USING ENERGY 5.1 ENERGY AROUND US

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

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

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

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 = 2 500 000J Calculate how many megajoules of energy are contained in: C) 2 200 000 J D) 3 500 000 000 J 2 200 000 ÷ 1 000 000 = 2.2 MJ 3 500 000 000 ÷ 1 000 000 = 3 500 MJ

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

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

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

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.

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

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

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

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

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

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