States of Matter (Solid, Liquid, Gas) Definition, Classification FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:46 PM IST

Introduction to Matter

What is matter in science?

The matter is explained as anything that has mass and volume (occupies space)". Matter can be defined as the substance which constitutes the observable universe. Matter, along with energy, is known to form the basis of every objective phenomenon. In classical physics and general chemistry, the matter is applied to determine any material that contains mass and occupies volume. The matter is composed of several atoms or molecules. The different arrangements of these atoms or molecules give matter various states and properties. The force of interaction between these particles provides matter its physical states, based on which matter can be classified into solid, liquid, and gas mains. The force of interaction between atoms/molecules is highest in solids, least in gas, and intermediate in gas.

This Story also Contains

Introduction to Matter
Types of matter: (What are the states of matter?)
Solid matter
Properties of solid, liquid, and gas with examples
Liquid state of matter
Gas state of matter
plasma state of matter
Bose-Einstein Condensates
What are solid liquid and gas?

In this unit, we will learn more about these three physical states of matter particularly – solid, liquid, gas.

Also read -

Types of matter: (What are the states of matter?)

7 states of matter

solid liquid gas pictures

Solid matter

(Solid state of matter)

Solid Definition (solid definition chemistry)

A solid can be defined as a substance that occupies a specific volume in a very rigid form hence, does not change its shape. This rigidity achieves due to the closely packed atoms whose kinetic energies are much lower than those of liquids and gases.

Properties of solid, liquid, and gas with examples

In solids, particles are tightly or closely packed due to the strongest intermolecular force of interaction.
The gaps between the particles are very small and therefore, tough to compress. As a result, Solid has a fixed shape and volume.
Because of the rigid nature of the solid, particles in the solid can only vibrational motion along with their mean position and cannot move.
The force of attraction between particles is obstinate.
In solids, the diffusion rate is very small.
Example of Solid: solid ice, sugar, rock salt, vapour, etc.

These are the properties of solid liquid and gas.

Three-Dimensional Lattice

The unique and special arrangement of atoms or molecules within a crystal is referred to as the lattice structure of that material. The 3-D lattice structure shows the periodic arrangement of the atoms which forms a crystalline substance. Crystalline materials are so highly systematic that a crystal lattice is formed from repetitions along all three spatial dimensions of the same pattern. The crystal lattice represents the three-dimensional structure of the atomic/molecular components of the crystal.

The Unit Cell

The structure seen within the crystalline lattice of a material can be described in a different way. The most common way to describe a crystal structure is to refer to the size and shape of a characteristic unit cell of matters, i.e., the simplest repeating unit within the crystal. These unit cells repeat to create a three-dimensional lattice.

unit cell of fluorite states of matter images

Unit Cell of Fluorite: the above diagram shows the simplest repeating unit within a crystal of the molecule calcium fluoride (CaF₂). Calcium ions are indicated as grey spheres, and fluorine ions are indicated as yellow.

Packing of Atoms Within a Unit Cell

Within a crystalline material, each atom can be considered as a sphere that is packed into unit cells. Each and every sphere that is present in a crystal structure consists of a coordination number, which corresponds to the number of spheres within the crystalline structure that touches the sphere that is being evaluated.

molecular diagram of solid (Sodium chloride crystal lattice) solid examples pictures solid liquid gas pictures

Liquid state of matter

liquid definition.

It is composed of molecules or atoms in such a way so that they can move freely among themselves but do not tend to separate like gases and it occupies the shape of the container in which it is kept,

Intermolecular Structure of Liquid

Characteristics of liquid state.

In a liquid matter, particles are less tightly packed than solid.
Liquids occupy the shape of the container in which they are kept.
Liquids are difficult almost incompressible as particles have less intermolecular space to move.
Liquids have fixed volume but do not possess any particular shape.
The rate of diffusion in liquids is higher than that of solids but lesser than that of gas.
The Force of attraction between the particles is weaker than solids but higher than that of gas.
Liquid exhibits some properties like viscosity and surface tension.

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Example of a liquid state of matter/ Examples of liquid/ examples of liquids: water, milk, blood, coffee, etc.

Related Topics,

Types of liquids

Liquids may be divided into two general types:

pure liquids and liquid mixtures.

Diffusion of solids in liquids

Diffusion is a phenomenon in which substances move from an area of high concentration to an area of low concentration.
The movement of the molecule takes place from the area of higher concentration to the area of lower concentration until it becomes the same. Liquid molecules and gases molecule undergo diffusion as they move freely. The process diffusion is based on the concentration gradient.
Solid can diffuse in liquid. When sugar is added to water, whole water becomes sweet without stirring it because of the diffusion of sugar into the water.

Gas state of matter

Definition of gas state.

A state of matter in which it will expand freely to fill the whole of a container, having no fixed shape (unlike a solid) and no fixed volume (unlike a liquid).

gas state of matter

Characteristic of gas

In this state of matter, the intermolecular distances are large (in the range of 10⁻⁷–10⁻⁵cm10⁻⁷–10⁻⁵cm).
The intermolecular Force of attraction between the particles is negligible, and they can move freely.
Gases have neither a fixed volume nor a fixed shape, hence, occupies the shape of the container.
The compressibility is higher in gases as compared to solids and liquids.
The diffusion rate is higher in gases than solids and liquids.
The kinetic energy of particles is higher than in solids and liquids.
Gases example include air, nitrogen, helium, oxygen, carbon dioxide, etc.

pictures of different gases:

plasma state of matter

What is plasma in chemistry?

Plasma is the fourth state of matter known as the superheated state of matter. The plasma includes 99% of the universe which is visible.

plasma state

Properties of plasma state

Plasma behaves like an intermediate state of gas and liquid
plasmas show no fixed shape or volume. It is denser than solids or liquids.
"Plasma is a charged gas, with strong Coulomb [or electrostatic] interactions,"
Plasma consists of particles that possess extremely high kinetic energy.
Plasma is used in the formation of the sun and stars.

Examples of plasma: sun, stars, lightning, solar wind, fusion devices, welding arcs, neon signs, aurora, nebulae, galaxies, etc.

Also, students can refer,

Bose-Einstein Condensates

The 5th state of matter is Bose-Einstein Condensates.

It is defined as a state of matter in which separate atoms or subatomic particles, cooled to near absolute zero temperature (0 K or, − 273.15 °C).

Bose-Einstein Condensates diagram

Characteristics:

Bose-Einstein condensates of matter were made with the help of advanced technology.
Carl Weiman and Eric Cornell froze a sample of rubidium with the help of magnets and lasers to within a few degrees of absolute zero.
At that temperature, the motion of the molecules becomes negligible or almost tends to zero. As this lowers the kinetic energy, the atoms no longer stay separated and begin to clump together. Since the atoms join together, they form a super-atom.
Light slows down as it passes through a Bose-Einstein condensate of matter, helping scientists to study more about the nature of light as a wave and particle.
Bose-Einstein condensates also show properties of a superfluid which implies, it flows without friction.

What are solid liquid and gas?

The principal physical states of matter are solid liquid and gas.

Solid: A solid can be defined as a substance that occupies a specific volume in a very rigid form hence, does not change its shape. This rigidity achieves due to the closely packed atoms whose kinetic energies are much lower than those of liquids and gases. Liquid: composed of molecules or atoms in such a way so that they can move freely among themselves but do not tend to separate like gases and it occupies the shape of the container.

Gas: a state of matter in which it will expand freely to fill the whole of a container, having no fixed shape (unlike a solid) and no fixed volume (unlike a liquid).

Also check-

NCERT Chemistry Notes:

Frequently Asked Questions (FAQs)

1. . What are the physical states of matter?

Solid liquid gas

2. Which is the fifth state of matter?

Bose-Einstein Condensates.

3. There are how many states of matter? / what are the types of matter?

There are 7 states of matter;

Solids, Gases, Liquids, Ionized Plasma, Bose-Einstein Condensate, and Fermionic Condensate, Quark-Gluon Plasma.

4. Define plasma in chemistry.

Plasma is an ionized gas and the fourth state of matter.

5. List two properties that are common in liquid and solids.

1] Both liquids and solids have definite shapes.

2] Both liquids and solids are formed of molecules.

6. Write matter definition physics.

In physics, matter can be defined as the quantity having mass and occupying space and it makes the whole universe.

7. Which is the 4th state of matter?

Plasma

8. What is supercritical fluid, and how does it relate to states of matter?

A supercritical fluid is a substance at a temperature and pressure above its critical point, where distinct liquid and gas phases don't exist. It has properties of both gases and liquids, blurring the line between these states.

9. What is the relationship between intermolecular forces and the energy required for phase changes?

Stronger intermolecular forces require more energy to overcome during phase changes. This results in higher melting and boiling points and greater latent heats of fusion and vaporization.

10. How does the kinetic molecular theory explain the behavior of gases?

The kinetic molecular theory states that gas particles are in constant, random motion, colliding with each other and container walls. This explains gas pressure, diffusion, and how gases fill their containers.

11. How does the concept of vapor pressure relate to the states of matter?

Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid or solid phase. It increases with temperature and relates to the tendency of a substance to change from liquid or solid to gas.

12. What is the relationship between temperature and particle motion in different states of matter?

As temperature increases, particle motion (kinetic energy) increases. This leads to more vibration in solids, increased movement in liquids, and faster, more energetic motion in gases.

13. What is the difference between evaporation and vaporization?

Evaporation is the process of a liquid changing to a gas at the surface, occurring at any temperature. Vaporization is a broader term that includes both evaporation and boiling (rapid vaporization throughout the liquid).

14. How does the volume of a substance typically change when transitioning between states?

Generally, substances expand when transitioning from solid to liquid to gas. However, there are exceptions, such as water expanding when it freezes (unlike most substances).

15. What is the difference between intensive and extensive properties of matter, and how do they relate to states of matter?

Intensive properties (like density or boiling point) don't depend on the amount of substance and are often used to characterize states of matter. Extensive properties (like mass or volume) depend on the amount of substance present.

16. What is meant by the term "volatility," and how does it relate to states of matter?

Volatility refers to a substance's tendency to vaporize (change from liquid or solid to gas). More volatile substances have weaker intermolecular forces and transition to the gas state more easily.

17. What is the process called when a substance changes from a solid to a liquid?

The process of changing from a solid to a liquid is called melting or fusion. It occurs when the substance absorbs enough energy to overcome the attractive forces holding the particles in a fixed position.

18. What is latent heat, and how does it relate to changes of state?

Latent heat is the energy absorbed or released by a substance during a phase change without a change in temperature. It represents the energy needed to overcome intermolecular forces during state transitions.

19. How do impurities affect the melting and boiling points of a substance?

Impurities typically lower the melting point and raise the boiling point of a substance. This is why, for example, salt is used to melt ice on roads and why salt water has a higher boiling point than pure water.

20. How does atmospheric pressure affect the boiling point of liquids?

Higher atmospheric pressure increases the boiling point of liquids by exerting more force on the surface, requiring more energy for vapor bubbles to form. Lower pressure decreases the boiling point.

21. What is the critical point of a substance, and why is it important?

The critical point is the temperature and pressure at which the distinction between liquid and gas phases disappears. Above this point, the substance becomes a supercritical fluid with unique properties.

22. How do intermolecular forces affect the state of matter?

Stronger intermolecular forces tend to favor more condensed states (solids and liquids) by holding particles closer together. Weaker forces allow for more particle movement, favoring gases.

23. What is the difference between melting point and freezing point?

Melting point is the temperature at which a solid changes to a liquid, while freezing point is the temperature at which a liquid changes to a solid. For pure substances, these points are typically the same temperature.

24. How does the arrangement of particles differ in solids, liquids, and gases?

In solids, particles are tightly packed in a fixed arrangement. In liquids, particles are close but can move around each other. In gases, particles are far apart with no fixed arrangement.

25. What is sublimation, and can you give an example?

Sublimation is the process where a solid changes directly into a gas without passing through the liquid state. An example is dry ice (solid carbon dioxide) sublimating to carbon dioxide gas at room temperature and normal atmospheric pressure.

26. How does pressure affect the state of matter?

Increasing pressure generally favors more condensed states of matter. For example, increasing pressure can cause a gas to liquefy or a liquid to solidify by forcing particles closer together.

27. What is the difference between an amorphous solid and a crystalline solid?

Crystalline solids have a regular, repeating arrangement of particles, while amorphous solids lack this long-range order. Examples include crystalline quartz (regular structure) and glass (amorphous structure).

28. How does the strength of intermolecular forces compare between solids, liquids, and gases?

Intermolecular forces are strongest in solids, weaker in liquids, and weakest in gases. This difference in strength accounts for the varying properties and behaviors of the three states of matter.

29. How does the concept of diffusion differ in solids, liquids, and gases?

Diffusion occurs fastest in gases, slower in liquids, and slowest in solids. This is due to the differences in particle mobility and spacing in each state of matter.

30. What is the triple point of a substance, and what does it represent?

The triple point is the unique combination of temperature and pressure at which a substance can exist simultaneously in solid, liquid, and gas phases in equilibrium. It represents a point where all three phases coexist.

31. What is Brownian motion, and how does it relate to states of matter?

Brownian motion is the random movement of particles suspended in a fluid (liquid or gas), caused by collisions with other particles. It's most noticeable in fluids but can occur to a lesser extent in some solids.

32. Can all substances exist in all three states of matter?

Not all substances can exist in all three states under normal conditions. Some substances decompose before changing state, while others may require extreme temperatures or pressures to reach certain states.

33. How do phase diagrams help us understand states of matter?

Phase diagrams visually represent how temperature and pressure affect a substance's state of matter. They show phase boundaries, triple points, and critical points, helping predict a substance's state under various conditions.

34. What is meant by the term "phase transition"?

A phase transition is the transformation of a substance from one state of matter to another. Examples include melting, freezing, vaporization, condensation, sublimation, and deposition.

35. What is the difference between condensation and deposition?

Condensation is the process of a gas changing to a liquid, while deposition is the process of a gas changing directly to a solid. Both involve the release of energy as particles come closer together.

36. What is the difference between an exothermic and endothermic phase change?

An exothermic phase change releases energy to the surroundings (e.g., condensation, freezing), while an endothermic phase change absorbs energy from the surroundings (e.g., melting, vaporization).

37. What are the three main states of matter?

The three main states of matter are solid, liquid, and gas. These states represent different physical forms that substances can take based on the arrangement and behavior of their particles.

38. How do particles behave differently in solids, liquids, and gases?

In solids, particles are tightly packed and vibrate in fixed positions. In liquids, particles are close together but can move around each other. In gases, particles are far apart and move freely in all directions.

39. What determines the state of matter of a substance?

The state of matter is determined by the balance between the kinetic energy of particles (their motion) and the attractive forces between them. Temperature and pressure play crucial roles in influencing this balance.

40. Can a substance exist in more than one state of matter simultaneously?

Yes, a substance can exist in multiple states simultaneously at its triple point. For example, water can exist as solid ice, liquid water, and water vapor at a specific temperature and pressure.

41. How does evaporation differ from boiling?

Evaporation occurs at the surface of a liquid at any temperature, while boiling occurs throughout the liquid at a specific temperature (the boiling point). Evaporation is a gradual process, while boiling is more rapid and involves bubble formation.

42. What is plasma, and why is it sometimes called the fourth state of matter?

Plasma is an ionized gas containing a significant number of free electrons and ions. It's often called the fourth state of matter because it behaves differently from solids, liquids, and gases due to its unique electrical properties.

43. What is meant by the term "phase boundary" in a phase diagram?

A phase boundary in a phase diagram is a line that separates two different phases of a substance. It represents the conditions (temperature and pressure) at which two phases can coexist in equilibrium.

44. How does the concept of dynamic equilibrium apply to phase changes?

Dynamic equilibrium in phase changes occurs when the rate of particles leaving one phase equals the rate of particles returning to that phase. This balance maintains a constant amount of each phase at equilibrium.

45. How do intermolecular forces affect the boiling points of different substances?

Stronger intermolecular forces result in higher boiling points because more energy is required to overcome these forces and separate the particles into the gas phase.

46. How do hydrogen bonds affect the properties of water in its different states?

Hydrogen bonds give water unique properties in all states. They cause high boiling and melting points, expansion upon freezing, and high surface tension in the liquid state. In ice, they create a less dense crystal structure.

47. How does surface tension relate to the liquid state of matter?

Surface tension is a property of liquids caused by cohesive forces between molecules at the surface. It creates a "skin-like" effect on the liquid surface and is responsible for phenomena like water beading up on surfaces.

48. What is viscosity, and how does it differ in liquids and gases?

Viscosity is a measure of a fluid's resistance to flow. Liquids generally have higher viscosity than gases due to stronger intermolecular forces. In both states, viscosity typically decreases with increasing temperature.

49. How does the compressibility of matter differ between solids, liquids, and gases?

Gases are highly compressible due to the large spaces between particles. Liquids are slightly compressible, while solids are generally considered incompressible due to their tightly packed particles.

50. What is the relationship between vapor pressure and boiling point?

The boiling point of a liquid is reached when its vapor pressure equals the atmospheric pressure. Substances with higher vapor pressures at a given temperature have lower boiling points.

51. What is supercooling, and how does it relate to the liquid state?

Supercooling occurs when a liquid is cooled below its freezing point without solidifying. This metastable state can persist until disturbed, at which point rapid crystallization occurs.

52. How does the ideal gas law relate to the behavior of gases?

The ideal gas law (PV = nRT) describes the relationship between pressure, volume, amount, and temperature of an ideal gas. It helps predict gas behavior under various conditions, though real gases may deviate from this model.

53. How does the concept of vapor pressure equilibrium apply to the liquid-gas transition?

Vapor pressure equilibrium occurs when the rate of evaporation equals the rate of condensation in a closed system. This equilibrium pressure increases with temperature until it equals atmospheric pressure at the boiling point.

54. How does the concept of mean free path differ between gases, liquids, and solids?

Mean free path is the average distance a particle travels between collisions. It's largest in gases, much smaller in liquids, and extremely small in solids due to the differences in particle spacing and mobility.

55. How does the concept of partial pressure apply to gaseous mixtures?

Partial pressure is the pressure exerted by each gas in a mixture as if it alone occupied the container. The total pressure of a gas mixture is the sum of the partial pressures of its components (Dalton's Law).

56. What is the difference between elastic and inelastic collisions in gases, and how do they relate to gas behavior?

In elastic collisions, kinetic energy is conserved, while in inelastic collisions, some kinetic energy is converted to other forms. Most gas particle collisions are nearly elastic, contributing to the ideal gas behavior.

57. How does the concept of critical temperature relate to the ability to liquefy a gas?

The critical temperature is the highest temperature at which a gas can be liquefied by pressure alone. Above this temperature, no amount of pressure can cause the gas to liquefy, as the kinetic energy of the particles overcomes intermolecular attractions.