you need
• - 2 plastic cups;
• - ordinary water;
• - microwave.
Guide
1
Take a plastic cup, fill it with water and put in the freezer.To make sure the water in the cup is completely cold, it is better to leave it in the freezer for at least a day.
2
Explain principle of the microwave oven heated food because under the influence of microwave food and water molecules begin to move and rotate around its axis at a tremendous speed.During this movement continuously molecules collide with each other and rub against each other.As a result of this friction generates heat which heats and products.
3
Demonstrate children cups with water and ice.Ask: What would happen if you put the two cups in the microwave for 2 minutes?Most likely, the children will say that the water in both cups warm up approximately the same.H
ear all of the assumptions that express the children.
4
Put two cups in the microwave and turn it on for 2 minutes at maximum power.
5
When the microwave oven is turned off, remove the glasses and put them on the table in front of children.It turns out that the ice is not melted, while in another beaker almost boiled water.Ask the children why they think it happened.
6
Tell the children that the water has several states of aggregation: solid, liquid and gaseous.In the liquid and gaseous state the molecules are in a free state, and under the influence of microwaves begin to move very quickly.In the solid state of the water to form crystals in which molecules are fixed rigidly, almost motionless.When the ice is exposed to microwaves, the molecules are only slightly vibrates, shakes without causing friction sufficient to significantly heat up the ice.
7
Remind the children that may be thawed in a microwave products.Ask why microwave oven failed to break the ice, but she manages to cope with the frozen food?After listening to the assumption of children, explain to them that the defrosting is due to the fact that the microwaves heat the air in the oven.When the hot air and steam thawed the upper layer products, the molecules are released from their shackles ice and begin to move fast, heat.This heat is transferred deeper into the frozen product, and gradually piece of thawed completely.If the glass of ice left in the microwave oven for a long time, the ice will melt in it too.