Definitions

• Sublimation


  Changing the state of a substance from solid to gas without passing through the liquid state
• Diffusion

  The spreading of a substance through another from a region of high concentration to a region of low concentration due to the random motion of particles
• Mixture


  Contains more than one substance, they are mixed together and not chemically combined and can be separated by physical methods
• Solution


  It consists of solute which dissolves in solvent
• Solvent


  A substance that allows solutes to dissolve in e.g. water and ethanol
• Atom


  The smallest possible particle of an element that can exist and share in reaction without being changed
• Atomic (proton) number


  The number of protons in one atom of the element
• Mass (nucleon) number


  The total number of nucleons, which is the sum of protons and neutrons in one atom of the element
• Isotopes


  Atoms of the same element having the same atomic number but different mass number due to the difference in the number of neutrons
• Element


  A substance that consists of only ONE type of atoms. It can't be broken down into anything simpler e.g. aluminium
• Compound


  A substance which consists of two or more elements chemically combined together e.g. water
• Ionic bond


  A strong electrostatic attraction force between oppositely charged ions
• Covalent bond


  A chemical bond formed by the sharing of one or more pairs of electrons between two atoms
• Valence


  The number of electrons lost, gained or shared by an atom to reach the stability of nearest inert gas
• Ion


  An atom that loses or gains electrons
• Law of conservation of mass


  The total mass of all products of a chemical reaction is equal to the total mass of all the reactants
• Relative atomic mass (RAM/Ar)

  The average mass of naturally occurring atoms of the element, using a scale where an atom of carbon-12 has mass exactly 12
• Relative molecular mass (RMM/Mr)


  The sum of the relative atomic mass of all atoms in a molecule
• Oxidizing agent


  The substance that is reduced and gained electrons
• Reducing agent


  The substance that is oxidized and lost electrons
• Oxidation


  The process of losing electrons or gaining oxygen
• Reduction


  The process of gaining electrons or losing oxygen
• Metallic elements


  Elements that conduct electricity when solid or molten. The current is carried by loosely held electrons, which move from one atom to the next
• Conduction


  The passage of electricity through a metallic substance or graphite where the electricity is carried by free electrons
• Electrolytes


  Liquids that conduct electricity by the movement of ions
• Non-electrolytes


  Substances that do not conduct an electric current, either when molten or in solution, because no ions are present
• Electrolysis


  The breakdown of an ionic compound, molten or in aqueous solution, by the passage of an electric current through it
• Cathode


  The electrode that is connected to the negative pole of the battery
• Anode


  The electrode that is connected to the positive pole of the battery
• Inert electrode


  Electrodes that don't undergo reaction and the electrolyte is the one that participates in the reaction
• Active electrode


  When the electrode is a metal such as silver or copper, the anode participates in the reaction by dissolving and losing electrons, converting into positive ions
• Electroplating


  Coating one metallic object with another metal using electrolysis
• Synthesis reactions


  Reactions where two or more substances combine to form a more complicated one
• Decomposition reactions


  Reactions where a complex molecule is broken down to make simpler ones, the opposite of synthesis reactions
• Combustion reactions


  Reactions where a substance reacts with oxygen to form water and carbon dioxide, causing the release of energy (exothermic)
• Displacement reactions


  Reactions where a more reactive element will displace a less reactive one from a solution of its compounds
• Single displacement


  One element replaces another element in a compound
• Double displacement

  Two compounds switch ions between each other
• Neutralization reaction

  A reaction that takes place between an acid and a base to produce salt and water
• Reaction rate


  A measure of how fast the reaction takes place, often expressed in terms of the concentration (amount per unit volume) of a product that is formed in a unit of time or the concentration of a reactant that is consumed in a unit of time