additives

In the context of polymers, substances added to modify properties, for example making it more flexible, or more stable
See also plasticiser, stabiliser

alloy

Material made from a metal that has been mixed with other metals or non-metals in order to give it specific properties

amalgam

An alloy which is a mixture of mercury and one or more other metals

amphoteric

A compound that can behave as both an acid and a base

anaerobic

Reactions (usually biological) that take place in the absence of oxygen

aromatic

Compounds with cyclic (ring) structures containing delocalised electrons, often compoundws of benzene

azeotropic mixtures

A liquid mixture of two or more substances that retains the same composition in the vapour state as in the liquid state when distilled or evaporated under some conditions

batch process

Chemical manufacturing process in which a measured quantity of reactants is added to the reaction vessel, the reaction is carried out, and the products are removed. This contrasts with “continuous processes”, where reactants are continually fed in, and products taken out

benign (environmentally)

Not having any damaging consequences to the environment

biomass

Material that has been produced by normal biological growth, like plants. Biomass may be used as a chemical resource

biosynthetic

Synthetic processes that rely on biological reactions (often using enzymes) in order to manufacture a product

biotechnology

Technological applicatiosn that makes use of biological systems or living organisms, either directly or in a modified form

brine

A saturated solution of sodium chloride

carbon reservoirs

Chemical or biological systems, like forests, that contain a lot of carbon “tied up” as compounds

carcinogen

Substance that is know to increase the likelihood of cancer in someone exposed to it

closed-loop recycling

Recycling in which products at end of useful life are used as a resource to remanufacture the same product
S ee also open-loop recycling

complex (ion)

When a simple ion (or atom) is surrounded by several other groups of atoms (or ions) that are bound to it, the resulting species is called a complex ion

condensation reaction

A reaction in which a small molecule (like water or ammonia) is produced when two substances join together, for example in polymerisation

cracking

The process of breaking large molecules into smaller ones using heat, steam or catalysts – used in processing oil

cyclic compound

A compound (usually of carbon) in which some of the atoms form a continuous loop

dehydrating

A process that removes water

disproportionation

A chemical reaction in which a single reactant breaks up to produce two different products

electrolysis

Conduction of electricity through a substance with accompanying chemical reaction

emulsifier

A material which helps the formation of an emulsion (this contains small droplets of one liquid dispersed throughout another with which it is immiscible)

endothermic

Word used to describe a reaction in which more energy (usually heat) is used than given out, resulting in a reduction in temperature

exothermic

Word used to describe a reaction in which more energy (usually heat) is given out than used, resulting in an increase in temperature

extrusion

The process of forcing a material through a shaped opening, to give a long section with a fixed cross-section. Used for polymers and some metals (eg aluminium, copper)

fixing (nitrogen)

When atmospheric nitrogen gas is converted into a material that plants can make use of, it said to have been “fixed”

floatation

A process used to separate different materials based on their ability to float or sink in a liquid

fractional distillation

The process used to separate a mixture of several liquids, based on their different boiling points

free radicals

An uncharged atom or molecular species that has one or more unpaired electrons. Free radical are very reactive

functional group

In organic chemistry, a specific structure of one or more atoms that is responsible for the chemical behaviour of a substance

geothermal power

A source of energy from the heat that can be obtained from rocks several metres below ground

hydration

The addition of water to a substance

hydropower

Energy generated from water pressure

initiator

A substance that is used to start a chemical reaction

intermediate

A substance that is not made to be used directly, but in order to produce other useful compounds

isomers

When two materials with different properties and/or structures share the same chemical formula, they are said to be isomers

Lewis acid

The term “acid” has several definitions. One is a substance that is an electron acceptor, and this type of acid is called a “lewis” acid after the scientist gilbert lewis (1875-1946)

mass spectrometer

The instrument used in an analytical technique that uses a magnetic field to separate ions according to the ratio of mass/charge, and so identify a material by its “mass spectrum”

molecular sieve

Several materials (for example zeolites) have a porous structure that allows some molecules to pass through, but prevent others. These can be used to separate molecules, rather like using a sieve

monomer

A small molecule that can become bonded repeatedly to form a large molecule (called a polymer)

nanocomposites

Plastics are often reinforced by the use of glass or carbon fibre – these are “composites”. Very narrow particles (on the nanometre scale) can also be used, and these give rise to nanocomposites

neurotransmitter

Chemical substances used in the transmission of nerve impulses and in the brain

nitrogenous fertiliser

A plant fertiliser that contains a high proportion of nitrogen

opencast mining

A mining technique in which material is extracted by digging a large hole, rather than tunnelling

open-loop recycling

Recycling in which products at end of useful life are used as a resource to manufacture other products
S ee also closed-loop recycling

Parkinson's disease

A disease of the brain that affects the control of muscles, and so may affect movement, speech and posture

pilot plant

A chemical plant built to test the large-scale feasibility of a production process

plasticisers

Many material are added to polymers to modify the properties of a plastic. Plasticisers increase flexibility
See also stabilisers, additives

polar solvents

A solvent that can dissolve substances that possess charges – like ionic salts

polymer

A large molecule made from many repeating units joined together
See also monomer

polymerisation

The process of creating a polymer from one or more monomers

promoter

When catalysts are used in reactions, the activity of the catalyst can sometimes increased by using another substance, called a promoter

residence time

The length of time that reactants spend in a reactor (may affect the products obtained)

retro-fitting

Modifying existing chemical plant to operate a new process without a complete rebuild

scrubbing

Cleaning emission gases from a chemical reactor, generally with sprays of solutions that will absorb gases

solar power

Energy generated from the heat or light from the sun

stabilisers

Some polymers are naturally reactive, so additives, called stabilisers, are used to prevent the resulting plastic deteriorating
See also plasticisers, additives

steam crackers

“Cracking” is the word used to describe any process that breaks large molecules into smaller ones. This may be brought about by heat, steam or catalysts

surfactants

These are substances that that have detergent properties, and consist of molecules with a water-compatible part (“hydrophilic”) and a water-incompatible part (“hydrophobic”)

synthesis gas

Methane and steam will react to give a mixture of hydrogen and carbon monoxide, known as synthesis gas, which can be used as the starting point for many different reactions

tail gas

These are the “leftover” gases at the end of a continuous chemical manufacturing process, that are neither product nor recyclable reactants, but are the result of various side reactions

thermoplastic

A plastic that can be re-melted in order to be moulded to shape

thermosetting (plastic)

A plastic that cannot be re-melted, but must be made in a mould of the desired shape

venturi (tube)

A specially shaped tube that affects the speed and pressure of a flowing fluid (gas or liquid)

volatile

Volatile liquids change into vapour very easily, even well below their boiling point

zeolite

These are crystalline solids (usually containing silicon, aluminium and oxygen) that have a regular, open, porous structure. They are either naturally occurring minerals or synthetically produced, and have applications including as catalysts and molecular sieves