Year 8 Energy Flashcards
What is the difference between heat and temperature?
Heat is a type of energy that is measure in Joules and can be transferred from one object to another, whereas temperature is measured in celsius, fahrenheit or kelvin and is measured using a thermometer
Why does temperature of an object decline rapidly at first, but slow down over time?
The larger the difference in temperature between objects, the quicker they will try to reach a thermal equilibrium
Why does the temperature of an object stay level when it is freezing?
When an object freezes bonds are formed between atoms in the object. To break bonds apart energy is required, so during the opposite (bonds forming), energy is released. This keeps the temperature level
Why are radiators made of metal?
Metal conducts heat, so it allows the heat to conduct from inside the room to out into the room
What is conduction in terms of heating?
When a substance is heated its particles gain energy and vibrate more vigorously. The particles bump into nearby particles and make them vibrate more. This passes the thermal energy through the substance by conduction, from the hot end to the cold end
What is convection in terms of heating? Explain using a heater in a room
The wall heater heats up the nearby air. As the air warms up, its density decreases. The less dense air rises. Cooler, denser air moves into its place. A convection current is set up. The heater eventually heats all the air in the room
In what states of matter can convection occur?
Liquids and gases
What is radiation in terms of heating?
All hot things emit infrared radiation. The hotter you are, the more IR radiation you emit. This radiation is the same as heat.
How does the sun transfer its heat to us and why?
By radiation, because conduction and convection require particles to be spread
What surfaces are good at absorbing IR radiation?
Dull, rough, dark surfaces
What surfaces are poor at absorbing IR radiation?
Smooth, shiny surfaces
What are the four types of heat transfer?
Radiation, convection, conduction and evaporation
How does a thermos flask prevent heat transfer?
There is a vacuum to prevent heat transfer through conduction and convection, there is a silver coating to reflect radiant heat back into the liquid, there is a plastic stopper which is a poor conductor of heat and trapped air, which is a poor conductor of heat
What is evaporation in terms of heat transfer?
All the particles in a liquid contain energy. When a particle evaporates it takes its energy away with it, so the liquid has slightly less energy, making it slightly cooler
