Question

A cup of coffee(140g) cools from 75 degrees Celsius down to comfortable room temperature 20 degrees Celsius. How much energy does it release to the surroundings.

Answer 1

Energy releases to the surroundings = -32.2 kJ

Further explanation

Heat can be calculated using the formula:

Q = mc∆T

Q = heat, J

m = mass, g

c = specific heat, joules / g ° C

∆T = temperature difference, ° C / K

mass of coffee(m) = 140 g

∆T = temperature difference :

final temperature - initial temperature = 20-75=-55°C

specific heat coffee= specific heat water = 4.18 J/g° C

The heat releases :

`\tt Q=140* 4.18* -55\\\\Q=-32186~J\approx -32.2~kJ`