Science KS4 Vocab
Acids
Dissolve in water to produce solutions with a ph of less than 7
Acid rain
Rain which has been made more acidic by pollutant gases
Activation energy
The energy needed for a chemical reaction to happen
Addition polymer
A very long molecule resulting from polymerisation, e.g. Polythene
Aggregate
Gravel added to cement and sand to make concrete
Alkali metals
The metals in group 1 of the periodic table
Alkalis
Compounds which produce hydroxide ions in water
Alkanes
A family of hydrocarbons with all single carbon-carbon covalent bonds and general formula ctn
Alkenes
A family of hydrocarbons with one double carbon-carbon bond and general formula
Allotropes
Different forms of the same element
Alloy
A mixture of a metal with one or more other metals or non-metals to change the properties of the metal
Alpha particles
Radioactive particles which are helium nuclei – helium atoms without the electrons (they have a positive charge)
Ammeter
Meter used in an electric circuit for measuring current
Anion
Ion with a negative charge; they move to the anode during electrolysis
Anode
Electrode in electrolysis with a positive charge
Aquifer
Underground layer of permeable rock or loose materials (gravel or silt) where groundwater is stored
Atom
The basic ‘building block’ of an element, the smallest part of an element that can take part in a chemical reaction
Atomic number
The number of protons in the nucleus of an atom
Avogadro’s constant
The number of atoms, molecules or ions in one mole of a given substance, and is 6.02 x 1023 per mole
Balanced symbol equation
Chemical equation written in chemical symbols showing the number of atoms on each side of the equation balance
Base
Reacts with an acid to form a salt
Bioleaching
Process that uses bacteria to leach metal compounds from rocks
Biological catalyst
Molecules in cells of living organisms that speed up chemical reactions
Boiling point
Temperature at which the bulk of a liquid turns to vapour
Buckminsterfullerene
A very stable spherical structure of 60 carbon atoms joined by covalent bonds (an allotrope of carbon)
Carbon
An element present in all living things and forms a huge range of compounds with other elements
Carbon-14
Radioactive isotope of carbon
Carbon dioxide (co2)
A greenhouse gas which is emitted into the atmosphere as a product of combustion
Carbon footprint
The total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event.
Catalyst
A chemical that speeds up a reaction but is not used up by the reaction
Cathode
The negative electrode in electrolysis
Charge(s)
A property of matter, charge exists in two forms, positive and negative, which attract each other
Chemical properties
The characteristic chemical reactions of substances
Chlorination
Addition of chlorine to water supplies to kill micro-organisms
Chromatography
A method for separating substances, used to identify compounds and check for purity
Close-packed atoms
Structure of many metals
Collision frequency
The number of collisions between particles that happen in one unit of time
Combustion
Exothermic reaction of a substance with oxygen
Compound
Two or more elements which are chemically joined together, e.g. Hp
Concentration
The amount of chemical dissolved in a certain volume of solution conductors materials which transfer thermal energy easily; electrical conductors allow electricity to flow through them
Conservation of energy
Principle stating that energy cannot be created or destroyed conservation of mass the total mass of reactants equals the total mass of products formed in a chemical reaction
Covalent bonds
Bonds between atoms where a pair of electrons is shared
Cracking
The process of breaking down large hydrocarbons into smaller molecules
Curved line
Line of changing gradient
Decay
To rot or decompose
Delocalised electrons
Electrons which are free to move from atom to atom in a giant structure or a molecule
Density
The density of a substance is its mass divided by its volume
Diesel oil
Fuel for diesel engines, traditionally obtained from crude oil but other forms such as biodiesel have been developed
Direct current
An electric current that flows in one direction only
Displacement reaction
Chemical reaction where an element takes the place of or ‘pushes out’ another element from a compound
Distillation
The process of evaporation followed by condensation
Displayed formula
A representation of a molecule where every atom is shown by its symbol and the covalent bonds are shown as lines between the atoms
Dot and cross diagram
A diagram representing the number of electrons in the outer shell of atoms or ions
Electrical conductors
Materials that let electricity pass through them
Electrode
Ions are discharged at the electrodes during electrolysis
Electrolysis
The process of passing direct current through a melted ionic compound or a solution of an ionic compound so ions are discharged and the compound is broken down
Electrolyte
A liquid or solution that conducts electricity and breaks down during electrolysis
Electronic structure
The arrangement of electrons in the sequence that they occupy the shells or energy levels, e.g. The 11 electrons of sodium are arranged 2,8,1
Electrons
Small negatively charged particles within an atom that are outside the nucleus
Electrostatic attraction
Attraction between opposite charges, e.g. Between na+ and cl-
Elements
Substances made out of only one type of atom with the same number of protons in the nucleus
Empirical formula
Simplest ratio of atoms or ions in a compound
Endothermic reaction
Chemical reaction which takes in thermal energy
Energy
The ability to ‘do work’
Enzymes
Biological catalysts that increase the speed of chemical reactions
Equilibrium
When the forwards and backwards reactions are occurring at the same rate in a closed system
Estimate
Calculate approximately the value of something
Evaporation
When a liquid changes to a gas, it evaporates
Exhaust gases
Gases discharged into the atmosphere from an engine as a result of combustion of fuels
Exothermic reaction
Chemical reaction in which thermal energy is given out
Explosion
A sudden, loud, violent release of energy by a chemical reaction
Extrapolation
Making an estimate by continuing a trend or graph line beyond the range of results
Flammability
How easy it is to light something on fire
Formulation
A mixture that has been designed as a useful product
Fractional distillation
Crude oil is separated into fractions using this process of distillation where a mixture of liquids is vaporised and compounds with different boiling points condense at different temperatures
Force
A push or pull which is able to change the velocity or shape of a body
Fossil fuels
Fuels which are the fossilised remains of plants or animals, such as coal, oil and gas
Fullerenes
Cage-like carbon molecules containing many carbon atoms, e.g. Buckyballs
General formula of alkane
Cnh2n+2
Giant covalent structure
A large regular arrangement of atoms all joined together by covalent bonds
Giant ionic lattice
The regular three-dimensional arrangement of ions in an ionic compound, also called a giant ionic structure
Gradient
Rate of change of two quantities on a graph; change in y divided by change in x
Graphite
A type of carbon made of layers of atoms
Greenhouse gas
Any of the gases whose absorption of solar radiation is responsible for the greenhouse effect, e.g. Carbon dioxide, methane
Group
Within the periodic table the vertical columns are called groups. Group 1 the elements in group 1 of the periodic table, the alkali metals. Group 7 the elements in group 7 of the periodic table, the halogens
Half equation
A redox reaction is made up of two half equations, one in which electrons are lost and one in which electrons are gained.
Halogens
Reactive non-metals in group 7 of the periodic table, e.g. Chlorine
Hardness
Resistance of a solid material to cutting, indentation or scratching
Homologous series
A series of organic compounds that have the same general formula, i.e. The general formula of alkanes is cnh,,
Hydrocarbons
Compounds containing only hydrogen and carbon
Incomplete combustion
Takes place when there is not enough oxygen present for complete combustion
Indicator
Used to show ph of a solution or when the end point of a titration is reached
Insoluble salt
Salt which is not soluble in water intermolecular force force between molecules
Intermolecular forces
The attraction between two molecules
Interpolation
Making an estimate of a value from values on either side of the point
Ionic bond
The chemical bond between ions of opposite charges
Ionic equation
An equation showing changes to the ions involved in a reaction
Ionises
Adds or removes electrons from an atom leaving it charged
Ions
Charged particles (can be positive or negative)
Isotopes
Atoms with the same number of protons but different numbers of neutrons
Joule
Unit of work done and energy
Kilogram (kg)
Unit of mass
Kinetic energy
The energy that moving objects have
Le chatelier’s principle
If a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract the change
Life cycle assessments
(lcas) are carried out to assess the environmental impact of products in each of the stages involved in their manufacture, use and disposal
Limewater
A solution of calcium hydroxide in water – the colourless solution turns milky in the presence of carbon dioxide
Limiting reactant
Chemical used up in a reaction that limits the amount of product formed
Line spectrum
A spectrum produced by gaseous atoms showing individual lines at particular wavelengths that is unique for each element
Lustrous
Shiny
Lysis
To split apart
Magnitude
Size of something
Mass
The amount of matter in something; it is measured in kilograms (kg)
Mass number
The sum of the number of protons and neutrons in a nucleus
Melting point
The temperature at which a solid turns into a liquid
Metal halide
A compound of a halogen and a metal, e.g. Potassium bromide
Metallic bonding
The bonding between atoms in a metal due to delocalised electrons
Metallic properties
The physical and chemical properties specific to a metal, such as lustre, electrical conductivity and the ability to form positive ions
Metalloids
Elements with properties of both metals and non-metals; in the periodic table they are between the metals and non-metals
Metals
Elements that are usually solid, lustrous, conduct electricity and form ions by losing electrons
Minerals
Natural solid materials with a fixed chemical composition and structure, rocks are made of collections of minerals
Mobile phase
In chromatography this is the phase that moves
Mole
A unit for a standard amount of a substance. One mole of any substance contains the same number of particles, atoms, molecules or ions as one mole of any other substance
Molecular formula
The formula of a chemical using chemical symbols, e.g. Methane has the molecular formula ch4
Molecule
Two or more atoms covalently bonded to form the smallest unit of an element or compound, e.g. O2, h2o
Molten
A substance in its liquid state, often referring to a substance which is solid at ordinary temperatures, such as rock, ores, metals or salts, when heated to temperatures above its melting point
Negative ion
An ion with a negative charge, such as when atoms gain electrons
Neutral
A neutral solution has a ph of 7
Neutralisation
The reaction that takes place when an acid and base react to produce a salt and water
Neutron
Particle which does not have a charge found in the nucleus of an atom
Non-metals
Elements that are solids, liquids or gases that do not conduct electricity and bond covalently or form negative ions by their atoms gaining electrons
Non-renewable
Something which is used up at a faster rate than it can be replaced e.g. Fossil fuels
Nucleus
Central part of an atom that contains protons and neutrons
Optimum conditions
The conditions, such as temperature and pressure, that give the products of a chemical process at the lowest cost
Order of magnitude
Values that differ by one order of magnitude are 10 times larger or smaller than each other
Oxidation
When a reactant gains oxygen or loses electrons
Particulates
Small particles in the air often caused by burning fuels
Period
A row in the periodic table
Periodic table
A table of all the chemical elements in order of their atomic numbers
Petrol
Volatile mixture of mainly hydrocarbons used as a fuel
Pharmaceuticals
Medical drugs
Physical property
Property that can be measured without changing the chemical composition of a substance, e.g. Hardness
Phytomining
Process that uses plants to extract metals
Pollutants
Substances that can cause damage to the environment
Pollute
Put unwanted or harmful substances into the environment
Pollution
Contamination of the environment as a result of human activities
Polymer
Very large molecule formed from many similar smaller molecules (monomers) linked together
Positive ion
An ion with a positive charge, such as when atoms lose electrons
Potable water
Water that is safe to drink and has low levels of dissolved solids and microbes
Precipitate
Solid formed in a solution by a chemical reaction
Precipitation reaction
Chemical reaction in which a solid is formed when two solutions are mixed, e.g. In chemical tests for ions
Product
Substance produced by a chemical reaction (shown on the right-hand side of the chemical equation)
Protons
Positively charged particles found in the nucleus of an atom
Pure
A pure substance is a single element or compound that is not mixed with any other substance
Random
Having no regular pattern
Rate of reaction
The speed with which a chemical reaction takes place, measured by the amount of a reactant used or amount of product formed in a given time
Reactants
Chemicals that react together in a chemical reaction (shown on the left-hand side of the chemical equation)
Recharging
Battery or cell being charged with a flow of electric current
Reduction
When a reactant loses oxygen or gains electrons
Refine
The refining process turns crude oil into usable forms such as petrol
Relative atomic mass
The mass of an atom compared to 1/12 of the mass of a carbon-12 atom
Relative formula mass
The sum of the relative atomic masses in a compound
Renewable energy
Energy from a resource that is rapidly replaced
Renewable resource
Any resource that can be replenished at the same rate that it is used, e.g. Biofuels
Reservoir
A water resource where large volumes of water are held
Reversible reaction
A chemical reaction where the reactants form products that, in turn, react together to give the reactants back
Rf
In chromatography is the distance a substance moved divided by the distance the solvent moved
Saturated hydrocarbon
A hydrocarbon containing the maximum number of hydrogen atoms and only single carbon-carbon bonds; alkanes are saturated hydrocarbons
Sea water
Water from the sea that contains high levels of dissolved salts making it undrinkable
Sedimentation
A process during water purification where small solid particles are allowed to settle
Single covalent bond
Chemical bond between atoms where each atom shares one pair of electrons
Solar energy
Energy from the sun
Soluble
A soluble substance can dissolve in a liquid, e.g. Sugar is soluble in water
Solution
When a solute dissolves in a solvent, a solution forms
Solvent
The liquid used to dissolve a solute
Stable electronic structure
The electronic structure of a noble gas, with two electrons in the first shell and eight electrons in every other outer shell, e.g. He 2; ne 2,8; ar 2,8,8; kr 2,8,18,8
Standard form
A way of writing a large number with one number before the decimal point, multiplied by a power of 10, e.g. 1 200 = 1.2 x 103
Stationary phase
The phase in chromatography that does not move; in paper chromatography it is the paper
Straight line
Line of constant gradient
Strength (of an acid)
Strong acids ionise completely in water; weak acids partially ionise
Sub-atomic particles
Particles that make up an atom, e.g. Protons, neutrons and electrons
Sublimation
Change of state of a substance from a solid directly to a gas; e.g. Iodine
Thermal decomposition
The breaking down of a compound into two or more products on heating
Thermal energy
Energy that can be transferred as heat
Toxic
A toxic substance is one which is poisonous and causes harm to living organisms
Transition element
An element in the middle section of the periodic table, between the block containing groups 1 and 2 and the block containing group 3 to group 0
Unsaturated hydrocarbon
A hydrocarbon containing fewer than the maximum number of hydrogen atoms possible, and so at least one double bond.
Vacuum
Space containing no particles of matter
Viscosity
The thickness of a liquid
Voltage (also called the potential difference)
The difference in electrical potential between two points or objects
Voltmeter
Instrument used to measure voltage (potential difference)
Volt (v)
Unit used to measure voltage
Water conservation
Reducing water consumption through planned choice, e.g. Hosepipe bans and water metering
Water resources
Places from where water is extracted or where it is stored, e.g. Aquifers, reservoirs or lakes
Wavelength
Distance between two wave peaks or the distance between identical points in adjacent cycles of a wave
