# How many calories of energy must be added to a 1 gram of water to increase its temperature by 1 degree?

The nice thing about working in $\text{cal}$s is that the specific heat capacity of water is unambiguously $\text{1 cal/g"^@ "C}$. With $\text{J}$, some places define it as $4.184$, some other places define it as $4.186$, and yet other places define it as $4.181$... that you should specify your source if you want to be precise. With $\text{cal}$, you know it's $1$.
The specific heat capacity is the amount of heat (e.g. $\text{cal}$, $\text{J}$, etc) that needs to be added for every $\text{g}$ of substance you have in order to raise the bulk substance's temperature by ${1}^{\circ} \text{C}$.
So if ${s}_{w} = \text{1 cal/g"^@ "C}$, then you would need $\text{1 cal}$ to raise the temperature of $\text{1 g}$ of water by ${1}^{\circ} \text{C}$.