A 300 W heater is used to boil 500g of water at l00 °C. How long should the heater be switched on? (The specific latent heat of vaporization of water is 2230 J/g).
Correct answer: A. 62min
- A. 62min
- B. 62 sec
- C. 1.5 hour
- D. 0.5 hour
Explanation
t = Q/P= m x lf/P= 500 x 2230/300 = 3717 seconds = 62 minutes
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Thermal equilibrium means that bodies in contact have the same temperature and no net heat flows between them. The topic distinguishes heat from temperature, uses the zeroth law of thermodynamics, and covers heat transfer, specific heat capacity, thermal expansion and the conditions for reaching equilibrium.
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