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Energy • Most people have some idea of

what energy is.

• We can usually understand statements like; “I have LOTS of energy!” “We are running out of energy.”

• Energy also comes in many forms: chemical, electrical etc...

• It is a lot more difficult to actually explain what energy is.

• Write down a definition (sentence) that explains what energy is.

• Write down as many forms of energy as you can.

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Energy

• Write down a definition that explains what energy is.

The ........................... to do work.

• Write down as many forms of energy as you can. Energy can be…

................................................................................................................................................................................

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Forms of Energy

Two basic types of energy Potential and Kinetic.

Potential Energy Kinetic Energy

FORM Example Form Example

Gravitational Movement

Chemical Light

Electric Sound

Elastic Wave

Nuclear

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Conservation of Energy • Energy can never be created or destroyed.

• It can only be transformed from one form to another.

Energy Conversion

Fuel Where

Used

From To

Coal

Paraffin

Petrol

Liquid Petroleum

Gas (LPG)

Wood

Uranium

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Energy Transformations

A light bulb connected by an electric circuit to a battery.

• Electrical energy is converted to heat and light energy.

Human beings stay alive and can do things only because they consume energy in their food.

• Chemical energy (food) -> heat & movement

An exploding bomb converts chemical to heat, movement and light.

Energy Transformations

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Calculating Energy

• Weight: Fg = m.g

• Work: W = F.d

• Power: P = W/t

100g

1m

1 Joule of energy!

How much power does it take to lift 100g a distance of 1m in

1s?

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Measuring Energy • Calculate the energy used if

you climb a staircase and use 1J of energy per 100g of mass per meter lifted.

1. Measure height of a step.

2. Count the number of steps.

3. Work out height of stairs in meters.

4. Divide your mass by 100g.

5. Now multiply by 1J for each 100g and each meter.

Time for an object to fall top to bottom

Each step =

No of

steps =

Height =

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Energy Efficiency - Light Bulb

• Input: .................................

• Outputs: ............................

• Electrical: ..............

• Light: ....................

• Heat: .....................

• Efficiency =

...................

Efficiency of light bulb =

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Bouncing Efficiency

• H/W: Explain all the energy

changes taking place.

• Explain why the bounce of a

squash ball is only about

50% efficient. Where is

energy “lost”?

Gravitational

.............................

Energy

.......................

Energy

.......................

Energy

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Heat

1. Using the diagram on page 111 draw a pie chart

showing the heat losses in a house.

2. Write down a definition for heat.

3. Write down ways that these energy losses could be

prevented.

4. Write down how heat is transferred. (3 ways)

Energy on the move (in transit).

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Heat - energy on the move

1. Radiation - - ................... of energy (Infra red

radiation) that move in ............................through

space.

2. Convection - movement of heat energy through

the moving of .....................................in a current of

liquid or gas. Hot air/liquids ...................... (less

dense) causes convection currents.

3. Conduction - Heat transmitted through a

substance by ........................................ particles

bump into each other.

H/W: Identify and label each of these in the diagram on the next

slide.

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Heat Transfer

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Convection in liquids

Hot water,

................... dense,

................... to the

top.

Cooler water, ................. dense, ....................... to the bottom.

Water ..................... as it passes along the surface.

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Heat - preventing heat loss.

Show ways that energy losses in a house can be prevented – in

each case state whether the heat would have been lost by

radiation, convection or conduction.

Ceiling insulation

- Aerolite

Cavity wall (insulation)

Carpets - underfloor heating

Windows

- curtains

- draft

excluders

- double

glazing

Doors -

draft

excluders

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Geothermal Power

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Hydro Electric Power

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Wind Power

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Tidal Power

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Wave Power

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Nuclear Power

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Koeberg

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Coal Powered Electricity

• Supply appropriate names for each of the missing labels in the diagram above.

• Write out an energy flow diagram for the power station – include all the components.

• Write out a short description of the processes taking place at each of the 9 numbered spots.

9

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Hi -

This is a SAMPLE presentation only.

My FULL presentations, which contain loads more slides (with all the gaps filled in) as well as

other resources, are freely available on my resource sharing website:

www.sciencecafe.org.za

(paste into your browser if link above does not work)

Have a look and enjoy!

Keith Warne