The temperature of a 700. g bar of iron decreases by 30oC when the iron is plunged into 500. g of water. What is the temperature increase of the water, assuming that no heat is lost in the transfer?

4.5 °C

Explanation:

According to the law of conservation of energy, the sum of the heat lost by the iron and the heat gained by the water is zero.

Qi + Qw = 0

Qi = -Qw   [1]

We can calculate each heat using the following expression.

Q = c × m × ΔT   [2]

where,

Replacing [2] in [1], we get

ci × mi × ΔTi = -cw × mw × ΔTw

ΔTw = -ci × mi × ΔTi / cw × mw

ΔTw = -0.108 cal/g.°C × 700 g × (-30 °C) / 1 cal/g.°C × 500 g

ΔTw = 4.5 °C