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TAKS Objective 5Energy and Heat

It Is All Around You…

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Heat transfers in three ways:

ConductionConvectionRadiation

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ConductionConductionOuch!

…is the transfer of heat by the direct contact of particles of matter.

The heat of the boiling liquid directly contacts the metal spoon and causes the spoon to transfer the heat to the hand.

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Air above the flame heats and expands and you feel the heat transferring into

your hand.

Cool water is pushed downCool water is pushed down

As the heated water rises…As the heated water rises…

ConvectionConvection…is the transfer of heat by the actual motion of a

fluid (liquid or gas) in the form of currents.

The heated water rises as

the cooler water is

pushed down. The water that was

pushed down is then heated

and …

then rises pushing the now

cooler water down.

This causes a current in the

water.

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Convection link

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Convection Currents• Hot liquids and gases expand and

rise while the cooler liquid or gas falls

1. Hot air rises

2. Goes across

3. Then down

4. And across

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RadiationRadiation…is heat transfer by electromagnetic waves.

MATTER is not necessary for this transfer of heat.

A common type of radiation comes from the sun. Examples include –

• Ultraviolet• Visible Light Color

spectrum – (ROYGBIV)• Infrared

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Radiation

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Heat_Transfer.asf

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Lets Identify Types of Heat Transfer

• Using your slate write down if the following pictures represent:

Conduction•Convection, or •Radiation

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Picture One

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Picture Two

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Picture Three

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Picture Four

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Picture Five

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• Now identify the next five pictures on your handout independently.

TAKS OBJECTIVE 5

Energy Sources

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Energy SourcesEnergy sources are considered to be renewable or nonrenewable.

• A renewable resource is a resource that can be replenished in a short period of time (ex. Solar, wind, water, geothermal, biomass)

• A nonrenewable resource is a natural resource that cannot be replenished (re-made or re-grown) as quickly as it is used (ex. Nuclear energy and fossil fuels such as coal, oil, natural gas)

Energy Resources have their advantages and

disadvantages

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Fossil fuels are fuels formed by natural resources in the geological past from the remains of

once living organisms.  

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Disadvantages of Fossil Fuels• As earth reserves of nonrenewable fossil

fuels decrease, they become harder to obtain and more expensive

• Burning them harms our environment (particles in smoke cause breathing problems)

• Burning carbon containing fuels produces CO2 that may contribute to Global warming.

Advantages of Fossil Fuels

• Used to generate almost 70% of electricity such as Petroleum, oil, natural gas, and coal.

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Nuclear Energy Is energy created from the energy

locked up in atoms. When an atom is split (nuclear fission) into smaller fragments, energy is released.

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Advantages of Nuclear Energy•It doesn’t produce air pollution and CO2

• Nuclear fuel is inexpensive and easy to transport

24 Disadvantages of Nuclear Energy

• They produce large amounts of excess heat, which can harm fish and other animals in nearby lakes and streams.

• Nuclear accidents have the potential to cause radiation sickness and take human lives.

• Produces waste that remain hazardous for thousands of years.

• Only produce 20% of U.S. electricity today in nuclear power plants.

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Solar Energy

a renewable resource in which the electromagnetic radiation from the sun can be converted to electricity by the use of solar cells and photoelectric cells

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Advantages of Solar Energy

• It is replaced nearly as quickly as it is used.

• The sun’s radiant energy can be used to heat homes and provide hot water.

• Solar energy is nonpolluting. • Photovoltaic cells convert solar

energy to electricity, which powers calculators.

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Disadvantages of Solar Energy

• Converting solar energy to electricity is only 15-20% efficient.

• The conversion cost more money.

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Batteries

Batteries convert chemical energy to electrical energy.

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Advantages of Batteries• Rechargeable batteries are more

environmentally friendly than disposable ones.

Disadvantages of Batteries•Manufacturing batteries require large amounts of energy.•Larger batteries pose environmental hazards because they contain heavy metals such as lead.

30 Energy from Wind and Water (Hydro)

Advantages• Wind energy can

be useful in areas with high and consistent winds

• Both Hydroelectric and wind energy are renewable and nonpolluting.

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Energy from Wind and WaterDisadvantages• Wind energy is inconsistent• Pose danger to birds from turning of

blades• Requires a lot of land• Hydroelectric power plants generate

only about 4% of U.S. electricity today.• Artificial dams are not possible in many

areas.• Dams may disrupt fish migration and

other aspects of natural ecosystems.

32 Geothermal Energy is thermal energy contained deep in the Earth. Advantages: • geothermal power plants are about 80% efficient

in converting geothermal energy to electricity.• it is a clean process that does not cause pollution• only uses a small amount of land and doesn’t

disrupt the ecosystems Disadvantages:• this process is only feasible where magma is

close to the Earth’s surface such as Iceland.• very expensive to drill deep into the earth to

capture the geothermal energy