Black or white?

Colour and light play an important part in transmitting heat or thermal energy.

Black or white?

Colour and light play an important part in transmitting heat or thermal energy.

Set up time

10 mins

What you need

Thermometer, aluminium cans, black paint, white paint, clock, cardboard, measuring jug, water


To demonstrate how some colours reflect heat, while others absorb heat.

Learning outcomes


Your students will learn how to make predictions before conducting an experiment.


Your students will observe the effect that different colours have on the temperature of an object.


Your students will use a thermometer to measure temperature, and create graphs to record results.



When light shines on an object some colours bounce off the object and other colours are absorbed. We see the colours that bounce off the object or are reflected. The more an object absorbs light, the more energy is absorbed which converts to heat. 

Take two aluminium cans. Paint one black, the other white. Pour identical amounts of cold water in each.

Measure the starting temperature in each can. Ask students to predict which can will get hotter.

Place both cans in the full sun, and then measure the temperature in each can every 20 minutes.

At 60 minutes, measure the final temperature. Discuss the results and record in a graph.

In this experiment, is there anything apart from the can’s colour that could affect the results?
What is another experiment you could do to explore the relationship between colour and heat transfer?

Time required
70 mins

Extension: Make a solar shower

A hot shower is one of life’s luxuries. But heating the water using electricity or gas can use a lot of energy There are many ways to heat water, such as using the sun’s energy. This is called Solar energy.

About a quarter of the energy we use at home is to heat up water


By thinking creatively, there are many ways we can heat water using the sun’s energy.


In this video, the presenter has chosen black buckets to heat the water. Why did he choose to use black buckets?


Have you ever been camping and used a camp shower? These work in exactly the same way!


What are some other ideas for heating and using hot water? What are some ways you could reduce the amount of hot water you use?