Phases of matter

Physics> Phases of Matter

There are four phases of matter: solid, liquid, gas and plasma.

Learning challenge

  • To be able to distinguish the four states of matter by their characteristics.

Key points

  • Solids are free from compression and have a stable volume and shape.
  • Liquids have a constant volume, do not compress, but are able to change shape. It depends on the container in which they are located.
  • Gases lack a stable volume and shape. If they get into a container, they try to fill the entire area with themselves.
  • The shape and volume of the plasma are in a variable state. It contains ions and electrons that can move freely.


  • Enthalpy is the total amount of energy in the system (internal and required to displace the environment).
  • Plasma is a state of matter, partially represented by ionized gas.
  • Sublimation is the transition of a substance from a solid phase to a vapor state (liquid is bypassed).

The material has many properties that help determine which state we are facing: solid, liquid, gas or plasma.


The solid is endowed with a stable shape and volume. The particles are densely located, and the forces between them are so high that they deprive them of free movement and only allow them to vibrate. Because of this, the solid becomes stable, does not shrink, and its volume is determined.

Solids have a fixed volume and shape


Liquid substances maintain a stable volume, but the shape depends on the vessel in which they are placed. However, they have an uncontrollable free surface. The particles are located close, but not in the same way as in solids. They are still able to move, providing fluidity to the liquid. They usually have a lot of volume with the exception of some molecules like water (H2O).

Liquids are endowed with a stable volume, but the shape depends on the vessel in which they are placed


The distance between particles in gases exceeds their diameter. It resembles a liquid in behavior: the particles are displaced, but continue to attract, creating the effect of fluidity. The gas will try to fill any vessel with itself, adapting to the given volume.

The particles are located farther than their diameter and are constantly moving


Plasma is an ionized gas. That is, the gas has a sufficient amount of energy, so the electrons are able to leave their atoms or molecules. Plasma contains freely moving ions and electrons. Such matter has a variable shape and volume. It is the most common form of visible matter in space. Examples include sparks, the sun, lightning, neon lights.

It has variable shape and volume. Accommodates a large number of freely moving electrons and ions

Phase transitions

A substance is capable of performing state transitions (between phases). A solid can become liquid with increasing enthalpy. The reverse process is melting. A liquid can become a gas if it exceeds the boiling point, and a plasma if the enthalpy increases. With a decrease in enthalpy, the liquid can freeze to a solid state. Sometimes the freezing process for a solid is skipped, and it immediately becomes a gas (sublimation).

Physics Section

  • Phases of matter
  • What is liquid?
Density and pressure
  • Pressure
  • Change in pressure with depth
  • Static balance
  • Pascal’s principle
  • Gauge pressure and atmospheric pressure
  • Gauge pressure and barometer
  • Body pressure
Archimedes principle
  • Buoyancy and the Archimedes principle
  • Full immersion
  • Buoyancy
Cohesion and adhesion
  • Surface tension and capillary action
Fluids in motion
  • Flow rate and equation of continuity
Deformation of solids
  • Length
  • Form
  • Volume
  • Stress and strain

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