9 HEAT CONDUCTORS AND THEIR CHARACTERISTICS - SCIENCE - 2025

The heat conductors are materials whose structure is such that heat can pass through them easily. It must be remembered that all matter is composed of atoms and molecules in constant vibratory movement, and that the heat translates into greater agitation of these particles.

Some materials conduct heat better than others, because their internal configuration facilitates this energy flow. Wood, for example, is not a good conductor of heat because it takes a long time to heat up. But on the other hand, iron, copper and other metals are, which means that their particles acquire kinetic energy very quickly.

Thermal grease used in computer chips is a good conductor of heat, but not electricity. Source: Wikimedia Commons.

This is why metals are the favorites for making kitchen utensils, such as pots and pans. They heat up quickly and reach temperatures high enough for food to cook properly.

However handles and handles, which are in contact with the user's hands, are made of other heat-insulating materials. In this way, the pans are easy to handle even when they are hot.

Types of conductors

Depending on their way of conducting heat, materials are classified into:

- Thermal conductors: diamond and metals such as copper, iron, zinc and aluminum, among others. Usually good conductors of electricity are also good conductors of heat.

- Thermal insulators: wood, rubber, fiberglass, plastic, paper, wool, anime, cork, polymers are good examples. Gases are not good conductors, either.

Thermal conductivity of materials

The property that intrinsically characterizes the way each of them conducts heat is called thermal conductivity. The higher the thermal conductivity of a substance, the better it conducts heat.

The thermal conductivity of substances is determined experimentally. In the SI International System of Units, thermal conductivity is measured in Watt / (meter x kelvin) or W / (mK). It is interpreted as follows:

Another unit for thermal conductivity used in Anglo-Saxon countries is BTUH / (ft.ºF), where BTUH stands for British Thermal Unit per hour.

Heat flows through the solid when there is a difference in temperature between its ends. Source: Wikimedia Commons.

Thermal conductivity values

Below are the thermal conductivities of some elements and materials found in nature and that are frequently used in industry.

However, it should be noted that there are synthetic compounds, still in the experimental phase, whose thermal conductivity far exceeds that of diamond, which heads the table.

Temperature is decisive in the value of the thermal conductivity of metals. As the temperature increases, so does the thermal conductivity (although the electrical conductivity decreases). For non-metals, the thermal conductivity is roughly constant over a wide temperature range.

The values ​​in the table are specified at 25ºC and 1 atmosphere pressure.

When selecting a material for its thermal properties, it is necessary to take into account that it expands with heat. This capacity is given by the coefficient of thermal expansion.

Main heat conductors

Diamond

Diamond is the best thermal conductor in nature. Source: Robert Lavinsky via Wikimedia Commons.

It is the best thermal conductor at room temperature, much better than copper and any other metal. In diamond, which is an electrical insulator, heat does not flow through conduction electrons but through the propagation of vibrations in its highly organized crystalline structure. These vibrations are called phonons.

It also has a low coefficient of thermal expansion, which means that its dimensions will remain close to the original ones when heated. When a good heat conductor is required that does not conduct electricity, diamond is the best option.

As a result, it is widely used to remove the heat produced by circuits in computers and other electronic devices. But it has a major disadvantage: it is extremely expensive. Although there are synthetic diamonds, they are not easy to make and they are also expensive.

Silver

Silver coins

It is a highly appreciated metal for ornamentation due to its shine, color and malleability. It is resistant to oxidation and among all metals it is the one with the highest thermal conductivity, as well as excellent electrical conductivity.

For this reason, it has multiple applications in industry, both alone and in alloys with other elements such as nickel and palladium.

With pure silver, printed circuits, high-temperature superconducting cables are made and conductors used in electronics are coated, in addition to being used in alloy to make electrical contacts.

It has the disadvantage of being relatively scarce and therefore expensive, but the unique combination of physical properties for these applications make it an excellent alternative, as it is very flexible and with it, conductors of good length are obtained.

Copper

Copper wires

It is one of the most used metals when good thermal conductivity is required, because it does not corrode easily and its melting point is quite high, which means that it will not melt easily when exposed to heat.

Other advantages it has is its ductility, in addition to not being magnetic. Copper is recyclable and is much less expensive than silver. However, its coefficient of thermal expansion is high, which means that its dimensions change appreciably when heated.

Due to its good thermal properties, it is widely used in kitchen utensils, such as copper pots covered with steel, for example. Also to manufacture heat exchangers in hot water tanks, in central heating systems, car radiators and to dissipate heat in electronic devices.

Gold

Prehispanic gold mask

It is the precious metal par excellence and occupies a preponderant place in the history of mankind. Apart from this special meaning, gold is malleable, resistant and an excellent conductor of heat and electricity.

Since gold does not corrode, it is used to carry small currents in solid state electronic components. These currents are so small that they can be easily interrupted at the slightest sign of corrosion, which is why gold guarantees reliable electronic components.

It is also used to manufacture headphone connectors, contacts, relays, and in patch cables. Devices such as smartphones, calculators, laptops and desktops, and televisions contain small amounts of gold.

The special glasses for air conditioning spaces also contain dispersed gold, in such a way that they help to reflect the sun's radiation outside, keeping the freshness inside when it is very hot. In the same way, they help to maintain the internal heat in the building when it is winter.

Lithium

Lithium ion battery. Author: Mr. ち ゅ ら さ ​​ん. Lithium_Battery * photography day, August, 2005 * photography person Aney. Source: Wikimedia Commons.

It is the lightest of all metals, although very reactive so it corrodes easily. You also have to handle it with great caution, because it is highly flammable. Due to this, although it is abundant, it is not found in the free state but in compounds, which is why it must be isolated generally by electrolytic methods.

Its thermal conductivity is similar to that of gold, but it is much cheaper than this. Lithium carbonate is a compound used in the manufacture of heat-resistant glass and ceramics.

Another widespread use of lithium is the manufacture of long-lasting, lightweight batteries, for which lithium chloride is used to extract metallic lithium. Added in the processing of aluminum, it increases its electrical conductivity and lowers operating temperatures.

Aluminum

Aluminum metal bucket. Source: Carsten Niehaus

This lightweight, inexpensive, highly resistant and easy-to-work metal is one of the main materials used to make heat exchangers in air conditioning equipment such as air conditioners and heaters.

Both domestically and industrially, aluminum utensils are used extensively in kitchens around the world.

Aluminum utensils such as pots, pans, and baking sheets are extremely efficient. They do not change the flavor of food and allow heat to spread quickly and evenly when cooking.

Regardless, aluminum pots and pans have been displaced by stainless steel, which is not as good a heat conductor. This is because stainless steel does not react with stronger acids, such as tomato sauce for example.

That is why it is preferable to make tomato sauces in steel utensils, to prevent aluminum from entering the food, since some have associated aluminum - present in antacids, talcs, deodorants and many other products - with the appearance of degenerative diseases, although most of the experts, as well as the FDA, reject this hypothesis.

Aluminum saucepan in the foreground. Source: Pixabay.

Cookware made from anodized aluminum does not have the risk of releasing aluminum particles and can in principle be used with greater safety.

Bronze

The bronze of these ancient bells demonstrates the usefulness of metals for ornamental or religious purposes. Source: Pxhere.

Bronze is an alloy of copper and tin mainly, with other metals to a lesser extent. It has been present since ancient times in the history of mankind.

It is so important that a period of Prehistory has even been named as the Bronze Age, the time when people discovered and began to use the properties of this alloy.

Bronze is resistant to corrosion and easy to work with. Initially it was used to make various utensils, tools, jewelry, art objects (sculptures for example) and weapons, as well as to mint coins. Today it is still used to make pipes, mechanical parts and musical instruments.

Zinc

Watch glass with zinc oxide. Source: Adam Rędzikowski

It is a very malleable and ductile bluish-white metal, easy to work with, although with a low melting point. It has been known since ancient times, mainly used in alloys.

It is currently used to galvanize steel and thus protect it from corrosion. Also to manufacture batteries, pigments and manufacture special zinc sheets for the construction industry.

Iron

Iron filings on a magnet. Source: Aney via Commons Wikimedia.

Iron is another metal with great historical significance. Like bronze, iron is linked to a stage of prehistory in which great technological advances occurred: the Iron Age.

Today cast iron continues to have many applications to make tools, utensils, in construction and as a material for the manufacture of automotive parts.

Iron is a very good conductor of heat, as we have seen. Iron objects distribute heat very well and keep it for a long time. It also has a high melting point, which makes it resistant to high temperatures, hence its usefulness in the manufacture of all types of ovens, both industrial and domestic.

References

1. CK-12. Thermal Conductors and Insulators. Recovered from: ck12.org.
2. Copper: Properties and Applications. Recovered from: copperalliance.org.
3. Effunda. Properties of commons solid materials. Recovered from efunda.com
4. Hill, D. Thermal Properties of Cast Iron. Recovered from: ehow.com.
5. King, H. The many uses of gold. Recovered from: geology.com.
6. Lithium. Recovered from: gob.mx.
7. Re-creative physics. Heat transmission. Recovered from: fisicarecreativa.com.
8. Wikipedia. List of thermal conductivities. Recovered from: es.wikipedia.org.