Glossary


Acid: A substance that produces hydrogen ions (H+) as the only positive ions when dissolved in water.

Activation energy: The minimum energy that molecules must possess during their collisions in order for a chemical reaction to occur.

Addition reaction: A reaction in which a molecule (element or compound) adds to an unsaturated compound to form a single new compound.

Alcohol: An organic compound containing the hydroxyl group, -OH.

Alkali: A base that is soluble in water.

Alkali metals: The elements in Group 1 of the Periodic Table.

Alkane: Hydrocarbon having the general formula CnH2n+2

Alkene: Hydrocarbon that contains one or more carbon-carbon double bonds. Alkenes with only one carbon-carbon double bond have the general formula CnH2n.

Alloy: A mixture of a metal with non-metals or other metals.

Anhydrous: Anhydrous salts are salts without water of crystallization.

Anion: A negatively charged ion which moves towards the anode during electrolysis.

Anode: A positively charged electrode in an electrolytic cell.

Aqueous: Describing the solution of a substance in water, i.e. the aqueous solution. In chemical equations, aqueous solutions are represented by the symbol (aq).

Atom: The smallest particle of an element.

Avogadro’s constant: The number of particles in one mole of a substance. Its value is 6 x 1023.

Avogadro’s law: At constant temperature, the volume of a gas is directly proportional to the number of moles of the gas present.

Base: A substance that reacts with an acid to form a salt and water only.

Boiling point: The temperature at which a liquid turns rapidly to its vapour.

Carboxylic acid: An organic acid containing the carboxyl group, -COOH.

Cathode: A negatively charged electrode in an electrolytic cell.

Cation: A positively charged ion which moves towards the cathode during electrolysis.

Chromatography: A method of separating the components in a mixture.

Collision theory: A chemical reaction can occur only if the reacting particles collide with one another.

Combustion: The chemical name for burning. Burning occurs when a substance reacts very rapidly with oxygen.

Compound: A substance formed in a chemical change when two or more elements are joined together.

Condensation: The process by which a vapour or a gas turns to liquid on cooling.

Corrosion: The wearing away of the surface of a metal by chemical reaction.

Covalent bond: The type of bond formed when electrons are shared between two non-metal atoms.

Cracking: The breaking down of long chain hydrocarbon molecules with heat and/or catalyst to produce smaller hydrocarbon molecules and/or hydrogen.

Decomposition: A chemical reaction that results in the breaking down of a compound into two or more components.

Diatomic molecule: A molecule that consists of two atoms.

Displacement reaction: A reaction in which an atom or molecule takes the place of another atom or molecule in a compound.

Distillation: A process of obtaining the pure solvent from a solution. When the solution is boiled, the solvent is vaporized and the vapour condenses to reform the pure liquid. 

Electrode: A rod or a plate which carries electricity in or out of an electrolyte during electrolysis.

Electrolysis: A process in which electrical energy is used to cause a chemical reaction to occur, typically to separate the electrolyte into its elements.

Electron: A negatively charged sub-atomic particle that surrounds the nucleus of an atom.

Electronic configuration: The arrangement of electrons in the various shells of an atom or a molecule.

Element: A substance made from only one type of atom. It cannot be separated into simpler substances by chemical processes or by electricity.

Endothermic reaction: A reaction which absorbs heat from the surroundings.

Evaporation: The process by which a liquid changed to its vapour on the surface of the liquid.

Exothermic reaction: A process that gives off heat to the surroundings.

Fermentation: The conversion of glucose by microorganisms such as yeast into ethanol and carbon dioxide.

Filtrate: The clear liquid which passes through the filter during filtration.

Filtration: The process of separating a solid from a liquid or a solution.

Fossil fuels: Fuels produced many millions of years ago from the decaying remains of animals or plants, includes oil, natural gas and coal.

Fractional distillation: A process that separates the components in a mixture on the bases of their different boiling points. The component with the lowest boiling point boils off first and is distilled over.

Freezing point: The temperature at which a liquid changes to a solid.

Fuel: A substance that burns easily to produce energy.

Functional group: An atom or group of atoms that gives characteristic properties to an organic compound.

Giant structure: A three-dimensional network of atoms or ions packed together in a regular pattern.

Group: A vertical column of elements in the Periodic Table.

Halogen: The non-metallic elements in Group VII (7) of the Periodic Table.

Homologous series: A family of organic compounds with members of the family having the same functional group and similar chemical properties.

Hydrated salts: Salts that contain water of crystallization.

Hydrocarbons: Organic compounds made up from the elements hydrogen and carbon only.

Hydrogenation: The addition of a hydrogen molecule across a double bond.

Immiscible: Two liquids that do not mix.

Indicators: Compounds that have distinctly different colours in acidic and alkaline solutions.

Ion: A positively or negatively charged particle. It is formed when an atom or group of atoms loses or gains electrons.

Ionic bond: The electrostatic force that holds positive and negative ions together in an ionic compound.

Isotopes: Atoms of the same element that have the same atomic number but different mass/nucleon number.

Melting point: The temperature at which a solid changes to a liquid.

Metal: An element that is shiny and conducts electricity in the solid state. Metals burn in oxygen to form basic oxides or amphoteric oxides.

Mixture: A substance made by mixing other substances together. The components in a mixture can be easily separated by physical methods because they are not chemically joined together like in compounds.

Mole: The amount of a substance which contains 6 x 1023 particles.

Molecule: A group of atoms held together by covalent bonds. Molecules may be elements or compounds.

Nucleon number: Also known as the mass number. It is the sum of the number of protons and neutrons in the nucleus of an atom.

Neutralization: The reaction between an acid and a base to produce a salt and water only.

Neutron: A sub-atomic particle in the nucleus of an atom. It has a mass but no electrical charge.

Organic chemistry: The branch of chemistry that deals with carbon compounds.

Oxidation: A reaction where a substance gains oxygen or loses hydrogen. Oxidation is also defined as the loss of electron(s) or the increase in the oxidation state of the element.

Oxides: Compounds of an element with oxygen.

Oxidizing agent: A substance that brings about oxidation. It is itself reduced. An oxidizing agent is an acceptor of  electrons.

Period: A horizontal row of elements in the Periodic Table.

Periodic table: A table that contains horizontal rows and vertical columns of elements. The elements are arranged in order of their atomic numbers and in accordance with their chemical properties.

pH scale: A scale that measures the acidity or alkalinity of a solution.

Pollution: The presence in the environment of toxic substances which are harmful to living things.

Polymer: A very large molecule built up of a number of repeating units called monomers.

Polymerization: A chemical reaction in which simple molecules, called monomers, react with each other to form larger molecules called polymers.

Polyunsaturated: Vegetable oils that contain many carbon-carbon double bonds in their molecules.

Precipitate: An insoluble solid that is produced in a solution as a result of a chemical reaction.

Protein: A polymer of amino acids.

Protons: Positively charged sub-atomic particles found in the nucleus of an atom.

Proton number: The number of protons in the nucleus of an atom.

Pure substance: A single substance which is not mixed with other substances. It has definite melting and boiling points. (e.g. pure water boils at exactly 100°C and freezes at 0°C)

Reactivity series: A list of elements in order of their reactivity. The more reactive the element, the higher its position in the series. An element higher up the series will displace a less reactive one from a solution of its salt.

Redox reaction: A reaction where both oxidation and reduction take place simultaneously.

Reducing agent: A substance that brings about reduction. It is itself oxidized. A reducing agent is a donor of electrons.

Reduction: The removal of oxygen, the addition of hydrogen, the gain of electrons, or the decrease in the oxidation state of the substance.

Relative atomic mass: The number of times the mass of one atom of an element is heavier than 1/12 of the mass of a carbon-12 atom.

Relative molecular mass: The sum of the relative atomic masses of each of the atoms in one molecule of a substance.

Residue: The solid which remains on the filter paper after filtration.

Respiration: The slow combustion of food in the cells of living organisms to release energy.

Rusting: The slow oxidation of iron in the presence of air and water to form hydrated iron (III) oxide (rust).

Salt: The ionic compound formed by the replacement of one or more hydrogen ions of an acid by a metallic ion or an ammonium ion.

Saturated hydrocarbons: Hydrocarbons that contain only single bonds between carbon atoms.

Solute: The substance that dissolves in a solvent to form a solution.

Solvent: The liquid in which a solute dissolves.

Steel: An alloy of iron and carbon.

Structural formula: A formula which shows how the atoms are arranged in a molecule.

Sublimation: The process of changing from the solid state directly to the gaseous state without passing through the liquid state.

Suspension: A mixture of a liquid and an insoluble solid where the insoluble solid remains suspended throughout the solution.

Titration: The gradual addition of a solution from a burette to another solution in a conical flask until the chemical reaction between the two solutions is complete; the 2 solutions tend to be an acid and an alkali.

Unsaturated molecule: Any hydrocarbon that contains one or more carbon-carbon double bonds.

Valence electrons: Electrons in the outer shell that are used by the atom for forming chemical bonds.

Water of crystallization: Water molecules that are chemically bonded in the crystals of some salts.

3 comments:

  1. thnx ! this blog is very useful ...

    ReplyDelete
  2. yess very helpful but oxidation is loss and gain of hydrogen? isnt it electrons?

    ReplyDelete
    Replies
    1. oxidation is the loss of electrons

      Delete

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