Reading Time: 2 minutes
Thermal Expansion: Understanding the Effects of Heat in A-Level Science
What Is Thermal Expansion?
Thermal expansion refers to the increase in size of a material when its temperature rises due to the increase in the kinetic energy of its particles.
Types of Thermal Expansion
Linear Expansion
Change in length of solids:
![\[ \Delta L = \alpha L_0 \Delta T \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-0141e370774cafa3128a3b185da7d01c_l3.png "Rendered by QuickLaTeX.com")
Where:
: Change in length (m)
: Coefficient of linear expansion (1/°C)
: Original length (m)
: Temperature change (°C)
: Change in length (m)
: Coefficient of linear expansion (1/°C)
: Original length (m)
: Temperature change (°C)Areal Expansion
Change in surface area:
![\[ \Delta A = 2\alpha A_0 \Delta T \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-5437dcb9cd2bbbc2070e2534e957c324_l3.png "Rendered by QuickLaTeX.com")
Where 
is the original area (m²).
Volume Expansion
Change in volume of solids and liquids:
![\[ \Delta V = \beta V_0 \Delta T \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-ccbec7bd0bda7205efac95612714fa9b_l3.png "Rendered by QuickLaTeX.com")
Where:
: Change in volume (m³)
: Coefficient of volume expansion (1/°C)
: Original volume (m³)
: Change in volume (m³)
: Coefficient of volume expansion (1/°C)
: Original volume (m³)Real-Life Applications of Thermal Expansion
Bridges and Railroads
Expansion joints are used to prevent buckling due to temperature changes.
Thermometers
Thermal expansion of liquids is used to measure temperature.
Bimetallic Strips
Used in thermostats to control heating and cooling systems.
Example Problem
A steel rod of length 
expands when heated from 
to 
. The coefficient of linear expansion for steel is 
. Find the change in length.
- Formula:
![\[ \Delta L = \alpha L_0 \Delta T \]](data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHdpZHRoPSIxMTAiIGhlaWdodD0iMTUiIHZpZXdCb3g9IjAgMCAxMTAgMTUiPjxyZWN0IHdpZHRoPSIxMDAlIiBoZWlnaHQ9IjEwMCUiIHN0eWxlPSJmaWxsOiNjZmQ0ZGI7ZmlsbC1vcGFjaXR5OiAwLjE7Ii8+PC9zdmc+ "Rendered by QuickLaTeX.com")
- Substitute Values:
![\[ \Delta L = 12 \times 10^{-6} \times 2 \times (100 - 20) = 0.00192 \, \text{m} \, \text{or} \, 1.92 \, \text{mm} \]](data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHdpZHRoPSI0NDQiIGhlaWdodD0iMjIiIHZpZXdCb3g9IjAgMCA0NDQgMjIiPjxyZWN0IHdpZHRoPSIxMDAlIiBoZWlnaHQ9IjEwMCUiIHN0eWxlPSJmaWxsOiNjZmQ0ZGI7ZmlsbC1vcGFjaXR5OiAwLjE7Ii8+PC9zdmc+ "Rendered by QuickLaTeX.com")
![\[ \Delta L = 12 \times 10^{-6} \times 2 \times (100 - 20) = 0.00192 \, \text{m} \, \text{or} \, 1.92 \, \text{mm} \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-3fd9f73dfb9befa6f3048f834ab18315_l3.png "Rendered by QuickLaTeX.com")
Common Mistakes in Thermal Expansion Problems
- Forgetting to convert units (e.g., mm to m)
- Mixing up coefficients of linear and volume expansion
- Using the wrong formula for specific expansion types
Practice Questions
- A copper rod expands
when heated. If its original length is 
and 
, find . - Explain the purpose of expansion joints in bridges.
- Describe one application of volume expansion in liquids.
when heated. If its original length is 
and 
, find