# Thermal Conductivity Kids

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Do you know why your car doors and its body get really heated up when parked under direct sunlight in peak summer?

Why do we have bakelite plastic handles for cooking pots and pans? Why is the cooking pot’s bottom made out of metal? Why do we take caution while grabbing a cup of hot tea? Inside the home, why do the tiles get cooler or warmer more easily than a rug or carpet on the same floor? We are going to learn about the fascinating thermal conductivity in this blog. Watch this really simple yet intuitive experiment on thermal conductivity.

Since it needs boiling water, adult supervision is a must for this experiment. All you need for this experiment is a tablespoon of butter, three tablespoons made of three different materials viz.

## Which metal is the best thermal conductor?

plastic, stainless steel & wood. Glass of boiling water and jar to hold them all. Thanks to Cool Science Experiments Headquarters for this video. The thermal conductivity of a material is a measure of its ability to conduct heat.

The denser the material better the thermal conductivity is. Metals and stones have better thermal conductivity than gas or air because they are more denser. Wait then why wood is not a better thermal conductor than metal, even though it’s denser? It’s not just the density of the material alone but also the chemical bond [Not the fictional British Secret Service agent 007] that plays a role in its thermal conductivity.

Wood has covalent bonds which are not conducive for thermal conductivity. Metallic bonding accounts for many physical properties of metals, such as strength, malleability, ductility, thermal and electrical conductivity, opacity, and luster.

## Uses of highly thermal conductive materials [Practical applications]

Below listed table shows the thermal conductivity of many metals and alloys at different temperatures. Silver tops the list on metals and steel has the lowest thermal conductivity on alloys. Since silver is costly copper & aluminum would be the next choice for many applications.

$\frac{\partial Q}{\partial t} = -k \oint_S{\nabla T \cdot \,dS}$
Free electrons – Free electrons play an important role in thermal conductivity.

As mentioned above metals have more free electrons because of metallic bond and they are good conductors of heat due to the migration of free electrons.

Q is the amount of heat transferred, and
t is the time taken, and
k is the material's thermal conductivity' and
S is the area through which the heat is flowing, and
T is the temperature.

Metal Purity – Thermal conductivity of the pure material is higher than that of alloy materials. Alloying of metals and presence of impurities cause a decrease in thermal conductivity.

## Why are metals good thermal conductors? Whereas wood is a bad thermal conductor

thermal conductivity of pure copper is 385 W/mK but copper having content of arsenic, thermal conductivity is 142 W/mK.