Energy Types and Transfers

energy forms and transfer

Law: Conservation of energy

Energy cannot be created or destroyed, only transformed into different forms of energy

There are many types of energy.

• Electrical - Magnetism

• Sound

• Thermal (heat)

• Light

• Chemical (ALL FUELS) potential

• Gravitational potential

• Kinetic (MOVEMENT)

Potential energy is a more scientific name for stored energy.

Potential energy can be divided into three types:

• gravitational potential

• Chemical potential

• Elastic potential (springs)

Open Ended

What is the law of conservation of energy?

Open Ended

List 4 energy types

Draw the energy changes for these:

• lamp

• geothermal power station

• coal fired power station

• radio

• wind up children's toy

answers

• lamp: electrical> light> heat

• Geothermal: heat> electrical

• fossil fuel: chemical> kinetic> electrical>heat

• radio: electrical> sound> heat

• toy: elastic> kinetic> sound> heat

Changing energy

There are many different ways for energy to change its form. 

We use Sankey Diagrams to show energy transfers:

In this diagram light is the useful energy.

Thermal energy is being wasted

Thermal Energy

• Hot objects have heat energy. Heat energy always moves from something hot to something colder. There is no such thing as cold energy, so an object can only get colder by heat energy moving away from it.

• There are three ways that heat energy can move:

• Conduction.

• Convection.

• Radiation.

Conduction

• When you first pour boiling water onto a Pot Noodle, the plastic container feels cool on the outside.

  
  

• Soon, the heat energy has worked its way through the plastic and the container starts to feel hot on the outside.

• Heat energy has travelled through the solid plastic container. This process is called conduction

ATOMS

• Atoms in a substance are always vibrating. If the substance gets hotter,the atoms vibrate more. The heat energy is given to the atoms, which makes them move about faster. 

• Note: the atoms don't swap places, or move around they just vibrate more on the spot.

• 
  

• Solids are better at conducting than liquids and gases because the atoms are closer together. If the atoms are too spaced out it makes it harder for the atoms to pass the energy along.

  
  

• Metals are the best solids for conducting heat energy. In metals, there are free electrons that can move through the metal. These electrons are able to move from hot parts of the metal to colder parts, taking the heat energy with them.

• The poorest conductors are gases as their molecules are too far apart to affect each other much. This means that air is a terrible conductor of heat energy.

  
  

Convection

• Hot air rises in cold air. Hot water rises in cold water. This way of moving energy is called convection. When hot air rises, colder air has to move in to replace it. When hot water rises in a cup, colder water sinks to replace it.

  
  

• This movement of a liquid or gas is called a convection current.

  Convection cannot happen in solids, as the atoms aren't able to move around.

  
  

• When a liquid or gas heats up, the particles move around more. This makes the particles spread out, so they have more room to move.

  
  

• This lowers the density of the substance. The hotter it gets, the lower the density goes. It is this lower density that makes the hotter substance rise.

• The cooler substance has a higher density, which makes it sink.

Radiation

• "How to toast bread!" When a piece of bread is put in a toaster the wires inside the toaster glow red hot on either side of the bread.

  
  

• How does the heat energy get to the bread?

• Is it by conduction?

  No, the heat energy cannot conduct through the air to the bread because air is a very bad conductor.

  
  

• Is it by convection?

  No, hardly any of the heat energy could have travelled to the bread by convection, as the hot air particles would rise out of the toaster.

Infrared radiation

• The heat energy must have reached the toast some other way. It travelled as radiated heat. This heat energy movement is sometimes called heat waves, but strictly speaking, it is infrared radiation.

• Hot objects radiate heat to their colder surroundings. The weird thing is that the surface colour of an object makes a difference.

  Black and dull surfaces emit (give out) and absorb radiation well.

• White and shiny surfaces do not emit radiation well and reflect radiation instead of absorbing it.

Multiple Select

Select the THREE types of thermal energy transfer

• conduction

• connection

• radiation

• convection

Multiple Choice

During convection, hot particles rise because they are ............. ......... than cold particles

• more dense

• less dense

• same density

• faster than

Multiple Choice

A change of state from liquid to gas happens when particles have enough ............ to transform

• juice

• movement

• speed

• energy

Multiple Choice

Which state of matter is best at 'conducting'

• solid

• liquid

• gas

Multiple Choice

What does the image show?

• radiation

• convection

• conduction

Multiple Select

convection happens in ......

• solids

• liquids

• gases

• fluids

Multiple Choice

What does this image show?

• convict

• conduction

• radiation

Multiple Choice

white objects ............. radiation

• absorb

• relflect

• emit

• emit and absorb

Multiple Choice

dark objects

• emit and absorb

• emit

• absorb

• reflect

Multiple Choice

What does the image show?

• conduction

• convection

• radiation