Student Activity - Heat absorption

Activity Idea

In this simple experiment, students use soda bottles to demonstrate how different colours affect heat absorption. They should discover that black surfaces are good absorbers of light energy, transforming the radiant energy into heat, while white surfaces are poor absorbers of light energy, reflecting the light away.

Instructions

Lots of factors affect the way an object absorbs heat – the type of material it is made out of, what colour it is and what kind of texture it has. On a hot day, is it better to wear a black T-shirt or a white one? Use this experiment to test your answer.

What you will need:

• two plastic soda bottles (the greater the surface area to volume ratio, the better)
• plenty of Blu Tack
• two thermometers
• water
• white and black paint
• paintbrush

Instructions

• Paint one bottle white and the other black, and set aside to dry.
• Insert one thermometer into each bottle opening, and use Blu Tack to create a seal and keep the thermometer in place.
• Take the thermometer seal off and fill each bottle with an equal amount of water, so that the thermometer end is surrounded by water.
• Re-attach thermometer seal and place each bottle in a sunny location (such as inside near a window in direct sunlight).
• Record the initial temperature.
• Continue recording the temperature from both bottles every minute for ten minutes, or until a constant temperature is reached in either (no change in temperature for three minutes).
• Repeat twice and compare your readings.

Questions

• Which thermometer had the greatest change in temperature?
• Which thermometer showed the fastest increase in temperature?
• What absorbs heat better – a dark or light object?