Making things happen Energy What is energy Forms

Making things happen: ‘Energy’ • What is energy? • Forms of energy and energy changes • Wasted energy • Conservation of energy • Renewable energy or non-renewable energy

Brain Storming -What is energy? Sit in a group of 5 or 6 people. � Select someone to write down all the ideas. � Everyone should try to give at least one input about energy. Some suggestions: � Think of a sentence with the word ‘energy’ in it � Draw something with a lot of energy � What do we use energy for? � What is energy?

Sun is our big energy source.

Plants need sunshine to grow through the process of photosynthesis, and some plants will become food for us.

Some animals eat plants and they produce or become our food.

Running cars have energy.

Running wind has energy-Tornado

Running water has energy. Tsunami

Water stored in the dam has energy.

Because once it’s released, it can do work.

When catapult is pulled, it has energy.

Burning wood has energy.

Sound has energy too.

Electrical energy

Your Mac needs electrical energy to run as well.

What is energy? We can’t really see energy, but we could know something has energy when something happens. If you have a lot of energy, then you can do a lot of work. You do work when you use a force to move something. Energy is the ability to do work. The more energy something has, the more work it can do.

What is work? Work is the product of force and distance. Work = Force times distance �Anything that does work must have a supply of energy.

Measuring energy Energy is measured in joules (J), kilojoules (k. J) and megajoules (MJ). 1 kilojoule = 1000 joules Or 1 k. J = 1000 J 1 megajoule = 1000 joules Or 1 MJ = 1000 J

Energy from food �Aim: To find out how much energy is released when a small piece of food burns. �Materials: refer to handout provided �Method: �Results: Mass (g) Burger ring Nutri grain �Discussion: Initial temperature of water (o. C) Final temperature of water (o. C) Temperature increase (o. C)

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Forms of energy �Kinetic energy �Gravitational potential energy �Elastic potential energy �Chemical energy �Nuclear energy �Sound energy �Heat energy �Light energy �Electrical energy

Energy Changes Energy can be transferred from one object to another. e. g. (i) in golf, a ball at rest is made to move by a moving golf club. Some of the kinetic energy of the club is transferred to the ball. e. g. (ii) When you heat water on a stove, heat energy is transferred from the gas flame or the electrical heating element to the water, causing it to boil

. Energy can also be converted or transformed from one form into another. e. g. (i) if you rub your hands together they become warm. You have converted the kinetic energy of your moving hands into heat energy. Kinetic energy heat energy e. g. (ii) a candle is designed to convert stored chemical energy into light, but some of the stored energy becomes heat. chemical energy light energy + heat energy (iii) When you use an electric drill, electrical energy is converted into kinetic energy, sound energy and heat energy (the drill becomes hot) Electrical energy kinetic energy + sound energy +

Electrical energy is useful because you can easily convert it into other forms of energy.

The law of conservation of energy �Energy cannot be created or destroyed – it can only be converted from one form to another. This is called the law of conservation of energy. �If all the input energy could be added up and compared with all the output energy, it would always be the same. energy input = energy output �The total energy remains constant, but the type of energy will change.

Energy efficiency �The efficiency of an energy converter is the percentage of the input energy which is turned into useful energy. �Efficiency = useful energy x 100 � input energy �For example, the efficiency of a car is about 25%. Because there is always some waste energy, the efficiency of an energy converter is always less than 100%.

Energy efficiency =useful energy x 100 input energy = 900 x 100 1300 = 69%