LC Chemistry: Definitions Master List

Atomic Absorption Spectrum

The spectrum emitted when white light passes through an element.

Arrhenius Acid

A substance that dissociates in aqueous solution to form hydrogen ions (H+)

Bronsted-Lowry Acid

A proton donor

Activation Energy

The minimum energy required for an effective collision

Addition reaction

monomers (small molecules) combining to form a polymer (large molecule)

Aliphatic

Straight chain or branched hydrocarbon compound

Aromatic

Hydrocarbon compound containing at least one benzene ring

Alloy

A mixture of two or more metals

Alpha Particle

2 Protons and 2 Neutrons emitted from a nucleus.

Anion

Negatively charged ion.

Anode

Positively charged electrode

Atom

Smallest particle of an element

Atomic Number

The number of protons in the nucleus of an atom

Atomic Orbital

Region of high probability of finding an electron

Atomic Radius

Half the distance between the nuclei of identical atoms that are bonded together

Auto-ignition

Ignition without a spark

Avogadro's Constant

Number of molecules in 1 mole = 6x10²³

Avogadro's Law

Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

Arrhenius Base

A substance that dissociates in aqueous solution to form hydroxide ions (OH-)

Bronsted-Lowery Base

Proton acceptor

Batch Process

Something produced in groups and not in a continuous stream

Beta Particle

An electron emitted by an unstable nucleus

Biochemical Oxygen Demand

amount of oxygen consumed when sample kept in the dark for five days at 20oC (293 K)

Bond Energy

Energy required to break a bond

Boyle's Law

pressure inversely proportional to volume (PV = k) , for definite mass of gas at constant temp

Carbonium Ion

Carbon ion with positively charged carbon atom.

Catalyst

substance that alters (speeds up) rate of reaction but not used up

Catalyst Poison

A substance that deactivates a catalyst.

Catalytic Converter

An exhaust emission control device containing a catalyst for converting pollutant gases into less harmful ones.

Catalytic Cracking

splitting (breaking) of long chain molecules to give short chain molecules

Cathode

Negatively charged electrode

Cation

Positively charged ion

Charle's Law

As temperature decreases so does volume.

Chemical Equilibrium

The point at which the reactions offset one another exactly

Chlorofluorocarbons (CFCs)

Hydrocarbons with chlorine and fluorine that destroy ozone

Chromatography

Technique used for separating mixtures based on differences in absorbency.

Combined Gas Law

Pressure is inversely proportional to volume and directly proportional to temperature.

Compound

A substance made up of atoms of two or more different elements joined by chemical bonds

Conjugate Acid

Molecule formed when a base gains a H+

Conjugate Base

Molecule formed when an acid loses a H+

Conjugate Pair

Two molecular species that easily transfer a H+ between them.

Continuous Process

Something produced in an ongoing stream and not in groups.

Co-product

Produced alongside main product.

Corrosion

Destruction by chemical action

Covalent Crystal

A crystal in which the atoms are held together by covalent bonds.

Crystal

A solid whose atoms are arranged in a regular, repeating pattern

Chemical dehydration

Chemical reaction involving the loss of H2O.

Deionised Water

Water with ions removed.

Dibasic Acid

Produces two H+ ions in solution

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.

Dipole-Dipole Force

Intermolecular force between polar molecules

Distilled Water

Pure water collected by condensing steam.

Electrolysis

The use of electricity to break a molecule down into smaller units

Electroplating

The process of depositing a thin layer of metal on an object during electrolysis.

Electronegativity

Relative attraction an atom has for a pair of electrons in a covalent bond

Element

A substance that cannot be broken down into simpler substances

Elimination Reaction

The removal of a molecule from a saturated molecule to make an unsaturated molecule

Empirical Formula

A formula showing the lowest whole number ratio of atoms in a compound

Endothermic Reaction

Reaction in which energy is absorbed.

Energy Level

The fixed energy value an electron in an atom may have.

Enzyme

Biological Catalyst

Equilibrium Constant

A measure of how far forwards or backwards a reaction goes. Kc

Esterification

A chemical reaction between an alcohol and an acid, in which an ester is formed.

Eutrophication

the over-abundant growth of plants and algae arising from excess nutrients in the water

Exothermic Reaction

Reaction in which energy is emitted.

Feedstock

Raw material used in a manufacturing process

First Ionisation Energy

The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms in their ground state

Flocculation

Clumping of small insoluble particles by the addition of alum

Fractionation

Splitting oils into products based on boiling point.

Free Chlorine

Chlorine not bound to other substances.

Free Radical

An atom with an unpaired electron

Gamma Radiation

High-energy radiation emitted by the nuclei of radioactive atoms.

Gay-Lussac's Law

The volumes of reacting gases are in whole number ratios at same temperature & Pressure

Greenhouse Effect

The trapping of heat near a planet's surface by certain gases in the atmosphere.

Half-Life

Time taken for half of the nuclei in a radioactive sample to decay

Hard Water

water which does not easily form lather with water

Heat of Combustion

The heat of reaction for the complete burning of one mole of a substance in excess O2

Heat of Formation

The heat of reaction for the formation of one mole of a substance.

Heat of Reaction

The quantity of energy released or absorbed as heat during a chemical reaction

Heisenberg Uncertainty Principle

It is impossible to know exactly both the velocity and the position of a particle at the same time

Hess' Law

Heat change for a reaction depends only on initial and final states

Heterogeneous Catalysis

reactants & catalyst in different phases

Homogeneous Catalysis

Reactants and catalyst in the same phase.

Homologous Series

Family of organic molecules having
same general formula
differ by CH2 group
same functional group
similar chemical properties
gradation in physical properties
similar method of preparation

Hydrated

A crystalline compound containing water molecules

Hydrocarbon

Compounds composed of only carbon and hydrogen

Hydrogen Bond

Attraction between a slightly positive hydrogen atom and a slightly negative atom (N,O,F)

Hydrolysis

Breaking down complex molecules by the chemical addition of water

Ideal Gas

A gas that behaves exactly as the Kinetic Molecular Theory describes

Intermolecular Force

Forces of attraction between molecules

Instantaneous Rate

The reaction rate at a specific time

Ion

A charged atom

Ionic Bond

force of attraction between oppositely-charged ions

Ionic Crystal

Positive and negative ions arranged in regular structure

Kilogram Calorific Value

of a fuel is the heat energy produced when 1 kg of a fuel is completely burned in oxygen.

Isomerisation

Changing straight-chain alkanes into their isomers.

Isotope

Atoms of the same element with different numbers of neutrons

Law of Conservation of Energy

Energy (Matter) is neither created nor destroyed, but merely changes from one form to another.

Law of Conservation of Mass

(In a closed system) The total mass of the products of a chemical reaction is the same as the total mass of reactants.

Le Chatelier's Principle

If a stress is applied to a system at equilibrium, the system readjusts to relieve the stress applied.