1. What is energy? Energy is the ability to do work or cause a change.
Energy has many forms. Even though one form can change into another form, energy cannot be made or destroyed.
Different forms of energy, including mechanical, light, thermal, electrical, and sound energy, have many uses.
1. Identify Give an example of how electrical energy can be changed into light energy. Give an example of how mechanical energy be changed into sound energy.

2. What are some forms of energy and their uses?
Objects that are moving or stretching have mechanical energy.
Mechanical energy is the energy that results from the motion or position of an object. You use this form of energy when you move objects.
Light energy travels through space in waves.
Most light energy comes to Earth from the sun.
(contd.)

3. Laser light can be used to “read” music on a compact disc.
Laser light in a fiber optic cable can carry information.
2. Explore How is mechanical energy used in your classroom? How is light energy used?
(contd.)

4. An object that gains thermal energy gets hotter
An object that gains thermal energy gets hotter. Thermal energy is the total energy of the particles in an object.
When the thermal energy of an object increases, its particles move faster, making it feel warm to the touch.
Thermal energy is used in cooking food, boiling water, and heating buildings in the winter.
Electrical energy, or electricity, is produced by electric charges that are moving.
Electrical energy is used to power lights, computers, and home appliances.
3. Explore How is thermal energy used in your classroom? How is electrical energy used?
(contd.)

5. Sound waves above the range of human hearing are called ultrasound.
Sound is a form of energy that travels in waves. Sound waves can move as vibrations through air, liquids such as water, and solid matter.
Sound waves above the range of human hearing are called ultrasound.
Humans use sound energy to speak, sing, and play musical instruments.
Sound energy is used in sonar devices to locate objects underwater and to map the sea floor.
Sound energy is also used in medicine to create sonograms.
4. Explore How is sound energy used in your classroom?