Question

What will be the result when 400 g of copper clips at 500°C are placed in 800 g of crushed ice at 0°C?

[SHC of copper = 0.42 J g⁻¹°C⁻¹ and SLH of ice = 340 J g⁻¹]

Answer 1

Assuming no heat is lost to the surroundings, the heat lost by copper clips when they cool from 500°C to 0°C:

Q = mcΔT

= 400 × 0.42 × 500

= 84000 J

Heat needed to melt all the ice:

Q = mL

= 800 × 340

= 272000 J

Since 84000 J < 272000 J, only part of the ice melts.

Hence the final temperature is 0°C.

Mass of ice melted $$(m) = \frac{84000}{340}$$

= 247.06 g

Ice left unmelted: 800 − 247.06 = 552.94 g ≈ 553 g

Therefore, about 553 g of ice does not melt and the final temperature is 0°C.