- abscisic acid:plant growth substance that bringd about the dormanvy of seeds
- absorption : To take into; the process of taking something in. account :
- Finance: A record of income and expenditure. To explain (v), e.g. “Account for why the sky is blue”.
- acetic : Pertaining to vinegar; an organic molecule containing two carbons. See organic, eth- for more.
- acetone : Propanone. CH3COCH3; the ketone of acetic acid. See ketone for more.
- acetylene : Ethyne, C2H2. Used in welding torches (blowtorches). See also alkene.
- acid : A proton donor or substance that ionises into H+ or H3O+ when dissolved in water; sour-tasting substance; corrosive; pH below 7. See also base and alkali.
- acidified : To have been made acidic.
- acidity : How acid something is. activated : Made to function. Chemistry: something moved into an unstable higher-energy level or state. Usually “activated complex”, the combination of reactants just before they turn into products. See also reactant, reagent, product.
- activation : The process of activating something. “Activation energy”, the required energy to create an activated complex.
- aerosol : A solution of substances in air or other gas, e.g. as in an aerosol can.
- alcohol : In common usage, ethanol C2H5OH. Technically, any organic substance or molecule containing an -OH group. See organic.
- aldehyde : Any organic molecule containing -CHO, formed by oxidising alcohols. See alcohol and organic.
- algae : Adjective: algal (pertaining to algae); an aquatic plant (lives in water), which lacks leaves, stems, roots.
- algebra : A mathematical system where unknown quantities are represented by letters, which can be used to perform complex calculations through certain rules.
- alkali : See base.
- alkane : An organic molecule or compound or substance which contains only single bonds between carbons. See organic.
- alkene : An unsaturated organic molecule, compound or substance, which contains at least one double bond between carbons. See organic and unsaturated.
- alkyl : A prefix (word part) which shows that the word after it has an alkane group attached to it, by removing one hydrogen from the alkane.
- alkyne : An unsaturated organic molecule, compound or substance, which contains at least one triple bond between carbons. See organic and unsaturated.
- amalgam : General use: a mixture. In chemistry, specifically a mercury alloy.
- amide : An organic compound containing the group -C(O)NH2; an inorganic compound containing the group NH2–.
- amine : The same as an amide except the -NH2 can be attached to anything, and does not have the CO group shown above.
- ammonia : NH3. ammonium : NH4+, found as a cation or as part of a salt. See salt and cation.
- amphiprotic : See ampholyte.
- ampholyte : A substance that can act as an acid or base. See acid, base.
- affinity : A liking for something an attraction to something; a tendency to react with something (chemistry). See also paraffin.
- anions : A negative ion. See cation, ion.
- anode : The negative electrode of a cell or current supplier; the positive electrode of an electrolytic system; attracts negative ions. See electrode, cathode.
- antacid : A substance used to neutralise (react with) acid. E.g. chalk. See acid, neutralise.
- apparatus : Equipment; parts of a scientific experiment.
- aqueous : Dissolved in water.
- arrhenius : Arrhenius’ theory of acids and bases: That acids produce H+ or H3O+ in water, and bases produce OH–. See Brønsted-Lowry.
- asbestos : A fireproof fibrous substance containing silicon used for fireproofing.
- asbestosis : A lung disease caused by inhaling asbestos fibres, can lead to cancer.
- atm : Abbreviation: atmospheres of pressure (1 atm = 101,3 kPa). The pressure of the air at sea level. Same as “bar” (barometric pressure).
- ATM : Abbreviation: automatic teller machine.
- atmosphere : The air or the gases surrounding a planet; the sky; as a unit of measurement, see atm. atmospheric
: To do with the atmosphere.
- atom : The smallest unit of a chemical element, which, if broken down further, no longer behaves in the same way chemically. Consists of a nucleus or centre part which is positively charged, and an electron cloud (negatively charged) which surrounds the nucleus. See nuclear.
- attract : To bring something closer.
- average : Mathematics: The sum of parts divided by the quantity of parts. In common use: neither very good, strong, etc., but also neither very weak, bad, etc; the middle. In Physical Science and Mathematics: if you are asked to find the average, you always have to calculate it using the information you have. For example, the average of (1;2;3) is 2, because (1+2+3)/3 = 2. See also mean, median and mode.
- avogadro (constant or number) : 6,023 × 1023 particles; one mole. See mole and mol.
- axis (sing), axes (pl, pronounced “akseez”) : A line along which points can be plotted (placed), showing how far they are from a central point, called the origin. See origin. “Vertical axis” or “y-axis” refers to how high up a point is above the origin (or how far below). “Horizontal axis” or “x-axis” refers to how far left or right a point is away from the origin
- bakelite : A type of hard, brittle plastic that can’t melt once it has set or taken shape (thermosetting), made from phenol C6H5OH, and formaldehyde (methanal), CH2O.
- balance ( :). To make two things equal (v); a scale to weigh objects : Chemistry: to compare two sides of a chemical equation and make sure that there are the same numbers of atoms on both sides.
- base : A proton acceptor, or substance that ionises into OH– when dissolved in water; a bitter-tasting substance, corrosive, pH above 7. See also acid. Do not confuse with common everyday use, meaning “the bottom” or “low”.
- basic : Bitter or made of a base. Do not confuse with popular use, meaning “low” or “simple” or “crude”.
- battery : A collection of cells connected in series (end-to-end). See cell. In common use, “battery” is used to mean the same as “cell” (e.g. a penlight or AA cell), but this use is incorrect except for a car battery, which consists of a series of cells. benzoic : Contains benzene or a benzene ring. bi- : Two.
- bicarbonate : Any salt containing the ion -HCO3–. So called because the carbonate (CO32–) attaches to another ion and the hydrogen (two bonds). The name “hydrogen carbonate” is now preferred. biodegradable : Can be broken down by natural processes e.g. involving bacteria, moulds, fungus, etc.
- biodiesel : Diesel (a type of petrol) made from plants rather than fossil fuels (coal, oil).
- BODMAS : Brackets, of/orders (powers, squares, etc), division, multiplication, addition, subtraction. A mnemonic (reminder) of the correct order in which to do mathematical operations.
- boil : Physics: to cause a liquid’s vapour pressure to exceed the pressure of the gas in the container, usually by heating it, but it can be done by lowering the pressure of the gas in the container, too. See vapour pressure. In common usage, to make a liquid hot until it bubbles.
- bond : A connection. In physics and chemistry, between atoms and molecules.
- breadth : How wide something is. From the word “broad”.
- brine : A saturated salt solution (a mixture of water and salt which can’t dissolve any more salt).
- bromide : Something containing bromine, usually one ion. See ion. bromo- : Something containing bromine.
- bromothymol (blue) : A type of acid-base indicator used to tell whether something is an acid or base. Turns blue (in base) or yellow (in acid).
- Brønsted-Lowry : A theory of acids and bases which says that acids are proton donors (they give away protons), and bases are proton acceptors (they take protons). Since H+ is just a proton, this does not mean something different from the Arrhenius theory that an acid is a substance that dissolves into H+ in water. See proton, Arrhenius.
- but- : Four carbons. Pronounced “beaut”. E.g. butane is a fourcarbon alkane.
- calibrate : To adjust a measuring tool or measurement against a known accurate measurement to ensure that the measuring tool or measurement is accurate; to check a measurement or measuring tool’s accuracy; to mark with accurate measurements using a standard scale like cm, mm, mℓ, etc. Common use: to assess or evaluate carefully.
- carbohydrate : Organic compounds containing carbon and hydrogen, occurring in foods and living tissues and including sugars, starch, and cellulose. They contain hydrogen and oxygen in the same ratio as water (2:1). Not the same as hydrocarbons, which are any substances containing mostly hydrogen and carbon.
- carbonate : -CO32– carbonic : Anything containing carbon, or more specifically, CO2 carbonyl : Containing double bonded carbon and oxygen: =C=O. carboxyl : Containing -COOH. carboxylic : Carboxyl-containing. Cartesian : Anything believed or proposed by Rene Descartes. In particular, the x-and-y axis coordinate system.
- catalyst : A substance that alters the rate of a chemical reaction without itself being consumed in the reaction. Without qualification, or as “positive catalyst”, something that starts or speeds up a reaction. A “negative” catalyst slows down a reaction.
- catalytic : Containing or using a catalyst.
- cathode : The positive electrode of a cell or current supplier; the negative electrode of an electrolytic system; attracts positive ions. See electrode, anode, ion. cathodic : Involving a cathode. Cathodic protection: To use a more reactive metal to protect a less reactive metal from oxidation. See anode, cathode, oxidise.
- cation : A positively charged ion. See anion, ion. caustic : Basic; a base.
- cell : An apparatus that generates electricity using electrochemistry. An AA or Penlight battery, as it is commonly called, is a cell. A car battery consists of a number of cells inside a single container.
- CFC : A chlorofluorocarbon. A substance containing carbon, chlorine and fluorine. Responsible for breaking down ozone (O3) which protects us from too much UV radiation from the sun.
- chain : Chemistry: a long series of atoms bonded together, usually carbon.
- charge : Chemistry: having too many or too few electrons (most commonly), resulting in a substance ionising. A positive charge results from too few electrons, and a negative charge from too many electrons. Physics: a basic feature of all physical electromagnetic particles, except, e.g. neutrons and photons, which have zero charge. All protons have a positive charge, all electrons have a negative charge.
- chart : To draw a diagram comparing values on Cartesian axes.
- Le Châtelier’s Principle : That in reversible reactions, chemical systems will favour the forward or reverse reaction to minimise the change imposed on the system. If a chemical equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change.
- chloro- : Containing chlorine. chlorofluorocarbons See CFC.
- chloroform : CHCℓ2. A liquid formerly used as an anaesthetic.
- chlorophyll : A green substance found in plants which enables photosynthesis (broadly, generating food from CO2). See photosynthesis.
- coefficient : A constant value placed next to an algebraic symbol as a multiplier. Same as constant (see below). Or: a multiplier or factor that measures a property, e.g. coefficient of friction.
- combustion : The process of burning, usually in oxygen. Rapid oxidation.
- completion : Chemistry: when a reaction no longer proceeds (continues) because it has run out of one or more of the reactants. See reactant, reaction.
- complex (activated) : See activated
- compound : A substance made up of molecules consisting of more than one different type of atom, chemically bonded in a constant ratio. E.g. Water (H2O) is a compound, but Sulphur powder (S) is not. In a compound, the original chemicals (reactants) have reacted or merged to form a new substance. Compare to mixture. compressed : Subjected to pressure, squashed.
- concentration : The number of moles of substance per unit volume. See mol, moles. How “strong” a solution is. See solution.
- condensation : When a vapour or gas cools down and starts to collect into larger droplets; changing phase from vapour or gas to liquid. Condensation reaction: to produce a larger molecule from two smaller ones.
- conditions (STP) : Physics and Chemistry: how the environment is: temperature and pressure. STP (Standard Temperature and Pressure is 25°C and 1 atm).
- conjugate : To join together. Chemistry: two things that belong together, e.g. conjugate acid-base pairs.
- conservation : A law which describes something that does not change. E.g. the conservation of matterenergy says that matter-energy cannot be created or destroyed, only transformed from one form into another. There are a number of other conservations, e.g. momentum and torque.
- constant : See coefficient. Means “unchanging”.
- contaminate : Chemistry: to introduce impurities or other substances which are not meant to be part of a reaction.
- control (n. and v.). To ensure something does not change without being allowed to do so (v); an experimental situation to which nothing is done, in order to compare to a separate experimental situation, called the ‘experiment’, in which a change is attempted. The control is then compared to the experiment to see if a change happened.
- control variable : A variable that is held constant in order to discover the relationship between two other variables. “Control variable” must not be confused with “controlled variable” (see independent variable).
- coordinate : The x or y location of a point on a Cartesian graph, given as an x or y value. Coordinates (pl) are given as an ordered pair (x, y).
- correlate : To see or observe a relationship between two things, without showing that one causes the other.
- correlation : That there is a relationship between two things, without showing that one causes the other.
- correspond : To pair things off in a correlational relationship. For two things to agree or match. E.g. A corresponds to 1, B corresponds to 2, C corresponds to 3, etc.
- corrode : Chemistry: to destroy by gradual chemical action. Usually refers to acidic action. Compare to erode. General use: to destroy gradually. corroding
: A process or substance that corrodes; to be subject to corrosion.
- corrosion : To corrode. corrosive : To be capable of corroding something.
- counteract : Oppose or resist. covalent : Chemistry: a bond which results from sharing electrons between atoms. Compare ionic bond.
- cracking : A process of breaking a complex organic molecule into simpler parts using heat and pressure.
- cubed : The power of three; multiplied by itself three times.
- cubic : Shaped like a cube; having been multiplied by itself three times.
- current : Flowing electrons.
- decompose : To break down into components.
- degradable : Capable of breaking down or being broken down.
- dehydrating (agent) : To remove water from. A “dehydrating agent” is a substance which can remove water from another substance. E.g. H2SO4, ethanol.
- dehydration : The process of removing water from a substance.
- dehydrogenation : The process of removing hydrogen from a substance.
- dehydrohalogenation : To remove hydrogen and a halogen from a substance. See halogen.
- denominator : See divisor. In popular speech: a common factor.
- depend : To be controlled or determined by something; to require something to happen or exist first.
- dependent (variable) (adj/n). A variable whose value depends on another; the thing that comes out of an experiment, the effect; the results. See also independent variable and control variable. The dependent variable has values that depend on the independent variable, and we plot it on the vertical axis.
- depleted : Having been used up; run out of.
- deposit : Finance: to place money into an account. Physical Science: to cover a surface of one substance with another substance, e.g. metal plating on an electrode. determine(s) (causation)
: To cause; to ensure that; to set up so that; to find out the cause of. di- : Two.
- diamine : A substance containing two amine groups. See amine.
- diammonium : Having two ammonium (NH4) groups. See ammonium.
- diaphragm : A thin sheet of any substance covering a gap. Biology: the muscle below the lungs which moves to cause breathing. Electrochemistry: a thin sheet inside a cell which separates the electrodes. It is porous and allows solutions containing ions through, but serves to separate gas products.
- difference : Mathematics: subtraction. Informally: a dissimilarity. How things are not the same.
- dilute : To lower the concentration of a solution. See solution and concentration (v): a solution which has had its concentration lowered :
- dilution : The opposite of concentration; how low a concentration is, measured in mol/dm3; the process of diluting.
- dimer : A molecule made of two identical parts. See also polymer.
- diode : A semiconductor device with two terminals (electrodes), usually allowing current to flow in one direction only.
- diol : A molecule with two alcohol/ hydroxyl (OH) groups.
- dipole : A polarised molecule with a distinctly positive and distinctly negatively-charged end.
- diprotic : Having two protons.
- displace : To move or relocate something.
- dissipate : To disperse or scatter (e.g. gas). Thermodynamics (Energy): to cause energy to be lost as heat. Popular use: to disappear.
- dissociate : To break apart; to no longer be associated with.
- dissolve : To break up into ions within a solution (usually water); to mix a solid (usually powder) into a liquid, to form a solution. See solution, ion. Alternative popular use: to bring to an end.
- distil(l) : To purify through repeated heating of a liquid and collection of condensation. The heating process causes the liquid to form gas or vapour, which condenses on the side of the heating vessel (container) or an exit tube, leaving impurities behind in the heating vessel.
- distribution : How something is spread out. Mathematics: the range and variety of numbers as shown on a graph.
- disturb : Chemistry: to mix or stir a liquid or solution; to shake it up.
- divisor : The number below the line in a fraction; the number that is dividing the other number above the fraction line. See numerator, denominator.
- domain : The possible range of x-values for a graph of a function. See range.
- durable : Tough; something that can endure.
- dynamic : Changing often. Relating to forces that produce motion. Opposite of static. See static and electrostatic.
- ecosystem : An integrated, complex, interacting, mutually dependent living system or environment.
- electric : Containing electricity (electrons).
- electro- chemical : Where chemical reactions cause the release of electrons, usually into a circuit. General use: anything relating to electrical and chemical phenomena.
- electrode : General use: the point where electrons enter or exit a power source or a circuit. Specifically (Electrochemistry): Part of a circuit dipped into a solution to receive or release electrons. See anode and cathode.
- electrolysis : The splitting of a chemical into ions. (The chemical is usually dissolved in water or another solution.) It is done by means of electricity. See electrochemical.
- electrolyte : A substance (usually liquid or gel solution) which contains a compound that will be split by electricity. Ionisable solutions or components.
- electromotive : Usually electromotive force or emf. The potential difference caused by electromagnetism, which causes current to flow. Producing a current with electromagnetism. See emf.
- electron : A fundamental physical particle bearing a negative charge, weighing approximately 9 × 10−28g, which is found around atomic nuclei in areas called ‘orbitals’. Responsible for electricity and chemical reactions. Symbol e–. See proton, nucleus.
- electroplate : To cover a surface of a less valuable substance with a more valuable metal, using electrolysis.
- element : Mathematics: part of a set of numbers. Physics: a pure substance made only of atoms of one type, with the same number of protons in each nucleus. An element cannot be broken down further without losing its chemical properties. Each element has a unique atomic number which is the number of protons in the nucleus. See nucleus, atom, isotope. Popular use: part of.
