1.3 - Making Use of Energy

• Heat always transfers from hot to cold
• how heat transfers depends on the material or state of the matter
• Conduction happens in solids.
• Metals are the best conductors as they have free electrons
• Air is a poor conductor as it is a gas
• Convection happens in liquids and gases
• Loft insulation reduces heat loss due to conduction.
• All warm things emit heat radiation in the form of infrared waves
• Black surfaces absorb radiation best and emit radiation best
• Shiny surfaces reflect radiation well but are poor emitters and absorbers.
• radiation travel in all directions from the hot body into a colder body.
• Floor insulation reduces heat losses due to conduction
• Double glazed windows reduce heat losses due to conduction.
• Stopping draughts reduces convection
• Cavity walls reduce heat losses due to conduction
• Convection happens in liquids and gases.
• The greater the difference in temperature, the greater the rate of heat transfer
• density = mass / volume
• Heat is thermal energy
• Heat can be transferred by:

  • Conduction
  • Convection
  • Radiation
• CONDUCTION

  • Conduction occurs when vibrating particles pass extra energy to neighbouring particles through kinetic energy

  • Conduction mainly happens in solids

  • Metals are an example of good conductors of heat – they have free electrons which carry the kinetic energy around the solid

  • Non-metals tend to be bad conductors of heat, or insulators
• CONVECTION

  • Convection occurs when hotter areas expand, become less dense, and rise above cooler, denser surroundings

  • This process continues, creating a circulation (convection current)

  • Convection mainly happens in fluids (liquids and gases)
• RADIATION

  • Radiation can travel through a vacuum

  • Energy is carried by electromagnetic waves
• Payback time = installation cost / annual savings
• 3 methods of reducing heat loss in a building:

  • double glazing
  • loft and wall insulation
  • thicker walls
• Three methods of reducing heat loss in a building are double glazing, loft and wall insulation, and thicker walls.
• Density is the mass per unit volume of a material, represented by the equation ⍴ =m/v.
• The three states of matter from lowest to highest density of atoms are Gas, Liquid, and Solid.
• When a substance undergoes a change of state, the mass is always conserved.
• The three different types of energy transfer are Conduction, Convection, and Radiation.
• Convection is a process where heated fluids expand, making the particles spread out, and making the fluid less dense, causing less dense fluids to rise above cooler more dense fluids, and these cooler fluids then heat up and rise upwards, creating a cyclic motion of particles, known as a convection current.
• Conduction in a metal is a process where a metal consists of positive ions and free electrons, as temperature increases, the ions gain kinetic energy and vibrate, this energy is then passed on via collisions to free electrons which can move throughout the whole metal, these electrons transfer kinetic energy (again via collisions) to ions further through the metal, increasing their temperature.
• How are convection currents caused?

  Temperature differences, hot water expands to become less dense
• carbon footprint can be reduced if your house is well insulated
• electricity from the plug sockets (mains) is alternating current.
• Batteries and cells are sources of direct current