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
