Question 16
Change of State and VapoursAn electric heater is used to melt a block of ice, mass 1.5 kg. If the heater is powered by a 12 V battery and a current of 20 A flows through the coil, calculate the time taken to melt the block of ice at 0°C. (Specific latent heat of fusion of ice = 336 × 103 J kg−1).
- A.76.0 min
- B.35.0 min
- C.21.0 min
- D.2.9 min
Show the answer and explanation
Answer: B (35.0 min)
Explanation
Heat needed = 1.5 × 336 000 = 504 000 J. Power = 12 × 20 = 240 W. t = 504 000/240 = 2100 s = 35 min.