Isochoric specific heat of gases and vapors under standard conditions

Isochoric specific heat of gases and vapors under standard conditions

Junjie Chen

Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China

Contributor: Junjie Chen, ORCID: 0000-0001-5055-4309, E-mail address: komcjj@gmail.com

A gas is one of the three fundamental states of matter, with distinctly different properties from the liquid and solid states. The remarkable feature of gases is that they appear to have no structure at all. They have neither a definite size nor shape, whereas ordinary solids have both a definite size and a definite shape, and liquids have a definite size, or volume, even though they adapt their shape to that of the container in which they are placed. Gases will completely fill any closed container; their properties depend on the volume of a container but not on its shape. Gases nevertheless do have a structure of sorts on a molecular scale. They consist of a vast number of molecules moving chaotically in all directions and colliding with one another and with the walls of their container. Beyond this, there is no structure, the molecules are distributed essentially randomly in space, traveling in arbitrary directions at speeds that are distributed randomly about an average determined by the gas temperature. The pressure exerted by a gas is the result of the innumerable impacts of the molecules on the container walls and appears steady to human senses because so many collisions occur each second on all sections of the walls. More subtle properties such as heat conductivity, viscosity (resistance to flow), and diffusion are attributed to the molecules themselves carrying the mechanical quantities of energy, momentum, and mass, respectively. These are called transport properties, and the rate of transport is dominated by the collisions between molecules, which force their trajectories into tortuous shapes. The molecular collisions are in turn controlled by the forces between the molecules and are described by the laws of mechanics.

Gases and vapors, Isochoric specific heat (kilojoules per kelvin per kilogram)

Acetone      1.32

Acetylene      1.37

Air      0.718

Alcohol (ethanol)       1.67

Alcohol (methanol)       1.53

Ammonia      1.66

Argon      0.312

Benzene      0.99

Blast furnace gas      0.73

Bromine              0.2

Butane      1.53

Carbon dioxide      0.655

Carbon monoxide      0.72

Carbon disulphide      0.55

Chlorine              0.36

Chloroform      0.55

Ethane      1.48

Ether (diethyl ether)       0.48

Ethylene      1.23

Helium      3.12

Hydrochloric acid      0.567

Hydrogen      10.16

Hydrogen chloride      0.57

Hydroxyl      1.27

Krypton      0.151

Methane      1.70

Natural gas      1.85

Neon      0.618

Nitric oxide      0.718

Nitrogen      0.743

Nitrogen tetroxide      4.6

Nitrous oxide      0.69

Oxygen      0.659

Propane      1.48

Propene (propylene)       1.31

Contributor: Junjie Chen, ORCID: 0000-0001-5055-4309, E-mail address: komcjj@gmail.com, Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China