Glossary SPM Chemistry
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Transcript of Glossary SPM Chemistry
e–GlossaryA
AcidAn acid is a substance that contains hydrogen ions, H+, as the only positive ions in an aqueous solution.
Acid-base titrationA quantitative experimental technique used to carry out complete neutralisation reaction between an acid and an alkali
Activation energyMinimum energy the reactant particles must have before effective collision between them can result in a chemical reaction
AlcoholA homologous series containing the hydroxyl group, –OH, with the general formula CnH2n+1OH, where n = 1, 2, 3, …
AlkaliA base that is soluble in water
AlkaneAlkanes are saturated hydrocarbons with the general formula CnH2n+2, where n = 1, 2, 3, …
AlkeneAlkenes are unsaturated hydrocarbons with the general formula CnH2n, where n = 2, 3, 4, …
AlloyA mixture of two or more metals (sometimes non-metals) in a specific proportion. The added metals are usually in small amounts
AnalgesicA modern medicine that relieves pain
AnionThe negative ion that is formed when an atom gains electrons
AnodeAn electrode which is connected to the positive terminal of a battery
AntibioticA modern medicine that kills bacteria
AntioxidantA food additive that prevents oxidation of food
AtomThe smallest particle of an element that can participate in a chemical reaction
Avogadro constantThe number of particles in one mole of any substance, which refers to the value of 6.02 × 1023 mol-1
BBase
A substance that reacts with an acid to give only a salt and water
CCarbon compound
A compound that contains carbon combined with other elements
Carboxylic acidA homologous series containing the carboxyl group, –COOH, with the general formula CnH2n+1COOH, where n = 0, 1, 2, …
CatalystA substance which increases the rate of a chemical reaction, without itself being chemically changed at the end of the reaction
CathodeAn electrode which is connected to the negative terminal of a battery
CationThe positive ion that is formed when an atom loses electrons
Coagulation of latexSeparation of rubber molecules from the water in the latex
Collision theoryA theory used to explain the rate of chemical reactions in terms of effective collisions between particles
Composite materialAn advanced material that is formed by combining two or more different materials. The properties of this new material are more superior compared to those of its original materials
CompoundA substance that contains two or more elements that are chemically bonded
ConcentrationThe concentration of a solution is the amount of a solute that dissolved in a unit volume of a solution. The concentration of a solution can be expressed in terms of gram of solute per litre (dm3) of a solution, g dm-3, or number of moles of solute per litre (dm-3) of solution, mol dm-3
CondensationProcess of changing gas to liquid
ConductorA substance which conducts electricity but does not change chemically during the conduction
Contact processAn industrial process to manufacture sulphuric acid from sulphur
Covalent bondA bond that is formed between atoms of non-metals by overlapping their outermost shells. In covalent bonding, each atom in a molecule contributes an equal number of electrons for sharing.
CrystallisationA technique used to prepare crystals of a substance from its saturated solution
DDecomposition
A chemical reaction in which a compound is broken down into simpler substances
DehydrationA reaction where water molecules are removed from the reactants
DetergentThe sodium salt formed when an alkyl hydrogen sulphate is neutralised by an alkali (sodium hydroxide)
DiffusionThe movement of particles of a substance from higher concentration to a medium of lower concentration
DilutionAddition of a solvent to a more concentrated solution to produce a more diluted solution
DistillationProcess of extracting a substance by vapourising it and then condensing the vapour at a fixed temperature
DyeA food additive that colours food or replaces lost colours
EElectrochemical series
A list of metals arranged in descending order of their atomsí tendency to lose electrons to form positive ions. The more electropositive metals are placed higher up in the series.
ElectrodeAn electric conductor which carries electric current in and out of an electrolyte
ElectrolysisThe conductivity of electricity in an electrolyte, leading to its decomposition to its constituent elements
ElectrolyteElectrolytes are compounds that conduct electricity in a molten state or in an
aqueous solution and are decomposed to their constituent elements in the process.
ElectronA negatively-charged subatomic particle that surrounds the nucleus of an atom
Electron arrangementThe way electrons are arranged in an atom
Empirical formulaThe chemical formula which shows the simplest whole number ratio of the atoms of each element present in a compound
Endothermic reactionA chemical reaction that absorbs heat energy from the surroundings
Energy level diagramA graph that shows the energy content of reactants and products with the energy change of a chemical reaction
Energy profile diagramA graph that shows the energy change as reactants change to become products in a chemical reaction
EsterA homologous series containing the carboxylate group, –COO–, with the general formula CnH2n+1COOCmH2m+1, where n = 0, 1, 2, … and m = 1, 2, 3, …
EsterificationThe reaction between a carboxylic acid and an alcohol to form an ester and water. The reaction is catalysed by concentrated sulphuric acid.
EvaporationThe change of a liquid into a gas at the surface of a liquid
Exothermic reactionA chemical reaction that releases heat energy to the surroundings
Extraction of metalThe process of obtaining a metal from its ore
FFat
A natural ester of fatty acid and glycerol
Fatty acidA carboxylic acid that has a long chain of about 10 to 20 carbon atoms. It has only one carboxyl group.
FermentationThe reaction in which yeast converts glucose into ethanol
FiltrationThe separation of a solid and a liquid by pouring the mixture into a porous material such as filter paper. The liquid passing through the filter paper is called filtrate. The solid trapped on the filter paper is called the residue.
Flavouring agentA food additive that gives flavour to food or enhances its natural flavour
Food additiveAny substance that is added to food to preserve it or improve its flavour and appearance
Fractional distillationThe separation of two liquids with different boiling points by distillation using a fractionating column
Functional groupAn atom or a group of atoms that is responsible for the characteristic chemical properties of an organic compound
GGlycerol
An alcohol that has three hydroxyl groups
GroupThe vertical columns of elements in the Periodic Table. The group number is determined by the number of valence electrons in the atoms of the elements
HHaber process
An industrial process to manufacture ammonia from nitrogen and hydrogen
Half-equationAn ionic equation showing either oxidation or reduction that explicitly shows the electrons involved
Heat of combustionThe amount of heat given off when one mole of a substance is completely burnt in excess oxygen
Heat of displacementThe amount of heat energy given off when one mole of metal is displaced from its aqueous solution (by the more electropositive metal) under standard conditions
Heat of neutralisationThe amount of heat given off when one mole of water is produced from the neutralisation reaction between an acid and an alkali under standard conditions
Heat of precipitationThe amount of heat given off when one mole of precipitate is formed when mixing the aqueous solutions of the ions of insoluble salt under standard conditions
Homologous seriesA family of organic compounds with each member of the family differing from the previous member by having one more group of atoms –CH2–
HydrationA reaction where water molecules are added to a compound
HydrocarbonOrganic compounds that contain hydrogen and carbon atoms only
HydrogenationThe addition of a hydrogen molecule to the carbon atom of the double bond
HydrolysisA reaction of a compound with water to produce smaller products
IIon
A positively-charged or negatively-charged particle formed as a result of losing electrons or gaining electrons in an atom
Ionic bondA bond that is formed when electrons are transferred from metal atoms to non-metal atoms to form positive and negative ions. The ionic bond is the strong electrostatic forces of attraction between positive and negative ions.
IsomerIsomers are different compounds that have the same molecular formula but different structural formula
IsotopeAtoms of the same element but are different in the number of neutrons
MMatter
Anything that occupies space and has a mass
MeltingThe change of a solid into a liquid
Molar massThe mass of one mole of any substance
Molar volumeThe volume occupied by one mole of any gas, which is 22.4 dm3 at s.t.p. or 24 dm3 at room conditions
MolarityThe number of moles of solute present in 1 dm3 of solution
MoleA basic S.I. unit used to measure the amount of substances. One mole of substance contains as many particles as the number of atoms in 12 g of carbon-12.
MoleculeA group of two or more atoms which are chemically bonded together
Molecular formulaThe chemical formula which shows the actual number of atoms of each element in a molecule
MonomerThe smaller molecules that make up the repeating units in polymers
NNeutralisation
The reaction between an acid and a base (or alkali) to produce only water and a salt
NeutronAn electrically neutral subatomic particle found in the nucleus of an atom
Noble gasA gas that is inert and monoatomic because it has stable electronic structures (octet or duplet)
Non-electrolyteA substance that does not conduct electricity even in a molten state or in an aqueous solution
Non-hydrocarbonOrganic compounds containing other elements such as nitrogen and oxygen besides hydrogen and carbon
Nucleon numberThe total number of protons and neutrons in the nucleus of an atom
NucleusThe central part of an atom consisting of neutrons and protons
OOrganic compound
A carbon compound that is derived or obtained from living or once living things
OxidationOxidation occurs when there is a gain in oxygen, a loss of hydrogen, a loss of electrons or an increase in the oxidation number of a substance
Oxidation numberThe imaginary change of an atom if it exists as an ion
Oxidising agentA substance that oxidises another substance and is reduced in the redox reaction
PPeriod
The horizontal rows of elements in the Periodic Table. The period number is determined by the number of electron-filled shells in atoms of the elements.
pH scaleA measure of how acidic or alkaline an aqueous solution is
PolymerMolecules that consist of a large number of small identical units joined together repeatedly
PolymerisationThe process of joining together a large number of small molecules to form polymers
PrecipitateAn insoluble solid produced from a solution during a chemical reaction
PreservativeA food additive that prevents or slows down spoilage of food
ProtonA positively-charged subatomic particle found in the nucleus of an atom
Proton numberThe number of protons in an atom
RRate of reaction
The rate of a chemical reaction is determined by measuring how quickly a reactant is used up or how quickly a product is produced over a period of time
Reactivity series of metalsA list where metals are placed in the order of their reactivity with oxygen
Redox reactionA reaction in which oxidation and reduction occur spontaneously
Reducing agentA substance that reduces another substance and is oxidised in the redox reaction
ReductionReduction occurs when there is a loss of oxygen, a gain in hydrogen, a gain in electrons or a decrease in the oxidation number of a substance
Relative atomic massThe relative atomic mass of an element is defined as the average mass of one atom of that element compared with of the mass of a carbon-12 atom
Relative formula massThe relative formula mass of a substance is defined as the average mass of one formula unit of an ionic substance compared with of the mass of a carbon-12 atom
Relative molecular massThe relative molecular mass of a substance is defined as the average mass of a molecule of that substance compared with of the mass of a carbon-12 atom
SSalt
A compound formed when the hydrogen ion of an acid is replaced by a metal ion or an ammonium ion
SaponificationSaponification is hydrolysis of an ester by a hot aqueous alkali solution to form an alcohol and sodium (or potassium) salts of carboxylic acids
Scientific methodA systematic approach used by scientists to investigate a phenomenon
Semi-metalAn element that possesses the intermediate properties between metals and non-metals
ShellThe orbit surrounding the nucleus of an atom in which electrons move
SoapThe sodium or potassium salt of a fatty acid
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StabiliserFood additives that improve the texture and consistency of food
StoichiometryThe relationship between the amount (usually in mole) of reactants and products involved in a chemical reaction
Structural formulaA formula that shows how atoms are bonded to each other in a molecule
SublimationThe change from a solid into a gas without going through liquid state
Substitution reactionA reaction in which one atom replaces another atom of a molecule
TTitration
A laboratory technique in which a standard solution is used to determine the concentration of an unknown solution using an indicator to detect the end point during neutralisation
Transition elementAn element in Group 3 to Group 12 of the Periodic Table
VValence electrons
The electrons in the outermost shell of an atom
ViscocityA measure of the resistance of fluids to flow
Voltaic cellA cell that produces electrical energy by means of chemical reaction. It converts chemical energy to electrical energy. It is also known as an electrochemical cell or a galvanic cell.
VulcanisationThe process of treating natural rubber with sulphur to form vulcanised rubber
WWhitening agent
A detergent additive that makes clothes look white and cleaner