insulation

• What is one way to reduce unwanted energy transfers?

  Using insulation materials
• How does the kinetic energy of a football change when kicked directly upwards?

  It decreases as it rises
• How does the gravitational energy of a football change as it is kicked upwards?

  It increases as it rises
• How does a football lose energy to the surroundings when kicked?

  Through air resistance and sound
• What is the purpose of the required practical for thermal insulation?

  To investigate how different materials insulate
• What is the equation for kinetic energy?

  Kinetic energy = $\frac{1}{2}mv^2$
• Calculate the kinetic energy of a football with a mass of 200g traveling at 4m/s.

  Kinetic energy = $\frac{1}{2} \times 0.2 \times 4^2 =$$1.6 \text{ J}$
• What is the equation for elastic potential energy?

  Elastic potential energy = $\frac{1}{2}kx^2$
• What is the spring constant of a spring that stores 100J of energy when stretched 0.4m?

  Spring constant = $\frac{2 \times 100}{0.4^2} =$$1250 \text{ N/m}$
• Calculate the velocity of a 0.1kg apple falling from a height of 5m, assuming $g=$$9.8 \text{ N/kg}$.


  Velocity = $\sqrt{2gh} =$$\sqrt{2 \times 9.8 \times 5} \approx 9.9 \text{ m/s}$
• Why is it important to measure the starting temperature of the water in the practical investigation?

  To ensure accurate comparisons of data
• Suggest two ways to improve the precision of data in the insulation investigation.

  Using a digital thermometer and measuring at more frequent intervals
• Why is it important to use the same mass of insulating material each time?

  To ensure consistency in the experiment
• What are the ways to improve the insulation experiment?

  • Adding a lid
  • Measuring the mass of the insulating material
  • Measuring temperature change over a longer period
  • Measuring at more frequent intervals
  • Using a digital thermometer
• What factors determine why some materials are better insulators than others?

  • Density of the material
  • Structure and composition
  • Air pockets within the material
  • Thermal conductivity
• What is the process to identify the best insulator from experimental data?

  1. Record temperature changes for each material
  2. Compare the temperature changes
  3. Identify the material with the least temperature change as the best insulator
• conduction occurs when particles collide with one another causing energy to be transferred from hotter to cooler parts of the material
• Convection occurs due to differences in density caused by different temperatures, which causes movement of air or liquid.
• Radiation occurs when electromagnetic waves transfer heat between objects without any medium being involved.
• A good insulator will have low thermal conductivity, high specific heat capacity and contain lots of trapped air pockets.
• • Heat loss through the roof can be reduced by laying loft insulation. Air is trapped between the fibres of the insulation, reducing heat loss by conduction.
• • Heat loss through walls can be reduced using cavity wall insulation. This involves blowing insulating material into the gap between the brick and the inside wall. Insulating materials are bad conductors and so this reduces the heat loss by conduction. The material also prevents air circulating inside the cavity, therefore reducing heat loss by convection.
• • Heat loss through windows can be reduced by using double glazing. These windows have dry, trapped air between two panes of glass. This reduces heat loss by conduction and convection. Air is a poor conductor and by trapping it between the panes, convection currents cannot be set up.
• The thermal conductivity. of a material is a measure of how quickly energy transfers through it by heating: