Cooling Food: Microwave vs. Oven

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Updated on Sep 06, 2012

You get home from school, hungry and tired. Nothing sounds better than a warm snack to fill your rumbling tummy before dinnertime, but should you use the microwave or the oven to heat up your tasty treat? Both kitchen appliances will heat your food, so what's the difference?

Well, one way to test the difference is to see whether microwaves and ovens keep food warm for the same amount of time. Quickly cooling food can be annoying, especially when you're expecting something hot to keep you cozy during chilly afternoons. In this science experiment, we'll explore whether a microwave or an oven does a better job at keeping food warm.

Problem:

Do mashed potatoes cooked in a microwave cool faster or slower than food cooked in an oven?

Materials:

  • Instant mashed potato flakes
  • Microwave
  • Oven
  • Water
  • Measuring cup
  • Mixing bowl
  • Microwave safe bowl
  • Baking dish
  • Food thermometer
  • 2 dinner plates
  • Timer
  • Notebook
  • Pencil

  1. Make your mashed potatoes by combining 1 1/2 cups of your instant potato flakes in a mixing bowl with 2 cups of warm water.
  2. Stir the mixture until the flakes transform into fluffy clouds of mashed potatoes.
  3. Put half of your mashed potatoes in a microwave safe bowl and the other half in a baking dish.
  4. Think about what you know about microwaves and ovens. Which one do you use if you want to heat a quick snack? Which one does your family use to make dinners? Why do you think we have both a microwave and an oven in our kitchens if they both heat food? Write down any thoughts you have about microwaves and ovens in your notebook.
  5. Make a guess about what will happen in your experiment. Will the microwave or the oven keep the mashed potatoes warm longer? Write down your guess, or hypothesis, in your notebook.
  6. Place the microwave safe bowl in the microwave and cook for three minutes.
  7. Ask an adult to remove the bowl for you. It'll be hot!
  8. Test the temperature with your food thermometer. You want the thermometer to read 140 degrees Fahrenheit. If it hasn't gotten that hot yet, microwave it for another 30 seconds.
  9. As soon as the thermometer inside the mashed potatoes reaches 140 degrees Fahrenheit, move the mashed potatoes to a dinner plate. Make sure you leave the thermometer inside the potatoes.
  10. Start your timer.
  11. In your notebook, write down how long it takes for the thermometer to read 130 degrees Fahrenheit. Write down the times for it to reach 120, 110, 100 and 90 degrees Fahrenheit as well.
  12. Set your oven to 350 degrees Fahrenheit. Wait for it to pre-heat.
  13. Insert your baking dish.
  14. Check the temperature of the mashed potatoes after 15 minutes to see if it has reached 140 degrees Fahrenheit. If not, recheck every 5 minutes.
  15. Ask an adult to take out the baking dish from the oven.
  16. Set your oven cooked mashed potatoes on a dinner plate.
  17. Repeat steps 10-11 with the oven cooked mashed potatoes.
  18. Compare your results to see which cooking method cooled the mashed potatoes faster.

Results:

The mashed potatoes heated in the microwave should cool faster than the mashed potatoes heated by the oven.

Why?

Remember how you had to wait for your oven to pre-heat before you put in the mashed potatoes? You had to do this because in an oven the air has to heat up before the food can. Heat moves from the outside of food to the inside. In a microwave, the opposite is true. Microwave radiation, waves of energy that give the microwave its name, targets the food instead of the air around it. That's why microwaves heat food so much faster than ovens!

As you saw in this science experiment though, faster heating might also equal faster cooling food. Thanks to thermalization, the process in which food absorbs heat molecules, the mashed potatoes heated by the microwave cooled very quickly. The microwave radiation heated the mashed potatoes so fast that it didn't give the thermalization process enough time to finish. In other words, your mashed potatoes didn't have enough time to absorb all the heat. In an oven, the slower heating gave the mashed potatoes plenty of time to fully absorb the heat, resulting in potatoes that stayed warmer longer.

Do you think this experiment would have the same results if you tried different types of food? What if you tried heating up a can of soup or a piece of chicken? Try experimenting with heat by seeing what melts ice cream faster. Guessing and testing new ways to experiment with science is the most important part of a scientist's job. Think like a scientist and come up with your own unique heat experiments!

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