physical change



We explain what a physical change is, how it occurs and how it differs from a chemical change. Also, examples and explanations.

The passage of a metal from a solid to a liquid state when molten is a physical change.

What is a physical change?

Physical changes in matter are changes that alter its shape without modifying its composition. During a physical change, the substance does not vary, that is, it does not imply a chemical reaction. It is about changes of state of matter aggregation (solid, liquid, gaseous) and other physical properties such as color, density or magnetism. Physical changes are usually reversible since they alter the shape or state of matter, but not its composition.

As the name implies, physical changes involve alterations in some of the properties physics of matter, such as its state of aggregation, its hardness, its shape, size, color, volume or density.

Only rarely does this type of change involve a substantial rearrangement of the atoms (as occurs in the formation of crystals).

Man uses physical methods (based on physical changes in matter) on a daily basis in the industry, in medicine and in many other applications. Examples of these are the physical methods of separation of mixtures (as the distillation, the decantation, the filtration and sedimentation) as well as the application of high pressures to liquefy a gas or the application of high temperatures to transform a liquid into vapor.

Examples of physical change

When you dissolve sugar in coffee, only a physical change occurs.

Some examples of physical change are as follows:

  • Evaporation of liquids. Through this process, a liquid is passed into the vapor phase by administering heat. Evaporation occurs slowly, and liquid molecules located on the surface are the first to go into the vapor phase. In this process, the chemicals are not chemically modified. molecules that make up the liquid. The water steam, for example, remains chemically Water (H2O), even if it is in gaseous state.
  • Condensation of gases. It is a process that consists of cooling (removing heat) a gas to become a liquid. This process is the opposite of vaporization. For example, when we bathe in hot water and the steam it condenses on the mirror and clouds it with minimal droplets, what happens is that the steam in contact with the mirror transfers heat to it, which condenses in the form of these droplets on the mirror.
  • Solidification of liquids. It is the process by which by increasing the Pressure, a liquid can transform into solid. The simplest example is the freezing of water into solid ice, without changing its chemical composition at all. But in this case the water turns into ice and the pressure of liquid water increases a lot.
  • Solutions of solids in liquids. When we dissolve salt in water or sugar in coffee, we stop observing the added solids, but we still feel their effect on the mixture. All you have to do is vaporize the liquid to find the solid again at the bottom of the container, in its unchanged chemical form.
  • Magnetization from metals. Metals such as iron and other similar metals, when in contact with a source of electric power or magnetic, partially acquire magnetic charge and attract other metals. An example of this can be seen when we zoom in on clips to a magnet. In this case we will see how the clips stick to the magnet, but their chemical composition and shapes remain unaltered.

Physical change and chemical change

Oxidation is a type of chemical change.

Chemical changes are those that alter the distribution and bonds of the atoms of matter and they manage to combine differently to obtain substances different from the initial ones.

When a chemical change occurs, you always get the same amount of matter that you had in the beginning, even if it is in different proportions and combinations, since matter cannot be created or destroyed, only transformed. Unlike physical changes, chemical processes are usually irreversible and consume or release energy, since in the process one or more chemical substances they become others, recombining their atoms in an always specific way.

It is not possible to separate the components of a chemical compound by physical separation methods, so it is necessary to use methods that involve chemical changes. For example, if we boil water, the resulting steam will continue to be made up of water molecules, only now in the gaseous state, in this case, a physical change has occurred. On the other hand, if we react water with sulfur trioxide (SO3), we will obtain sulfuric acid (H2SO4), a totally different compound (in this case, a chemical change has occurred).

!-- GDPR -->