Energy Transfer By Heating Flashcards
The hotter the object…?
The more infra red radiation it emits.
What is Infra red radiation part of?
It is part of the electromagnetic spectrum and can travel in a vacuum.
How is infra red detected?
- Thermometer
- Sensors
- Infra red cameras
Light shiny surfaces are best at…?
Reflecting infra red
Dark matt surfaces are best at…?
Absorbing and emitting infra red
Solids
- particles are next to each other in fixed positions
- they vibrate about their fixed positions
- the forces between them are strong
Liquids
- particles move at random and are in contact with each other
- a liquid doesn’t have its own shape and can flow
- forces are weaker than solids
Gases
- particles move randomly and are further apart which means the density of the gas is less than a solid or liquid
- the particles have a lot more energy
- forces between them are very small
How can a substance change from one state to another?
By heating or cooling
What is a good conductor?
Metal
What is a bad conductor?
Insulators
What are fluids?
Liquids and gases
What does convection do?
Heat energy is transferred from hot places to cooler places by convection.
What don fluids do when they are heated?
They expand
How does a liquid evaporate?
When it’s molecules escape into the surrounding air
What happens when water condenses on glass?
Water molecules in the air form a liquid on the glass.
What happens when a liquid evaporates?
It looses it’s faster-moving molecules and it cools.
How can evaporation be increases?
The surface area
What does the rate of energy transfer depend on?
The SHAPE, SIZE and TYPE.
The materials the object is in contact with.
The TEMPERATURE and DIFFERENCE between the object and it’s surroundings.
As Electronic components can stop working if they over heat what is one way to prevent this.
They are fixed to metal plates to keep them cool.
What and why is loft insulation made up of what it is?
Fibreglass because it reduces the rate of energy transfer through the roof because it is a good insulator.
How are solar panels designed to suit their purpose?
They are matt black to absorb heat.
Plastic is a good conductor true/false?
False
Why are metals good conductors?
Metals are the best conductors of heat because they have free electrons which diffuse (spread out) and collide with other free electrons and ions. In this way they transfer kinetic energy.
Why is fibreglass a good insulator?
They are poor conductors because they have no free electrons
Convection?
A convection current is created when hot, less dense fluid rises and cold, denser fluid sinks
Evaporation?
Evaporation is when a liquid is turned into a gas and can be increased by increasing the surface area of the liquid, increasing the temperature or by creating a draught of air
What causes cooling?
This is due to the fast moving molecules that escape the liquid, this results in the kinetic energy decreasing.
What is condensation?
Condensation is when a gas turns into a liquid.
What do U Values do?
‘U-values’ tell us how much energy per second per m2 passes through different materials. The lower the U-value, the better the insulator
Why are solar panels expensive?
Because use solar radiation to heat water.
