Explanation of specific heat capacity:

https://www.youtube.com/watch?v=5we65e7EOcg

More history behind Calories and calories:

https://spectrum.ieee.org/tech-history/dawn-of-electronics/how-counting-calories-became-a-science

More information on the Atwater system and its flaws:

https://www.livescience.com/62808-how-calories-are-calculated.html