Heat Energy

Excerpt from NSTA Sci Links:
Have you ever touched a hot pot? If you have, you know that heat energy can move from one object to another object, or from the pot to your hand. Heat energy also moves from one area to another area-for example, from a warm room to a cool room.

Heat energy always moves from a warmer object or area to a cooler object or area. If you hold an ice cube in your hand, heat energy moves from your hand to the ice and melts it. If you open a door on a cold winter day, heat energy moves from inside your warm house to the cold outdoors.

Heat energy moves in three different ways. They are conduction, convection, and radiation.

1. Conduction:
The movement of heat between objects that touch each other.
Example: Think of cooking vegetables in a pan. Heat energy moves from the hot metal to the vegetables.

Some materials allow heat to move through them more easily than others. We will learn more about these materials later this week.

2. Convection:
The movement of heat energy through liquids and gases in currents.
Example: Think of water heating up on a stove. As the water heats up, the particles at the bottom start moving faster and farther apart. The water at the bottom of the pot becomes lighter than the cooler water above it. The lighter, warmer water rises in the pot. The heavier water falls to the bottom of the pot. In this way, heat moves upward in the pot in currents. This movement in currents is called convection.

3. Radiation:
Heat energy that moves through space.
Example: Energy from the Sun travels to Earth by radiation. When the energy reaches Earth, it warms the Earth's surface. The heated surface then heats the air above it. If you sit near a fireplace or campfire, you feel heat coming from the burning logs. The heat reaches you by radiation.