27539591 Glossary SPM Chemistry

8/7/2019 27539591 Glossary SPM Chemistry

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A

AcidAn acid is a substance that contains hydrogenions, H+, as the only positive ions in an aqueoussolution.

Acid-base titrationA quantitative experimental technique used tocarry out complete neutralisation reaction betweenan acid and an alkali

Activation energy Minimum energy the reactant particles must have

be ore e ective collision between them can resultin a chemical reaction

AlcoholA homologous series containing the hydroxylgroup, OH, with the general ormula C

nH2n +1OH,

where n = 1, 2, 3,

AlkaliA base that is soluble in water

Alkane

Alkanes are saturated hydrocarbons with thegeneral ormula C

nH2n +2, where n = 1, 2, 3,

AlkeneAlkenes are unsaturated hydrocarbons with thegeneral ormula C

nH2n , where n = 2, 3, 4,

Alloy A mixture o two or more metals (sometimes non-metals) in a speci c proportion. Te added metalsare usually in small amounts

AnalgesicA modern medicine that relieves pain

AnionTe negative ion that is ormed when an atomgains electrons

AnodeAn electrode which is connected to the positiveterminal o a battery

AntibioticA modern medicine that kills bacteria

AntioxidantA ood additive that prevents oxidation o ood

AtomTe smallest particle o an element that canparticipate in a chemical reaction

Avogadro constantTe number o particles in one mole o any substance, which re ers to the value o 6.02 1023 mol-1

B

BaseA substance that reacts with an acid to give only asalt and water

C

Carbon compoundA compound that contains carbon combined withother elements

Carboxylic acidA homologous series containing the carboxyl group,COOH, with the general ormula C

nH2n +1COOH,

where n = 0, 1, 2,

CatalystA substance which increases the rate o a chemicalreaction, without itsel being chemically changedat the end o the reaction

CathodeAn electrode which is connected to the negativeterminal o a battery

CationTe positive ion that is ormed when an atom loseselectrons

Coagulation o latex Separation o rubber molecules rom the water inthe latex


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Collision theory A theory used to explain the rate o chemicalreactions in terms o e ective collisions betweenparticles

Composite materialAn advanced material that is ormed by combiningtwo or more di erent materials. Te properties o

this new material are more superior compared tothose o its original materials

CompoundA substance that contains two or more elementsthat are chemically bonded

ConcentrationTe concentration o a solution is the amount o asolute that dissolved in a unit volume o a solution.Te concentration o a solution can be expressedin terms o gram o solute per litre (dm3) o a

solution, g dm-3

, or number o moles o solute perlitre (dm -3) o solution, mol dm-3

CondensationProcess o changing gas to liquid

ConductorA substance which conducts electricity but doesnot change chemically during the conduction

Contact processAn industrial process to manu acture sulphuricacid rom sulphur

Covalent bondA bond that is ormed between atoms o non-metalsby overlapping their outermost shells. In covalentbonding, each atom in a molecule contributes anequal number o electrons or sharing.

CrystallisationA technique used to prepare crystals o a substance

rom its saturated solution

D

DecompositionA chemical reaction in which a compound isbroken down into simpler substances

DehydrationA reaction where water molecules are removed

rom the reactants

DetergentTe sodium salt ormed when an alkyl hydrogensulphate is neutralised by an alkali (sodiumhydroxide)

Di usionTe movement o particles o a substance romhigher concentration to a medium o lowerconcentration

DilutionAddition o a solvent to a more concentratedsolution to produce a more diluted solution

DistillationProcess o extracting a substance by vapourisingit and then condensing the vapour at a xedtemperature

DyeA ood additive that colours ood or replaces lostcolours

E

Electrochemical seriesA list o metals arranged in descending order o their atoms tendency to lose electrons to ormpositive ions. Te more electropositive metals areplaced higher up in the series.

ElectrodeAn electric conductor which carries electriccurrent in and out o an electrolyte

ElectrolysisTe conductivity o electricity in an electrolyte,leading to its decomposition to its constituentelements

ElectrolyteElectrolytes are compounds that conduct electricity in a molten state or in an

aqueous solution and are decomposed to theirconstituent elements in the process.

ElectronA negatively-charged subatomic particle thatsurrounds the nucleus o an atom

Electron arrangementTe way electrons are arranged in an atom

Empirical ormulaTe chemical ormula which shows the simplestwhole number ratio o the atoms o each elementpresent in a compound


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Endothermic reactionA chemical reaction that absorbs heat energy romthe surroundings

Energy level diagramA graph that shows the energy content o reactantsand products with the energy change o a chemicalreaction

Energy profle diagramA graph that shows the energy change as reactantschange to become products in a chemical reaction

EsterA homologous series containing the carboxylategroup, COO, with the general ormulaC

nH2n +1COOC m H2m +1, where n = 0, 1, 2, and

m = 1, 2, 3,

EsterifcationTe reaction between a carboxylic acid and analcohol to orm an ester and water. Te reaction is

catalysed by concentrated sulphuric acid.Evaporation

Te change o a liquid into a gas at the sur ace o a liquid

Exothermic reactionA chemical reaction that releases heat energy tothe surroundings

Extraction o metalTe process o obtaining a metal rom its ore

F

FatA natural ester o atty acid and glycerol

Fatty acidA carboxylic acid that has a long chain o about10 to 20 carbon atoms. It has only one carboxylgroup.

FermentationTe reaction in which yeast converts glucose intoethanol

FiltrationTe separation o a solid and a liquid by pouringthe mixture into a porous material such as lterpaper. Te liquid passing through the lter paper iscalled ltrate. Te solid trapped on the lter paperis called the residue.

Flavouring agentA ood additive that gives favour to ood orenhances its natural favour

Food additiveAny substance that is added to ood to preserve itor improve its favour and appearance

Fractional distillationTe separation o two liquids with di erent boilingpoints by distillation using a ractionating column

Functional group

An atom or a group o atoms that is responsibleor the characteristic chemical properties o anorganic compound

G

GlycerolAn alcohol that has three hydroxyl groups

GroupTe vertical columns o elements in the Periodic

able. Te group number is determined by thenumber o valence electrons in the atoms o theelements

H

Haber processAn industrial process to manu acture ammonia

rom nitrogen and hydrogen

Hal -equationAn ionic equation showing either oxidation orreduction that explicitly shows the electronsinvolved

Heat o combustionTe amount o heat given o when one mole o asubstance is completely burnt in excess oxygen

Heat o displacementTe amount o heat energy given o when one moleo metal is displaced rom its aqueous solution (by the more electropositive metal) under standardconditions

Heat o neutralisationTe amount o heat given o when one mole o water is produced rom the neutralisation reactionbetween an acid and an alkali under standardconditions

Heat o precipitationTe amount o heat given o when one mole o precipitate is ormed when mixing the aqueoussolutions o the ions o insoluble salt understandard conditions


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Homologous seriesA amily o organic compounds with each membero the amily di ering rom the previous memberby having one more group o atoms CH 2

HydrationA reaction where water molecules are added to acompound

HydrocarbonOrganic compounds that contain hydrogen andcarbon atoms only

HydrogenationTe addition o a hydrogen molecule to the carbonatom o the double bond

HydrolysisA reaction o a compound with water to producesmaller products

IIon

A positively-charged or negatively-charged particleormed as a result o losing electrons or gaining

electrons in an atom

Ionic bondA bond that is ormed when electrons aretrans erred rom metal atoms to non-metal atomsto orm positive and negative ions. Te ionicbond is the strong electrostatic orces o attractionbetween positive and negative ions.

IsomerIsomers are di erent compounds that have thesame molecular ormula but di erent structural

ormula

IsotopeAtoms o the same element but are di erent in thenumber o neutrons

M

MatterAnything that occupies space and has a mass

Melting Te change o a solid into a liquid

Molar massTe mass o one mole o any substance

Molar volumeTe volume occupied by one mole o any gas, whichis 22.4 dm3 at s.t.p. or 24 dm 3 at room conditions

Molarity Te number o moles o solute present in 1 dm 3 o solution

MoleA basic S.I. unit used to measure the amount o substances. One mole o substance contains asmany particles as the number o atoms in 12 g o carbon-12.

MoleculeA group o two or more atoms which are chemically bonded together

Molecular ormulaTe chemical ormula which shows the actualnumber o atoms o each element in a molecule

MonomerTe smaller molecules that make up the repeatingunits in polymers

N

NeutralisationTe reaction between an acid and a base (or alkali)to produce only water and a salt

NeutronAn electrically neutral subatomic particle ound inthe nucleus o an atom

Noble gasA gas that is inert and monoatomic because it hasstable electronic structures (octet or duplet)

Non-electrolyteA substance that does not conduct electricity evenin a molten state or in an aqueous solution

Non-hydrocarbonOrganic compounds containing other elementssuch as nitrogen and oxygen besides hydrogen andcarbon

Nucleon numberTe total number o protons and neutrons in thenucleus o an atom

NucleusTe central part o an atom consisting o neutronsand protons

O

Organic compoundA carbon compound that is derived or obtained

rom living or once living things


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OxidationOxidation occurs when there is a gain in oxygen, aloss o hydrogen, a loss o electrons or an increasein the oxidation number o a substance

Oxidation numberTe imaginary change o an atom i it exists as anion

Oxidising agentA substance that oxidises another substance and isreduced in the redox reaction

P

PeriodTe horizontal rows o elements in the Periodic

able. Te period number is determined by thenumber o electron- lled shells in atoms o theelements.

pH scaleA measure o how acidic or alkaline an aqueoussolution is

PolymerMolecules that consist o a large number o smallidentical units joined together repeatedly

PolymerisationTe process o joining together a large number o small molecules to orm polymers

PrecipitateAn insoluble solid produced rom a solutionduring a chemical reaction

PreservativeA ood additive that prevents or slows downspoilage o ood

ProtonA positively-charged subatomic particle ound inthe nucleus o an atom

Proton numberTe number o protons in an atom

R

Rate o reactionTe rate o a chemical reaction is determined by measuring how quickly a reactant is used up orhow quickly a product is produced over a periodo time

Reactivity series o metalsA list where metals are placed in the order o theirreactivity with oxygen

Redox reactionA reaction in which oxidation and reduction occurspontaneously

Reducing agentA substance that reduces another substance and isoxidised in the redox reaction

ReductionReduction occurs when there is a loss o oxygen, again in hydrogen, a gain in electrons or a decreasein the oxidation number o a substance

Relative atomic massTe relative atomic mass o an element is de nedas the average mass o one atom o that elementcompared with o the mass o a carbon-12 atom

Relative ormula massTe relative ormula mass o a substance is de nedas the average mass o one ormula unit o anionic substance compared with o the mass o acarbon-12 atom

Relative molecular massTe relative molecular mass o a substance isde ned as the average mass o a molecule o that substance compared with o the mass o acarbon-12 atom

S

SaltA compound ormed when the hydrogen ion o anacid is replaced by a metal ion or an ammoniumion

SaponifcationSaponi cation is hydrolysis o an ester by a hotaqueous alkali solution to orm an alcohol andsodium (or potassium) salts o carboxylic acids

Scientifc methodA systematic approach used by scientists to

investigate a phenomenonSemi-metal

An element that possesses the intermediateproperties between metals and non-metals

ShellTe orbit surrounding the nucleus o an atom inwhich electrons move

SoapTe sodium or potassium salt o a atty acid

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StabiliserFood additives that improve the texture andconsistency o ood

Stoichiometry Te relationship between the amount (usually in mole) o reactants and products involved in achemical reaction

Structural ormulaA ormula that shows how atoms are bonded toeach other in a molecule

SublimationTe change rom a solid into a gas without goingthrough liquid state

Substitution reactionA reaction in which one atom replaces anotheratom o a molecule

T

TitrationA laboratory technique in which a standardsolution is used to determine the concentration o an unknown solution using an indicator to detectthe end point during neutralisation

Transition elementAn element in Group 3 to Group 12 o the Periodic

able

V

Valence electronsTe electrons in the outermost shell o an atom

Viscocity A measure o the resistance o fuids to fow

Voltaic cellA cell that produces electrical energy by meanso chemical reaction. It converts chemicalenergy to electrical energy. It is also known as anelectrochemical cell or a galvanic cell.

VulcanisationTe process o treating natural rubber with sulphur

to orm vulcanised rubber

W

Whitening agentA detergent additive that makes clothes look whiteand cleaner

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27539591 Glossary SPM Chemistry