In other words, air (at standard temperature and pressure) is much less dense than water. (There is also a small amount of heat loss via conduction, where the can is in direct contact with the shelf.) The molecules in a gas, such as air, are spread out over a much larger volume than molecules in a liquid. In both the freezer and the refrigerator, cold air is removing heat from the room-temperature soda can by convection. Incandescent objects-like light bulb filaments, molten metal, or the sun-radiate at visible wavelengths as well. For most objects you encounter every day, this would be infrared radiation: light beyond the visible spectrum. Radiation is the final way to transfer heat. Thus, as molecules evaporate from a liquid, they take away energy from the liquid, cooling it. This transition requires energy, since a molecule in the vapor phase has more energy than a molecule in the liquid phase. When molecules of a liquid vaporize, they escape from the liquid into the atmosphere. These circulating currents serve to transfer heat, and are an example of convection.Įvaporation is another method of heat transfer. As the hot air rises, it creates currents of air flow. You've probably heard the saying that "hot air rises." This happens because it is less dense than colder air. The water molecules colliding with the inside surface of the cup transfer energy to the cup, warming it up.Ĭonvection is heat transfer by mass movement. For example, when you pour hot water into a cup, the cup soon feels warm. Heat can be transferred from one piece of matter to another by four different methods:Ĭonduction is heat transfer by direct molecular interactions, without mass movement of matter. Heat is a measure of the average molecular motion of matter. Even in solids, the molecules are constantly vibrating. All matter is made of atoms and molecules that are constantly in motion. Here is a quick summary, so that you can be familiar with the terms you will encounter. In order to get the most out of this project, you will need to do some background research on heat and heat transfer. What else could you try? How about putting the soda on ice, or immersing it in an ice-water bath? Which method do you think would be most efficient at cooling a soda? You could also try the freezer, since it's colder, it may cool faster than the fridge. Maybe more time than you're willing to wait on a hot summer day. Sure, you could put the soda in the refrigerator, but you probably know from experience that it's going to take awhile to get really cold that way. How can you cool off a can of soda to take it from room temperature down to a nice, cold, drinkable temperature quickly, with materials that are readily available in your house?
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