system
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human
Is there a correlation between 1 cal = 4.184 J and water’s heat capacity of 4.184 J/g°C?

I’m in an online introduction class to chemistry. Today’s lesson covered energy, temperature, heat capacity and such. There was one part of the lesson that said 1 calorie is equal 4.184  joules. Later in the lesson there was a part that said water’s heat capacity is 4.184 J/g°C. I noticed that numbers were the same between the two. No where in the lesson did it address this similarity. So I was wondering if there’s a reason that these numbers are the same or if some there is some kind of correlation out side of having joule as part of the measurement? Or is this just coincidence?
gpt
It's not a coincidence at all. The "calorie" unit is defined to be the amount of energy required to increase the temperature of 1 gram of water by 1 Kelvin (or °C, which represents the same temperature increment). As such, it is directly linked to the heat capacity of water.

The heat capacity of water depends on the pressure and starting temperature, so the amount of energy that 1 cal represents changes slightly with these variables. The conversion value of 4.184 corresponds to water at atmospheric pressure with a temperature somewhere around 18 °C. It was picked as the standard conversion rate between calories and Joules.