1. Energy and Energy Sources
IPC

2. I. The Nature of Energy A. Energy is the ability to cause change.
1. Kinetic energy – energy in the form of motion.
a. The amount of kinetic energy an object has depends on its mass and its velocity.
b. Kinetic Energy = mv2 2
c. Joules- the SI unit to measure energy.
2. Potential Energy - energy stored in a motionless object, giving it the potential to cause change.

3. I. The Nature of Energy A. Energy is the ability to cause change.
3. Elastic potential energy - energy stored by things that stretch or compress.
4. Chemical potential energy – energy stored in chemical bonds between atoms

4. I. The Nature of Energy A. Energy is the ability to cause change.
5. Gravitational potential energy – energy stored by things that are above the Earth.
a. the amount of GPE and object has depends on its mass, the acceleration due to gravity, and its height above ground.
b. GPE= mass(kg) x 9.8 m/s2 x height(m)

5. II. Conservation of Energy
A. Energy Conversions – energy changing from one form to another.
1. Fuel store energy in the form of chemical potential energy.
2. Mechanical energy – the total amount of potential and kinetic energy in a system.

6. II. Conservation of Energy
B. Law of Conservation of Energy – Energy may change from one form to another, but the total amount of energy never changes.
1. Example – as a swing moves back and forth, its energy continually converts from kinetic to potential and back.
2. If the energy of the swing decreases, then the energy of some other object must increase by an equal amount.
3. Friction converts on the mechanical energy into thermal energy.

7. II. Conservation of Energy
C. Converting mass to energy – you must think of mass as energy when discussing nuclear reactions. The total amount of mass and energy is conserved.
1. Nuclear fusion – two nuclei are fused together – takes place in the sun.
2. Nuclear fission – two nuclei are broken apart.

8. II. Conservation of Energy
D. Conservation of Energy in your body.
1. Chemical potential energy from food that is stored in your body is used to fuel the processes that keep you alive.
2. The food calorie is used to measure how much energy you get from various foods.
3. One calorie is equal to 4,180 J.

9. III. Energy Sources – Fossil Fuels
A. Energy can not be created nor destroyed according to the law of conservation of energy, but energy can be converted from one form to another.
B. Fossil fuels – formed from decaying remains of ancient plants and animals.
1. Burning fossil fuels converts energy from chemical bonds to light and heat.
2. Chemical energy in fossil fuels is more concentrated than in other fuels such as wood.

10. III. Energy Sources – Fossil Fuels
C. Petroleum- thick, greenish-brown, highly flammable liquid formed by decayed ancient organisms
1. A process called fractional distillation separates the compounds in petroleum.
2. Petroleum is used for plastics, synthetic fabrics, and other products in addition to its use as a fuel.

11. III. Energy Sources – Fossil Fuels
D. Natural gas is also a product of ancient organisms.
1. It contains more energy per kilogram than petroleum or coal.
2. It burns more cleanly than other fossil fuels.
3. It provides about one-fourth of the energy consumed in the United States.

12. III. Energy Sources – Fossil Fuels
E. Coal – a solid fossil fuel found underground.
1. It produces more pollution when burned than natural gas or petroleum.
2. It provides about one-fourth of the energy produced in the United States.
3. About 90 percent of coal burned in the United States is used to produce electricity.

13. III. Energy Sources – Fossil Fuels
F. Electricity is generated when fossil fuels are burned.
1. The burned fuel releases thermal energy.
2. The thermal energy produces high pressure steam.
3. The steam spins a turbine.
4. The spinning turbine produces an electric current.
5. The electric current is transmitted through power lines to consumers.

14. III. Energy Sources – Fossil Fuels
G. Only about 35% of the energy in fossil fuel reaches consumers since some energy is lost in every stage of the process.

15. III. Energy Sources – Fossil Fuels
H. Fossil fuel have some undesirable side effects.
1. Fossil fuel pollute the environment and increase carbon monoxide in the atmosphere.
2. Mining coal can cause health problems for miners.

16. III. Energy Sources – Fossil Fuels
I. Fossil fuels are nonrenewable resources, so it is important to not waste energy.

17. IV. Nuclear Energy
A. About 20% of the electricity in the U.S. come from nuclear power plants.
B. Nuclear reactors contain a fuel, rods to control nuclear reactions, and a cooling system.
1. Heat is produced by nuclear fission – energy is released when U-235 nuclei split in two after being struck by a neutron.
2. Special rods absorb excess neutrons to prevent dangerous chain reactions

18. IV. Nuclear Energy
C. Nuclear Power plants use the heat of nuclear fission to produce steam.
1. The steam drives a turbine.
2. The Turbine rotates an electric generator.

19. IV. Nuclear Energy
D. Nuclear power plants produce nuclear waste—radioactive by-products from radioactive materials.
1. Low-level wastes contain only a small amount of radioactive material.
2.High-level wastes must be disposed of extremely carefully because they will remain radioactive for tens of thousands of years.

20. IV. Nuclear Energy
E. Nuclear Fusion—the joining together of nuclei—is not a practical energy source due to the high temperature fusion requires.

21. V. Renewable Energy Sources
A. A renewable resource can be replaced as quickly as it is used.

22. V. Renewable Energy Sources
B. Solar energy is converted into electricity by a photovoltaic cell or solar cell.
1. A solar cell converts only 15 to 20 percent of the sun’s energy into electricity.
2. Energy produced by solar cells is more expensive than energy produced with fossil fuels.
3. Energy from solar cells must be stored in batteries when the Sun is not shining.

23. V. Renewable Energy Sources
C. Hydroelectricity is produced by moving water; it is about twice as efficient as fossil fuels or nuclear power.

24. V. Renewable Energy Sources
D. Tidal energy uses moving water, but it can only be used in places where high and low tides are different enough.

25. V. Renewable Energy Sources
E. Windmills can be used to generate electricity, but are useful only when the wind blows consistently.

26. V. Renewable Energy Sources
F. Geothermal energy—thermal energy contained in hot magma; limited to areas where magma is close to the surface.

27. V. Renewable Energy Sources
G. Alternative fuels include hydrogen gas and biomass—renewable organic matter such as wood or animal manure.