The word microwave is a word with more than one meaning. It is used to describe the machine that you use to heat food and also the tiny micro-waves that are used in the process. A microwave is able to heat up foods and liquids by heating the water content in them and when it does so over a prolonged period of time, it can even cook foods to completion.
Any food that contains even a little amount of water can be cooked or heated using this machine. A microwave oven contains a small machine called a magnetron. This sends out tiny waves or micro waves that vibrate the water molecules in the food. When molecules move a lot they generate heat, so the more these water molecules move, the hotter they get.
Since this process is manipulating the water content of the food, it is necessary to cover the item when heating it, otherwise the water will evaporate and leave your food dry. They can only heat things that have some amount of water and can pass through most materials like ceramic and glass. Since these microwaves are magnetic, you cannot put metal into a microwave since this will reflect it and make it explode. Other materials like plastic and aluminium will melt when exposed to these shaking waves.
Gather three different things you want to heat- start with a mug of water, some dal, and a potato. Heat these foods up and see which of these get hottest when exposed to the same amount of micro waves. You may notice that the denser the material, the less the microwaves can penetrate through to the middle. Can you confirm this?
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