Chapter 3 Energy

1. Chapter 3Energy

2. Section 1: Energy exists in different forms. • Different forms of energy have different uses. • Energy: the ability to cause change or the ability to do work.

3. Forms of Energy • Mechanical energy: the energy needed to move an object. Ex: moving a book from the floor to the desk. • Sound energy: vibrations in the air create sounds that your hear. Ex: teacher talking, TV • Chemical energy: energy stored in the chemical composition or makeup of a substance. Ex: food, gasoline, wood • Thermal energy: the total amount of energy from the movement of particles (atoms or molecules) in matter. Ex: heat • Electromagnetic energy: also called radiant energy. This type of energy is transmitted through empty space in waves. Ex: light, x-rays, microwaves, sun • Nuclear energy: energy stored in the nucleus of an atoms. Ex: nuclear fission in nuclear power plants; nuclear fusion in the sun

4. Kinetic energy and potential energy are the two general types of energy. • Kinetic energy • The energy of motion • Depends on two factors: mass and speed • Potential energy • Stored energy that an object has due to its position or chemical composition • Depends on two factors: mass and height above the ground • Potential energy can also come from stretching an object (rubber band) or compressing an object (a spring)

5. Section 2: Energy can change forms but is never lost. • Energy changes forms. • Conversions between potential energy and kinetic energy • Potential energy can be converted into kinetic energy • Kinetic energy can be converted into potential energy • Ex: ski jumper, skateboarder, roller coaster • Using energy conversions • People use energy conversions to generate electricity • Ex: potential energy from a dam is turned into kinetic energy, then that kinetic energy is turned into electrical energy. • Almost all energy on the earth started out as energy from the sun before it got converted into some other form of energy.

6. Energy is always conserved • Law of conservation of energy: energy can not be created or destroyed, it can just change forms. • This is a law because it is true in all known cases. • The total amount of energy in the universe can never change. • Ex: in the dam the amount of potential energy stored in the water held behind the dam is equal to the kinetic energy produced as the water flows through the dam plus the sound energy created by the rushing water and the thermal energy created by the friction between the water and the tunnels. • Energy conversions may produce unwanted forms of energy. • Energy efficiency: a measurement of usable energy after an energy conversion. • If an appliance is efficient, it doesn’t waste a lot of energy producing unwanted energy forms. • Ex: regular or incandescent light bulbs are not efficient because a lot of electrical energy is turned into unwanted thermal energy, or heat. Fluorescent light bulbs are more efficient because they do not convert a lot of electrical energy into heat.

7. Technology improves the ways people use energy. • Technology improves energy conversions. • Efficient lights • LED: light –emitting diodes that convert almost all of the electricity they use into light • Uses of LEDs: traffic signals, remote control for TVs, fiber optic cables • Efficient cars such as hybrids don’t waste as much energy

8. Technology improves the use of energy resources. • Solar energy • Solar cells: light-sensitive materials sandwiched together to harness the electromagnetic energy of the sun. ex: calculator • Advantages: renewable, does not pollute like fossil fuels, quiet • Disadvantages: expensive to make, not efficient, it’s not always sunny • Used to produce electrical energy and heat • Wind energy • Advantages: clean, renewable • Disadvantages: requires a lot of space, loud, wind doesn’t always blow • Uses: electricity, pump water, grind grain