Problem 100P

If 1.45 L of water is initially at 25.0 °C, what is its temperature after absorption of 9.4 × 10−2 kWh of heat?

Solution 100P

Answer :

One widely-quoted value for the specific heat of water is " 4.187 kJ / kg K ", meaning 4,187 joules to change the temperature of 1 kg of water 1 Kelvin (or 1° C). -- To make it easy on ourselves, we assume without proof or discussion that the mass of our 1.45L of water is 1.45 kg.So it takes (4,187 x 1.45) = 6,071 joules to accomplish each °C that we want to raise its temperature in the question, because it doesn't give us any defined amount of energy. instead of "94 kilowatts", we use "94 kilowatt-seconds", THEN we would have 94,000 joules. If the water were to absorb every single erg of that and settle 1 into thermal equilibrium, its temperature would rise by 94,000 / 6,071 = 5.48° C and its final temperature would be 40.48° C.