Conservation of Energy Unit 9-3

I. The Law of Conservation of Energy This law states that energy cannot be created or destroyed. It can only be changed from one form to another. A closed system is a physical system that does not interact with other systems. The total amount of energy in a closed system always stays the same. For instance, light energy from the sun is converted to chemical energy in an apple, but the amount of energy stays the same. If the sun gave 10 joules of light energy, it will be converted into 10 joules of chemical energy.

II. Friction and Energy When energy is converted, some of that energy might be changed in a different way due to friction. In all energy conversions, some of the energy is converted into thermal (heat) energy. i. Example: When a roller coaster goes down a hill, potential energy converts to kinetic energy but some energy is also converted to thermal energy (heat) from the friction of the wheels on the track.

III. Energy Efficient If a machine is energy efficient, it means that the amount of energy before a conversion is close to the amount of useful energy after the conversion. An example would be an energy efficient car. A car with high energy efficiency can go farther than other cars with the same amount of gas. Do you have an energy efficient car?

Energy Resources Unit 9-4

Energy Resources An energy resource is a natural resource that can be converted into other forms of energy in order to do useful work. Nonrenewable Renewable

IV. Nonrenewable Resources Nonrenewable resources are energy sources that cannot be replaced or are replaced much more slowly than we are using them up. Fossil fuels like oil and natural gas are nonrenewable resources that take millions of years to create.

V. Fossil Fuels Fossil fuels like oil, coal, and natural gas are formed from the buried remains of plants and animals that lived long ago. They are concentrated forms of the sun’s energy. The energy is released when we burn them.

What fossil fuel do we use the most?

VI. Fossil Fuels and Electricity Electric generators convert the chemical energy in fossil fuels into electrical energy that we use in our homes and schools. b. This is the main source of electrical energy in the United States today.

VII. Nuclear Energy Another way to generate electricity is to use nuclear energy. Nuclear energy is generated from radioactive elements such as uranium. The supply of uranium is limited, so nuclear energy is a nonrenewable resource, like oil and coal.

VIII. Renewable Resources Some forms of energy can be replaced more quickly than they are used. These are known as renewable resources.

ii Wind Energy: Energy that is gathered from moving air. b. Some examples of Renewable Resources and Sources of Energy (places we get energy from): i.Solar Energy: Energy from sunlight changed in solar cells. ii Wind Energy: Energy that is gathered from moving air. iii. Energy from water: Energy that is gained from falling water (dams). iv. Biomass Energy: Caused by the burning of plant, wood, and waste matter. v. Geothermal Energy: Caused by the heating of Earth’s crust .

IX. Advantages and Disadvantages There are many advantages and disadvantages to the different forms of renewable resources. For example, geothermal energy can only be obtained from certain “hot spots” on Earth. Can you think of a disadvantage to each form of energy? (biomass, wind, solar, water energy)

Brainstorm with your group the advantages and disadvantages of using the various forms of energy. -Give each group 10 minutes then have the groups share their answers.

Energy Resource Advantage Disadvantage Biomass -Renewable -is inexpensive -requires large areas of farmland -produces smoke Fossil Fuels -provide electricity -used in cars for gasoline -nonrenewable resource that we will eventually we will run out of Wind Energy -is renewable -is relatively inexpensive to generate -does not produce air pollution -only works in windy areas Solar Energy -is an almost limitless source of energy -is expensive to use for large-scale energy production -is practical in only sunny areas Water Energy -requires dams, which disrupt a river’s ecosystem -is available only where there are rivers.

Quickie Quiz 1. If you have a car that drives a long way on a small amount of fuel, it is because: Your car has friction. Your car has potential energy. Your car is energy efficient. Your car converted electrical energy to chemical energy.

Quickie Quiz 2. The Law of Conservation of Energy states that: Energy cannot be created or destroyed. Energy cannot be converted. Energy can be created or destroyed. Energy in a closed system changes all the time.

Quickie Quiz 3. Which of the following is NOT a renewable resource? Wind energy Coal energy Solar energy Biomass energy

Quickie Quiz 4. Which type of energy is a nonrenewable resource? Solar Geothermal Natural gas Water

Quickie Quiz 5. Which form of energy is inexpensive and renewable, but requires large amounts of farmland and produces smoke? Geothermal Wind Water Biomass

Quickie Quiz 6. Which form of energy does not produce pollution, but produces radioactive waste? Solar Biomass Nuclear Wind

What do you think? Which form of energy do YOU feel we should most explore for future energy use? Why?