Heat wave! What does a microwave oven do that allows it to cook food so much faster than a conventional oven?? A conventional oven cooks food starting on the outside and moving to the inside over time.
A microwave oven works differently. The heat created inside a microwave is absorbed very quickly by things like water, fats, and sugars.
Unlike a conventional oven, a microwave oven's rays are able to start creating heat about an inch deep into a piece of food right away by exciting the molecules of water, fat, and sugar within. If a piece of food is really thick, the microwave's heat can't start cooking the very center right away, but it can penetrate its heat deeper into the piece of food more quickly than a conventional oven.
When the microwave's special rays excite the fat, sugar, and water molecules, it causes them to move around and create heat that cooks the food very quickly!
That means there's no time waiting for the heat to start on the outside. Additionally, a microwave's heat is not absorbed by microwave-safe cooking containers, nor does a microwave's heat saturate the rest of the air in the microwave. This means more of the heat is focused on the piece of food and it's able to cook more quickly! Wow!
Before people had microwaves or conventional ovens like we have today, food had to be cooked over a fire, like you might have done if you've ever been camping! What kinds of foods have you eaten that were cooked by a fire? Potatoes, beans, and hot-dogs might be a few of them. And don't forget about yummy, gooey, roasted marshmallows! Did you know that sometimes even pizzas are made with a fire? There are special ovens made of bricks which can hold a hot fire in the back, and cook a pizza up near the front! YUM!!
Because of the way a microwave cooks, certain foods are better suited to cooking in a microwave than others. Although they're faster, some foods won't cook properly or taste nice if they're made in a microwave. Always follow the cooking instructions of the food item, recipe, or grown-up you are working with!