WHAT IS ENERGY?

Energy

The 3 main types of energy are:

• Potential energy• Kinetic energy• Chemical energy

Energy

• Scientists define energy as the ability to do work.

• Energy makes things happen. • The energy in sunlight makes plants grow, the

energy in food enables us to move and helps us to keep warm, and the energy in fuel powers engines.

Energy

• Energy comes in many different forms and can be converted from one form into another.

Potential Energy

• Energy that is stored up ready to be used in the future is called potential energy, because it has the potential (or ability) to do something useful later on.

Potential Energy

• An object usually has potential energy because a force has moved it to a different position or changed it in some other way.

• When an object releases its stored potential energy, this energy is converted into energy of a different form.

Kinetic Energy

• Moving objects have a type of energy called kinetic energy. The more kinetic energy something has, the faster it moves.

Kinetic Energy

When objects slow down, their kinetic energy is converted into another type of energy, such as heat or sound.

Objects at rest have no kinetic energy. Kinetic energy is often produced when objects release their potential energy.

Example: Hammer striking a nail

• A moving hammer has a lot of kinetic energy. As it strikes the nail, it slows down and loses its kinetic energy. The energy does not disappear, however. Some of it goes to split the wood to make way for the nail, some passes into the wood as heat energy, and some is converted into sound.

Potential / Kinetic Energy Example

Potential / Kinetic Energy Example

Potential / Kinetic Energy Example

Potential / Kinetic Energy Example

Chemical Energy

• This is the energy involved in chemical reactions, when elements join together into compounds.

• This energy is stored inside the compounds as chemical potential energy. The stored energy can be released by further chemical reactions.

Chemical Energy

• The food we eat stores energy that is released by digestion.

• Energy can also be released by burning the chemicals in a process called combustion.

• Fuels are chemical compounds that release heat energy by combustion.

Food as Chemical Energy

• When humans or other animals eat food, they use its stored energy to keep warm, maintain and repair their bodies, and move about.

• Different types of food store different amounts of energy. The amount of energy a food contains is measured in kilocalories (called Calories for short).

Chemical Energy

Chemical Energy Examples

Chemical Energy Examples

Energy Examples

Task

• In your groups list as many examples of:– Potential Energy– Kinetic Energy– Chemical Energy

• List as many energy transfers that you can think of. Think of the hammer example.