Heating and cooling Flashcards
How can heat energy be transferred?
By conduction,
convection,
and radiation
How much infrared radiation is an object that is hotter than its surroundings emitting compared to absorbing?
It emits more radiation than it absorbs because it’s cooling down.
What kind of material absorb and emit infrared radiation better?
Dark, matt surfaces.
What is the structure of a solid?
Strong forces of attraction hold particles close together,
in a fixed regular arrangement,
The particles don’t have much energy so they can only vibrate about their fixed positions.
What is the structure of a liquid?
They have weaker forces of attraction between the particles.
Particles are close together but they can move past each other and form irregular arrangements.
They have more energy than the particles in a solid.
What is the structure of a gas?
No forces of attraction between the particles.
More energy than in liquids or solids, free to move.
Travel in random directions at high speeds.
Describe the conduction of heat energy.
Conduction of heat energy is the process where vibrating particles pass on their extra kinetic energy to neighbouring particles.
Why do metals conduct heat so well?
Because they have free electrons that move around inside the metal.
What is convection?
Convection occurs when the more energetic particles move from the hotter region to the cooler region and take their heat energy with them.
Explain the convection current in an immersion heater
Particles near the bottom are heated and gain energy so they start moving faster which means they spread out and become less dense.
The hot water rises over the denser cold water, which gets heated.
Then the hot water cools down it becomes denser and sinks.
Creating a convection current.
What is condensation?
Particles in gas have different energies.
When particles in a gas cool they may not have enough energy to remain as separate particles, they come close together and bonds form between them.
What is evaporation?
The particles in a liquid have different energies.
Some will have enough energy to escape from the liquid and become a gas.
The remaining particles in the liquid have a lower average kinetic energy than before, so the liquid cools down as evaporation happens.
Why does sweating cool you down?
The sweat absorbs energy from your skin, so that it can continue to evaporate.
What does the rate at which an object transfers energy by heating depends on? (Name three)
Surface area and volume
The material from which the object is made
The nature of the surface with which the object is in contact.
Why do car engines have cooling fins?
Because they increase the surface area, so more infrared waves can be emitted from the surface so the quicker the transfer of heat.
