# HEAT ENERGY - PowerPoint PPT Presentation

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## HEAT ENERGY

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### HEAT ENERGY What is HEAT? Form of energy and measured in JOULES Particles move about more and take up more room if heated this is why things expand if heated – PowerPoint PPT presentation

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Title: HEAT ENERGY

1
HEAT ENERGY
• What is HEAT?
• Form of energy and measured in JOULES
• Particles move about more and take up more
room if heated this is why things expand if
heated
• It is also why substances change from
solids liquids gases when
heated

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2
Heat and Temperature
• The temperature of an object tells us how HOT it
is
• Measured in degrees Celsius - C
• It is NOT the same as heat energy although the
two quantities are related.

3
Heating and Cooling
• If an object has become hotter, it means that it
has gained heat energy.
• If an object cools down, it means it has lost
energy

4
Heating and Cooling cont
• Heat energy always moves from HOT object
COOLER object
• e.g.Cup of water at 20 C in a room at 30C -
gains heat energy and heats up its temperature
rises
• Cup of water at 20 C in a room at 10C loses
heat energy and cools down its temperature will
fall.

5
HEAT ENERGY
• Energy transfer Conduction

6
Conduction
• Heat is transferred through a material by being
passed from one particle to the next
• Particles at the warm end move faster and this
then causes the next particles to move faster and
so on.
• In this way heat in an object travels fromthe
HOT end the cold end

7
Conduction cont
• Occurs by the particles hitting each other and so
energy is transferred.
• Can happen in solids, liquids and gases,
• Happens best in solids-particles very close
together
• Conduction does not occur very quickly in liquids
or gases

8
Conductors
• Materials that conduct heat quickly are called
conductors
• All metals are good conductors of heat
• Copper is a very good conductor of heat
• Pans for cooking are usually made with a copper
or aluminium bottom and plastic handles

9
Insulators/poor conductors
• Materials that conduct heat slowly or poorly are
called insulators
• Glass, wood, plastic and rubber are poor
conductors (good insulators)
• Nearly all liquids including water are poor
conductors (good insulators)
• Gases, including air are poor conductors,e.g.,
wool feels warm because it traps a lot of air
• A fridge has insulation material round it to keep
it cold reduces amount of heat conducted to
inside from the warmer room

10
Convection
• Takes place in material where particles can move
around inside the material, i.e. liquid or gas
• The heat is carried by the particles themselves
moving Convection currents
• Occur because an area with warm particles expands
and becomes less dense than the cooler areas
nearby. The warm area rises.Cooler particles
fall into the space left by the warm particles
and convection current is set up

11
Convection Currents
• Hot liquids and gases expand and rise while the
cooler liquid or gas falls

2. Goes across
3. Then down
1. Hot air rises
4. And across
12
Convection cont
• The Sun can cause large convection currents -
WINDS
• During daytime the land warms up more than the
sea. The warm air rises over the land and cool
air falls over the sea. So we feel a sea breeze.
• Rising convection currents can be uses by glider
pilots to keep their planes in the air and by
birds to stay aloft.

13
• Transfer of heat directly form the source to the
object by a wave, travelling as rays.
• Heat radiation is also known as
• All objects that are hotter than their
surroundings give out heat as infra-red radiation
• Heat transfer by radiation does not need
particles to occur and is the only way energy can
be transferred across empty space

14
KEY WORDS
• 1-1 Heat A form of energy
• Heat
• Molecule
• Heat transfer
• Conduction
• Insulator
• conductor
• Convection