Encyclopedia of Earth: Physics & Chemistry: Gas

Article explaining what methane is, its impact as a greenhouse gas on global warming, and natural and man-made sources of methane. (Published: April 30, 2010)

Discusses what phosphates are, their role in the phosphorous cycle, where they occur in the natural world, their chemistry, and the impact of the use of phosphate fertilizers in agriculture.

Explains what petrochemicals are, the main hydrocarbon feedstocks that form the basis of petrochemical industries, sources, uses, and products made from petrochemicals. (Published: September 25, 2011)

Explains what carbon dioxide is, where it is found, sources of it, and describes human activities that contribute to carbon depletion and increased levels of carbon dioxide in the atmosphere. (Updated: February 22, 2013)

A description of the chemical and physical properties of carbon monoxide, its toxic effect on humans, sources of this gas, and beneficial uses. Includes a list of safety resource websites.

Information about the element, Calcium, atomic number 20. Covers physical and atomic properties, sources, its role in geochemical cycles, how abundant it is on the Earth, its isotopes, some compounds of calcium, and its importance to...

Discusses the chemistry of nitrate, the negative agricultural effects of too much nitrate in soil and in water sources, its toxicity to plants and livestock, and the impact on human health.

Explains what pH is and its use in defining what acids and bases are. Also talks about the importance of pH for regulating metabolism in life forms. Includes a chart showing the pH values of common liquids. (Published: July 30, 2010)

Defines inertial and gravitational mass, their scientific history, formulas used in their calculation, the definition of weight, units used for mass, and mass as perceived in the theory of special relativity.

Gives definition of catalysis, an explanation of how it works, different kinds of catalysis and examples, substances that impact on the catalytic process, the many applications of catalysis, and a history of catalyst technology.