Thermal Properties of Materials

The term “thermal properties of materials” refers to material traits or features that are affected by temperature or heat. The thermal characteristic of solids is defined as the response of a solid substance to a thermal change, such as an increase or reduction in heat or temperature.

The sensitivity of materials to temperature variations and heat application is referred to as their thermal characteristics. A solid’s temperature rises and its dimensions expand as it absorbs energy in the form of heat.

Thermal Properties

When heat is applied to a solid body, a liquid, or a gas, thermal characteristics are connected with a material-dependent response. A temperature rise, a phase transition, a change in length or volume, the start of a chemical reaction, or a change in some other physical or chemical quantity could all be examples of this response.

Temperature and Heat

Temperature is a degree of measuring hotness and coolness, according to the definition.

Heat, on the other hand, is the energy that is transported over a system’s boundary to modify the differential between the system and its surroundings.

Note: That heat and temperature are not the same thing. Heat is the energy we put into the water, and temperature is the amount of energy we put into the water.

Thermal Properties of Materials

The following are the various thermal characteristics of Material:

1. Specific Heat

2. Heat capacity

3. Thermal conductivity

4. Melting point

5. Thermal diffusivity

6. Thermal shock resistance

Specific Heat

The attribute of specific heat determines which materials heat up quickly. As a result, specific heat is the amount of heat required to alter 1 unit degree in one unit mass. The symbol for it is ‘s’, and the unit is joule/kg Kelvin.

Mathematical Expression:

1m(∆Q∆T)

Where

∎  m= Mass

∎  T= Temperature

∎  Q= Energy content

Note: Specific heat varies for all materials.

Heat Capacity

The heat capacity of a substance is a feature of the material that determines how much heat energy is required to bring about a 1-degree unit change.

In this case, we’re talking about the quantity of heat required to raise the temperature of the entire substance by 1 degree. The symbol for it is (H), and the unit is joule/Kelvin.

Mathematical expression:

H=m×s=∆Q/∆T

Thermal Expansion

When heat energy is applied to a substance, it expands, which is known as thermal expansion. That is, its dimension is shifting, and it is shifting in all directions.

If we look at it in a linear manner, we call it linear expansion; if we look at it in an area, we call it area expansion; if we talk about it in volume, we call it volume expansion.

Interatomic forces govern thermal expansion. As the temperature rises, the space between the molecules expands, increasing the size of the molecules.

Because we increased the temperature, its energy increased, causing vibration in the molecule, which drove it to expand.

There are three types of thermal expansion:

1. Linear expansion

2. Superficial expansion

3. Cubical expansion

Thermal conductivity

Thermal conductivity is a material property that allows heat energy to move freely. In these materials, this determines the material’s ability to conduct heat.

The amount of thermal material that allows the material to conduct heat refers to how much of it is allowed to pass heat from the material. It’s referred to as the material’s thermal conductivity.

The unit is watt/meter Kelvin, and it is indicated as K.

Melting point

The melting point of a substance is the temperature at which it transitions from a solid to a liquid state. The melting point of pure metal is constant, whereas that of alloys fluctuates.

It also depends on the forces that hold it together. The greater the melting point, the stronger the bonding force. Covalent bonds melt at a higher temperature than ionic bonds and are the final metallic molecular bonds to form.

Safety equipment such as fuse wire, fuse plugs, and boiler safety devices have a low melting point.

Thermal diffusivity

Thermal diffusivity is the ratio of our thermal conductivity to our heat capacity. When we deliver heat to a material, thermal diffusivity tells us how quickly the heat will be distributed to the opposite end of the material.

This means that if the heat supply to our material has a high diffusivity, the heat will be distributed at a rapid rate.

E.g. We have a rod that we heat from the corner, so it’s 100 degrees there.

So, if our thermal diffusivity is high, our metal will reach 100 degrees Celsius in a short period at the other end. Heat will be distributed fast using these methods.

A material with a high thermal diffusivity responds swiftly to changes in the thermal environment in order to establish a steady-state.

Thermal shock resistance

When the temperature of a substance changes suddenly, this is the condition.

Thermal shock resistance refers to a body’s ability to remain unchanged in the face of an abrupt temperature change.

For example, ductile materials have a better thermal shock resistance than brittle materials.

Conclusion

Material qualities or attributes that are changed by temperature or heat are referred to as “thermal properties of materials.” The response of a solid substance to a thermal change, such as an increase or decrease in heat or temperature, is known as its thermal characteristic.

Thermal characteristics are linked to a material-dependent response when heat is delivered to a solid body, a liquid, or a gas. This response could be a temperature rise, a phase transition, a change in length or volume, the commencement of a chemical reaction, or a change in any other physical or chemical property.

Heat, on the other hand, is energy that is carried across a system’s boundary in order to change the difference between the system and its surroundings.