Content
The expansion and contractionof a solid element can be produced by action of hot (it is when the expansion of the element occurs) and by the action of the cold (contraction).
When there is a sudden change in temperature (rise) most of the elements expand. When this temperature decreases, the elements contract.
However, it is important to make a fundamental clarification: when solids expand as a result of heat, it does not mean that they increase in volume. What happens is that the distance between molecule and molecule increases causing the element to have a expansion. Is expansion (or dilatation) exerts a considerable force.
This condition of solids is important to take into account, especially in bridge constructions, 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.
But nevertheless not all solids expand in the same way and under the same temperature. For example, aluminum expands 2 times more than iron metal.
What happens inside the solid?
As the temperature increases, what happens is that the internal energy of the particles increases and the degree of agitation of these increases.
In other words what happens is that each particle begins "to vibrate " and it is separated from the particle that it has next to it, in this way the expansion of the element occurs.
When the heat descends, the particles decrease the internal energy and little by little they get closer until they are next to each other again.
Examples of heat expansion and contraction
- When a bowl is placed in the refrigerator and removed. In order to remove the cold from the edge of the container, the same hermetic container must be submerged in hot water, in this way the plastic expands allowing the contents to be extracted from its interior.
- Water. When heated (boiled) the molecules expand, when they cool down they contract, and when they freeze, the water molecules compact.
- 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 expands (expand) and the iron becomes molten iron. The same is true of other metals such as aluminum, mercury, lead, etc.
- Chewing gum. When chewing gum is at a high temperature, it melts. This is seen during a hot day. Then, if we put this gum in the refrigerator, it contracts and hardens.
- The muscles of the body on a day with very low atmospheric temperatures. For this reason, some people have sore muscles after aerobic training or on very hot days and then very cold. Who regulates this is the liquid (water) of our body. But the pain intensifies if the body is dehydrated.
- Water carbonated in the freezer.
- Timber. A very hot day it expands. Then, when the temperature drops, it begins to generate noise as it contracts again.
- Railroad tracks. These are built with a certain distance being slightly separated. Then tar is placed in this space to allow the metal to expand on very hot days and then, as the temperature drops, it contracts again.
- Glass. If we place a glass of ordinary glass and add boiling water, the inside of the glass expands while the outside is cold. This causes the glass to break.
- The thermometer. This is made up of liquid mercury. As in liquid elements the particles are relatively distant from each other, the mercury, when exposed to heat (for example body fever), the mercury rises up the thermometer since it has become more liquid.
