IGCSE · 2 · structured
Thermal physics · Question 8
Thermal physics · Original GioPhysics question with a detailed, mark-by-mark answer guide.
- Demand
- demanding
- Marks
- 9
- Topics
- 1
- Answer
- Complete
A 2.0 kW electric kettle contains 0.50 kg of water at 20 °C. The specific heat capacity of water is 4200 J/(kg °C) and the specific latent heat of vaporisation of water is 2.3 × 10⁶ J/kg.
- (a)
Define Define specific latent heat of vaporisation.
2 marks - (b)
Calculate Calculate the energy needed to raise the water from 20 °C to its boiling point of 100 °C.
2 marks - (c)
Calculate Assuming no energy is transferred to the surroundings, calculate the time taken for the water to reach its boiling point.
2 marks - (d)
Determine The kettle is left switched on after the water boils. Determine the mass of water that boils away in the next 60 s.
3 marks
Ready to self-mark?Reveal the detailed answer guide
(a)
Define Define specific latent heat of vaporisation.
Identify what the question is testing, organise the response into distinct mark-earning points, and make every conclusion traceable to a physical principle or to the evidence supplied.
- 1
the energy required to change unit mass of a substance from liquid to gas
- 2
without a change in temperature
(b)
Calculate Calculate the energy needed to raise the water from 20 °C to its boiling point of 100 °C.
List the given quantities with units, identify the required quantity, write the governing relationship before substituting, and keep extra digits until the final line so rounding does not distort the result.
- 1
E = mcΔθ = 0.50 × 4200 × 80
- 2
E = 168 000 J = 1.7 × 10⁵ J
(c)
Calculate Assuming no energy is transferred to the surroundings, calculate the time taken for the water to reach its boiling point.
List the given quantities with units, identify the required quantity, write the governing relationship before substituting, and keep extra digits until the final line so rounding does not distort the result.
- 1
t = E / P = 168 000 / 2000
- 2
t = 84 s
(d)
Determine The kettle is left switched on after the water boils. Determine the mass of water that boils away in the next 60 s.
List the given quantities with units, identify the required quantity, write the governing relationship before substituting, and keep extra digits until the final line so rounding does not distort the result.
- 1
energy supplied = 2000 × 60 = 120 000 J
- 2
m = E / L = 120 000 / 2.3 × 10⁶
- 3
m = 0.052 kg (52 g)
Private on this device