What's up with aluminum foil?

Question

Why does aluminum foil barely get hot in the oven, but catch fire in the microwave?

Answer 1

The surface of aluminum converts to aluminum oxide which has a low heat conductivity, ie it's a heat insulator.  So in the conventional oven it absorbs very little heat.  In the microwave the metal aluminum will suscept to the microwaves as they don't even see the aluminum oxide layer, and will heat up almost instantly.

Aluminum can be used to pull oxygen out of water and thus produce hydrogen by stripping the water of its oxygen:  to wit:

http://www.physorg.com/news98556080.html

Answer 2

Yea whats with that any way.

Answer 3

Aluminum foil in the oven will quickly reach whatever temperature the oven is at. The reason it's cool when you take it out is that it equally quickly comes back to room temperature outside the oven. This is because the foil is very thin, so it has a lot of surface area, relative to its thermal mass, to exchange heat with its environment.

In the microwave oven, microwave radiation makes electric current flow in the aluminum, causing it to overheat.

Answer 4

Your fsats are wrong.    Al foil gets hot in the oven and doesn't cstch fire in the micowave

Answer 5

It has to do with the resonance of the microwave radiation with the 'points' on the aluminium foil.

We don't think of foil as having 'points'...to us it looks smooth.  However, when the microwave bouce around in the oven, they find each and every uneven surface on the foil.  In layman's terms, the microwaves 'collide', causing a build-up of charge and energy.

You'll notice that many pre-packaged microwave meals contain a 'crisping' area on the cardboard that resembles aluminium.  This is a specially treated foil that won't set up a resonance, but instead will concentrate the microwaves in a particular area, causing the food to cook much faster in a small, external area.

The result:  a nice, crispy shell on your otherwise limp and tasteless Hot Pocket!  Enjoy!

Answer 6

the oven radiates heats it up by heating it from the outside in

the microwave radiates microwaves to get water, sugar, and fat moving, heating the food from the inside and the outside. since the foil has none of these the bombardment of waves has a different effect. the atomic structure of the foil burns when it gets hit with microwaves