Question

How many calories are required to raise the temperature of 105 g of water from 30.0°c to 70.0°c?

Answer 1

Answer: 4200 calories

Let's start by explaining that 1 Calorie ($1 cal$) is defined as a unit of thermal energy that is equivalent to the amount of heat ($Q$) needed to raise the temperature of 1 gram $1g$ of water by 1 degree Celsius $1\°C$.

The formula to calculate it is:

$Q=m. c. \Delta T$   (1)

Where:

$m$  is the mass

$c$  is the specific heat of the element. In the case of water $c=1cal/g$

$\Delta T$  is the variation in temperature, which in this case is  $\Delta T=70\°C-30\°C=40\°C$  

Rewriting equation (1) with the known values:

$Q=(105g)(1 cal/g)(40\°C)$  

$Q=4200 cal$