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physical object > natural object > collection of particles > phase of matter > gas

gas
subject			fact

gas	is a part of disk
	has definition A phase of matter consisting of a low density collection of particles which have no short range order
	has definition The gaseous component of a galaxy, includes nebula
	is a kind of phase of matter
physical object	has location or center of gravity
	has angular momentum
	has mass
	has velocity
	has momentum
	has temperature
	has volume
	has extent
	has material

Kinds of gas :

• barotropic gas (2 facts) - A gas in which the pressure is a function of the density only.
• ideal gas (4 facts) (perfect gas) - A nondegenerate gas in which the individual molecules are assumed to occupy mathematical points and to have zero volume, and in which the mutual attraction of neighboring molecules is zero., he pressure of a gas is directly proportional to the product of its temperature and density (p = CρT). The higher the temperature and the more rarefied a gas, the more closely it obeys the ideal gas laws, so the gases in most stars closely approximate ideal gases. For a degenerate gas, the pressure depends only on the density and is independent of the temperature.
• interstellar gas (4 facts) - Sparse, cool gas (mainly hydrogen) in interstellar space. Dust absorbs and scatters radiation; gas does not interact directly with radiation but is coupled to the dust by collisions. Interstellar gas affects only light of certain wavelengths. Temperature 10-100 K.
• plasma (1 kind, 7 facts) - A completely ionized gas; the so-called fourth state of matter (besides solid, liquid, and gas) in which the temperature is too high for atoms as such to exist and which consists of free electrons and free atomic nuclei.