Chemistry Definitions Flashcards
Definition of: acid
A substance that produces hydrogen ions (H+) when dissolved in water.
Definition of: acid-alkali indicator
A substance used to show if a solution is acidic or alkaline. It will have a different colour in each type of solution.
Definition of: acidic solution
A solution that has a pH < 7.
Definition of: acidic rain
Rain that has a pH < 5; produced when gases such as sulfur dioxide dissolve in rainwater.
Definition of: activation energy
The minimum energy required by colliding particles for reaction to occur.
Definition of: alkali
A base that dissolves in water to form hydroxide ions (OH-).
Definition of: alkaline solution
A solution that has a pH > 7.
Definition of: alkane
A saturated hydrocarbon with the general formula CnH2n+2.
Definition of: alkene
An unsaturated hydrocarbon with the general formula CnH2n.
Definition of: anion
A negatively charred ion. For example, Cl- , O^2- , OH- , NO3- , etc.
Definition of: atom
The smallest particle of an element that can take part in a chemical reaction.
Definition of: atomic number
The number if protons in the nucleus of an atom.
Definition of: base
A substance that neutralises an acid to form a salt.
Definition of: bauxite
The main ore of aluminium, from which aluminium is extracted.
Definition of: brine
A concentrated solution of sodium chloride in water.
Definition of: catalyst
A substance that speeds up a chemical reaction but which is chemically unchanged at the end of the reaction.
Definition of: cation
A positively charged ion. For example, Na+ , Mg^2+ , Al^3+ , NH4+ , etc.
Definition of: combustion
A chemical reaction involving burning.
Definition of: compound
A substance made up of two or more elements chemically combined together.
Definition of: contact process
The name of the industrial process used for making sulfuric acid.
Definition of: corrosion
A chemical reaction between a metal and oxygen.
Definition of: covalent bond
The force of attraction between the nuclei of two atoms and a pair of electrons shared between them.
Definition of: cracking
The process of breaking long-chain alkane molecules into short-chain alkanes and alkenes.
Definition of: crude oil
A naturally occurring mixture of many hydrocarbons.
Definition of: cryolite
A mineral of aluminium used in its molten form for dissolving aluminium oxide in the electrolytic manufacture of aluminium.
Definition of: decomposition
Breaking down a compound into simpler substances (either elements and/or other compounds).
Definition of: diffusion
The movement of particles (atoms, molecules or ions) from an area of high concentration to one of lower concentration.
Definition of: displacement reaction
A reaction in which one substance replaces another, for example chlorine displacing bromine from a bromide or zinc displacing copper from a copper salt or zinc displacing copper from copper(II) oxide.
Definition of: distillation
The process of separating a liquid from a solution of a solid in the liquid.
Definition of: dynamic equilibrium
The condition that exists when the rate of the forward and backward reactions in a reversible reaction mixture are equal.
Definition of: effervescence
The rapid production of bubbles of gas produced during a reaction taking place in aqueous solution.
Definition of: electrode
A solid electrical conductor that forms the connection between the electrolyte and the external electrical circuit in electrolysis.
Definition of: electrolysis
The decomposition of a substance by passing an electric current through it.
Definition of: electronic configuration
The way that the electrons are arranged into shells in an atom, for example Na 2.8.1
Definition of: electron
A negatively charged sub-atomic particle with next to no mass.
Definition of: element
A substance made up of atoms that all contain the same number of protons
Definition of: empirical formula
Proportions of elements available in a compound
Definition of: endothermic reaction
A reaction that takes in heat energy
Definition of: exothermic reaction
A reaction that gives out heat energy.
Definition of: Faraday constant
The quantity of electric charge carried by one mole of electrons.
Definition of: fermentation
The conversion of glucose to ethanol and carbon dioxide.
Definition of: flame test
A method of identifying a metal cation by the colour it produces in a non-luminous Bunsen flame.
Definition of: fraction
A mixture containing several compounds all of which have similar boiling points.
Definition of: fractional distillation
The process of separating the liquids in a mixture of miscible liquids, using the fact that the liquids have different boiling points.
Definition of: Haber process
The name of the industrial process used for making ammonia.
Definition of: halogen
An element in Group 7 of the Periodic Table.
Definition of: homologous series
A group of organic compounds in which each member differs from the next member by a –CH2– unit.
Definition of: hydrocarbon
A compound made up of only the elements hydrogen and carbon.
Definition of: immiscible liquids
Liquids that do not mix together.
Definition of: intermolecular force
The force of attraction between individual molecules.
Definition of: ion
An electrically charged atom or group of atoms e.g. Na+ , Cl- , NH4+ , SO4^2-
Definition of: ionic bond
The force of attraction between oppositely charged ions in a compound.
Definition of: isomers
Compounds that have the same molecular formula but different displayed formulae.
Definition of: isotopes
Atoms of the same element that have different masses. They contain the same number of protons but different numbers of neutrons.
Definition of: litmus
The most common acid-alkali indicator. It is red in a solution with a pH 8.
Definition of: mass number
The sum of the number of protons and neutrons in the nucleus of an atom.
Definition of: metallic bond
The force of attraction between the positive metal ions and the delocalised electrons in a metal.
Definition of: mineral
A rock found in the Earth’s crust that contains a metal or a metal compound.
Definition of: miscible liquids
Liquids that can mix together.
Definition of: mixture
A combination of two or more substances (elements and/or compounds) that are not chemically joined together.
Definition of: molar enthalpy change
The net heat energy change per mole in a chemical reaction.
Definition of: molar volume
The volume of one mole of a gas. At r.t.p it is 24dm^3.
Definition of: mole
The amount of substance containing 6 x 10^23 particles (atoms, modules or formulae) of the substance.
Definition of: molecular formula
The exact number of atoms of each element present in a molecule of a substance.
Definition of: molecule
The smallest particle of a substance that can have a separate, independent existence.
Definition of: monatomic molecule
A molecule that contains only one atom ( e.g. Those of the noble gases).
Definition of: monomer
The unit molecule from which a polymer is made.
Definition of: neutralisation
The reaction between an acid and a base to produce a salt.
Definition of: neutral solution
A solution that has a pH of 7.
Definition of: neutron
A neutral sub-atomic present in the nucleus of an atom.
Definition of: ore
A mineral that contains enough of a metal or a metal compound to make it worthwhile extracting the metal.
Definition of: oxidation
The removal of electrons from a substance, or the addition of oxygen.
Definition of: oxidising agent
A substance that is capable of oxidising another substance.
Definition of: Periodic Table
A table in which thy elements are arranged on order of increasing atomic number. Elements with similar properties appear in the same groups (vertical columns).
