1. © 2009 Marshall Cavendish International (Singapore) Private Limited

2. Questions to think about… What are the forms of energy? What are the uses of energy? Can one form of energy change into another form? © 2009 Marshall Cavendish International (Singapore) Private Limited

3. Forms of energy and their uses All living things need energy to survive. Plants get their energy from the Sun to make food and grow, while animals and people get their energy from the food they eat. Without energy, living things cannot move, grow or do any work. Non-living things need energy to work too. For example, a car needs energy stored in petrol and a sailboat needs energy from the wind. © 2009 Marshall Cavendish International (Singapore) Private Limited

4. Forms of energy and their uses There are different forms of energy: Forms of energy kinetic energy light energy electrical energy heat energysound energy potential energy gravitational potential energy elastic potential energy chemical potential energy © 2009 Marshall Cavendish International (Singapore) Private Limited

5. Kinetic energy A moving object has movement energy or kinetic energy. For example, when you swing your arm, your arm has kinetic energy. When you throw a ball, the moving ball has kinetic energy. © 2009 Marshall Cavendish International (Singapore) Private Limited

6. Kinetic energy The amount of kinetic energy an object has depends on the speed of the object. The faster the object moves, the more kinetic energy it has. For example: o the faster you stir a drink, the more kinetic energy the drink has. o the faster the water in a river flows, the more kinetic energy the river has. © 2009 Marshall Cavendish International (Singapore) Private Limited

7. Kinetic energy Its uses: o People use kinetic energy from the wind and waves for recreational activities. o Kinetic energy from running water allows these wood planks to be transported to sawmills. o Wind turbines use kinetic energy from the wind to generate electricity. © 2009 Marshall Cavendish International (Singapore) Private Limited

8. Potential energy Energy can be stored in objects and used later. Energy that can be stored in objects is known as potential energy or stored energy. Some forms of potential energy: o gravitational potential energy o chemical energy o elastic potential energy © 2009 Marshall Cavendish International (Singapore) Private Limited

9. Potential energy Gravitational potential energy o When an object is above the ground, on top of a slope or hanging from something, it stores energy. o The higher the object is, the more energy it stores. o We call it gravitational potential energy. © 2009 Marshall Cavendish International (Singapore) Private Limited

10. Potential energy For example, a stationary egg on top of the edge of a kitchen cabinet does not have kinetic energy. It has gravitational potential energy because of its position on top of the edge of the kitchen cabinet. If the egg falls over the edge, the potential energy is changed to kinetic energy. © 2009 Marshall Cavendish International (Singapore) Private Limited

11. Potential energy Gravitational potential energy o A pile driver is used to drive heavy piles into the ground. o The hammer has potential energy when it is lifted high above the ground. o The potential energy is changed to kinetic energy as the hammer falls down towards the pile on the ground. © 2009 Marshall Cavendish International (Singapore) Private Limited

12. Potential energy Gravitational potential energy Some things in the environment, such as a waterfall, have gravitational potential energy due to their position above the ground. © 2009 Marshall Cavendish International (Singapore) Private Limited

13. Potential energy Gravitational potential energy o Can you identify in the photos below, the things that have gravitational potential energy? © 2009 Marshall Cavendish International (Singapore) Private Limited

14. Potential energy Food, batteries and fuels also store energy. This stored energy is known as chemical potential energy. © 2009 Marshall Cavendish International (Singapore) Private Limited

15. Potential energy Chemical potential energy o Food Food stores chemical energy. The food that we eat gives us energy to do work and keep our bodies warm. © 2009 Marshall Cavendish International (Singapore) Private Limited

16. Potential energy Chemical potential energy o Batteries Batteries also store chemical energy. When we switch on a battery- operated equipment, the chemical energy inside the batteries is changed to electrical energy. This enables the equipment to work. o For example, chemical potential energy is stored in batteries and allows our watches to work. © 2009 Marshall Cavendish International (Singapore) Private Limited

17. Potential energy Chemical potential energy o Fuels When fuels are burnt, they give off heat and light energy. Some examples of fuels are oil, coal, gas, wood and charcoal. All fuels store chemical energy. The chemical energy is usually converted to other forms of energy during burning. Most power stations use fuels such as coal and oil to generate electricity. © 2009 Marshall Cavendish International (Singapore) Private Limited

18. Other things that have potential energy Objects such as springs and rubber bands can also store energy. o The more you stretch a rubber band, the more elastic potential energy it has. o When you wind up a wind- up toy, energy is stored in the wound-up spring. o When you let the toy go, the toy moves as the spring unwinds. o The elastic potential energy is changed to kinetic energy. © 2009 Marshall Cavendish International (Singapore) Private Limited

19. Light energy Light energy is a form of energy that allows us to see. The Sun is the primary source of light energy on Earth. Lamps, candles and torches are also sources of light energy. © 2009 Marshall Cavendish International (Singapore) Private Limited

20. Light energy Besides helping us to see, light energy is also used to ‘capture’ images on films. Film projectors, overhead transparency projectors and visualisers make use of light energy to project images on a screen. © 2009 Marshall Cavendish International (Singapore) Private Limited

21. Light energy Light energy is also used to communicate or send messages. For example: o Traffic lights help to control the flow of traffic at road junctions. o Signal lights of a vehicle let us know the direction that the vehicle is heading. signal light © 2009 Marshall Cavendish International (Singapore) Private Limited

22. Light energy More examples: o The strong beam of light from a lighthouse guides ships in the dark and warns them of danger. © 2009 Marshall Cavendish International (Singapore) Private Limited

23. Light energy More examples: o Lights on the runway help to guide planes in taking off and landing. lights on the runway © 2009 Marshall Cavendish International (Singapore) Private Limited

24. Electrical energy Electricity is a form of energy which is also known as electrical energy. We use electricity in our homes, schools, offices, and almost everywhere else. Some electrical equipment, like torches and clocks, use energy from batteries. © 2009 Marshall Cavendish International (Singapore) Private Limited

25. Electrical energy Other equipment, such as lamps and computers, are plugged into electrical sockets. They use electrical energy that is produced in power stations. an electrical socket © 2009 Marshall Cavendish International (Singapore) Private Limited

26. Electrical energy Solar-powered equipment, such as some watches and calculators, use electrical energy from solar cells. Solar cells capture energy from the Sun and convert it to electrical energy. solar cells © 2009 Marshall Cavendish International (Singapore) Private Limited

27. Electrical energy Electrical energy allows equipment to work because electrical energy can be changed into other forms of energy like kinetic, light, heat and sound energy. © 2009 Marshall Cavendish International (Singapore) Private Limited

28. Heat energy Heat energy is a form of energy that we can feel. Heat energy makes us feel warm or hot. The Sun o The Sun is our main source of heat energy. o Heat energy from the Sun can dry many things such clothes, shoes and mattresses. o It can also dry food like prawns, vegetables, herbs, fruits and salted fish. dried chili © 2009 Marshall Cavendish International (Singapore) Private Limited

29. Heat energy Movement o Movement is able to generate heat. o For example, we rub our hands together vigorously when we feel cold. This produces heat to keep our hands warm. o Heat energy is produced whenever things are rubbed together or when they are hit against each other. This foot massage generates heat energy. © 2009 Marshall Cavendish International (Singapore) Private Limited

30. Heat energy Electricity o Many electrical appliances provide us with heat to carry out various activities. o The rice cooker, oven and toaster help us to cook food. o The kettle and water heater help us boil or warm water. o We use electric irons to iron our clothes. o Electric blankets and radiators are used in cold countries to keep people warm. © 2009 Marshall Cavendish International (Singapore) Private Limited

31. Heat energy Burning fuels o Heat energy can be obtained from burning fuels. o Natural gas, oil, charcoal and wood are burnt to produce heat for cooking. © 2009 Marshall Cavendish International (Singapore) Private Limited

32. Heat energy Burning fuels o Heat energy is also used in the food manufacturing industry. o Heat is able to kill germs that are present in the food before the food is canned. © 2009 Marshall Cavendish International (Singapore) Private Limited

33. Sound energy Sound is a form of energy that we can hear. Sounds are all around us. They can be very noisy, like thunder, or soft, like a whisper. We use sounds to communicate. For example: o We make sounds when we speak. o The sounds from sirens and fire alarms warn us of emergencies or possible danger. © 2009 Marshall Cavendish International (Singapore) Private Limited

34. Sound energy Music is made up of sounds that are produced when people sing, or when musical instruments are played. Music is usually used for entertainment. Different musical instruments produce sounds in different ways. Some are strummed or plucked, while others are hit, shaken or have air blown into them. © 2009 Marshall Cavendish International (Singapore) Private Limited

35. Energy conversions Energy changes from one form to another. o For example, during photosynthesis, plants use energy from sunlight to make food. o Light energy from the Sun is changed to chemical energy in the plants. Sun plant food light energy chemical energy © 2009 Marshall Cavendish International (Singapore) Private Limited

36. Energy conversions Energy changes from one form to another. o When we connect a circuit, the chemical energy in the batteries is changed to electrical energy, and then to light and heat energy. chemical energy electrical energy light energy + heat energy © 2009 Marshall Cavendish International (Singapore) Private Limited

37. Energy conversions Energy changes from one form to another. o Our bodies convert chemical energy in the food we eat to kinetic energy. chemical energy kinetic energy © 2009 Marshall Cavendish International (Singapore) Private Limited

38. Energy conversions Energy changes from one form to another. o When we switch on a television, electrical energy is changed to light, sound and heat energy. electrical energy light energy + sound energy + heat energy © 2009 Marshall Cavendish International (Singapore) Private Limited

39. Energy conversions Energy changes from one form to another. o Light energy from the Sun can be used to generate electricity. o Solar cells in a solar- powered vehicle can change light energy from the Sun to electrical energy to move the vehicle. light energy electrical energy kinetic energy solar-powered car © 2009 Marshall Cavendish International (Singapore) Private Limited

40. Energy conversions Energy changes from one form to another. o On a roller coaster, the cars climb to the highest point where they have the most gravitational potential energy. o As the roller coasters descend, the potential energy is changed to kinetic energy. gravitational potential energy kinetic energy © 2009 Marshall Cavendish International (Singapore) Private Limited