# Thermal Properties of Materials

PhysicsThermal Properties of Matter

#### Class 11th Physics - Elasticity

6 Lectures 1 hours

#### Class 11th Physics - Oscillations

12 Lectures 2 hours

#### Class 11th Physics - Waves

14 Lectures 3 hours

## Introduction

The thermal properties of the materials are observed when the solid body absorbed the energy from the heat. After the heat absorption, the temperature of the materials is increased and the dimensions of the materials increased as well.

The properties of the materials with the application of heat are the rate of heat capacity, thermal expansion, as well as thermal conductivity. Thermal stress is also considered a significant property of the material properties.

## What are the thermal properties of materials?

The thermal properties of the material are dependent on several components like the specification of heat, heat capacity of the materials, the rate of thermal expansion as well as thermal conductivity. The melting and boiling point also influences the thermal expansion of the materials (Sukontasukkul et al. 2019).

The thermal properties also differ from the rate of thermal diffusivity as well as the "thermal shock resistance rate".

Figure 1: The thermal properties of the materials

In this figure, two different materials are taken.The thermal conductivity of the two materials is passed through Q. From the $\mathrm{T_1}$ body, the thermal conductivity passes through to the $\mathrm{T_2}$ body.

## Types of material properties

Four different types of material properties can be seen "Mechanical properties of materials", "Chemical properties of materials", and "Physical properties of materials", "Dimensional properties of materials" as well as "Thermal properties of materials" also significant categories of material properties.

• "Chemical properties of materials" include the rate of corrosion resistance hygroscopic, ph factor, the reactivity rate, as well as the surface tension of the metallic body.

• "Physical properties of materials", is relied on the density of the materials along with the conductivity, optical and combustibility of the metallic body.

• "Mechanical properties of materials" comprise the electricity, ductility, hardness, as well as toughness of the metallic body. "Dimensional properties of materials" is totally dependent on the size and shape of the metallic body.

## Heat capacity of the materials

The heat capacity refers to the amount of heat required by the material to change the one-degree temperature. The heat capacity of a material can be present in the form of joules or calories while the temperature of the metallic body can be denoted by Celsius or Kelvin.

For the calculation of the heat capacity rate of the materials, a simple formula is used.

$$\mathrm{Q = m\:c\:\Delta T}$$

In this formula, Q refers to the heat capacity of the material that is represented in Joules, m refers to the mass that is calculated in grams, and C is denoted by the specific heat that is represented by $\mathrm{J.K^{-1}}$. $\mathrm{\Delta T}$ in this formula stands for the temperature change that is represented by $\mathrm{0_K}$

## Thermal expansion of materials

Thermal expansion is one of the most significant components of the thermal properties that refer to the changes in height, length, and volume of the materials with the application of heat or temperature. The thermal expansion of material can be happened in terms of area, volume as well as the shape of the metallic body (Honorio, Bary & Benboudjema, 2018).

For example, the thermal expansion can be seen in the railway track or the roadway building.

## Thermal conductivity of the material

Figure 2: Thermal conductivity rate of the different materials

The thermal conductivity of the different materials depends on the temperature or heat. For example, the thermal conductivity of copper is 399 $\mathrm{W/m^0C}$ while the thermal conductivity of gold is 317 $\mathrm{W/m^0C}$. The thermal conductivity of wood is 0.087 $\mathrm{W/m^0C}$ and the glass is 0.81 $\mathrm{W/m^0C}$.

In the case of liquid materials, the thermal conductivity is a little lower. For example, the thermal conductivity of water is 0.6$\mathrm{W/m^0C}$ and the ethylene glycol is 0.26$\mathrm{W/m^0C}$ (Bruno et al. 2018). The thermal conductivity of hydrogen is 0.19 $\mathrm{W/m^0C}$ and the air is 0.026$\mathrm{W/m^0C}$. It is clearly seen that the thermal conductivity of the materials depends on the density.

## Coefficient of thermal properties of different materials

The coefficient of thermal properties of different materials depends on the thermal expansion rate with the changes in the dimension, sizes and shapes of the metallic body. The measurement of the linear thermal expansion proceeds with the formula $\mathrm{\frac{\Delta l}{l}=\alpha l.\Delta T}$ where l stands for the body length of the material, $\mathrm{\Delta l}$ denotes the changes in length, $\mathrm{\alpha l}$ refers to linear coefficient expansion as well as $\mathrm{\Delta T}$ represents the changes in heat.

Figure 3: Coefficient of thermal properties of the materials

The area thermal expansion proceeds with the formula

$$\mathrm{\frac{\Delta A}{A}=\alpha A.\Delta T}$$

where A stands for the area of the material, $\mathrm{\Delta A}$ denotes the changes in the area, $\mathrm{\alpha A}$ refers to area coefficient expansion as well as $\mathrm{\Delta T}$ represents the changes in heat (Jafarzadeh & Jafari, 2021).

The volumetric thermal expansion proceeds with the formula $\mathrm{\frac{\Delta V}{V}=\alpha V.\Delta T}$ where A stands for the volume of the material, $\mathrm{\Delta V}$ denotes the changes in the volume, $\mathrm{\alpha V}$ refers to volumetric coefficient expansion as well as $\mathrm{\Delta T}$ represents the changes in heat.

## Conclusion

Thermal stress is another component of the thermal properties of the materials that mainly happens through thermal expansion as well as thermal contraction of the metallic body. Specific heat is also included in the thermal properties of the metallic body which refers to the time duration when the metallic body is heated.

## FAQs

Q.1 What is the melting point of the materials?

Ans. The melting point of the material refers to the stage when the material starts to melt. The melting point of the material depends on the heat capacity.

Q.2 What is the boiling point of the materials?

Ans. The boiling point refers to when the material starts to boil. The boiling point of the material also depends on the heat capacity.

Q.3 What is the thermal diffusivity of the materials?

Ans. Thermal diffusivity refers to the ratio of the thermal conductivity as well as the heat capacity of the material. For example, copper has the highest thermal conductivity while air has the lowest.

Q.4 What is the thermal shock resistance?

Ans. The thermal shock resistance is a stage of the material which refers to the changes in temperature. This particular stage refers to the ability of shock resistance of a material.

Updated on 13-Oct-2022 11:19:47