Conductivity is the ability of a body or material to transmit heat. In doing so, it moves through a solid object or from one object to another, because both of them are in contact with each other. This is the only way for heat to pass through the entire body. The question arises: “How does air and other materials conduct heat?” Find out in the article!
Thermal conductivity
The ability to transfer heat within an object is called thermal conductivity. This property is denoted by the letter k, and is measured in W / (m × K). Thermal conductivity values vary for different materials. So, gold, silver and copper have high thermal conductivity. By the way, these materials are also good conductors of electricity. How does air conduct heat? The answer is short: it is a poor conductor. The high conductivity of gold, silver and copper is due to the fact that the electrons that are responsible for the transfer of charge also take part in the transfer of thermal energy.
But materials such as glass and mineral wool have low thermal conductivity. This is explained by the fact that they have very few "free" electrons for the transfer of thermal energy inside the solid. Materials of this type are called insulators. The rate of heat transfer (that is, the rate of movement of thermal energy) directly depends on the thermal conductivity, temperature difference and contact area and material that the body possesses. For the same reason, it cannot be said that air conducts heat well.
If the material is a good conductor of heat, then it quickly moves through the body. Metals are widely used for heat transfer purposes as they have properties that allow heat to be circulated while simultaneously withstanding the extreme temperatures associated with heating.
It is the electrons that are responsible for the transfer of thermal energy, as well as electric charge. Therefore, metals are good conductors of heat and electricity! This is where the answer to the question lies: “Why is air a poor conductor of heat?”
However, do not confuse electrical conductivity (which is related to the charge of electrons) when you mean thermal conductivity (which is related to electron energy transfer).
We prove by experience
Try holding one end of a metal rod over a flame - after a few minutes it will heat up.
Now hold the end of a wooden stick in a flame and the end will become so hot that it will eventually catch fire. However, the end of the stick for whichyou hold on, stay relatively cool.
Heat does not spread throughout the volume of the body due to its composition: its structure makes it difficult for electrons to transfer heat through the material.
Thus, everyday experience shows that wood is not a good conductor of heat. If you've ever seen a section of wood under a microscope, you've probably noticed the structure of wood: it's made up of individual cells that act as insulators because they're not interconnected. Cells are scattered like stones in a stream. Heat travels much more slowly through such a material than in metals, where the atoms are bound together in a three-dimensional "lattice".
Air is a poor conductor of heat. The experience of everyday life shows: remember the structure of windows. They always consist of at least two glasses, between which there is an air cushion. This layer helps to keep heat in the room without letting it out.
So, if thermal energy is applied directly to one part of a solid object, the electrons in the object become excited. This results in atomic lattice vibrations that travel through the object, raising the temperature as they pass. The closer the links within a solid, the faster the heat transfer.
Liquids are poor conductors of heat
If you fix an ice cube at the bottom of a test tube of water (you need to use a weight to do this, otherwise it will float on the surface, solike ice has a lower density than water) and then heat the water at the top of the tube, you will find that the water will boil at the top of the tube and the ice cube will remain frozen.
This is due to the fact that water is a poor conductor of heat. Most of the heat will move in the convection current inside the water at the top of the tube, only a small part of it will sink to the ice cube.
How does air conduct heat?
Air is a collection of gases. Although it is excellent for convection, the amount of heat it can transfer is minimal because the small mass of matter cannot store much heat - which is why it is not considered a good conductor. The insulating properties of air are used by mankind in everyday life. So, they are used to insulate coolers in the walls of a building. Even the work of a thermos is based on the fact that air does not conduct heat well. There are really many examples!
So what is causing this phenomenon? Because air is not dense, there is a certain amount of mass available to transfer thermal energy through conduction. Therefore, it is a poor conductor, but an excellent insulator. Nevertheless, the answer to the question: “Does air conduct heat?” - not so unambiguous. So, consider the following phenomena.
Radiation is the transfer of energy through waves or excited particles. The air creates a thermal gap that does not allow thermal energy to overcome it. Heat must be radiated from the surface toair particles, then it should be radiated from the air to the opposite surface. Heat moves very slowly between the three materials, and most of the transferred heat energy is absorbed in the air.
Convection is the movement of heat through a liquid or gas due to a decrease in density due to heat absorption. In this case, the properties of air become extremely useful. It also moves upward, transferring heat from an insulated container or space. Therefore, convection is used to remove heat and can be used to cool the surface. The distribution of heat through convection in air is somewhat inefficient, however it is used for many cooling purposes. Yes, air is a poor conductor of heat.
Insulation Examples
Insulation is used for many purposes. Some of these include cooling drinks and food, creating air gaps in walls, and introducing air pockets into kitchen utensils. Features of how air conducts heat even apply to insulating foam.
Conclusion
Conductivity is the passage of heat through a solid body. It differs from the phenomenon of convection in that no movement of matter occurs in the process. Now we know whether air conducts heat well, and why.
