What is Matter In Chemistry | Definition,Properties

Definition of Matter

Matter is anything which has mass and occupies space. Everything around us, for example, book, pen, pencil, water, air, all living beings, etc., are composed of matter. You know that they have ass and occupy space. Atoms and compounds are all made of very small parts of matter. Those atoms go on to build the things you see and touch every day. Matter is defined as anything that has mass and takes up space (it has volume).

Other Definitions of Matter

what is matter

Based on atoms

A definition of “matter” based on its physical and chemical structure is: matter is made up of atoms. Such atomic matter is also sometimes termed ordinary matter.

As an example, deoxyribonucleic acid molecules (DNA) are matter under this definition because they are made of atoms. This definition can be extended to include charged atoms and molecules, so as to include plasmas (gases of ions) and electrolytes (ionic solutions). Which are not obviously included in the atoms definition. Alternatively, one can adopt the protons, neutrons, and electrons definition.

Based on Protons, Neutrons and Electrons

A definition of “matter” more fine-scale than the atoms and molecules definition is: matter is made up of what atoms and molecules are made of, meaning anything made of positively charged protons, neutral neutrons, and negatively charged electrons.

This definition goes beyond atoms and molecules. However, to include substances made from these building blocks that are not simply atoms or molecules. For example electron beams in an old cathode ray tube television, or white dwarf matter—typically, carbon and oxygen nuclei in a sea of degenerate electrons. At a microscopic level, the constituent “particles” of matter such as protons, neutrons, and electrons obey the laws of quantum mechanics and exhibit wave–particle duality. At an even deeper level, protons and neutrons are made up of quarks and the force fields (gluons) that bind them together, leading to the next definition.

Based on Quarks and Leptons

Under the “quarks and leptons” definition, the elementary and composite particles made of the quarks (in purple) and leptons (in green) would be matter—while the gauge bosons (in red) would not be matter. However, interaction energy inherent to composite particles (for example, gluons involved in neutrons and protons) contribute to the mass of ordinary matter.

As seen in the above discussion, many early definitions of what can be called “ordinary matter” were based upon its structure or “building blocks”. On the scale of elementary particles, a definition that follows this tradition can be stated as: “ordinary matter is everything that is composed of quarks and leptons”, or “ordinary
matter is everything that is composed of any elementary fermions except antiquarks and antileptons”.

The connection between these formulations follows. Leptons (the most famous being the electron), and quarks (of which baryons, such as protons and neutrons, are made) combine to form atoms, which in turn form

Because atoms and molecules are said to be matter, it is natural to phrase the definition as: “ordinary matter is anything that is made of the same things that atoms and molecules are made of”. (However, notice that one also can make from these building blocks matter that is not atoms or molecules.)

Then, because electrons are leptons, and protons, and neutrons are made of quarks, this definition in turn leads to the definition of matter as being “quarks and leptons”, which are two of the four types of elementary fermions (the other two being antiquarks and antileptons, which can be considered antimatter as described later).

Carithers and Grannis state: “Ordinary matter is composed entirely of first-generation particles, namely the [up] and [down] quarks, plus the electron and its neutrino.” (Higher generations particles quickly decay into first-generation particles, and thus are not commonly encountered.)

This definition of ordinary matter is more subtle than it first appears. All the particles that make up ordinary matter (leptons and quarks) are elementary fermions, while all the force carriers are elementary bosons. The W and Z bosons that mediate the weak force are not made of quarks or leptons. And so are not ordinary matter, even if they have mass.

In other words, mass is not something that is exclusive to ordinary matter. The quark–lepton definition of ordinary matter, however, identifies not only the elementary building blocks of matter, but also includes composites made from the constituents (atoms and molecules, for example).

Such composites contain an interaction energy that holds the constituents together, and may constitute the bulk of the mass of the composite. As an example, to a great extent, the mass of an atom is simply the sum of the masses of its constituent protons, neutrons and electrons.

Based on Elementary Fermions (mass, volume, and space)

A common or traditional definition of matter is “anything that has mass and volume (occupies space)”.

For example, a car would be said to be made of matter, as it has mass and volume (occupies space). The observation that matter occupies space goes back to antiquity.

However, an explanation for why matter occupies space is recent, and is argued to be a result of the phenomenon described in the Pauli exclusion Principle, which applies to fermions.

Two particular examples where the exclusion principle clearly relates matter to the occupation of space are white dwarf stars and neutron stars, discussed further below.

Thus, matter can be defined as everything composed of elementary fermions. Although we don’t encounter them in everyday life, antiquarks (such as the antiproton) and antileptons (such as the positron) are the antiparticles of the quark and the lepton, are elementary fermions as well, and have essentially the same
properties as quarks and leptons, including the applicability of the Pauli exclusion principle which can be said to prevent two particles from being in the same place at the same time (in the same state), i.e. makes each particle “take up space”.

This particular definition leads to matter being defined to include anything made of these antimatter particles as well as the ordinary quark and lepton. And thus also anything made of mesons, which are unstable particles made up of a quark and an antiquark.

States of Matter

states of matter

A state of matter is one of the distinct forms that different phases of matter take on. Three states of matter are observable in everyday life: solid, liquid, and gas.


In a solid, the particles (ions, atoms or molecules) are closely packed together. The forces between particles are strong so that the particles cannot move freely but can only vibrate.

solid state

As a result, a solid has a stable, definite shape, and a definite volume. Solids can only change their shape by force, as when broken or cut.

In crystalline solids, the particles (atoms, molecules, or ions) are packed in a regularly ordered, repeating pattern. There are various different crystal structures, and the same substance can have more than one structure (or solid phase).

For example, iron has a body-centered cubic structure at temperatures below 912 °C, and a face-centered cubic structure between 912 and 1394 °C. Ice has fifteen known crystal structures, or fifteen solid phases, which exist at various temperatures and pressures.

Glasses and other non-crystalline, amorphous solids without long-range order are not thermal equilibrium ground states. Therefore they are described below as nonclassical states of matter.

Solids can be transformed into liquids by melting and can also change directly into gases through the process of sublimation.


Structure of a classical single atom liquid. Atoms have many nearest neighbors in contact, yet no long-range order is present.

liquid state

A liquid is a nearly incompressible fluid that conforms to the shape of its container. But retains a (nearly) constant volume independent of pressure.

The volume is definite if the temperature and pressure are constant. When a solid is heated above its melting point, it becomes liquid. Given that the pressure is higher than the triple point of the substance.

Intermolecular (or interatomic or interionic) forces are still important. But the molecules have enough energy to move relative to each other and the structure is mobile.

This means that the shape of a liquid is not definite but is determined by its container. The volume is usually greater than that of the corresponding solid, the best known exception being water, H2O. The highest temperature at which a given liquid can exist is its critical temperature.


A gas is a compressible fluid. Not only will a gas conform to the shape of its container, but it will also expand to fill the container.

gaseous state

In a gas, the molecules have enough kinetic energy so that the effect of intermolecular forces is small (or zero for an ideal gas), and the typical distance between neighboring molecules is much greater than the molecular size.

A gas has no definite shape or volume, but occupies the entire container in which it is confined. A liquid may be converted to a gas by heating at constant pressure to the boiling point, or else by reducing the pressure at constant temperature.

At temperatures below its critical temperature, a gas is also called a vapor, and can be liquefied by compression alone without cooling.

A vapour can exist in equilibrium with a liquid (or solid). In which case the gas pressure equals the vapor pressure of the liquid (or solid).

A supercritical fluid (SCF) is a gas whose temperature and pressure are above the critical temperature and critical pressure respectively.

In this state, the distinction between liquid and gas disappears. A supercritical fluid has the physical properties of a gas. But its high density confers solvent properties in some cases, which leads to useful applications.

For example, supercritical carbon dioxide is used to extract caffeine in the manufacture of decaffeinated coffee.

Changing States of Matter

Molecules can move from one physical state to another (phase change) and not change their atomic structure.

Oxygen (O2) gas has the same chemical properties as liquid oxygen. The liquid state is colder and denser (less energy), but the molecules are the same. Water (H2O) is another example. A water molecule is made up of two hydrogen (H) atoms and one oxygen (O) atom.

It has the same molecular structure whether it is a gas, liquid, or solid. Although its physical state may change because of different amounts of energy, its atomic structure remains the same. So what is a chemical change in matter?

Let’s start with that glass of pure water. If the formula of water were to change, that would be a
chemical change. If you could add a second oxygen atom to a water (H2O) molecule, you would have hydrogen peroxide (H2O2).

The molecules would not be “water” anymore. In reality, there are a variety of steps that go into creating hydrogen peroxide from water. Physical changes are related to changes in the immediate environment such as temperature, pressure, and other physical forces.

Chemical changes occur when the bonds between atoms in a compound are created or destroyed. Generally, the basic chemical structure does not change when there is a physical change. Of course, in extreme environments such as the Sun, no molecule is safe from destruction.

Properties of Matter

properties of matter

All properties of matter are either extensive or intensive and either physical or chemical.

Extensive properties, such as mass and volume, depend on the amount of matter that is being measured.

Intensive properties, such as density and color, do not depend on the amount of matter.

Both extensive and intensive properties are physical properties, which means they can be measured without changing the substance’s chemical identity.

For example, the freezing point of a substance is a physical property: when water freezes, it’s still water (H2O —it’s just in a different physical state.

A chemical property, meanwhile, is any of a material’s properties that becomes evident during a chemical reaction; that is, any quality that can be established only by changing a substance’s chemical identity.

Chemical properties cannot be determined just by viewing or touching the substance; the substance’s
internal structure must be affected for its chemical properties to be investigated.

Physical Properties of Matter

Physical properties are properties that can be measured or observed without changing the chemical nature of the substance.

Some examples of physical properties are:

  • Color (intensive).
  • Density (intensive).
  • Volume (extensive).
  • Mass (extensive).
  • Boiling point (intensive): the temperature at which a substance boils.
  • Melting point (intensive): the temperature at which a substance melts.

Physical properties Matter has mass and volume, as demonstrated by this concrete block. You can observe its mass by feeling how heavy it is when you try to pick it up; you can observe its volume by looking at it and noticing its size.

Mass and volume are both examples of extensive physical properties.

Extensive Property

Any characteristic of matter that depends on the amount of matter being measured.

Intensive Property

Any characteristic of matter that does not depend on the amount of the substance present.

Chemical Properties of Matter

Remember, the definition of a chemical property is that measuring that property must lead to a change in the substance’s chemical structure.

Here are several examples of chemical properties:

  • Heat of combustion is the energy released when a compound undergoes complete combustion (burning) with oxygen. The symbol for the heat of combustion is ΔHc.
  • Chemical stability refers to whether a compound will react with water or air (chemically stable substances will not react). Hydrolysis and oxidation are two such reactions and are both chemical changes.
  • Flammability refers to whether a compound will burn when exposed to flame. Again, burning is a chemical reaction—commonly a high-temperature reaction in the presence of oxygen.
  • The preferred oxidation state is the lowest-energy oxidation state that a metal will undergo reactions in order to achieve (if another element is present to accept or donate electrons).

Units for Measurement

We need to measure all physical quantities. We can express the value of a physical quantity as the product of the numerical value and the unit in which it is expressed.

Fundamental Units

Fundamental units are those units which can neither be derived from one another nor they can be further resolved into any other units.

Below, we have listed the seven fundamental units of measurement in S.I. system.

QuantityName of UnitAbbreviation
Amount of SubstanceMolemol
Electric CurrentAmpereA
Luminous IntensityCandelaCd

Derived units

Some quantities are expressed as a function of more than one fundamental units known as derived units. For example velocity, acceleration, work, energy etc

Quantity With SymbolS.I UnitSymbol
Velocity (v)Metre per secms-1
Area (A)Square metrem2
Volume (V)Cubic metrem3
DensityKilogram m-3Kgm-3
Energy (E)Joule (J)Kgm2s-2
Force (F)Newton (N)Kgms-2
Frequency (n)HertzCycle per sec
Pressure (P)Pascal (Pa)Nm-2
Electrical chargeCoulomb (C)A-s (ampere – second)

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