chapter 5 energy and energy resources. 5 – 1 what is energy ?

Chapter 5

Energy and Energy Resources

5 – 1 What is Energy ?

What is Energy ?

Energy – the ability to cause change. Everything has energy. Any time a change occurs, energy is

transferred from one object to another.

Kinetic Energy

Kinetic Energy the energy an object has due to its motion.

An object must be moving in order to have Kinetic Energy.

2 factors determine Kinetic Energy

1. Velocity of the object2. Mass of the object

Potential Energy

Potential Energy – the energy stored in an object because of its position.

2 factors determine Potential Energy

1. Height above the floor2. Mass of the object

Thermal Energy

Thermal Energy – the sum of the kinetic energy and potential energy of an object. All objects have thermal energy. Thermal energy increases as an

objects temperature increases.

Chemical Energy

Chemical Energy – the energy stored in the chemical bonds. Food supplies energy when the body

breaks these chemical bonds down and releases the stored energy.

Fuel supplies energy when it is burned, breaking the chemical bonds and releasing the energy.

Radiant Energy Radiant Energy – the energy

carried by light. The radiant energy is absorbed,

transmitted, or reflected. Absorbed radiant energy is

transformed into thermal energy. Transmitted radiant energy passes

through the object unchanged. Reflected radiant energy bounces off

of the object.

Electrical Energy

Electrical Energy – the energy that is carried by electric current. The amount of electrical energy is

measured in voltage. 20 % of the U.S. electrical energy is

produced by nuclear generators.

Nuclear Energy

Nuclear Energy – the energy contained in atomic nuclei. Releasing this energy is difficult and

leaves radioactive pollution that must be safely stored for millions of years.

5 – 2 Energy Transformations

Law of Conservation of Energy

Law of Conservation of Energy- energy is neither created nor destroyed. Energy can change the form in which

it appears.

Example

Identify the energy changes as you throw a ball up in the air, and then catch it as it falls back down.

Track the energy changes as a car accelerates, then comes to a stop.

Generating Electrical Energy Power plants use a Generator. Generator – a device that converts

kinetic energy into electrical energy.

Coal ( or some other fossil fuel ) is burned to release its chemical energy as thermal energy.

That thermal energy is used to turn liquid water into steam.

The steam is used to turn a Turbine.

The turbine turns the generator, changing the kinetic energy into electrical energy.

5 – 3 Sources of Energy

Energy Resources

The surface of Earth receives energy from two sources : Sun Radioactive atoms inside the Earth

Nearly all the energywe use comes from the Sun

Fossil Fuels

Fossil fuels include Coal, Oil and Natural Gas.

Oil and Natural Gas were formed from the remains of microscopic organisms that lived in oceans millions of years ago.

Coal was formed from the remains of plants that lived on land millions of years ago.

Using Fossil Fuels

Nonrenewable Resource – an energy resource that is used up much faster than it can be replaced. Fossil Fuels are nonrenewable.

Burning fossil fuels creates chemical compounds that cause pollution. They cause respiratory illness and acid

rain.

Nuclear Energy

Nuclear energy production takes place much like coal fired power plants.

Nuclear power plants produce almost no air pollution.

Nuclear power plants help make the supply of fossil fuels last longer.

Nuclear Energy is nonrenewable. The waste produced is highly

radioactive.

Renewable Energy

Renewable Energy – an energy resource that is replenished continually.

Hydroelectricity

20 % of the world’s energy is supplied from hydroelectricity.

Hydroelectricity is the largest renewable energy resource.

There is no pollution produced. Hydroelectricity disrupts the life

cycle of fish and other aquatic organisms. Fish ladders can be installed. Very expensive solution.

Alternative Energy Resources

Alternative Energy Resource – new sources of energy that are safer and cause less harm to the environment. Solar Wind Geothermal

Solar Energy

The Sun is the source of nearly all the energy on Earth.

The Sun is an inexhaustible source of energy.

Inexhaustible Resource – an energy source that cannot be used up by humans.

Less than 0.1 % of the energy used in the USA comes from the Sun. Solar Energy is more expensive than

fossil fuels.

Solar Heating

Solar collectors absorb the radiant energy from the Sun and store it in water.

The water is then pumped throughout the house to warm the house.

Photovoltaic

Photovoltaic – a device that converts the radiant energy from the Sun into electrical energy.

Geothermal Energy

Geothermal Energy - Heat that is generated inside the Earth.

The magma under the surface heats the rock around it.

If this is near the surface of the Earth, rainwater that seeps down can become heated and form geysers.

Wells can be drilled down to heat water and use it for heating and electrical production.

Geothermal is an inexhaustible resource.

Can only be located in certain areas of the Earth.

Heat Pump A closed loop of water is pumped

down into the Earth and then back up to the surface.

In the winter, the underground temperature is greater than the air temperature.

In the summer, the underground temperature is less than the air temperature.

Energy from the Oceans

The rise and fall of the tides can be converted into electrical energy.

The mechanical energy of the water can be transformed into electrical energy.

There is no pollution from using tidal energy.

It is an inexhaustible source of energy.

It is limited to only a few places on Earth where the rise and fall of the tide is large enough to justify building a large generating plant.

Wind

Kinetic energy of the wind is converted into electrical energy.

They require large areas of land. They make noise pollution.

Conserving Energy

One can conserve energy in order to make fossil fuels last longer.