Why doesn't aluminum foil get hot after taking it out of the oven?

Metallic aluminum can't hold much heat. In addition, foil is thin and has a relatively large surface area. A combination of all these factors prevents the foil from getting too hot to the touch, even if it is heated for a long time. Place the frozen pizza on a sheet of aluminum foil and place it in the oven. Then heat it up for a few minutes and remove, cheesy and delicious pizza. The pizza will be hot (and ready to serve), but the aluminum foil that has been under the pie and inside the oven for as long as the pizza has been hot to the touch! Why would that be the case? Why doesn't aluminum foil get hot after you take it out of the oven (or after any other heat), while almost everything else you put in the oven gets hot to the touch. Important: The word "oven," which is used several times in the article, refers to large convection ovens. It is not recommended to put aluminum or any other metal in a microwave oven, as the material can catch fire. Thermal conductivity of aluminum Thermal conductivity is a property of a substance that determines how quickly it is able to transfer heat. If a given object transfers heat quickly, it is considered to have high thermal conductivity. Similarly, objects with low thermal conductivity transfer heat longer.
It is therefore quite natural that substances with low thermal conductivity, that is, objects that do not transmit heat (Teflon-coated cookware), are used as heat insulators. For example, objects with relatively higher thermal conductivity are used to make radiators. Aluminum, as you may have guessed, has relatively high thermal conductivity, which makes it ideal for use as foil for food packaging. But that's not all... There's another important thing that makes aluminum foil so unique. The low thermal mass of aluminum foil Not only does aluminum foil have high thermal conductivity, but it is also very thin (low mass) and obviously has a large surface area. Because of this, the heat that the foil absorbs is quickly lost to the surrounding air.
The flatness and large surface area of aluminum foil result in a very low thermal mass. What is thermal mass? The thermal mass of an object is its ability to store or absorb heat. Things that are considered "difficult" to heat usually have a high thermal mass. Bricks or concrete, for example, only heat up after a lot of thermal energy has been applied to them. In contrast, lightweight objects such as wood have low thermal mass because they do not absorb or store heat well. Aluminum foil has low thermal mass because it has such low mass and such a large surface area. This is why aluminum foil is not capable of "holding" much heat. These factors combine to make aluminum an ideal choice for packing because it doesn't retain much heat. And whatever small amount of heat it retains, it is quickly transferred out of it due to the high thermal conductivity of the metal.
Another important factor that is often attributed to the effectiveness of aluminum foil is the specific heat capacity. Specific heat capacity of aluminum Specific heat capacity measures the amount of heat energy required to raise the temperature of 1 kg of an object by 1 Kelvin (In the International System of Units (SI)). It is a common misconception that aluminum has a low specific heat capacity. In fact, aluminum has a relatively high specific heat capacity compared to some other metals such as copper and iron. In fact, this is why certain cookware is made of aluminum. However, aluminum foil is too thin and has a very high surface area to effectively transfer enough heat to the human hand. Think of it this way... a very small container can only hold a small amount of water. If you empty a container filled with water over your head, you won't get wet because the water in the container is too small in volume. In short, aluminum foil doesn't feel hot to the touch because it quickly loses heat to the surrounding air after being removed from the oven; the little heat it still has is enough to heat only a small part of your finger (but not your whole hand).


You must be logged in to post a comment.