Question

A 200 g piece of iron is heated to 100°C. It is then dropped into water to bring its temperature down to 22°C. What is the amount of heat transferred to water? (ciron = 0.444 J/g°C)

Answer 1

The amount of heat transferred to water is equal to the amount of heat that is lost by the piece of iron dropped to it. To solve for the quantity of the heat in either direction, we use the equation,
                                   H = mcpdT
where H is heat, m is mass, cp is the specific gravity, and dT is the change in temperature. Substituting,
                                   H = (200g)(0.444 J/g°C)(100°C - 22°C)
                                      H = 6926.4 J
Thus, the heat lost by the piece of iron is approximately 6926.4 J. 

Answer 2

Answer - B) 6.9 kJ

Explanation - The amount of heat transferred depends on the mass of the object, the specific heat capacity of the material, and the change in temperature. So the heat lost by the piece of iron is:

Q = m x C iron x ΔT

Q = 200g × 0.444J/g°C × (22 – 100)°C

Q = –6926.4 J.

So the heat gained by the water (which was lost by the iron) must be the opposite of this, 6926.4 J