energy and heating

• What are the three methods of energy transmission through a substance?

  Conduction, convection, and radiation
• What is a conductor?

  A conductor is a material that allows internal (thermal) energy to be transmitted through it easily
• Which materials are considered good conductors?

  All metals
• How does energy transfer occur in a metal rod when heated?

  Energy causes ions in the rod to vibrate faster, leading to more frequent collisions and energy transfer
• What happens to the rate of energy transfer when collisions between ions increase?

  The rate of transfer increases
• What is an insulator?

  An insulator is a material that will not allow the easy flow of energy
• Why does a metal seat feel cold compared to a cushion?

  Because the metal conducts energy away from the body more easily than the cushion
• How can the conductivity of materials be compared?

  By examining the time taken to transmit energy through them
• What is thermal conductivity?

  Thermal conductivity is a measure of how well a material conducts energy when it is heated
• What is the thermal conductivity of copper?

  385.0 W/m/°C
• Why are materials like brick, wood, and plastic used in house insulation?

  Because they are poor conductors of energy
• What is the aim of the experiment to compare the effectiveness of different materials as thermal insulators?

  • To measure temperature and time accurately
  • To observe the effect of different materials as thermal insulators
  • To use appropriate methods to measure effectiveness
• What is the method for comparing thermal insulators using beakers?

  Place a small beaker in a larger one, fill it with hot water, cover it, and record temperature changes
• What does a shallow curve on a temperature vs. time graph indicate about an insulator?

  It indicates that the material is a good insulator
• How does the temperature difference between a beaker and surrounding air affect the rate of energy transfer?

  A larger temperature difference results in a higher rate of transfer
• What are the hazards and control measures when conducting insulation experiments?

  Hazards:

  • Boiling water: Scald skin
  • Knocking beaker off the desk: Scald skin

  
  

  Control measures:

  • Do not overfill kettle
  • Place beaker away from desk edge
• What is specific heat capacity?

  Specific heat capacity is the energy required to raise one kilogram of a material by one degree Celsius
• What is the specific heat capacity of water?

  4,200 J/kg°C
• Why do bricks take longer to heat up compared to lead?

  Because bricks have a higher specific heat capacity than lead
• How is thermal energy change calculated?

  Using the equation: change in thermal energy = mass × specific heat capacity × temperature change
• How much thermal energy is needed to heat 0.25 kg of water from 20°C to 100°C if the specific heat capacity is 4,180 J/kg°C?

  Using the formula: $\Delta E_t =$$m \cdot c \cdot \Delta \theta =$$0.25 \, \text{kg} \cdot 4180 \, \text{J/kg°C} \cdot (100 - 20) \, \text{°C} =$$83,600 \, \text{J}$
• What is the aim of the experiment to measure specific heat capacity?

  • To measure potential difference, current, and time accurately
  • To observe temperature change and energy transferred
  • To use appropriate methods to measure specific heat capacity
• What is the method for measuring specific heat capacity using an immersion heater?

  Place the heater in a block, insulate it, and record temperature changes over time
• What is a common source of experimental error in measuring specific heat capacity?

  Heat loss to the surroundings
• What should be done to avoid burns when using an immersion heater?

  Do not touch the heater when switched on and allow it to cool before handling