Chemistry

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Addition polymerisation

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The formation of one product, that is the polymer

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Anode

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The positive electrode

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Atom

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The unit particle of an element

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Boiling point

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The temperature at which a liquid changes into a vapour at a certain pressure

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Cathode

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The negative electrode

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*Concentration of a solution

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Measure of the amount of solute in unit volume of solution; units mol/dm³ or g/dm³

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Condensation polymerisation

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A reaction in which there are two products, the polymer and a small molecule, e.g. water

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Electrodes

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Pieces of metal or carbon through which the current enters and leaves the electrolyte

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Electrolysis

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The process of passing an electric current through a substance and bringing about a chemical reaction

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Electrolyte

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A substance that conducts an electric current when molten or dissolved in water, with chemical reaction at the electrodes

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Element

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A substance that consists of atoms all with the same proton number. It cannot be broken down into anything simpler by chemical means

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*Empirical formula

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This shows the simplest ratio of atoms present

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Group

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A vertical column in the periodic table. The number of occupied shells increases down the group but the number of valency electrons remains the same

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Isotopes

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Different atoms of the same element, which have the same proton number but different nucleon numbers

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Locating agent

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A substance that reacts with colourless spots on a chromatography and makes them visible as coloured spots

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Macromolecule

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A very large molecule made of repeating units These units can be atoms as in diamond, simple molecules of ethene in poly(ethene), or more complex molecules as in proteins and polyamides

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Melting point

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The temperature at which a solid changes into a liquid

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*Molar volume (Vm)

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The volume, approximately 24dm³, occupied by one mole of any gas at room temperature and pressure (r.t.p.)

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*Mole

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The amount of a substance that contains 6 x 10²³ atoms, ions or molecules. The number 6 x 10²³ is called the Avogadro constant. One mole of a substance has a mass equal to the relative formula mass in grams

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*Molecular formula

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This shows the number of atoms of each element present in one molecule of the substance

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Monomer

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Small molecules that join together to form one large polymer molecule

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Noble gases

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A gaseous element in Group 0, with stable electronic structure: its electron shells are full so its UN reactive

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Non-biodegradable

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Not broken down in the environment by micro-organisms in the presence of water and oxygen

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Non-electrolyte

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A substance that doesn't conduct in the liquid phase

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Nucleon number

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The number of nucleons, that is, the number of protons and neutrons in one atom of the element

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Period

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A horizontal row in the periodic table. It corresponds to a shell or energy level filling with electrons: the number of occupied shells is the same across the period but the number of valency electrons in the outer shell increases

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Polymer

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A very large molecule former from many monomer molecules

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Proton number

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The number of protons in one atom of the element

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Pure substance

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A single substance

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Relative atomic mass (Ar)

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The average mass of the naturally occurring atoms on a scale where an atom of ¹²C has a mass = 12.000 (Most naturally occurring elements are a mixture of isotopes. This means that not all the atoms have the same mass so the average has to be used)

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Relative formula mass

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(Mr)The sum of the relative atomic masses of all the elements shown in the formula (For substance that consist of simple molecules the term relative molecular mass (Mr) can be used instead of relative formula mass)

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Solution

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A mixture of a solute, usually a solid, dissolved in the solvent, a liquid

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Strong electrolyte

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A good conductor of electricity because it's completely ionized

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Volatile

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A volatile compound easily changes into a vapor. It has a low boiling point

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Weak electrolyte

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A poor conductor of electricity because it's only partially ionized - there are mainly molecules, few ions