Let's start by explaining that 1 Calorie ([tex]1 cal[/tex]) is defined as a unit of thermal energy that is equivalent to the amount of heat ([tex]Q[/tex]) needed to raise the temperature of 1 gram [tex]1g[/tex] of water by 1 degree Celsius [tex]1\°C[/tex].
The formula to calculate it is:
[tex]Q=m. c. \Delta T[/tex] (1)
Where:
[tex]m[/tex] is the mass
[tex]c[/tex] is the specific heat of the element. In the case of water [tex]c=1cal/g[/tex]
[tex]\Delta T[/tex] is the variation in temperature, which in this case is [tex]\Delta T=70\°C-30\°C=40\°C[/tex]
Rewriting equation (1) with the known values:
[tex]Q=(105g)(1 cal/g)(40\°C)[/tex]
[tex]Q=4200 cal[/tex]
