Burning Your Mouth on Your Coffee

If you want to drink your coffee at its hottest point do you put the cold milk in it at the store or when you get to your office?

If you think you should carry it all the way to your office and then put the cold shot of milk in it, you are wrong!

The amount of heat lost from your coffee depends on the temperature gradient from the coffee to the outside air - the bigger the difference the quicker the heat loss.

So, if the milk is going to drop the temperature of your coffee by 5º, your coffee will stay warmer by taking the 5º hit all at once at the beginning because less heat will be lost while walking with the cooler fluid.

What does this all mean?
Put the milk in your coffee at the coffee counter but bring back your buddy's coffee with nothing in it and let him drink cold coffee.