What is a state of matter?

Matter exists in different states, also known as phases, defined by distinct physical properties. The most commonly known states of matter are solid, liquid, and gas.

What are the main states of matter?

Matter exists primarily in four states: solid, liquid, gas, and plasma. A solid maintains its shape and volume because its atoms or molecules are arranged in a relatively ordered, three-dimensional structure. A liquid retains volume but adapts its shape to fit its container. A gas lacks a definite size or shape and will expand to fill any closed container. Plasma is an electrically conductive medium containing roughly equal numbers of positive and negative charges. It is often called the fourth state of matter.

How do solids, liquids, and gases differ from each other?

The three states of matter, solid , liquid , and gas , exhibit distinct properties. Solids have a definite shape and volume because their atoms are arranged in a relatively ordered, three-dimensional structure. They resist forces, whether perpendicular or parallel to their surface. Liquids maintain a definite volume but adapt to the shape of their container. Unlike solids, they cannot resist shear stress and flow under external force. Gases lack a definite size and shape, expanding to fill any closed container. Gas molecules move chaotically, with properties depending on the container's volume, not its shape.

What happens when a substance changes from one state of matter to another?

When a substance changes from one state of matter (or phase) to another, it undergoes a phase change . Matter can change between solid, liquid, and gas phases, as well as crystalline, colloid, glassy, amorphous, and plasma phases. Phase changes occur in response to alterations in pressure, temperature, or chemical composition. For instance, increasing temperature may cause a solid to melt, while increasing pressure may cause a low-density liquid to become a denser solid. During these changes, phases can be created, eliminated, or altered in composition.

What is evaporation and condensation?

Evaporation is the process where a substance changes from its liquid state to a gaseous state below its boiling point, notably when liquid water turns into vapor and enters the atmosphere during the water cycle . This happens when molecules gain enough kinetic energy to escape the liquid's surface. Temperature, humidity, wind speed, and solar radiation affect evaporation rates. Condensation is when a vapor turns into a liquid or solid, typically on a cooler surface. It occurs when the vapor's pressure exceeds the vapor pressure of the substance's liquid or solid phase at the surface temperature, releasing heat. In the atmosphere, condensation leads to dew, fog, and cloud formation when air temperature drops to the dew point or when enough water vapor saturates the air.

Are there states of matter besides solid, liquid, and gas? If so, what are they?

Yes, there are states of matter besides solid, liquid, and gas. Plasma is sometimes referred to as the fourth state of matter. Other phases include crystalline, colloid, glassy, amorphous, and Bose-Einstein condensate. Plasma is an electrically conducting medium containing roughly equal numbers of positively and negatively charged particles. Bose-Einstein condensate is a state of matter that arises when a set of atoms is cooled close to absolute zero. At this point, a statistical description of the positions of the atoms implies that they physically overlap each other and effectively form a single atom. Liquid crystals flow like liquids but display a certain degree of the symmetry characteristic of crystalline solids.

phase

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Images

Diagram showing four physical states of matter: solid with tightly packed molecules, liquid with loosely packed molecules, gas with widely spaced molecules, and plasma with free electrons and nuclei, each labeled with descriptions and an arrow indicating increasing energy.

Diagram showing the phase changes of matter with three circles labeled solid, liquid, and gas. Arrows indicate transitions: melting and freezing between solid and liquid, evaporation and condensation between liquid and gas, and sublimation and deposition between solid and gas.

An illustration shows an ice cube labeled solid, a puddle labeled liquid, and rising steam labeled gas, representing the three states of matter: ice, water, and water vapor, with the sun in the background.

At a Glance

phase summary

phase

state of matter

Written by

Ernest G. EhlersAll

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Britannica Editors

Last updated

Oct. 14, 2026 •History

Top Questions

What is a state of matter?
Matter exists in different states, also known as phases, defined by distinct physical properties. The most commonly known states of matter are solid, liquid, and gas.
- Solid Solids maintain their shape and volume because their atoms are arranged in a relatively ordered, three-dimensional structure.
- Liquid Liquids retain volume but conform to the shape of their container.
- Gas Gases have no definite size or shape and will expand to fill any closed container.
- Plasma Plasma is an electrically conducting medium containing roughly equal numbers of positively and negatively charged particles.
- Bose-Einstein condensate This state occurs when a set of atoms is cooled almost to absolute zero.
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What are the main states of matter?
Matter exists primarily in four states: solid, liquid, gas, and plasma.
- A solid maintains its shape and volume because its atoms or molecules are arranged in a relatively ordered, three-dimensional structure.
- A liquid retains volume but adapts its shape to fit its container.
- A gas lacks a definite size or shape and will expand to fill any closed container.
- Plasma is an electrically conductive medium containing roughly equal numbers of positive and negative charges. It is often called the fourth state of matter.
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How do solids, liquids, and gases differ from each other?
The three states of matter, solid, liquid, and gas, exhibit distinct properties.

Solids have a definite shape and volume because their atoms are arranged in a relatively ordered, three-dimensional structure. They resist forces, whether perpendicular or parallel to their surface.

Liquids maintain a definite volume but adapt to the shape of their container. Unlike solids, they cannot resist shear stress and flow under external force.

Gases lack a definite size and shape, expanding to fill any closed container. Gas molecules move chaotically, with properties depending on the container's volume, not its shape.
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Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What happens when a substance changes from one state of matter to another?
When a substance changes from one state of matter (or phase) to another, it undergoes a phase change. Matter can change between solid, liquid, and gas phases, as well as crystalline, colloid, glassy, amorphous, and plasma phases.

Phase changes occur in response to alterations in pressure, temperature, or chemical composition. For instance, increasing temperature may cause a solid to melt, while increasing pressure may cause a low-density liquid to become a denser solid. During these changes, phases can be created, eliminated, or altered in composition.
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What is evaporation and condensation?
Evaporation is the process where a substance changes from its liquid state to a gaseous state below its boiling point, notably when liquid water turns into vapor and enters the atmosphere during the water cycle. This happens when molecules gain enough kinetic energy to escape the liquid's surface. Temperature, humidity, wind speed, and solar radiation affect evaporation rates.

Condensation is when a vapor turns into a liquid or solid, typically on a cooler surface. It occurs when the vapor's pressure exceeds the vapor pressure of the substance's liquid or solid phase at the surface temperature, releasing heat. In the atmosphere, condensation leads to dew, fog, and cloud formation when air temperature drops to the dew point or when enough water vapor saturates the air.
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Are there states of matter besides solid, liquid, and gas? If so, what are they?
Yes, there are states of matter besides solid, liquid, and gas. Plasma is sometimes referred to as the fourth state of matter. Other phases include crystalline, colloid, glassy, amorphous, and Bose-Einstein condensate.

Plasma is an electrically conducting medium containing roughly equal numbers of positively and negatively charged particles. Bose-Einstein condensate is a state of matter that arises when a set of atoms is cooled close to absolute zero. At this point, a statistical description of the positions of the atoms implies that they physically overlap each other and effectively form a single atom. Liquid crystals flow like liquids but display a certain degree of the symmetry characteristic of crystalline solids.
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phase, in thermodynamics, chemically and physically uniform or homogeneous quantity of matter that can be separated mechanically from a nonhomogeneous mixture and that may consist of a single substance or a mixture of substances. The three fundamental phases of matter are solid, liquid, and gas (vapour), but others are considered to exist, including crystalline, colloid, glassy, amorphous, and plasma phases. When a phase in one form is altered to another form, a phase change is said to have occurred.

General considerations

A system is a portion of the universe that has been chosen for studying the changes that take place within it in response to varying conditions. A system may be complex, such as a planet, or relatively simple, as the liquid within a glass. Those portions of a system that are physically distinct and mechanically separable from other portions of the system are called phases.

Phases within a system exist in a gaseous, liquid, or solid state. Solids are characterized by strong atomic bonding and high viscosity, resulting in a rigid shape. Most solids are crystalline, inasmuch as they have a three-dimensional periodic atomic arrangement; some solids (such as glass) lack this periodic arrangement and are noncrystalline, or amorphous. Gases consist of weakly bonded atoms with no long-range periodicity; gases expand to fill any available space. Liquids have properties intermediate between those of solids and gases. The molecules of a liquid are condensed like those of a solid. Liquids have a definite volume, but their low viscosity enables them to change shape as a function of time. The matter within a system may consist of more than one solid or liquid phase, but a system can contain only a single gas phase, which must be of homogeneous composition because the molecules of gases mix completely in all proportions.

System variables

Systems respond to changes in pressure, temperature, and chemical composition, and, as this happens, phases may be created, eliminated, or altered in composition. For example, an increase in pressure may cause a low-density liquid to convert to a denser solid, while an increase in temperature may cause a solid to melt. A change of composition might result in the compositional modification of a preexisting phase or in the gain or loss of a phase.

The phase rule

The classification and limitations of phase changes are described by the phase rule, as proposed by the American chemist J. Willard Gibbs in 1876 and based on a rigorous thermodynamic relationship. The phase rule is commonly given in the form P + F = C + 2. The term P refers to the number of phases that are present within the system, and C is the minimum number of independent chemical components that are necessary to describe the composition of all phases within the system. The term F, called the variance, or degrees of freedom, describes the minimum number of variables that must be fixed in order to define a particular condition of the system.

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Phase diagrams

Unary systems

Phase relations are commonly described graphically in terms of phase diagrams (see Figure 1). Each point within the diagram indicates a particular combination of pressure and temperature, as well as the phase or phases that exist stably at this pressure and temperature. All phases in Figure 1 have the same composition—that of silicon dioxide, SiO₂. The diagram is a representation of a one-component (unary) system, in contrast to a two-component (binary), three-component (ternary), or four-component (quaternary) system. The phases coesite, low quartz, high quartz, tridymite, and cristobalite are solid phases composed of silicon dioxide; each has its own atomic arrangement and distinctive set of physical and chemical properties. The most common form of quartz (found in beach sands and granites) is low quartz. The region labeled anhydrous melt consists of silicon dioxide liquid.

Different portions of the silicon dioxide system may be examined in terms of the phase rule. At point A a single solid phase exists—low quartz. Substituting the appropriate values into the phase rule P + F = C + 2 yields 1 + F = 1 + 2, so F = 2. For point A (or any point in which only a single phase is stable) the system is divariant—i.e., two degrees of freedom exist. Thus, the two variables (pressure and temperature) can be changed independently, and the same phase assemblage continues to exist.

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Point B is located on the boundary curve between the stability fields of low quartz and high quartz. At all points along this curve, these two phases coexist. Substituting values in the phase rule (2 + F = 1 + 2) will cause a variance of 1 to be obtained. This indicates that one independent variable can be changed such that the same pair of phases will be retained. A second variable must be changed to conform to the first in order for the phase assemblage to remain on the boundary between low and high quartz. The same result holds for the other boundary curves in this system.

Point C is located at a triple point, a condition in which three stability fields intersect. The phase rule (3 + F = 1 + 2) indicates that the variance is 0. Point C is therefore an invariant point; a change in either pressure or temperature results in the loss of one or more phases. The phase rule also reveals that no more than three phases can stably coexist in a one-component system because additional phases would lead to negative variance.

phase

General considerations

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System variables

The phase rule

Phase diagrams

Unary systems