Energy Flashcards
Define infrared radiation.
All objects are continually emitting and absorbing infrared radiation. Infrared radiation is emitted from the surface of an object.
How does the surroundings of an object affect the amount of heat emitted or absorbed?
Objects which are hotter than their surroundings will emit more heat than they absorb because the surroundings or cooler.
Objects which are cooler than their surroundings absorb more radiation than it emits.
What factor does radiation depend on?
colour of an object- black matt surfaces absorb infrared radiation better than light shiny surfaces. They also emit much more infrared radiation.
Light shiny surfaces reflect a lot of the infrared.
Explain kinetic theory.
Solids- strong forces hold particles together in a fixed regular arrangement, don’t have much energy so they only vibrate about their fixed position.
Liquids- weaker forces between particles, close together but can move past each other and form irregular arrangements. More energy than solids but move at low speeds.
Gases- No forces between particles, lots of energy and move freely, travel in random directions at high speeds.
Define conduction.
conduction only happens in a solid. Particles in a solid are heated which makes the particles vibrate in their fixed position, this causes them to collide with neighbouring particles and pass on their kinetic energy until the whole solid is heated. Conduction is faster in denser solids as the particles are closer together so collide more frequently and pass on kinetic energy.
Why are metals good conductors?
Metals are good conductors because they have free electrons between particles which increases collision and transfers kinetic energy faster as more particles are colliding with each other.
Define convection.
Convection occurs in liquids and gases. The fluid is heated which causes the particles to gain more energy and spread out, becoming less dense. The particles will then begin to rise and hit the cooler part of the fluid, the particles start to slow down and lose kinetic energy they become more dense and begin to fall. This forms a convection current.
What is condensation?
When a gas cools and particles in the gas slow down and lose kinetic energy, pulling the particles closer together.
What is evaporation?
When particles escape from a liquid.
Particles near the surface of a liquid can escape and become gas particles if the particles are travelling in the right direction and fast enough to overcome the forces.
How do we speed up the rate of evaporation?
increase temperature
decrease density
increase surface area
How do we speed up the rate of condensation?
decrease temperature
increase density
smaller surface area
What does the rate of heat transfer depend on?
Material object is on.
Material and colour of object.
surface area.
difference in temperature between object and surroundings.
Name 3 features you may want to install in your house to keep it well insulated and state what type of heat transfer they reduce.
Cavity wall insulator-
without foam- conduction
with foam- conduction and convection.
Loft insulation-
conduction and radiation
Double glazing-
without vacuum- conduction
with vacuum- convection and conduction
What do u- values do?
u-values show how fast heat can transfer through a material. Higher u-values mean that heat transfers faster through a material, good insulators have LOW u-values.
what is specific heat capacity?
How much energy stuff can store.
