Question

One way to keep the contents of a garage from becoming too cold on a night when a severe subfreezing temperature is forecast is to put a tub of water in the garage. If the mass of the water is 125 kg and its initial temperature is 20°C, (a) how much energy must the water transfer to its surroundings in order to freeze completely and (b) what is the lowest
possible temperature of the water and its surroundings until that happens?​

Answer 1

Answer:

Explanation:

The water ( of mass m ) releases energy in two steps, first by its temperature from 20

o

C to 0

o

C, and then by freezing into ice. Thus the total energy transferred from the water to the surroundings is

Q=C

W

​

mΔT+L

p

​

m=(4190 J/kg.K)(125 kg)(20

o

C)+(333 kJ/kg)(125 kg)=5.2×10

7

J.