V. Analysis and Conclusion

Thermal expansion is the ability of matter to change its dimension whenever there is a change in its temperature through heat transfer. When the substance is heated, the kinetic energy of the substance increases, thus, beginning to move the molecules more. When the temperature of the substance increases, its dimensions expand while when the temperature of the substance decreases, its dimensions contract. The amount of expansion depends on (1) the change in temperature, (2) nature of the substance which is the coefficient of thermal expansion and (3) the original length.

In thermal expansion, it was observed that gases experience the greatest change in dimension given that its molecules are far away from each other, thus, spaces for its molecules to move due to heat transfer, followed by liquid substances and last, solid substances experiences the least expansion given it is rigid and has the resistance to changes in shape or volume unlike in liquids and gases. Therefore, thermal expansion differs due to the difference in the molecular structure of the substance when it is in different state.

The coefficient of thermal expansion depends on the type of thermal expansion. There are three types of thermal expansion which are (1) Linear expansion, (2) Area Expansion and (3) Volume Expansion. Each type has a different coefficient – for linear, the coefficient of thermal expansion is represented by α, for area, the coefficient of thermal expansion is represented by γ and for volume, the coefficient of thermal expansion is represented by β. The coefficient of thermal expansion in area is also equal to twice the value of α while the coefficient of thermal expansion in volume is equal to thrice the value of α. The change in dimension can be computed using the equations shown below.

ΔL = αLoΔT ΔA = γAoΔT ΔV = βVoΔT

As shown in the equations for thermal expansion, the change in dimension is directly proportional to the coefficient of thermal expansion (α, β, γ), the initial dimension (Lo, Ao, Vo) and the change in temperature (ΔT). Substituting the equation for the change in dimension, the final dimension can be computed by the equation shown below.

L = Lo(1+ αΔT) A = Ao(1+ γΔT) V = Vo(1+ βΔT)

Generally, thermal expansion is the property of matter to change its dimension through heat transfer where there is a change in the substance’s temperature which causes its molecules to increase or decrease its kinetic energy that makes the substance expand or contract. Thermal expansion is dependent on the nature of the substance, the original length and the change in temperature. Simplifying the equations, the longer the initial length of the substance and the greater the difference of the temperatures, the greater the expansion or contraction of the substance. The change in dimensions depends on the sign of the change in temperature – when the sign is negative (-), the substance contracts while when the sign is positive (+), the substance expands. Thermal expansion also depends on the nature of the substance which is also known as the coefficient of thermal expansion and differs depending on the molecular structure of the substance when it is in a different state – a substance in its gas state experiences the greatest change in dimension while substances in its solid state experiences the least change in dimension. The substance may either expand or contract depending on the sign of the change in temperature – expansion for a positive difference of the temperatures while contraction for a negative difference.