IGCSE Thermal physics

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IGCSE Thermal physics
2015-10-06 13:29:18
Thermal physics

Thermal Physics
Show Answers:

  1. What we call the process of giving off radiation
  2. What type of surfaces reflect radiation the best?
  3. What is the change of state from liquid to gas?
  4. Which state of matter fits the container shape (but doesn't fill it)?
  5. What type of materials make the best thermal conductors?
  6. Which two states of matter are fluids?
    Liquids and gases
  7. Why do hot fluids rise?
    Heating causes them to expand so they become less dense and so rise
  8. What type of surfaces are the best emitters of radiation?
    Dark coloured / rough
  9. What are the 3 common states of matter?
    • solids
    • liquids
    • gases
  10. What is the change of state from solid to liquid?
  11. What is the change of state from gas to liquid?
  12. Why are metals good conductors of heat?
    They have free electrons that are free to move, can collide with each other, and pass on their energy.
  13. What is convection?
    The circulation of a fluid caused by warmer fluids rising and colder fluids falling.
  14. Does evaporation warm things up or cool them down?
    Cools them down
  15. The type of radiation emitted by all warm things
  16. What type of surfaces absorb the most radiation?
    Dark coloured (and rough)
  17. Which state of matter has the lowest density?
  18. What do we call something that is a poor conductor of thermal energy?
  19. Why does convection not happen in solids?
    The particles in solids are not free to move around
  20. Name 4 ways to speed up the rate of evaporation
    • increase the surface area,
    • increase the temperature,
    • increase the air flow
    • reduce humidity
  21. Name five methods of heat transfer
    • conduction,
    • convection,
    • radiation,
    • evaporation,
    • condensation
  22. In the equation,
    Q = mcΔT (or E=mcθ)

    what does c  represent?
    The specific heat capacity of the material
  23. Why does good double glazing have a vacuum between the two panes of glass?
    Vacuums do not contain air particles so reduce energy loss through convection and conduction
  24. Which heat transfer mechanism works in a vacuum?
  25. Is air a good or bad insulator?
    Good, (because it is a gas the particles are far apart)
  26. If air is such a good insulator, why is cavity wall insulation more effective than just air?
    Cavity wall insulation traps air so reduces convection as well as conduction
  27. What is wrong with saying that heat rises?
    It is the hot fluid (carrying the thermal energy) that rises, not the heat
  28. Will a large difference in temperature between an object & its surroundings make its temperature change faster or slower?
  29. In the equation,

    Q = mcΔT (or E=mcθ)

    what does θ  represent?
    The temperature change
  30. Which is the only heat transfer mechanism that uses electromagnetic (EM) waves?
  31. What type of materials contain free electrons?
  32. Does a large block of copper need more or less energy to heat up by 5oC than a small block of copper?
    • More
    • (Remember that Q = mcΔT)
  33. What is the unit of energy (name and symbol)?
    Joule (J)
  34. Water has a high specific heat capacity. What does this mean?
    It takes a lot of energy to increase its temperature

    • Remember
    • Q = mcΔT (or Q=mcθ)
  35. Which heat transfer mechanism relies on particles passing energy from one to the other
  36. Why are car radiators painted matt black?
    Dark dull surfaces emit more heat energy than shiny light ones
  37. Why are solar heating panels usually painted black?
    Dark colours absorb more heat radiation than light ones so will be more efficient
  38. At what temperature does water evaporate?
    All temperatures above freezing. (The higher the temperature the faster it evaporates)
  39. What effect does increasing temperature have on the speed of particles in a gas?
    The higher the temperature, the higher the speed
  40. State some evidence of the random motion of particles
    • Brownian motion - Massive particles (smoke, pollen) may be moved by light, fast-moving molecules (air, water)
  41. What happens to the pressure of the gas if it's temperature is increased and the volume kept constant?
    The pressure increases(the high temperature means particles are moving faster which means more collisions per second with the walls of the container)
  42. Name three advantages of using a thermocouple to measure temperature
    • Measure a wide range of temperatures
    • Respond quickly to changes in temperature
    • Can be used in small inaccessible locations
  43. What is meant by "specific latent heat of fusion"?
    The quantity of heat energy needed to change unit mass from solid to liquid without temperature change
  44. What is meant by "specific latent heat of vaporisation"?
    The quantity of heat energy needed to change unit mass from liquid to vapour without change of temperature
  45. What is the difference between thermal capacity and specific heat capacity?
    Thermal capacity relates to a body and is the energy needed to raise the temperature of the body by 1°C.

    Specific heat capacity relates to a substance and is the energy required to produce a 1°C rise in 1 kg of the substance.

    i.e. Specific heat capacity only depends upon the substance an object is made of whereas thermal capacity ALSO depends upon its mass
  46. What are the two fixed points on the Celsius scale used to measure temperature?
    • -temperature of pure melting ice
    • 100°-the temperature of steam (above water boiling at normal atmospheric pressure)
  47. A gas is inside a container. What causes the pressure of the gas?
    Collisions between the molecules of gas and the wall of the container produce a force
  48. Which one of these does not need particles?
    A) conduction
    B) convection
    C) radiation
    C) radiation
    (this multiple choice question has been scrambled)