AQA Chemistry paper 1 key words

alkali

its solution has a pH value more than 7

displacement reaction

a reaction in which a more reactive element takes the place of a less reactive element in one of its compounds or in solution

reduction / reduced

a reaction in which oxygen is removed or electrons are gained

endothermic

a reaction that takes in energy from the surroundings

exothermic

a reaction that transfers energy to the surroundings

oxidation/oxidised

a reaction where oxygen is added to a substance / or when electrons are lost from a substance

electronic structure

a set of numbers to show the arrangement of electrons in their shells (or energy levels)

neutral

a solution with a pH value of 7 which is neither acidic nor alkaline. Alternatively, something that carries no overall electrical charge

product

a substance made as a result of a chemical reaction

polymer

a substance made from very large molecules made up of many repeating units

element

a substance made up of only one type of atom. An element cannot be broken down chemically into any simpler substance

compound

a substance made when two or more elements are chemically bonded together

reactant

a substance we start with before a chemical reaction takes place

balanced symbol equation

a symbol equation in which there are equal numbers of each type of atom on either side of the equation

ion

a charged particle produced by the loss or gain of electrons

salt

a compound formed when some or all of the hydrogen in an acid is replaced by a metal

neutron

a dense particle found in the nucleus of an atom. It is electrically neutral, carrying no charge

dot and cross diagram

a drawing to show only the arrangement of outer shell electrons of the atoms or ions in a substance

pipette

a glass tube used to measure accurate volumes of liquids

giant lattice

a huge 3D network of atoms or ions

giant covalent structure

a huge 3D network of covalently bonded atoms

electrolyte

a liquid, containing free-moving ions, which is broken down by electricity in the process of electrolysis

reactivity series

a list of elements in order of their reactivity

burette

a long glass tube with a tap at one end and markings to show volumes of liquid; used to add precisely known volumes of liquids to a solution in a conical flask below it

titration

a method for measuring the volumes of two solutions that react together

alloy

a mixture of two or more elements, at least one of which is a metal

pH / pH scale

a number which shows how strongly acidic or alkaline a solution is

particle theory

a theory that explains the properties of solids, liquids and gases based on the fact that all matter is made from tiny particles. It describes the movement of particles and the distance between them

electron

a tiny particle with a negative charge. Electrons orbit the nucleus of atoms or ions in shells

proton

a tiny positive particle found inside the nucleus of an atom

word equation

a way of describing what happens in a chemical reaction by showing the names of all reactants and the products they form

weak acids

acids that do not ionise completely in aqueous solutions

group

all the elements in the columns (labelled 1 to 7 and 0) in the periodic table

shell

an area in an atom, around its nucleus, where electrons are found

periodic table

an arrangement of elements in the order of their atomic numbers, forming groups and periods

half equation

an equation that describes reduction (gain of electrons) or oxidation (loss of electrons)

symbol equation

an equation that helps you see how much of each substance is involved in a chemical reaction by showing the chemical symbols and formulae of all the reactants and products involved

ionic equation

an equation that shows only those ions or atoms that change in a chemical reaction

isotope

atoms that have the same number of protons but different number of neutrons, i.e., they have the same atomic number but different mass numbers

delocalised electron

bonding electron that is no longer associated with any one particular atom

brine

concentrated sodium chloride solution the can undergo electrolysis to produce chlorine gas, hydrogen gas and sodium hydroxide solution

fullerene

form of the element carbon that can exist as large cage-like structures, based on hexagonal rings of carbon atoms

biofuel

fuel made from animal or plant products

ore

rock which contains enough metal to make it economically worthwhile to extract the metal

fuel cells

sources of electricity that are supplied by an external source of fuel

solids

substances that have a fixed shape and volume that cannot be compressed

liquids

substances that have a fixed volume, but they can flow and change their shape

gases

substances that have no fixed shape or volume and can be compressed easily

state symbol

the abbreviations used in balanced symbol equations to show if reactants and products are solid (s), liquid (l), gas (g) or dissolved in water (aq)

percentage yield

the actual mass of product collected in a reaction divided by the maximum mass that could have been formed in theory, multiplied by 100

concentration

the amount of a substance dissolved in a given volume of liquid

mole

the amount of substance in the relative atomic or formula mass of a substance in grams

intermolecular forces

the attraction between the individual molecules in a covalently bonded substance

relative atomic mass Ar

the average mass of the atoms of an element compared with carbon-12 (which is given a mass of exactly 12). The average mass must take into account the proportions of the naturally occurring isotopes of the element

covalent bond

the bond between two atoms that share one or more pairs of electrons

electrolysis

the breakdown of a substance containing ions by electricity

neutralisation

the chemical reaction of an acid with a base in which a salt and water are formed. If the base is a carbonate or hydrogen carbonate, carbon dioxide is also produced in the reaction

ionic bond

the electrostatic force of attraction between positively and negatively charged ions

bond energy

the energy required to break a specific chemical bond

states of matter

the forms in which matter can exist. A substance can be solid, liquid or gas

yield

the mass of product that a chemical reaction produces

activation energy

the minimum energy needed for a reaction to take place

aqueous solution

the mixture made by adding a soluble substance to water

cathode

the negative electrode in electrolysis

Avogadro constant

the number of atoms, molecules, or ions in a mole of any substance (i.e., 6.02 × 10-23 per mol)

atomic number

the number of protons (which equals the number of electrons) in an atom. It is sometimes called the proton number

mass number

the number of protons plus neutrons in the nucleus of an atom

base

the oxide, hydroxide, or carbonate of a metal that will react with an acid, forming a salt as one of the products. (If a base dissolves in water it is called an alkali). Bases are proton (H+ ion) acceptors

equilibrium

the point in a reversible reaction at which the forward and backward rates of reaction are the same. Therefore, the amounts of substances present in the reacting mixture remain constant

end point

the point in a titration where the reaction is complete and titration should stop

anode

the positive electrode in electrolysis

chromatography

the process whereby small amounts of dissolved substances are separated by running a solvent along a material such as absorbent paper

limiting reactant

the reactant in a chemical reaction that when used up causes the reaction to stop

atom

the smallest part of an element that can still be recognised as that element

nanoscience

the study of very tiny particles or structures between 1 and 100 nanometres in size - where 1 nanometre = 10-9 metres

law of conservation of mass

the total mass of the products formed in a reaction is equal to the total mass of the reactants

relative formula mass Mr

the total of the relative atomic masses, added up in the ratio shown in the chemical formula, of a substance

nucleus (of an atom)

the very small and dense central part of an atom that contains protons and neutrons

noble gases

the very unreactive gases found in Group 0 of the periodic table. Their atoms have very stable electronic structures

strong acids

these acids completely ionise in aqueous solutions

inert

unreactive

acid

when dissolved in water, its solution has a pH value less than 7. Acids are proton (H+ ion) donors