Question

As 390-g of hot milk cools in a mug, it transfers 30,000 J of heat to the environment.

How does the temperature of the milk change? (cmilk = 3.9 J/g°C)


a) It increases by 77°C.

b) It decreases by 77°C.

c) It increases by 20°C.

d) It decreases by 20°C.

Answer 1

Q = m.s.Δt
Δt = Q /m.s
Here, Q = 30,000 J
m = 390 g
s = 3.9 J/g C

Substitute their values,
= 30,000 / 390 *3.9
= 30,000 / 1521
= -20 C (approx.) [-ve sign 'cause temperature is decreasing ]

In short, Your Answer would be Option D

Hope this helps!