Unit 3 Nature’s Energy 1

1. Heat Energy

Energy passed as heat from one object to another Heat always passes from a hotter object to a cooler object

If you hold an ice cube in your hand, it will start to melt

Heat energy passes from your hand to the ice cube The heat energy makes the molecules in the ice move faster

The ice begins to melt, or become a liquid

Heat energy can be passed in 3 ways Conduction Convection Radiation

When heat passes through solids Vocabulary conduction When heat passes through solids 8

When one object passes heat to another by conduction, The heat keeps flowing until both objects are equally hot 9

Have you ever eaten hot soup with a metal spoon? After a while, the spoon gets hot 10

The hot soup causes the molecules in the spoon to move faster Heat travels from the soup up the spoon to your hand 11

When heat passes through liquids and gasses in currents Vocabulary convection When heat passes through liquids and gasses in currents 12

Molecules in liquids and gases move apart when they are heated This happens during convection 13

When you heat water on the stove, The bottom layer of water is heated first The molecules in this layer of water move farther apart 14

Then floats to the top, and the cooler, heavier water on the top falls to the bottom 15

These molecules are called convection currents In winter, convection heats the air in your house 16

Vocabulary Convection currents movement of warm molecules rising as they push the cooler molecules downward

Solar heat comes in radiation waves 18

Movement of energy in waves Vocabulary radiation Movement of energy in waves

Microwave ovens heat food by radiation 20

Heat energy can be passed in 3 ways Conduction - contact Convection - current Radiation - waves 21