Chem

Absorption In chemistry absorption can mean two things: Firstly it can imply that powerful forces exist holding two substances together, and that seperation of the two is not easily accomplished. Secondly it can mean absorption of heat, light etc.. . The absorption of ultraviolet, visible and infrared radiation is the basis of some forms of spectrometry which can be used to identify different chemical compounds. See also infrared radiation.

Acid A substance that when dissolved in water dissociates and can donate a hydrogen (proton) to another molecule. Examples include sulphuric acid and nitric acid. Under these conditions nitric acid dissociates according to the following equation:

In water the protons attach themselves to the water molecules, giving the following equation:

Actinides This is a group of elements within the periodic table and are also known as the transuranics. The name refers to those elements with increasing atomic no. from actinium, which all have similar chemical properties, like the lanthanides. The first few members of the group are the naturally occuring elements actinium, thorium, proactinium and uranium. Beyond this elements have been made artificially by radioactive bombardment. These artificial elements are unstable, some have very short lifeimes and undergo spontaneous radioactive decay.

Adhesive Any compound that can stick two surfaces together is classified as an adhesive. Simple adhesives are of cellulose, starch and rubbers. Modern adhesives are based upon complex polymeric materials. The adhesive is spread in an unpolymerised form, and the adhesive properties increase as polymerisation occurs between the two surfaces.

Adiabatic A chemical or mechanical process which takes place without heat entering or leaving the system. The term is only applicable to enclosed and isolated systems - so in essence is idealistic and purely theoretical and is important in the study of thermodynamics.

Adrenaline This was the first...