Question

you pour 130 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 61.0°C. The material of the cup has a specific heat of 0.2604 kcal/(kg · °C) and the specific heat of both the coffee and cream is 1.00 kcal/(kg · C). If no heat is lost to the surroundings or gained from the surroundings, how much cream did you add?

Answer 1

In the given problem mass of cream or cream add can be find using below formula

According to law of mixtures,

Heat lost by Hot body = Heat gain by cold body

Heat lost by Coffee = Heat gain by Cream and Cup

Heat lost or gain can be find by the formula

Where S= specific heat of material

Mass of cream or cream add, M=21.2 g or 0.0212 kg