Translations of Encyclopedia about Physics

Change in a Substance’s Phase

The phase of a substance is its aggregate state. There are three possible phases which substances may have: solid, liquid and gaseous states. Almost all substances can be found in any one of these phases. The phase at which a substance may be found depends on its temperature, pressure and density. Each substance has two critical temperatures where it changes its phase.

Besides its phases, each substance can also be described according to other criteria: whether they are a crystal, amorphous or gaseous.

Amorphous substances are generally liquid substances whose elements are held together by a very weak attractive force, which are not fixed in a certain position and which are able to move around each other. Besides liquids, solid, noncrystal substances, such as glass, wax and sealing wax, can be considered as amorphous substances and are sometimes referred to as subcooled substances.

Gaseous substances are those whose particles are able to move totally freely.

Solid or crystal substances whose elements easily oscillate around their own axis are easily heated. When heated, the oscillations or the vibrations speed up and the solid bonds between the particles and molecules are disturbed and the object melts. The phenomenon when a substance moves from solid to liquid state is referred to as melting. The change of a substance directly from its solid to gaseous state, without first passing through a liquid state, is referred to as sublimation.

If we add heat to a liquid, we break the bonds between its already, relatively freely moving particles, gradually changing it to a gaseous state, a process referred to as evaporation. On the other hand, when a gas is sufficiently cooled, it turns to a liquid form, a phenomena referred to as condensation. Lowering the temperature further will eventually change the substance into a solid state.

During a change of phase, a substance maintains a so-called latent (hidden) heat, for which reason no change in temperature is observed during this change. The latent heat is only released once the change in phase is complete.

A change in a substance’s phase can often be used for practical purposes. The change in water’s phase is used, for example, in generating energy. In practice, we often take advantage of the fact that some substances have differing melting and boiling points, creating materials with certain substance characteristics. When adding heat, many compounds can be broken down into their various components.

Translating Dutch Hungarian Translations Hungarian Dutch Translating Swedish Czech Translations Czech Swedish Translating Russian