You pour 140 g hot coffee at 78.7°C and some cold cream at 7.50°C to a 115-g cup

Question

You pour 140 g hot coffee at 78.7°C and some cold cream at 7.50°C to a 115-g cup that is initially at a temperature of 22.0°C. The cup, coffee, and cream reach an equilibrium temperature of 60.0°C. The material of the cup has a specific heat of 1091 J/(kg · K) and the specific heat of both the coffee and cream is 4190 J/(kg · K). Assume that no heat is lost to the surroundings or gained from the surroundings. (b) What is the absolute value of the heat transferred to the cream? (c) How much cream was added?

Explanation / Answer

heat lost or gain=massX sp heatX temp difference.

heat lost by coffee=0.140X4190X(78.7-60)----1

heat gained by cup=.115X1091X(60-22) -----2

heat gained by cold cream= mass X 4190X (60-7.5) ----3

when there is no loss of heat to the surroundings

heat lost=heat gained

so eq 1 = eq 2+ eq 3

solving we will get the value of mass of cream that was added.

after that when we substitute the value of mass in eq 3 we will get the absolute value of the heat transferred to the cream

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