Physics Lesson 13.2.1 - What is Thermal Expansion and Thermal Contraction?

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Welcome to our Physics lesson on What is Thermal Expansion and Thermal Contraction?, this is the first lesson of our suite of physics lessons covering the topic of Thermal Expansion, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.

What is Thermal Expansion and Thermal Contraction?

Volume of objects can change in three ways:

By adding or removing material from it. This is a mechanical process, during which we change the mass of the object as well. However, the density of material does not change.
By stretching or compressing an object manually, without adding to or removing material from it, i.e. the mass of object does not change. This is a mechanical process too, and any change in one dimension is accompanied by another (reverse) change in the other dimension. For example if you pull a chewing gum, it becomes longer but also thinner at the same time. The same phenomenon can be also observed when we pull an elastic thread. Anyway, the density of material still does not change considerably.
By supplying or removing some heat energy to the object. In this process, mass does not change. However, there is a change in volume because when the object becomes hotter its molecules vibrate more than before and thus, the volume increases as the particles in the outer layers of the object move farther from each other.

In this tutorial, we are concerned about the third method of objects' change in dimensions, i.e. in thermal expansion (contraction) as this process occurs without any mechanical work done on the object. We need only a heat source to make an object expand, or we can just move it away from the heat source to make it contract. It is obvious that the temperature of objects increase when they expand and decreases when they contract. By definition,

Thermal expansion is the general increase in the volume of a material as its temperature is increased. Also, thermal contraction, is the general decrease in the volume of a material as its temperature is decreased.

Thermal expansion (contraction) has no unit; it is represented through a fractional change in length, area or volume of material in respect to the original dimensions. Let's see this quantity more closely in the next paragraph.

You have reached the end of Physics lesson 13.2.1 What is Thermal Expansion and Thermal Contraction?. There are 7 lessons in this physics tutorial covering Thermal Expansion, you can access all the lessons from this tutorial below.

More Thermal Expansion Lessons and Learning Resources

Thermodynamics Learning Material
Tutorial ID	Physics Tutorial Title	Revision Notes	Revision Questions
13.2	Thermal Expansion
Lesson ID	Physics Lesson Title	Lesson	Video Lesson
13.2.1	What is Thermal Expansion and Thermal Contraction?
13.2.2	Linear Thermal Expansion and Contraction
13.2.3	Area Thermal Expansion and Contraction
13.2.4	Volume Thermal Expansion and Contraction
13.2.5	Thermal Expansion and Contraction in Daily Life
13.2.6	Bimetallic Strip. Thermostat
13.2.7	Types of Thermometers

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Continuing learning thermodynamics - read our next physics tutorial: Absorption of Heat

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