Heat Energy Flashcards
What’s the difference between temperature and heat?
Heat: The amount of heat energy or particles there are.
Temperature: The average amount of energy there is within an object.
Temperature -
Of an object tells us how hot it is
Is measured using a defined scale
Unit is degrees Celsius
Heat and Temperature Difference -
It is NOT the same as heat energy, although the two quantities are related
e.g. a cup of water at 60 °C is hotter than a bath of water at 40 °C.
BUT the bath contains more joules of heat energy because there is a greater mass.
What’s convection?
Occurs in material where particles can move around inside the material.
The heat is carried by the particles moving, which often causes convection current.
This happens when an area with warm particles expands and become less dense than the cooler areas nearby. The warm area rises. Cooler particles nearby move into the space left by the warm particles and a convection current is set up.
What’s conduction?
Occurs by particles gaining energy, moving faster and hitting each other, which transfers their energy to other particles.
Can happen in solids, liquids and gases.
Conduction occurs very quickly in solids and more slowly in liquids or gases.
For example,
Materials that allow heat to move through them quickly are called thermal conductors.
Materials that do not allow heat to move through them quickly are called thermal insulators.
What’s radiation?
Heat transfer that does not require particles to transfer heat from one place to another.
The only way that energy can be transferred across empty space.
Objects that are hotter than their surroundings give out heat as infra-red radiation – they are emitters of radiation.
Radiation is the transfer of energy by electromagnetic waves.
Radiation = radiates (heat escaping the sun).
For example,
Fire
Heat Lamps
Sun
How does thermal/heat energy work?
Heat Energy: A type of energy that moves into materials to make them hotter and out of materials to make them cooler.
Amount of thermal energy
Measured in JOULES (J)
Particles move about faster and take up more room if heated – this is why things expand when heated.
It is also why substances change from solids to liquids to gases.
Heat and Cooling -
Heat energy always moves from hot to cold.
Heat Energy -
Heat energy can move/transfer from one object to another by conduction, convection and radiation.
What are the 3 ways that radiation is absorbed?
Transmission – the radiation passes through the object and heats up what’s inside it.
Absorption – the object ‘stores’ heat energy.
Reflection – the radiation is deflected from the object by a shiny surface, the object does not become significantly hotter.
Emitting thermal radiation, all objects give out some thermal radiation.
Surfaces with matt black surfaces are the best emitters but surfaces with silver or white or shiny surfaces are the worst emitters.
Heat Absorbers -
Cooler objects absorb heat.
Substances absorb heat at different speeds.
Dull, black surfaces absorb heat quickly.
Bright, shiny surfaces absorb heat slowly.
What’s the difference between radiation and infrared radiation?
The Earth is warmed by the heat energy from the sun.
The heat travels to Earth by infrared waves. These are similar to light waves and are able to travel through empty space.
Heat transfer from the sun to Earth is infrared radiation.
Heat transfer without particles is radiation.
