Do red cars get hotter than those painted in other colors?

IntroductionKey Stage 2 & 3

This experiment uses a data logger and thermocouples to investigate if cars that are painted red get hotter than cars that are painted in other colors.

VariablesEducational data logger

There are many variables that could affect the results of this experiment, including:

  • Weather conditions — for example, cloud cover and wind
  • Reflections — for example, from other objects
  • Car — for example, mode of car, size of car and size of windows

As this experiment is testing colour, ideally colour should be the only thing that changes during the experiment.

So as to decrease the effects of these variables all the cars will be the same model and will all be tested at the same time so that the relative weather conditions remain the same as well as the length of time in the sun.

Experiment setup

Cars used in experiment

Student with laptop and data logger

Figure 1: Measuring the temperature of the cars

  1. Park cars side by side, on the grass, fairly spaced apart pointed towards the sun.
  2. Measure out the thermocouple cable so that it can reach the back seat as well as the middle of each car.
  3. Using pliers, cut the thermocouple cable to the correct distance.
  4. On one end of each cable make a junction by cutting about 2 cm of the insulating cover off the cable.
  5. Twist the two wires tightly together.
  6. On the other end of each cable, take the cover off the same way, but then bend each single wire back to form a horseshoe shape and insert into the terminal.
  7. Ensure that each wire is tight in the terminal and that the terminal is in the shade.
  8. Connect the thermocouple data logger to the laptop computer.
  9. Open up Picolog on the computer and set the computer to take a new reading every one minute and to save regularly.
  10. Check that each cable is plugged into the correct channel and that it is given the correct name on the computer. Do this by holding the junction and watch to see if the right temperature goes up.
  11. Put the thermocouples in place inside the car and then shut the doors and don’t disturb.
  12. Press “start” on the computer.
  13. Watch and wait for about 2.5 hours or until the results are stable.
  14. Check the calibration by taking all thermocouples out of the respective cars and placing them all in the same place.
  15. Wait until the temperatures stabilize and ensure that they all come back to the same value.
Experiment layout

Figure 2: Experiment layout

Further study

Further study could include test other colors and also testing other variables such as whether the car has ordinary or metallic paint, clear or tinted glass windows, etc.

Credits, comments and further info

This experiment was written by Courtney Hayes of Australia.

Thanks to Rod Lawrence Ford for providing the cars that were used in the experiment, and to all the others who helped to set up the experiment.