state of matter's

1. State of matter:
States of matter in physics are the distinct forms that different phases of matter take on. Four states of
matter are observable in everyday life: solid, liquid,gas, and plasma. Many other states are known such
as Bose–Einstein condensates and neutron-degenerate matter but these only occur in extreme situations
such as ultra cold or ultra dense matter. Other states, such as quark-gluon plasmas, are believed to be
possible but remain theoretical for now. For a complete list of all exotic states of matter, see the list of
states of matter.
Historically, the distinction is made based on qualitative differences in properties. Matter in the solid state
maintains a fixed volume and shape, with component particles (atoms, molecules or ions) close together
and fixed into place. Matter in the liquid state maintains a fixed volume, but has a variable shape that
adapts to fit its container. Its particles are still close together but move freely. Matter in the gaseous state
has both variable volume and shape, adapting both to fit its container. Its particles are neither close
together nor fixed in place. Matter in the plasma state has variable volume and shape, but as well as
neutral atoms, it contains a significant number of ions and electrons, both of which can move around
freely. Plasma is the most common form of visible matter in the universe.
Solid:
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. 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-centred cubic structure at temperatures below
912 °C, and a face-centred cubic structure between 912 and 1394 °C. Ice has fifteen known crystal
[2]
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 liquids can be transformed into solids by freezing.
Solids can also change directly into gases through the process of sublimation.
Liquid:
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 most well known exception being water, H 2O.
The highest temperature at which a given liquid can exist is itscritical temperature.

2. Gas:
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.
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.
Definition
The common definition of matter is anything that has both mass and volume (occupiesspace). For
example, a car would be said to be made of matter, as it occupies space, and has mass.
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 Pauli exclusion principle. 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.
Protons, neutrons and electrons definition
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 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 (see Quarks and
leptons definition below).

3. DARK MATTER:
Dark matter is a type of matter hypothesized in astronomy and cosmology to account for a large part of
themass that appears to be missing from the universe. Dark matter cannot be seen directly with
telescopes; evidently it neither emits nor absorbs light or other electromagnetic radiation at any significant
[1]
level. Instead, the existence and properties of dark matter are inferred from its gravitational effects on
visible matter, radiation, and the large-scale structure of the universe. According to the Planck mission
team, and based on the standard model of cosmology, the total mass–energy of the known
[2][3]
universe contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy.
Thus, dark matter
is estimated to constitute 84.5% of the total matter in the universe and 26.8% of the total content of the
[4][5]
universe.
Astrophysicists hypothesized dark matter due to discrepancies between the mass of large astronomical
objects determined from their gravitational effects and the mass calculated from the "luminous matter"
they contain: stars, gas, and dust. It was first postulated by Jan Oort in 1932 to account for the orbital
velocities of stars in theMilky Way and by Fritz Zwicky in 1933 to account for evidence of "missing mass"
in the orbital velocities ofgalaxies in clusters. Subsequently, many other observations have indicated the
[6]
presence of dark matter in the universe, including the rotational speeds of galaxies by Vera Rubin, in
the 1960s–1970s, gravitational lensing of background objects by galaxy clusters such as the Bullet
Cluster, the temperature distribution of hot gas in galaxies and clusters of galaxies, and more recently the
pattern of anisotropies in the cosmic microwave background. According to consensus among
cosmologists, dark matter is composed primarily of a not yet characterized type of subatomic
[7][8]
particle.
The search for this particle, by a variety of means, is one of the major efforts in particle
[9]
physics today.
Although the existence of dark matter is generally accepted by the mainstream scientific community,
there is no generally agreed direct detection of it. Other theories, including MOND and TeVeS, are some
alternative theories of gravity proposed to try to explain the anomalies for which dark matter is intended to
account.
Antimatter
In particle physics, antimatter is material composed of antiparticles, which have the same mass
as particles of ordinary matter but have opposite charge and other particle properties such
as lepton and baryon number. Encounters between particles and antiparticles lead to the annihilation of
both, giving rise to varying proportions of high-energy photons (gamma rays), neutrinos, and lower-mass
particle–antiparticle pairs. Setting aside the mass of any product neutrinos, which represent released
energy which generally continues to be unavailable, the end result of annihilation is a release of energy
available to do work, proportional to the total matter and antimatter mass, in accord with the mass-energy
2 [1]
equivalenceequation, E=mc .
Antiparticles bind with each other to form antimatter just as ordinary particles bind to form normal matter.
For example, apositron (the antiparticle of the electron) and an antiproton can form an antihydrogen atom.
Physical principles indicate that complex antimatter atomic nuclei are possible, as well as anti-atoms
corresponding to the known chemical elements. To date, however, anti-atoms more complex than
antihelium have neither been artificially produced nor observed in nature. Studies of cosmic rays have

4. identified both positrons and antiprotons, presumably produced by high-energy collisions between
particles of ordinary matter.
There is considerable speculation as to why the observable universe is apparently composed almost
entirely of ordinary matter, as opposed to a more symmetric combination of matter and antimatter.
This asymmetry of matter and antimatter in the visible universe is one of the greatest unsolved problems
[2]
in physics. The process by which this asymmetry between particles and antiparticles developed is
called baryogenesis.
Antimatter in the form of anti-atoms is one of the most difficult materials to produce. Antimatter in the form
of individual anti-particles, however, is commonly produced by particle accelerators and in some types of
radioactive decay.