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JAMB Physics 1998 Question 21

Question 21

Change of State and Vapours

How many grams of water at 17 °C must be added to 42 g of ice at 0 °C to melt the ice completely? [Specific latent heat of fusion of ice = 3.4 × 105 J kg−1, Specific heat capacity of water = 4200 J kg−1 K−1]

  1. A.200 g
  2. B.300 g
  3. C.320 g
  4. D.400 g
Show the answer and explanation

Answer: A (200 g)

Explanation

Heat to melt the ice = 0.042 × 3.4 × 105 = 14 280 J. The water cools from 17 °C to 0 °C: m × 4200 × 17 = 14 280, so m = 0.2 kg = 200 g.