ANALYSISMatter namely solid, liquid and gas undergo change in dimension when theyexperience change in temperature. This change and transfer of temperature iscalled heat, and the change in dimension of a certain material made by such heat isthe so called heat or thermal expansion. Exploring the concept of thermalexpansion, it states that a rise in the temperature of a body causes the expansion inits dimension or specifically its length (linear expansion), and as the temperaturecools down, the body’s dimension contracts.Suppose a rod of material has a length Loat some initial temperature To. When the temperature changes by ΔT, the length changes by ΔL, we say that the change in length is directly proportional to change in temperature. If two rods made of the same material have the same temperature change, but one is twice as long as the other, then the change in its length is also twice as great. Therefore, change in length must also be proportional to change in temperature. Introducing aproportionality constant α (which is different for different materials), we may express these relationships in an equation:

We know that is the coefficient of linear expansion. It is the ratio of the change in length to the original length for every change in temperature. Its equation is:Expanding the equation using the change in length ΔL, we have:This proportion isn’t true for all solids, however, just for most. Some solids contract when heating them. For example, ice actually contracts as you raise its temperature from 0°C to 4°C as its molecules rearrange themselves from the crystalline structure of ice.On a molecular level, linear expansion happens because when you heatobjects up, the molecules bounce around faster, which leads to a physical expansion. When you heat up a solid, it expands by a few percent, and that percentage is proportional to the change in temperature.

#### You've reached the end of your free preview.

Want to read all 7 pages?

- Spring '11
- Agguire
- Physics, Thermodynamics, Heat, Aluminium, linear expansion, bimetallic strip