Physical Change - Concept, examples, chemical change

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

The transition from a solid to liquid state metal when it is molten is a physical change.

What is a physical change?

Physical changes are the type of transformations of matter that alter its state, but never its composition or nature.That is, it is those transits between one form or another of matter, without a significant chemical alteration, that is, without one type of matter becoming another by some type of chemical reaction.

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

Only rarely does this type of change imply a substantial rearrangement of atoms (as occurs in the formation of crystals).Typically, physical changes are usually reversible .

Physical changes, in addition, are the result of a physical method , which usually consists of the modification of energy, pressure or other variables in which matter is found.Many of these methods are In addition, they are useful for separating mixtures of matter, although they are not useful for separating the components of a chemical compound (the result of a chemical reaction).

Examples of physical change

When dissolving sugar in coffee, only a physical change occurs.

Some examples of physical change are as follows:

• Evaporation of liquids , increasing their amount of energy (heat) to convert them into gases, although without modifying their nature.Water vapor, for example, is still chemically water (H2O ), even if it is in a gaseous state.
• Gas condensation , the inverse process to the above, which takes place by extracting energy (heat) from a gas, allowing it to change to the liquid state.It is what happens when we bathe with hot water and the steam condenses in the mirror, filling it with minimal droplets.
• Solidification of liquids , as happens when removing energy (heat) or sometimes simply leaving them at rest long enough.The simplest example is the freezing of water in solid ice, without changing its chemical composition at all.
• Solids solutions in liquids , such as when we dissolve salt in water or sugar in coffee: we can stop observing the added solids, but not feeling their effect on the mixture.Bastara evaporate the liquid to find the new solid at the bottom of the container, in its unchanged chemical form.
• Metal magnetization , such as iron and other similar ones, when coming into contact with a source of electrical or magnetic energy.This can be done with clips and a magnet: if we put the first ones in contact with the magnet, we will notice how they partially acquire their magnetic charge and attract each other, without altering their shape or chemical composition.

Physical change and chemical change

Oxidation is a type of chemical change.

Unlike physical changes, chemical changes do involve a reaction in matter and therefore the alteration of its nature.These processes are usually irreversible and consume or release energy , since in the process one or more chemical substances become others, recombining their atoms in an always specific way.

The chemical changes do not respond to physical methods, and therefore we cannot separate the components of a chemical compound by physical changes : if we boil water, the resulting vapor will remain constituted by oxygen and hydrogen; while if we react water with sulfur trioxide (SO3) we will obtain sulfuric acid (H2SO4), a totally different compound.

More in: Chemical change