P1.1 Flashcards
What type of radiation do all objects emit and absorb?
Infrared radiation
How does the temperature of an object impact the amount of infrared radiation it emits?
The hotter the object, the more infrared radiation it emits.
What type of surfaces are good emitters and absorbers of infrared radiation?
Dark, matt surfaces
Which type of surfaces are the worst at absorbing and emitting infrared radiation?
Light, shiny surfaces
What types of surfaces are the best reflectors of infrared radiation?
Light, shiny surfaces
Which state particles have the most energy?
Gases
How are particles in a solid arranged?
Packed tightly together
Regular pattern
How do particles in a solid move?
They vibrate around a fixed position.
How are liquid particles arranged?
Close together
Random pattern
How do liquid particles move?
Slide around each other
How are gas particles arranged?
Far apart
Random pattern
How do gas particles move?
Rapidly
In any direction
Why can’t solids or liquids be squashed?
The particles in solids and liquids are packed close together and so can’t move into any spaces.
What is conduction?
The transfer of thermal energy throughout a substance.
What are poor conductors of heat called?
Insulators
Explain how conduction would occur in a solid metal
One part of the material is heated
Atoms gain energy and begin to vibrate as a result
Vibrations spread throughout the material because atoms are close together
Heat is conducted
What is the role of free electrons in conduction?
Electrons leave their atoms and move around freely once they became delocalised.
As electrons have left, the atoms become ionised.
The ions vibrate continually due to the kinetic energy they have.
The free electrons transfer the kinetic energy from hot parts of the material to colder parts.
The free electrons continue to move throughout the metal and hit more ions.
What are fluids?
Liquids and gases
What is convection?
When fluids with a lot of heat energy replace cooler particles.
What does convection transfer?
Heat energy
What happens when liquids and gases are heated?
They expand
Why do fluids expand when they are hotter?
They have more thermal energy and so move faster
The gaps between particles are larger
The fluid takes up a larger volume
If the fluid has expanded, how does its density change?
It decreases
How do convection currents occur?
When particles gain more heat energy, they expand and so become less dense.
Surrounding particles are more dense, so the hotter particles rise
Once the particles are surrounded by more cold particles and they bump into each other, heat energy is lost
The particles become more dense and so fall back down.
There is a continuous cycle of particles rising and falling back down again.
What is evaporation?
The process of a liquid changing into a gas
What does a liquid need in order to become a gas?
Lots of energy!
When evaporation occurs, why does the remaining liquid cool down?
Because the particles with the most energy are able to escape the liquid in order to become a gas
When these particles leave, the average kinetic energy level decreases
Therefore the liquid is cooler
Give an example of when evaporation cools you down.
Sweating.
What is condensation?
The process of a gas turning into a liquid.
Explain the process of condensation
If a gas is cooled down, particles may not have enough energy to remain separate from each other and so bonds are formed between them.
When this happens, energy is released therefore the particles cool down and become liquid.
When does the rate of condensation increase?
Is the temperature of the gas decreases
When does the rate of evaporation increase?
The temperature of the liquid increases
The surface area of the liquid increases
Air is moving over the surface of the liquid
Which factors impact the rate at which an object transfers energy by heating?
The difference in temperature between the object and its surroundings
Surface area to volume ratio
Material of object
The nature of the surface that the object is touching
How does surface area to volume ratio impact heat transfer?
The larger the surface area compared to the volume, the faster heat is transferred.
How must animals with a large surface area to volume ratio conserve energy due to heat loss?
They need to consume more food.
Give an example of an animal with a small surface area to volume ratio
An elephant
What problem do animals with small surface area to volume ratios face?
Overheating
How do animals with small surface area to volume ratios avoid overheating?
By having large ears to increase surface area and therefore maximise heat loss.
What effect do fins on car radiators have on heat transfer?
They increase surface area so that heat transfer is maximised.
How is the effectiveness of an insulator measured?
By its U-value
How do U-values show the effectiveness of materials as insulators?
The lower the U-value, the more effective the material is as an insulator.
How do solar panels work?
They contain water which is heated by the Sun’s radiation
The heat energy can then be used to heat buildings or provide hot water in houses.
What is specific heat capacity?
The amount of energy needed o change the temperature of a substance by 1 degree Celsius.
Give the formula for working out energy.
E= m x c x Ø
What does c represent in this formula?
Specific heat capacity
What does Ø represent?
Temperature change
What does m represent?
Mass
What is specific heat capacity measured in?
J/kg°C
