1669762
| Questão | Responda |
| Acetylene | A gas (formula C²H²) used as a fuel, for example in the oxy-acetylene torch |
| Acid Rain | Rain that is acidic because gases such as sulfur dioxide are dissolved in it (from burning fossil fuels) |
| Acidic Solution | Has a pH less than 7; an acidic solution contains H+ ions |
| Acid Fermentation | The process in which bacteria convert ethanol to ethanoic acid |
| Addition Reaction | Where a molecule adds onto an alkene, and the C=C double bond of the alkene changes to a single bond |
| Addition Polymerisation | Where small molecules join to form a very large molecule, by adding on at double bonds |
| Alcohols | A family of organic compounds, similar to the alkanes but with the OH functional group; ethanol is example |
| Alkali | A soluble base; for example sodium hydroxide |
| Alkali Metals | The group I elements of the periodic table |
| Alkaline Earth Metals | The group II elements of the periodic table |
| Alkaline Solution | Has a pH above 7; alkaline solutions contain OH- ions |
| Alkanes | A family of saturated hydrocarbons with the general formula CnH2n+2; 'saturated' means they have only single C-C bonds |
| Alkenes | A family of unsaturated hydrocarbons with the general formula CnH2n ; their molecules contain carbon=carbon double bond |
| Allotropes | Different forms of an element; diamond and graphite are allotropes of carbon |
| Alloy | A mixture where at least one other substance is added to a metal, to improve its properties; the other substance is often a metal too (but not always) |
| Amphoteric | Can be both acidic and basic in its reaction; for example aluminium oxide is an amphoteric oxide |
| Anion | Another name for negative ion |
| Anode | The positive electrode of a cell |
| Aquifer | Underground rocks holding a large volume of water; it can be pumped out to give a water supply |
| Atmosphere | The layer of gases around the Earth; here at the Earth's surface, we call it air |
| Atoms | Elements are made up of atoms. which contain protons, neutrons and electrons |
| Avogadro Constant | The number of particles in one mole of an element or compound; it is 6.02 x 10^23 |
| Back Reaction | The reaction in which the product breaks down again, in a reversible reaction |
| Bacteria | Tiny organisms, some of which can cause disease; other break down dead plant and animal material |
| Balanced Equation | A chemical equation in which the number of each type of atom is the same on both sides of the arrow |
| Base | A metal oxide or hydroxide; a base will neutralise an acid, to form a salt and water |
| Battery | A portable electrical cell; for example a torch battery |
| Biodegradable | Will decay naturally in the soil, with the help of bacteria |
| Biopolymer | A polymer made by bacteria |
| Blast Furnace | The chemical plant in which iron is extracted from its ore, iron(III) oxide |
| Boiling | The change from a liquid to a gas, which takes place at the boiling point |
| Boiling Point | The temperature at which a substance boils |
| Bond Energy | The energy needed to break a bond, or released when the bond is formed; it is given in kilojoules (kJ) per mole |
| Bonding | How the atoms are held together in an element or compound; there are three types of bonds: ionic, covalent, and metallic |
| Brittle | Breaks up easily when struck |
| Brine | The industrial name for a concentrated solution of sodium chloride in water; it can be made by dissolving rock salt |
| Burette | A piece of laboratory equipment for delivering a measured volume of liquid |
| Burning | An exothermic chemical reaction in which the reactant combines with oxygen to form an oxide; also called combustion |
| Carbon Cycle | The way carbon moves non-stop between the atmosphere, living things, the land, and the ocean; it moves in the form of carbon dioxide |
| Carboxylic Acids | A family of organic acids, which have the COOH functional group; ethanoic acid is an example |
| Cast Iron | Iron from the blast furnace that is run into molds to harden; it contains a high % of carbon, which makes it brittle |
| Catalyst | A substance that speeds up a chemical reaction, without itself being used up in the process |
| Catalytic Converter | A device in a car exhaust, in which catalysts are used to convert harmful gases to harmless ones |
| Catalytic Cracking | Where large molecules of hydrocarbons are split up into smaller ones, with the help of catalyst |
| Cathode | The negative electrode of an electrolysis cell |
| Cation | Another name for a positive ion |
| Cell (Biological) | The building blocks for animals and plants |
| Cell (Electrical) | A device that converts chemical energy to electrical energy |
| Cement | A substance used in building, made from limestone and clay |
| Ceramic | A hard, unreactive material that can withstand high temperatures, made by baking clay in a kiln; ceramics are non-conductors |
| Chalk | A rock made of calcium carbonate |
| Change of State | A change in the physical state of a substance - for example from solid to liquid, or liquid to gas |
| Chemical Change | A change in which a new chemical substance forms |
| Chemical Equation | Uses chemical symbols to describe a chemical reaction in a short way |
| Chemical Reaction | A process in which chemical change takes place |
| Chromatogram | The paper showing the separated coloured substances, after paper chromatography has been carried out |
| Climate Change | How climates around the earth are changing, because of the rise in average air temperatures |
| Coagulant | A substance that will make small particles stick together; coagulants are used in cleaning up water, ready for piping to homes |
| Coke | A form of carbon made by heating coal |
| Combination | Where two or more substances react to form a single substance |
| Combustible | Can catch fire and burn very easily |
| Combustion | Another name for burning |
| Compound Fertiliser | It provides nitrogen, potassium and phosphorus for plants |
| Compound Ion | An ion containing more than one element; for example the nitrate ion NO3- |
| Compound | A substance in which two or more elements are chemically combined |
| Concentration | Tells you how much of one substance is dissolved in another; usually given as grams or moles per dm^3 |
| Condensation | The physical change in which a gas turns into a liquid on cooling |
| Condensation Polymerisation | Where molecules join to make very large molecules, by elimenating small molecules (such as water molecules) |
| Condenser | A piece of laboratory equipment used to cool a gas rapidly, and turn it into a liquid |
| Conductor | A substance that allows heat or electricity to pass through it easily |
| Contact Process | The industrial process for making sulfuric acid |
| Corrosion | Where a substance is attacked by air or water, from the surface inwards; the corrosion of iron is called rusting |
| Covalent Bond | The chemical bond formed when two atoms share electrons |
| Covalent Compound | A compound made of atoms joined by covalent bonds |
| Cracking | Reactions in which long-chain hydrocarbon molecules are broken down to shorter, more useful molecules |
| Cross-linking | The chemical bonds between the long-chain molecules in some polymers, that hold the chains together |
| Crude Oil | The fossil fuel formed over millions of years from the remains of tiny sea plants and animals; it is also called petroleum |
| Crystallisation | The process in which crystal form, as a saturated solution cools |
| Decomposition Reaction | Where a substance breaks down to give two or more products |
| Denature | To destroy the structure of an enzyme by heat, or a change in pH |
| Degradeable | Will break down naturally (for example through the action of bacteria) |
| Density | Tells you how 'heavy' something is; the density of a substance is its mass per unit volume; for water it is 1g/cm3 |
| Diatomic | A substance is called diatomic if its molecules contain two atoms joined by a covalent bond |
| Diffusion | The process in which particles mix by colliding randomly with each other, and bouncing off in all direction |
| Displacement Reaction | A reaction in which a more reactive element takes the place of a less reactive one, in a compound |
| Dissolving | The process in which a soluble substance forms a solution |
| Distillation | Separating a liquid from a mixture by boiling it off, then condensing it |
| Double bond | A covalent bond in which two atoms share two pairs of electrons |
| Ductile | Can be drawn out into a wire; for example copper is ductile |
| Dynamic Equilibrium | Where forward and back reactions take place at the same rate, so there is no overall change |
| Electrodes | The conductors used to carry current into and out of an electrolyte; they could be graphite rods, for example |
| Electrolysis | The process of breaking down a compound by passing a current through it |
| Electrolyte | The liquid through which the current is passed, in electrolysis; the current is carried by ions in the electrolyte |
| Electron Distribution / Configuration | How the electrons in an atom are arranged in shells (2 + 8 + ......) |
| Electron Shells | The different energy levels which electrons occupy, around the nucleus |
| Electrons | The particles with a charge of 1- and almost no mass, in an atom |
| Electroplating | Coating one metal with another, using electrolysis |
| Element | A substance that cannot be split into anything simpler, in a chemical reaction |
| Empirical Formula | Shows the simplest ratio in which the atoms in a compound are combined |
| Endothermic | Takes in energy from the surroundings |
| Enzymes | Proteins made by living cells, that act as biological catalysts |
| Equation | It uses symbols to describe a chemical reaction (but a word equation uses just words) |
| Equilibrium | The state where the forward and back reactions are taking place at the same rate, in a reversible reaction; so there is no overall change |
| Ester | A compound formed when an alcohol reacts with carboxylic acid; ester often smell of fruit or flowers |
| Evapouration | The physical change where a liquid turns to a gas at a temperature below its boiling point |
| Exothermic | Gives out energy |
| Extract | To remove a metal from its ore |
| Fermentation | The process in which the enzyme in yeast break down sugars, to form ethanol and carbon dioixde |
| Fertilisers | Substances added to soil to help crops grow well |
| Filtering | Separating solids from liquids by pouring the mixture through filter paper |
| Filtrate | The liquid obtained from filtration (after the solid has been removed) |
| Flammable | Burns easily |
| Flue Gas Desulfurisation | The removal of sulfur dioxide from the waste gases at power stations, to stop it getting into the atmosphere |
| Formula | Uses symbols and numbers to tell you what elements are in a compound, and the ratio in which they are combined |
| Forward Reaction | The reaction in which the product is made, in a reversible reaction |
| Fossil Fuels | Petroleum (crude oil), natural gas, and coal; they are called fossil fuels because they were formed from the remains of living things, millions of years ago |
| Fractional Distillation | A method used to separate two or more liquids that have different boiling points |
| Fractions | The different groups of compounds that a mixture is separated into, by fractional distillation; fractions are collected one by one |
| Freezing | The change from liquid to solid, that occurs at the freezing point (= melting point) |
| Fuel | A substance we use to provide energy; most fuels are burned to release their energy (but nuclear fuels are not) |
| Functional Group | The part of the molecule of an organic compound, that largely dictates how it reacts; for example the OH group in molecules of the alcohol family |
| Galvanising | Coating iron with zinc, to prevent the iron from rusting |
| Giant Structure | Where a very large number of atoms or ions are held in a lattice by strong bonds; metals, diamond and ionic solids such as sodium chloride are all giant structures |
| Global Warming | The rise in average temperature taking place around the world; many scientists believe that carbon dioxide (from burning fossil fuels) is the main cause |
| Greenhouse Gas | A gas in the atmosphere that traps heat, preventing its escape into space; carbon dioxide and methane are examples |
| Group | A column of the Periodic Table; elements in a group have similar properties |
| Haber Process | The process for making ammonia from nitrogen and hydrogen, in industry |
| Half-equation | An equation that shows the reaction taking place at an electrode |
| Halogens | The Group VII elements of the Periodic Table |
| Heating Curve | A graph that showing how the temperature of a substance changes on heating, while it goes from solid to liquid to gas |
| Homologous Series | A family of organic compounds, that share the same general formula and have similar properties |
| Hydrated | Has water molecules built into its crystal structure; for example copper (II) sulfate: CuSO4 . 5H2O |
| Hydrocarbon | A compound containing only carbon and hydrogen |
| Hydrogen Fuel Cell | It uses the reaction between hydrogen (from a tank), and oxygen (from the air), to give an electric current |
| Hydrolysis | The breaking down of a compound by reaction with water |
| Hypothesis | A statement you can test by doing an experiment and taking measurements |
| Incomplete Combustion | The burning of fuels in a limited supply of oxygen; it gives carbon monoxide instead of carbon dioxide |
| Indicator | A chemical that shows by its colour whether a substance is acidic or alkaline |
| Inert | Does not react (except under extreme conditions) |
| Inert Electrode | Is not changed during electrolysis; all it does is conduct the current |
| In Excess | More than is needed for a reaction; some will be left at the end |
| Insoluble | Does not dissolve in a solvent |
| Insulator | A poor conductor of heat or electricity |
| Intermolecular Forces | Forces between molecules |
| Ion | A charged atom or groups of atoms formed by the gain or loss of electrons |
| Ionic Bond | The bond formed between ions of opposite charge |
| Ionic Compound | A compound made up of ions, joined by ionic bonds |
| Ionic Equation | Shows only the ions that actually take part in a reaction, and ignores any other ions present; the other ions are called spectators ions |
| Isomers | Compounds that have the same formula, but a different arrangement of atoms |
| Isotopes | Atoms of the same element, that have different numbers of neutrons |
| Lattice | A regular arrangement of particles |
| Lime | The common name for calcium oxide |
| Limewater | A solution of the slightly soluble compound calcium hydroxide, which is used to test for carbon dioxide |
| Locating Agent | Used to show up colourless substances, in chromatography; it reacts with them to give coloured substance e.g. : ninhydrin |
| Macromolecule | A very large molecule; for example a molecule in a polymer |
| Malleable | Can be bent or hammered into shape |
| Mass Spectrometer | An instrument used to find the masses of atoms and molecules |
| Melting Point | The temperature at which a solid substance melts |
| Melting | The physical change from a solid to a liquid |
| Metal | An element that shows metallic properties (for example conducts electricity, and forms positive ions) |
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