I have a really fundamental question regarding the internal heat energy of a body. From textbooks, we know: $$\Delta Q = m \cdot c \cdot \Delta T$$ where $m$ is the mass of the body, $c$ its specific heat and $\Delta T$ the temperature difference.
The last part of this equation implies that their need to be a difference in temperature to get a difference of the heat. Is it possible to say that the "absolute" amount of internal heat is defined as: $$Q = m \cdot c \cdot T,$$ where $T$ is the absolute temperature?
Think about $1\,\mathrm{kg}$ of water with a specific heat of $4.19\,\mathrm{\frac{kJ}{kgK}}$ at a temperature of e.g. $400\,\mathrm{K}$. Is it correct to state the internal heat (or internal heat energy) then equals to
$$Q = 1\,\mathrm{kg} \cdot 4.19 \mathrm{\frac{kJ}{kgK}} \cdot 400K = 1676\,\mathrm{kJ} \quad ?$$