can someone help me with this thermal dynamic question?

Question

If you take a bite of hot pizza, the sauce my burn your mouth while the crust, at the same temperature, will not. Explain.

Answer 1

The difference lies in thermal contact and thermal diffusivity. The issue is one of heat transfer rather than temperature. The sauce dumps heat into your mouth at a much greater rate than crust.

First is thermal contact. The dry rigid crust only makes spotty contact with your mouth so there isn't that much area to tranfer heat through. The air gaps where the crust doesn't touch conduct heat onlt about 1% as well as the areas in contact.

Second is thermal diffusivity. Another name for this, in this case, is volumetric heat capacity coupled with thermal conductivity. When your mouth touches the crust, a thin layer of the crust and of your mouth immediately come to the same temperature. Because the crust is quite light, it doesn't have to lose much heat to cool it down. Because the crust has lots of inner air pockets, it is a poor conductor of heat so the warmer crust deeper inside cannot effectively tranfer heat through the cooled layer to your mouth. Thuis the total heat transfer is small an does not burn you.

The sauce is mostly water, having one of the highest heat capacities of any substance. Thus it puts a lot of heat into your mouth before the temperature drops very far. Second, being a liquid, it conducts heat from deeper in the sauce at about 10-50 times the rate of the crust. These two additional factors make it burn so.

By way of credentials, I have taught thermodynamics at an accredited university.

Answer 2

the sauce retains heat because it is a semi-liquid of a sort, but since the crust rises, there are air pockets that will deflate and release hot air, which results in a lower temperature when you eat it...That's my explanation of it, any rebuttals welcome

Answer 3

Heat capacity.....the ability of something to conduct heat. Either to, or away from itself.

lol Jennifer!

Answer 4

the fourth law of thermodynamics: thermodynamics sucks.