Chapter 8

1. Chapter 8 Section 2 Energy Transformations

2. A. Energy is constantly changing from one form to another. B. The law of conservation of energy – states that energy is neither created or destroyed, it only changes forms. 1.The total amount of energy is the same before and after a transformation. 2. Some of the energy is not useable after a transformation, but it is not destroyed. 3. The wasted energy takes the form of thermal energy. 4. NO ENERGY CONVERSION IS EVER 100% EFFICIENT

3. C. Entropy is a measure of how disorganized energy is. • Useful energy is organized. 2. Energy that cannot be used is disorganized and it spreads out to where it is not needed. 3. The total amount of disorganized energy in the universe is always increasing.

4. D.  Examples of Energy Transformations 1) A biker eats food. Food contains chemical energy. 2) When a biker’s muscles move, the energy in food is turned into kinetic energy. 3) The biker’s working muscles make him hot. Some of the energy in his muscles is turned into thermal energy. 4) The biker’s muscles turn the pedals on the bike. This makes the bike move. So his muscle energy is transformed into kinetic and mechanical energy.

5. 1) When the ball leaves your hand it has all kinetic energy. 2) As it travels upward the ball has some potential and some kinetic energy. 3) At the very top of the arc the ball has all potential energy. 4) As the ball falls back down it has some potential and some kinetic energy. 5) All of the energy is transferred to kinetic energy as the ball hits your hand at the bottom. 6) The sum of the object’s kinetic and potential energy is its mechanical energy.

6. Chapter 8 Section 3: Sources of Energy

7. A. All energy comes from the naturalworld – mostly from the Sun but also from radioactive atomsdeep inside the Earth. 1. Energy resources are used to run power plants to make electricity. 2. In a power plant, a generator converts kinetic energy into electrical energy. 3. Energy resources can be classified into four types– renewable, nonrenewable, inexhaustible, and alternative energy sources.

9. B. Nonrenewable resources such as fossil fuels are usedup faster than they can be replaced. • Fossil fuels include oil, natural gas, and coal. a. Fossil fuels contain chemical energy from the Sun’s radiant energy during photosynthesis. b. The chemical energy is released when the fuels are burned. c. Burning fossil fuels creates air pollution and acid rain. 2. Nuclear energy is a nonrenewable resource which comes from the nuclei of uranium atoms.

10. C. Renewable resources are energy sources that are replaced continually. 1. Hydroelectricity from the potential energy of water is a renewable resource. 2. Hydroelectric plants make little pollution but they can upset the lifecycle of some animals.

11. D. Inexhaustible resources cannot be used up by humans. • E. Alternative resources are new renewable or inexhaustible energy sources.

12. 1. Solar energy can be captured using thermal collectors and photovoltaic cells. 2. Geothermal energy is when thermal energy contained in hot magma is harnessed by a geothermal power plant to make electricity. 3.Tidal energy comes from the changing of the tides 4. Wind energy works when the wind turns big propellers or wind mills. 5. The problem with many of these alternative energy resources is that they are either expensive or only work in very specific places on the planet.

13. F. Conserving energy will help prevent energy shortages and allow fossil fuels to last longer.