Podcast
Questions and Answers
What happens to molecules in a material when it is heated?
What happens to molecules in a material when it is heated?
- They gain kinetic energy and move slower.
- They lose mass and density decreases.
- They gain kinetic energy and start moving faster. (correct)
- They become more tightly packed.
Which material has the highest specific heat capacity listed?
Which material has the highest specific heat capacity listed?
- Water (correct)
- Brick
- Copper
- Aluminium
What is the specific heat capacity of brick?
What is the specific heat capacity of brick?
- 385 J/kg°C
- 129 J/kg°C
- 4,200 J/kg°C
- 840 J/kg°C (correct)
Which of the following statements is true regarding lead's specific heat capacity?
Which of the following statements is true regarding lead's specific heat capacity?
What factor does NOT influence the amount of energy needed to change a material's temperature?
What factor does NOT influence the amount of energy needed to change a material's temperature?
Why are bricks sometimes used in storage heaters?
Why are bricks sometimes used in storage heaters?
Which of these materials would require the least amount of energy to raise its temperature?
Which of these materials would require the least amount of energy to raise its temperature?
How much energy is needed to raise the temperature of 1 kg of water by 1°C?
How much energy is needed to raise the temperature of 1 kg of water by 1°C?
What is the specific heat capacity of water?
What is the specific heat capacity of water?
How is the thermal energy change calculated?
How is the thermal energy change calculated?
If a 0.25 kg mass of water needs to be heated from 20°C to 100°C, what is the temperature change (ΔΘ)?
If a 0.25 kg mass of water needs to be heated from 20°C to 100°C, what is the temperature change (ΔΘ)?
For a 2 kg steel block cooling from 300°C to 20°C, how would you calculate the thermal energy lost?
For a 2 kg steel block cooling from 300°C to 20°C, how would you calculate the thermal energy lost?
What is the required thermal energy to heat 0.25 kg of water from 20°C to its boiling point?
What is the required thermal energy to heat 0.25 kg of water from 20°C to its boiling point?
When a 3.5 kg brick is heated with 20,000 J of energy starting from 20°C, what is the increase in temperature?
When a 3.5 kg brick is heated with 20,000 J of energy starting from 20°C, what is the increase in temperature?
If a heating system using oil emits energy efficiently, what is its specific heat capacity?
If a heating system using oil emits energy efficiently, what is its specific heat capacity?
What does the specific heat capacity indicate about a material?
What does the specific heat capacity indicate about a material?
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Study Notes
Specific Heat Capacity
- Energy transmission occurs through conduction, convection, or radiation, with material conductivity assessed by energy transfer time.
- Heating materials increases molecular kinetic energy, resulting in temperature rise; temperature reflects average kinetic energy of molecules.
- Different materials require varying energy amounts for temperature changes, influenced by mass, substance (specific heat capacity), and desired temperature change.
Specific Heat Capacity of Materials
- Water's specific heat capacity: 4,200 J/kg°C; requires 4,200 Joules to raise 1 kg of water by 1°C.
- Other specific heat capacities include:
- Brick: 840 J/kg°C
- Copper: 385 J/kg°C
- Lead: 129 J/kg°C
- Lead warms up and cools down quickly due to low specific heat capacity; bricks retain heat longer, ideal for storage heaters.
- Common heater fluids: oil (1,800 J/kg°C) and water (4,200 J/kg°C) for effective energy retention.
Calculating Thermal Energy Changes
- The thermal energy change can be calculated using the formula: ΔEt = m × c × ΔΘ
- ΔEt = change in thermal energy (J)
- m = mass (kg)
- c = specific heat capacity (J/kg°C)
- ΔΘ = temperature change (°C)
Example Calculation
- Sadie’s model steam engine scenario:
- Mass of water: 0.25 kg
- Starting temperature: 20°C, boiling point: 100°C
- Specific heat capacity: 4,180 J/kg°C
- Thermal energy needed:
- Et = 0.25 × 4,180 × (100 - 20) = 83,600 J
Practice Questions
- Calculate thermal energy loss for a 2 kg steel block (c = 450 J/kg°C) cooling from 300°C to 20°C.
- Determine the final temperature of a 3.5 kg brick heated from 20°C using 20,000 J (20 kJ).
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