during cooking


If you teach primary science, click 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:
    • Carrying out comparative tests.
  • 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:

  • Observe that some materials change state when they are heated or cooled, and measure or research the temperature at which this happens in degrees Celsius.

Concepts supported

Children will learn:

  • The temperature at which water boils.
  • That irreversible chemical changes occur when food is cooked.

Suggested activity use

Due to the need to use boiling water, this activity is best carried out as class demonstration, or by small groups of children being closely supervised by an adult.

It is important to ask children how they could test whether cooking green vegetables with the lid on or off makes any difference to their colour, and to discuss their ideas before being shown the test samples to observe.

Practical considerations

To carry out this activity you will require access to a cooker or hob to boil the water.

You should be very careful with boiling water around children, and a risk assessment and other health and safety considerations should be carried out.