Chemistry Definitions F321 F322

Various definitions for chemistry A/S level.

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  • Created by: beccc
  • Created on: 06-05-12 14:41

Relative Isotopic Mass

the mass of an atom of an isotope compared with one twelfth of the mass of carbon-12.

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Relative Atomic Mass

the weighted mean mass of an atom of an element when compared with one twelfth of the mass of a carbon-12 atom.

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Relative Molecular Mass

the weighted mean mass of a molecule compared with one twelfth of the mass of the atm carbon-12.

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Mole

the amount of any substance containing as many particles as there are carbon atoms in exactly 12g of the carbon-12 isotope.

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Molar Mass

the mass per mole of a substance.

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Empirical Formula

the simplest whole number ratio of atoms of each element present in a compound.

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Concentration Of A Solution

the amount of solute dissolved in a solution per 1dm3.

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Acid

a species that is a proton donor.

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Base

a species that is a proton accepter.

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Alkali

a type of base that dissolves in water forming hydroxide iona (OH-).

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Salt

any chemical compound formed from an acid when a H+ ion has been replaced by a metal ion or another positive ion.

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Water Of Crystallisation

water molecules that form an essential part of the crystaline structure of a compound.

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Oxidation Number

a measure of the number of electrons that an atom uses to bond with atoms of another element.

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Oxidation

a loss of electrons or an increase in oxidation numer.

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Reduction

gain of electrons or a decrease in oxidation number.

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Atomic Orbital

a region of space within an atom that can hold up to two electrons, with opposite spins.

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Electronegativity

a measure of the attraction of a bonded atom for the pair of electrons in a covalent bond.

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Periodicity

a regular periodic variation of properaties of elements with atomic number and position in the Periodic Table.

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Thermal Decomposition

the breaking up of a chemical substance with heat in at least two chemical substances.

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Displacement Reaction

a reaction in which a more reactive element displaces a less reactive element from an aqueous solution of the latter's ions.

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Hydrocarbon

an organic compound which only contains hydrogen and carbon.

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Functional Group

the part of the organic molecule which is responsible for its chemical reactions.

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General Formula

the simplest algebraic formula of a member of a homologous series.

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Structural Isomers

molecules with the same molecular formula but with different structural arrangements of atoms.

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Steroeisomers

compounds with the same structural formula, but with different arrangements of atoms in space.

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Radical

a species with an unpaired electron.

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Homolytic Fission

the breaking of a covalent bond, with one of the bonded electrons going to each atom, forming two radicals.

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Heterolytic Fission

the breaking of a covalent bond with both of the bonded electrons going to one of the atoms forming a cation and an anion.

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Nucleophile

an atom that is attracted to an electron-deficient centre or atom, where it donates a pair of electrons to form a new covalent bond.

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Electrophile

an atom that is attracted to an electron-rich centre or atom, where it accepts a pair of electrons to form a new covalent bond.

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Cracking

the breaking down of long-chained saturated hydrocarbons to form a mixture of shorter-chained alkanes and alkenes.

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Pi-Bond

the reactive part of a double bond formed above and below the plane of the bonded atoms by sideways overlap of p orbitals.

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Esterification

the reaction of an alcohol with a carboxylic acid to produce an ester and water.

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Hydrolysis

a reaction with water or aqueous hydroxide ions that breaks a chemical compound into two compounds.

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Percentage Yield

actual amount of product / desired amount of product x 100 =                                    (mols)

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Atom Economy

molecular mass of desired product / molecular mass of all products x 100

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Fragmentation

the process in mass spectrometry that causes a positive ion to split into pieces.

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Exothermic

refers to a reaction where the enthalpy of the products is smaller than the enthalpy of the reactants, resulting in heat loss to the surroundings.

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Endothermic

refers to a reaction where the enthalpy of the products is greater than the enthalpy of the reactants, resulting in heat being taken in from the surroundings.

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Activation Energy

the minimum energy required to start a reaction by the breaking of bonds.

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Enthalpy Change of Formation

the enthalpy change that takes place when one mole of a compound is formed from it's elements in their standard states under standard conditions.

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Comments

Amina H.

This is really helpful, thank you

Daniel Tonkin

A few spelling mistakes, but other than that it's really helpful, thanks!

beccc

sorry about the few odd spelling mistakes, but I hope you find these helpful for your exams :-)!

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