Coffee with hot milk but without hot water compared to coffee with 75% hot milk and 25% hot water. Seems the latter retains more heat. Note: Final beverage quantity of both cases are same and also assume milk and water having same temperature while making beverage.
In: Physics
bc, water has a higher specific heat capacity, which means it can absorb and store more heat energy before its temperature changes. so, when you mix hot water with coffee, it stays hot longer than when you mix it with milk.
The terms you’re looking for are “thermal mass” (you can also read about specific heat) and “thermal conductivity.”
Water acts like a big canister for energy (heat) and milk is a little smaller canister. So it takes longer to empty all that stored heat from the water, compared to milk which is more easily emptied due to its lower capacity.
More heat is lost due to evaporation the hotter the drink is. You can do an experiment: fill two cups of coffee, pour milk in one of them. After two minutes, pour the same amount of milk in the other. You should get the result that the cup you poured milk in first is hotter due to this.
Are you mixing in hot milk or cold milk?
If the milk and the water being added are at the same temperature and added at the same time, there are only three factors at play: the specific heat capacity of the liquid being added, the boiling point of that liquid (or I suppose it’s corresponding volatility at the relevant temperature) and its thermal conductivity. The last two are pretty much the same between water and milk (<1%), but the former is around 10% lower for milk, which could explain the difference. That’s still pretty small though, so I feel there could be other factors at play (i.e. the first two criteria I stipulated are not met).
Edit: I guess four factors, as the latent heat of vaporisation is relevant to heat loss to evaporation as well as the boiling point. However it seems that this is more or less comparable to the specific heat between the two liquids (someone correct me if I’m wrong).
Fat is very good at transferring heat. It’s why we use it for cooking. Milk is an emulsion of water and fat. The fat in the milk is much better at transferring the heat out than the water is, so it gets colder faster.
Milk also has fat and proteins in it that lower the specific heat capacity compared to regular water.
Others have provided answers centering on specific heat capacity, which function to confirm your observation and give what you observed its established name. But these answer’s don’t explain, they just give a name.
Water has such a high specific heat capacity because of its molecular composition and structure.
1. There are 2 hydrogen atoms per molecule, and the hydrogen bonds are particularly strong, requiring a lot of energy to break and thus being able to store a lot of energy
2. The structure of the water molecule also boosts its storage capacity. The single oxygen molecule has two protons on one side, and two electron on the other side, and this makes the molecule polar (a difference in electrical charge from one side to the other), with a four-square, or tetrahedral structure. This optimizes the storage capacity of the hydrogen bonds discussed above.
As others have pointed out, milk is *mostly* water, but about 10% of milk is various compounds – fats, proteins, carbohydrates, each of which don’t store heat as effectively as water does. This lowers the specific heat capacity of milk when compared to water.
Can someone ELI5 what coffee without hot water is?
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