Absorbing microwave
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Materials needed:
Two microwave-safe containers
Measuring cup
Sugar
Water
Microwave oven
Oven mitt
Cooking thermometer
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Have you ever wondered how a microwave oven cooks food? In this experiment you will compare the microwave energy absorbed by sugar and water and learn more about cooking with microwave ovens.
Place 1-cup (0.24 l) of sugar in a microwave-safe container. Place I cup (0.24 l) of water in a second microwave-safe container. Never put metal objects into a microwave oven because they could damage the microwave oven when it is operating. Put both containers into a microwave oven and heat on full power for two minutes. Use an oven mitt to remove both containers and place them on a countertop.
Place a cooking thermometer into the container with the sugar. Leave the thermometer in the sugar for about 20 seconds and then check the temperature. What is the temperature of the sugar? Place the cooking thermometer in the second container and measure the temperature of the water. What is the temperature of the water?

You should find after heating in a microwave oven that the water is warm while the sugar remains cool. The temperature of the water may be 150°F (66°C) or higher. However, the thermometer in the sugar will probably not show any change, so the sugar has remained close to room temperature.

Microwaves are a type of electromagnetic energy. Microwave ovens use this energy to cook foods. The microwaves are absorbed by water molecules in food and cause the water molecules to rotate more rapidly The extra energy of these more rapidly rotating water molecules spreads out and causes other molecules to move more rapidly This causes the food to get warm and cook. Since the dry sugar does not contain water molecules, it does not absorb the microwave energy.
Microwaves go through glass and paper without heating them. Metal objects reflect microwaves and will damage microwave ovens if placed in them. The walls of microwave ovens are metal to help reflect the microwaves back to the food to be cooked.

A special electronic tube called a magnetron is used to convert the energy of electricity to microwave energy. The microwaves are scattered into the microwave oven by a stirrer that has moving metal blades like a fan. The advantage of the microwave cooking is that it is a quicker and more energy efficient that conventional electric cooking. In conventional electric cooking an electric current passes through a coil of wire that gets hot because of the resistance of the wire to the current flow.
The amount of heat generated in a microwave oven depends on the amount of water present in the flood. In general, the more water, the faster the food cooks. Other liquids such as oil may absorb microwaves, but not as efficiently as water does.

Electromagnetic waves may pass through matter or may absorbed by it. X-rays, used to take skeleton pictures, pass through air and paper but are absorbed by water and reflected by metal. Light passes through air and water but is blocked by paper and metal.