Thermal Energy Transfers - Physics

• When water is heated so that it changes state and becomes a gas state what happens to the density?

  The density decreases
• What can you say about the average kinetic energy of the molecules in a gas if its temperature is constant?

  It stays the same
• Define what is meant by internal energy.

  The sum of all the kinetic energies and potential energies of all the particles in the system
• What happens to the internal energy of a liquid when it freezes?

  It decreases
• Define specific latent heat.

  The energy required to change 1kg of a substance from one state to another
• What is specific latent heat of fusion ?

  The energy required to change 1kg of the substance from solid to liquid
• What is specific latent heat of vaporisation?

  The energy required to change 1kg of a substance from a liquid to gas
• What is the name of the process that transfers thermal energy through a metal?

  Conduction
• Why are metals good thermal conductors?

  They have free delocalised electrons
• What is the opposite of a thermal insulator?

  A thermal conductor
• What affects the rate of thermal energy transfer?

  Thermal conductivity of a material.

  Thickness of a material
• What is thermal conductivity?

  The rate at which a material conducts heat
• What do most good insulating materials have in common?

  They contain trapped air

  Air is good insulator as is a gas and the particles are too far apart to pass on the more vigorous vibrations
• How can a home-owner reduce heat loss from their home?

  Loft insulation

  Double glazing

  Cavity wall insulation

  Draught excluders

  Hot water jacket

  Curtains
• What is pay-back time?

  The time taken for the money saved on energy bills to pay for the cost of installing the energy saving home improvement
• Name the 7 groups of the electro spectrum.

  Radio waves

  Microwaves

  Infrared

  Visible

  Ultraviolet

  X-rays

  Gamma rays
• Which of the electromagnetic wave spectrum has the longest wavelength?

  Radio waves
• Which of the electromagnetic wave spectrum has the lowest frequency?

  Radio waves
• Which colour surface emits the most radiation?

  Matt black
• Which colour surface emits the least radiation?

  Shiny silver
• Which colour surface absorbs the most radiation?

  Matt black
• Which colour surface absorbs the least radiation?

  shiny silver
• How does the temperature of an object affect the intensity of the radiation it gives out?

  The higher the temperature , the higher the intensity
• How does the temperature of an object affect the frequency of the radiation it gives out?

  The higher the temperature , the higher the intensity of all frequencies , and the higher the peak frequency
• How does absorption and emission of radiation affect the temperature of an object?

  If absorption is higher than emission , the object‘s temperature increases
• What is the equation for density?

  Density = mass/volume

  p = m / v
• What do electromagnetic waves have in common?

  Transverse waves

  Travel at the same speed in a vacuum
• Describe the arrangement and movement of particles in a solid?

  Arranged in a regular pattern

  Vibrate around a fixed point
• Describe the arrangement and movement of particles in a liquid.

  The particles are touching but are arranged randomly

  They can slide past each other
• How do you calculate the increase in internal energy?

  Increase in internal energy = mass x specific latent heat