Energy is something you can do work with:

The forms of energy are:

• heat
• light
• sound
• electrical
• stored
• kinetic (movement)

The amount of energy can be measured in joules or kilojoules:

• 1 kilojoule = 1000 joules

Stored Energy

Stored energy comes in three forms:

• Chemical
  • in fuels like oil and coal
  • in batteries
  • in chemicals like magnesium and sodium

• Potential energy
  • in things high up
  • in springs
  • in stretched elastic

• Nuclear
  • in radioactive chemicals like uranium

Energy can neither be created or destroyed

• it just changes from one form into another

Energy and Work

Energy changes are required before any work can be done with it.

The main energy changes that occur in a variety of simple situations are:

• battery chemical electrical
• steam engine chemical kinetic
• parachutist potential kinetic

Machines

A machine is a device for changing or transferring energy

• machines are designed to change energy from a less useful form to a more useful form
  • the change is never perfect and some energy is wasted in useless forms.
  • You never get as much useful energy out of a machine as you put into it
  • Mostly the waste energy is heat.
  • In a light bulb the energy change is electrical light and heat.
  • The light is the useful energy and the heat is the wasted energy.

Fossil Fuels

The fossil fuels are:

• coal
• oil
• natural gas

How fossil fuels were formed

Coal:

• 250 million years ago forests covered much of the land on earth
• under them a thick layer of peaty material formed
• over millions of years these remains were buried under layers of rock
• slowly the heat and pressure changed the remains into coal

Oil and natural gas

• In ancient oceans and lakes tiny plants and animals lived and died
• At the sea/lake bed a tick layer of rotting remains formed
• over millions of years these remains were buried under layers of rock
• slowly the heat and pressure changed the remains into oil and gas

The advantages and disadvantages of using fossil fuels

• Advantages
  • A kilogram of fossil fuel contains a lot of kilojoules, more than wood or peat
  • They are still relatively cheap

• Disadvantages
  • They cause pollution when burned
    • smoke
    • acid rain
    • in particular they cause global warming
  • They will run out eventually
  • Extracting them from the earth can be dangerous

Renewable and non-renewable energy

Fossil fuels and nuclear fuel are decribed as non-renewable because they will run out eventually.

• Types of renewable energy are:
  • Solar (sun) power
  • wave power
  • wind power
  • Hydro-electric power

• Advantages:
  • pollution free
  • will not run out

• Disadvantages:
  • on a dull, windless day with little waves they do not generate power
  • hey are expensive to set up
  • Can be eyesores

Hydro-electric power.

Produced from the kinetic energy of water flowing downhill

• Advantages:
  • pollution free, will not run out.

• Disadvantages:
  • dams must be built and areas of countryside must be flooded
  • They are expensive to set up.
  • In a dry year the water can run out.

Energy in Living Things

The human body needs energy to:

• keep itself running
• repair damaged tissue
• to grow

Food contains chemical energy to do this

• Energy changes take place in the body:
• Muscles chemical to kinetic
• Eyes light to electrical
• Ears sound to electrical Voice box – chemical to sound

Food Calcultions

All foods have labels on them which tell you how many kilojoules there is in 100 grams of the food:

You should be able to carry out calculations like this:

• How much energy is there in three spoons of sugar if:?
  • one teaspoon weighs 8 g
  • there is 1698 kJ of energy in 100g of sugar
  • 100g of granulated sugar contains 1698 kJ
  • 1 teaspoonful weighs 8g therefore there is 8/100 x 1698 kJ in the teaspoon = 136 kJ
  • so three spoons in a cup of tea will give you 3 x 136 = 408 kJ

  Food Chains and Foodr Webs

  A food chain is a way of representing the flow of energy from one creature to another:

  • Grain chicken human
  • Grass rabbit buzzard

  The arrows represent the energy flow

  A food chain always starts with a plant

  You should be able to make a food chain from this information:

  • Blue whales eat krill
  • Krill eat animal plankton (tiny marine animals)
  • Animal plankton eat plant plankton (tiny marine plants)

  A food web is a number of interconnected food chains that shows how energy moves in the environment:

  

  Make a food web from this information:

  • Grouse and rabbits eat heather
  • Rabbits and field mice eat grass
  • Foxes eat rabbits and grouse
  • Polecats eat rabbits and field mice