Physics

# Examples Of Heat Expansion And Contraction In Everyday Life

The expansion and contraction of a solid element can be produced by the action of heat (this is when the expansion of the element occurs) and by the action of cold (contraction).

When a sudden temperature change (increase) occurs, most elements expand. When this temperature decreases, the elements contract. For example: on a very hot day the wood expands but when the temperature drops it begins to generate noise as it contracts again.

However, it is important to make a fundamental clarification: when solids expand as a result of heat, it does not mean that they increase their volume. What happens is that the distance between molecule and molecule increases, causing the element to expand. This expansion (or dilation ) exerts a considerable force.

This condition of solids is important to take into account, especially in bridge construction, since it has been proven that a metal bridge that measures 50 meters and that goes from 0º C to 15º C in a short time can expand up to 12 centimeters.

However, not all solids expand in the same way and under the same temperature. For example, aluminum expands 2 times more than the metal iron.

## What happens inside the solid?

As the temperature increases , what happens is that the internal energy of the particles increases and their degree of agitation increases.

In other words, what happens is that each particle begins to “ vibrate” and separates from the particle next to it, thus the expansion of the element occurs.

When the heat decreases, the particles decrease their internal energy and little by little they get closer until they are next to each other again.

## Examples of heat expansion and contraction

1. When a bowl is placed inside the refrigerator and removed . In order to remove the cold from the edge of the container, the same hermetic container must be immersed in hot water, in this way the plastic expands, allowing the contents inside to be extracted.
2. Water . When heated (boiled) the molecules expand, when cooled they contract and when frozen, the water molecules compact.
3. Iron . This metal is found in nature in a solid state, that is, its molecules are closer to each other. However, due to the action of heat, this metal dilates ( expands ) and the iron becomes molten iron . The same thing happens with other metals such as aluminum, mercury, lead, etc.
4. Chewing gum . When chewing gum is at a high temperature, it melts. This is seen during a hot day. Then, if we place this chewing gum in the refrigerator, it contracts and hardens.
5. The muscles of the body on a day with very low atmospheric temperatures . For this reason, some people have muscle soreness after aerobic training or on very hot and then very cold days. What regulates this is the liquid (water) of our body. But the pain intensifies if the body is dehydrated.
6. Carbonated water in the freezer.
7. Timber . On a very hot day it expands. Then, when the temperature drops, it begins to generate noises as it contracts again.
8. Train track rails . These are built with a certain distance, being slightly separated. Tar is then placed in this space to allow the metal to expand on very hot days and then contract again as the temperature drops.
9. Glass . If we place a regular glass glass and add boiling water, the inner part of the glass expands while the outer part is cold. This causes the glass to break.
10. The thermometer . This is composed of liquid mercury. As in liquid elements the particles are relatively distant from each other, when mercury is exposed to heat (for example body fever), the mercury rises up the thermometer since it has become more liquid.