Chemistry & Environmental Dictionary

CAA - Convection

CAA (Clean Air Act)

Passed by congress to have the air "safe enough to protect the public's health" by 5/31/1975. It was amended in 1990 to require EPA to develop more stringent and specific regulations for air emissions.

Caplan's syndrome

Pneumoconiosis associated with rheumatoid arthritis.


  1. Chicago Academy of Science
  2. Chemical Abstracts Service (which assigns CAS Numbers to chemicals)


A positively charged ion.


The exposure limit for a substance that should (or in the case of OSHA PEL's "shall") not be exceeded. If instantaneous monitoring is not feasible, then a 15-minute time weighted average is used.

Centigrade (Celsius)

The scale for measuring temperature used internationally where the freezing point of water is zero and the boiling point of water at sea level is 100 degrees. To convert from centigrade into Fahrenheit, multiply the centigrade temperature by 1.8 then add 32 to the product (C*1.8+32=F). To convert from Fahrenheit to centigrade, subtract 32 and then divide by 1.8 ((F-32)/1.8).

CERCLA (Comprehensive Environmental Response Compensation and Liability Act, Superfund Act)

Is responsible for the "cradle to grave law" that holds the generator of waste responsible for proper waste disposal and provides for cleanup of the most contaminated sites by the government, with the cost of cleanup being charged to the responsible parties. Basically a generator becomes responsible for waste from it's inception until it has been destroyed.


The emission of absorbed energy as light as the result of a chemical reaction. This occurs in thousands of compounds both organic and inorganic. Chemical glow sticks and fireflies are examples of this.

Coefficient of linear thermal expansion

The ratio of change in length per degree centigrade compared to the base length at zero degrees centigrade. The unit of measurement is centimeter per centimeter per degree centigrade (cm/cm/°C). This measurement means that for every centimeter of base length, the length will change X centimeters for every change of one degree centigrade.


a substance composed of atoms or ions of two or more elements that are chemically combined. Elements in a compound are present in definite proportions by mass and are bonded with each other in a specific manner.


  1. Thermal conduction the transfer of heat between two solid materials that are physically touching each other.
  2. Electrical conduction the transfer of electrical current through a solid or liquid.


The movement of heat by a moving liquid or gas. Convection results from the differences in the densities of a material at different temperatures. As a liquid or gas raises in temperature, it becomes less dense and thus lighter thereby rising above its cooler and denser counterparts, which in turn sink.

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