How does milk affect the cooling rate of coffee?

Specific Heat Capacity:

The specific heat capacity of a substance refers to the amount of heat required to raise its temperature by one degree Celsius. Milk has a higher specific heat capacity compared to coffee. This means that it requires more heat to raise the temperature of milk by the same amount as coffee.

Dilution:

When you add milk to coffee, you are diluting the coffee with a cooler liquid. This lowers the overall temperature of the coffee-milk mixture. The greater the amount of milk added, the more the coffee will be diluted and the lower its temperature will be.

Insulating Effect:

Milk acts as an insulator due to its fat content. The fat globules in milk create a barrier that slows down the transfer of heat from the coffee to the surroundings. This insulating effect helps retain heat and keeps the coffee warmer for a longer period.

Evaporation:

Milk has a higher surface tension compared to coffee. As a result, it forms a thinner layer on top of the coffee. This thin layer of milk reduces evaporation from the surface of the coffee, which further contributes to the slower cooling rate.

In summary, the addition of milk to coffee affects the cooling rate in multiple ways. The higher specific heat capacity, dilution effect, insulating properties, and reduced evaporation all contribute to slowing down the rate at which the coffee cools.