Question

How much heat in kcal must be added to 0.45 kg of water at room temperature (20°C) to raise its temperature to 49°C?_____ kcal

Answer 1

The heat is defined as:

$Q=mc\Delta T$

In this case the mass is 0.45 kg, the specific heat is 4200 and the change in temeperature is 29, then we have:

$\begin{gathered} Q=(0.45)(4200)(29) \\ Q=92610\text{ J} \end{gathered}$

Now that we know the heat we need to convert it to kcal:

$92610\text{ J}\cdot\frac{1\text{ kcal}}{4184\text{ J}}=22.13$

Therefore, we need 22.13 kcal of heat.