Heat Flashcards
Heat can cause ___________. For example ____________.
A steam engine
What is heat?
heat is a form of energy
What is heat measured in?
joules
what is temperature measured in?
degrees celsius
What happens to materials when heated?
They expand
What happens materials when cooled?
They contract
at what temperature does water behave like other liquids?
Above 4 degrees celsius
what happens to water above 4 degrees celsius?
It behaves like other liquids
What happens to water below 4 degrees
behaves oppositely to other liquids
At what temperature does water behave oppositely to other liquids?
below 4 degrees
what does reducing pressure do to water?
It lowers it’s boiling point below 100 degrees celsius
What does increasing pressure do to water?
It raises it’s boiling point above 100 degrees
What is temperature?
the measure of how hot or how cold something is
What is latent heat?
when heat causes a change in state and not a change in temperature
What is latent heat of fusion?
When heat changes a solid to a liquid with no temperature change.
What is latent heat of vaporisation?
when heat changes a liquid to a gas with no change in temperature
what are the three methods heat can travel by?
conduction, convection and radiation
What are insulators?
Materials that are poor conductors of heat
In general metals are __________________.
good conductors of heat
What happens to solids liquids and gases when…
(i) heated
(ii) cooled
(i) they expand
(ii) they contract
In what way does heat always move?
From something hot to something colder.
What is conduction?
conduction is the movement of heat through a solid without the particles in the solid moving out of position.
Metals are ____________. what does this mean?
conductors of heat. Heat passes through them easily by conduction.
name a good conductor
metals
What is an insulator?
a substance that does not allow heat to pass through it easily.
Insulators are…
poor conductors
Name two insulators.
wood and plastic
why are insulators used in the home?
Name 5 examples of this
to prevent heat loss
air trapped between two pains of glass in double glazed windows, feathers are used in bedding, fibreglass is used in attics to prevent heat loss, the material in a lagging jacket prevents heat loss from the hot water cylinder and polystyrene put between cavity walls in houses.
What is convection?
convection is the movement of heat through a liquid or gas by the movement of the particles in that liquid or gas.
What is radiation?
the movement of waves that can travel through a vacuum.
what is a vacuum? give an example
where there are no particles at all e.g. space
what is the difference in heat movement between a dull, black surface and a bright, shiny surface.
a dull, black surface radiates out heat better than a bright, shiny surface. a dull, black surface absorbs heats better than a bright, shiny surface.
what is latent heat?
the heat used by a substance to change it’s state - it does not raise the temperature.
What is the difference between heat and temperature.
heat is a form of energy, temperature is a measure of how hot or how cold something is. heat is measured in joules. temperature is measured in degrees celsius.
As heat is a ______________ it can be ________________.
As heat is a form of energy it can be converted into other forms
What do most materials do when heated?
Give an example
expand
Gaps are left in railway tracks to prevent the tracks from buckling when they expand in hot weather.
What do most materials do when cooled?
Give an example
contract
high voltage cables contract when cooled the cables are slack to avoid snapping in winter
Not all solids, liquids and gases expand by…
The same amount
what is the basic scientific principle behind the bi-metallic strip?
the fact that different solids expand by different amounts.
Name a use of the bi-metallic strip
switching on and off electrical circuits in response to a temperature change.
What happens when the bi-metallic strip is heated?
the copper expands more than the iron. this causes the bi-metallic strip to bend.
what will happen when the bi-metallic strip is cooled?
It will return to it’s original shape.
What is the special temperature for water?
4 degrees celsius
What will happen to water if you heat it above 4 degrees celsius
It will expand
What will happen to water if you cool it below 4 degrees celsius
It will expand
Above 4 degrees water…
behaves like any other liquids
below 4 degrees water…
behaves oppositely to other liquids
The behaviour of water makes it ________.
unique
What is the difference in relation to heat between a spoonful of boiling water and a pot of boiling water.
the pot full has more energy but the same temperature as the spoonfull.
Name a poor conductor and a good insulator
water
Poor conductors of heat are considered to be…
insulators
why are insulators important in the home?
to reduce heat energy losses
Heat will travel along a metal bar by….
The heat energy is…
The heat ________________ but the atoms do not ________________. They___________.
Conduction Passed from atom to atom along the bar. Moves along the bar Move along the bar Vibrate
What is happening if we heat something and the temperature does not rise?
It is changing state
If you continue to lower the temperature of water below 4 degrees celsius what will happen?
It will continue to expand
What happens to water at 0 degrees celsius?
It starts to turn into a solid called ice.
ice is ___________ than water
less dense
Because of ___________ the volume of ice is ___________ than the volume of water
volume
greater
ice _________ on water
floats
Name two examples where the unusual behaviour of ice has an effect on something.
Pipes burst in cold weather because water expands when it freezes.
When lakes freeze ice floats on top of the water because ice is less dense than water. This acts as a barrier between the cold air and the water below and allows fish to survive.
In conduction it is as if the heat is _______________. This is like…
passed from atom to atom
Pass the parcel
What does heat travel through liquids and gases by?
Convection
Name two examples of convection
When water molecules at the bottom of a saucepan get heat from the cooker these hot molecules move. The hot molecules bring the heat with them.
When air molecules get heat from heaters in a room these hot molecules move around the room. The hot molecules bring the heat with them.
how does heat reach the Earth from the Sun?
radiation
What does radiation not require?
medium
What is heat radiation considered to be?
electromagnetic waves
What do all hot objects emit?
heat by radiation
What is the average temperature of the human body?
37 degrees celsius
What does the human body emit?
heat by radiation
What can detect heat radiation?
special heat cameras
