Flashcards in Energy Transfer by Heating Processes Deck (20)
What is infrared radiation?
All objects emit and absorb infrared radiation. The hotter an object is the more infrared radiation it radiates in a given time.
What surfaces are the best absorbers of infrared radiation?
Dark, matte surfaces. They are also good emitters.
What surfaces are the worst absorbers and emitters of infrared radiation?
Light, shiny surfaces
What surfaces are good reflectors of infrared radiation?
Light, shiny surfaces
What is the use of the kinetic theory?
To explain the different states of matter
What state are solids in?
Strong forces of attraction hold the particles together in a fixed and regular arrangement. The particles don't have much energy so they can only vibrate about their fixed positions.
What state are liquids in?
There are weaker forces of attraction between the particles in liquids. The particles are close together, but can move past each other, and form regular arrangements. They have more energy than the particles in a solid- they move in random directions at low speeds.
What state are gases in?
There are no forces of attraction between the particles in a gas. The particles have more energy than those in liquids and solids- they are free to move and travel in random directions and at high speeds.
What is conduction?
When you heat a solid, you give its particles extra kinetic energy and cause them to vibrate more. The particles collide with their neighbouring particles and pass some of their extra energy onto them, this is called conduction.
What does conduction happen faster in denser solids and metals?
Because the particles are closer together in a denser solid and so will collide more often and pass energy between them. Metal contain free electrons that are able to move inside the metal and pass on their extra energy to other electrons and particles in the solid.
What is convection?
When the more energetic particles in a liquid or gas move from a hotter region to a cooler region- and take their heat energy with them. Convection cannot happen in solids because because their particles can only vibrate.
What is condensation?
When a gas cools, the particles in the gas slow down and lose kinetic energy. The attractive forces between the particles pull them closer together. If the temperature gets cold enough and the gas particles get close enough together that condensation can take place, the gas becomes a liquid.
What is evaporation?
It is when particles escape from a liquid and form a gas. Particles can evaporate from a liquid at temperatures that are much lower than the liquid's boiling point.
The rate of evaporation will be faster if:
The temperature is higher
The density of the liquid is lower
The surface area of the liquid is larger
The condensation will be faster if:
The temperature of the gas is lower
The temperature of any surface the gas touches is lower
Concentration is higher
The rate at which an object transfers energy by heating depends on:
Surface area and volume
The material which the object is made of
The nature of the service which the object is in contact with
What is the relationship between the temperature difference of an object and its surroundings and the speed of the energy transfer by heat?
The bigger the temperature difference between the object and its surroundings, the faster the rate at which the energy is transferred by heating
What are U-values?
They measure how effective a material is as an insulator. The lower the U-value, the better the material is as an insulator.
What can solar panels be used for?
Solar panels may contain water that is heated by radiation from the sun. This water may then be used to heat buildings or provide domestic hot water.