A steel bar weighing 200 g was given 6 kJ of heat, while it heated up to 80C.

A steel bar weighing 200 g was given 6 kJ of heat, while it heated up to 80C. What is the initial temperature of the bar? The specific heat of the steel is 500J.

Data: m (weight of a steel bar) = 200 g (0.2 kg); Q (the amount of heat imparted to the bar) = 6 kJ (6000 J); t (temperature to which the bar was heated) = 80 ºС.

Reference values: according to the condition Сс (specific heat capacity of steel) = 500 J / (kg * ºС).

We express the initial temperature of the steel bar from the formula: Q = Cc * m * (t – t0), whence t – t0 = Q / (Cc * m) and t0 = t – Q / (Cc * m).

Calculation: t0 = 80 – 6000 / (500 * 0.2) = 20 ºС.

Answer: The temperature of the steel bar before heating was 20 ºС.