Thermal Expansion
Solids and liquids expand on heating: DL = L α DT, with area and volume coefficients approximately 2 α and 3 α.
What is Thermal Expansion?
Solids and liquids expand on heating: DL = L α DT, with area and volume coefficients approximately 2 α and 3 α.
Key formula / rule: Linear, areal and volumetric coefficients are in the ratio 1:2:3.
Key points
- Compute dimensional change on heating for solids and liquids.
- Explain the anomalous expansion of water and its consequence.
Common exam trap
Forgetting that a hole in a heated plate also expands.
Definitions
- Term
Thermal Expansion
- Meaning
Solids and liquids expand on heating: DL = L α DT, with area and volume coefficients approximately 2 α and 3 α.
- Term
Thermal Expansion — explanation
- Meaning
Expansion is a consequence of the asymmetric interatomic potential. Differential expansion between joined materials is exploited in bimetallic strips and must be allowed for in construction.
Learning objectives
Compute dimensional change on heating for solids and liquids.
Explain the anomalous expansion of water and its consequence.
Formulae
- Key point
Linear, areal and volumetric coefficients are in the ratio 1:2:3.
- Key point
Water shows anomalous expansion below 4 degrees Celsius.
- Key point
Apparent expansion of a liquid excludes the container's expansion.
Common mistakes
Forgetting that a hole in a heated plate also expands.
Ignoring the anomalous behaviour of water.
Keywords
Thermal
Expansion
Practice preview
Which of the following formulas correctly represents the linear thermal expansion of a solid rod?…
easy
If alpha is the coefficient of linear thermal expansion, what is the approximate relationship between the coefficient of area thermal expansion (beta) and the coefficient of volume thermal expansion (gamma)?…
easy
A metal rod of length 2.0 m is heated from 20 degrees C to 70 degrees C. If its length increases by 1.2 mm, what is the coefficient of linear thermal expansion of the metal?…
easy