Aluminum foil is a common modern piece of technology found all over the place. Many people use it at home and at work. I work in a laboratory and we use aluminum foil all the time.
I'm going to focus on why we use aluminum foil when we cook. If you have ever baked something you have most likely covered what you were baking with a sheet of aluminum foil. For example, we are told to cover lasagna with aluminum foil so that it cooks more evenly.
Aluminum foil conducts (directs the heat) more evenly over the surface of the dish you are covering by allowing the heat to flow through it and into the item it covers. Aluminum foil also insulates the dish, it reflects the heat back onto it and does not allow water vapor and hot air
to escape. You see this when you remove the aluminum foil and there is a rush of steam. This is also why you sometimes want to remove the foil before the dish is done so that the top will get a little crispy. You can do the same with boiling water. Put the lid on top of a kettle and the water will boil faster because the heated air and water vapor can't escape.
The aluminum foil is acting as an insulator. For example, aluminum foil can be used to insulate houses. It will reflect the infrared heat coming from the sun to keep the home cooler in the summer and reflect the infrared hear coming from the house to keep it warmer in the winter. Infrared (radiation) is emitted by most objects. It is energy. When you heat up an item, the molecules inside of it get excited and emit infrared radiation. When the infrared radiation strikes another object, those molecules get excited as well (heat). This is also why you cover your food with aluminum foil to keep it warm.
At home experiment: Hold a piece of aluminum foil close to your face, without touching. Soon you will feel the warmth of your own infrared rays bouncing back from the foil.
Sources:
I'm going to focus on why we use aluminum foil when we cook. If you have ever baked something you have most likely covered what you were baking with a sheet of aluminum foil. For example, we are told to cover lasagna with aluminum foil so that it cooks more evenly.
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| Here I am using the aluminum foil to insulate the hotplate at work to get it to heat to temperature faster. (Photo by me: I'm not a photographer) |
to escape. You see this when you remove the aluminum foil and there is a rush of steam. This is also why you sometimes want to remove the foil before the dish is done so that the top will get a little crispy. You can do the same with boiling water. Put the lid on top of a kettle and the water will boil faster because the heated air and water vapor can't escape.
The aluminum foil is acting as an insulator. For example, aluminum foil can be used to insulate houses. It will reflect the infrared heat coming from the sun to keep the home cooler in the summer and reflect the infrared hear coming from the house to keep it warmer in the winter. Infrared (radiation) is emitted by most objects. It is energy. When you heat up an item, the molecules inside of it get excited and emit infrared radiation. When the infrared radiation strikes another object, those molecules get excited as well (heat). This is also why you cover your food with aluminum foil to keep it warm.
At home experiment: Hold a piece of aluminum foil close to your face, without touching. Soon you will feel the warmth of your own infrared rays bouncing back from the foil.
Sources:
- The Physics of Foil. (n.d.). Retrieved August 27, 2014, from http://www.insulation4less.com/Insulation4lessTechnicalArticles-2-The-Physics-of-Foil.aspx
- Aluminum Foil Insulation. Aerolam insulations Private Limited. N.p.. Web. 27 Aug 2014. http://www.aerolaminsulations.com/aluminum-foil-insulation.php
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