1. USING ENERGY
5.1 ENERGY AROUND US

2. An Introduction to Energy - Clips
The Essentials of Energy
ASAP science video

3. What is Energy?
Whenever an object is Lifted or forced to change shape, then work has been done.

4. Measuring Energy 1KJ = 1000J 1MJ = 1,000,000J
Energy is measured using a unit called joules (J)
You use 1 joule of energy when you lift 1kg of potatoes 10cm of the floor
Food energy is measured in kilojoules (KJ)
Electrical energy is measured in megajoules (MJ)
1KJ = 1000J
1MJ = 1,000,000J

5. Examples Calculate how many joules of energy are contained in:
A) 4 kJ B) 2.5 MJ
4 X 1000 = 4000J
2.5 X 1,000,000 = J
Calculate how many megajoules of energy are contained in:
C) J D) J
÷ = 2.2 MJ
÷ = MJ

6. Forms of Energy Kinetic Energy Potential Energy Kinetic Chemical Heat
Nuclear
Light
Gravitational
Sound
Elastic
Electrical
Lets examine each form…

7. Kinetic Energy Energy of movement
Faster a object moves more kinetic energy is has
When an object collides kinetic energy is changed to other forms of energy

8. Heat Energy
Energy obtained from the sun, flames, chemical reactions, electric devices or even from person or animal

9. Conduction
Conduction is the transfer of heat through a solid object from a region of higher temperature to a region of lower temperature.
Different substances conduct heat at different rates. For example, metals are more effective conductors of heat than wood.

10. Convection
Convection is the transfer of heat through the heating of fluids, such as water and air, causing it to rise.

11. Radiation
In the context of heat transfer, radiation is a form of heat energy that travels in waves in all directions from its source.
Radiant heat can travel trough space (no medium req’d)!
It is the direct heat you feel from a fire and comes from the flames and heated surface.

12. Light Energy
Energy obtained from the sun, light globes, fires and animals such as glow worms

13. Sound Energy The energy the air has when it is vibrating
Your ears and brain interpret the vibrating air as sound

14. Electrical Energy
Energy obtained from burning fossil fuels at power stations, solar energy from the sun, batteries and sparks such as lightning

15. STORED ENERGY
Many objects around you have stored energy or POTENTIAL ENERGY
For example;
Petrol in a car’s tank
Books on a shelf
Eating food is a type of chemical energy your body gets that is stored until needed
Plants have stored energy through photosynthesis

16. Types of potential energy
There are 4 types:
Gravitational potential energy
Chemical energy
Elastic potential energy
Nuclear energy

17. Gravitational Potential Energy
Energy stored in an object when it is above the ground
The greater the height the more potential energy an object has
For example the higher the waterslide the more gravitational energy you have at the top and the more kinetic energy you have on the way down

18. Chemical Energy Energy stored in substances
The energy released through digestion
The energy is released by cars when you burn fuel
The energy is released by batteries when you uses devices

19. Elastic Potential Energy
Energy stored in stretched or squashed springs
Stretched rubber bands also store elastic energy
When released, the energy is removed

20. Nuclear Energy Energy stored inside the atoms that make up all matter
Nuclear reactions produce heat and light

21. Energy transformation
Energy can be passed from one object to another. This is known as energy transfer.
For example: Kicking a ball energy from foot  ball moves

22. Energy transformation
Energy can change from one form to another. For example:
A toaster
Electrical energy
Heat energy

23. Elastic potential energy
For Example: An iPod
For Example: A wind up toy
Heat energy
Sound energy
Electrical energy
chemical energy
Kinetic energy
Sound energy
Heat energy
Elastic potential energy

24. Kinetic energy + heat + sound
Activity 1
When a glass is accidently knocked off the table, list the energy transformations as it falls into pieces.
Glass on bench
Gravitational energy
Glass falls
Kinetic energy + heat
Glass breaks
Kinetic energy + heat + sound

25. Kinetic + sound + heat energy
Activity 2
Discuss the energy transfer from the sun to a fan.
Sun
Light energy
Solar cell
Electrical energy
Fan
Kinetic + sound + heat energy

26. The law of conservation of energy
Energy cannot be created nor destroyed. It can only be transformed from one form to another.
Energy might be passed on or wasted, but it is never lost
If one object wastes energy, then it is always gained by another object, usually as heat.

27. Useful and Wasted Energy
Moving object has kinetic energy
When it slows the friction between it and the ground produces heat energy
Eventually it will stop and all the kinetic energy is now heat energy
The heat energy is wasted energy

28. Fill out the following table for energy conversion
Example
Initial energy
Useful energy produced
Wasted energy
Electric toothbrush
Electrical energy
Kinetic energy
Heat and sound energy
Playing soccer
Listening to music using an iPod
Light bulb
Dancing

29. Answers Example Initial energy Useful energy produced Wasted energy
Electric toothbrush
Electrical energy
Kinetic energy
Heat and sound energy
Playing soccer
Chemical energy from digested food
Kinetic energy of kicking the ball
Listening to music using an iPod
Chemical energy from batteries
Sound and light energy
Heat energy
Light bulb
Electrical energy from power point
Light energy
Dancing
Kinetic energy from moving your body

30. Your turn
Answer questions 1 – 18 from 5.1 on page 175 of the Pearson Science 8 text book