Transcript Slide 1

The following presentation
contains the meanings of the
terms you need to know in
Standard Grade Chemistry.
You should learn these as you
work through the course.
Don’t leave it until the end of the
course to try and learn them.
Topic 1
CHEMICAL REACTION - a reaction in which a new
substance (or new substances) is/are made.
ELEMENT - a substance containing only one type of
atom. e.g. magnesium is an element because the only
atoms in it are magnesium atoms.
COMPOUND - a substance made when two or more
elements JOIN together.
PRECIPITATE - a solid substance that comes out of
a solution during a chemical reaction e.g. when
carbon dioxide turns lime water milky, the milkiness is
a precipitate called calcium carbonate.
EXOTHERMIC - a reaction which releases energy .
The opposite is ENDOTHERMIC (takes in energy).
FILTRATION - using filter paper to separate
insoluble from soluble material.
FILTRATE - the liquid that passes through filter
paper.
SOLUBLE - a substance that dissolves.
INSOLUBLE - a substance of very low solubility - See
SQA data book.
DISTILLATION - a purification process involving
evaporation, followed by condensation.
Topic 2
A CATALYST speeds up a chemical reaction, but is
not used up in the reaction, and can be recovered
chemically unchanged after the reaction.
An ENZYME is a BIOLOGICAL CATALYST
(speeds up reactions that take place in living things))
DECOMPOSE means to break up into smaller parts.
CONCENTRATION refers to the quantity of
dissolved substance in relation to the volume of the
solvent.
Topic 3
GROUPS - vertical columns of elements in Periodic
Table e.g. Group 1 (The Alkali Metals)
ALKALI METALS - Group 1 elements (lithium, sodium,
potassium, rubidium and caesium)
HALOGENS - Group 7 elements (fluorine, chlorine,
bromine and iodine)
NOBLE GASES - Group 0 elements (helium, neon, argon,
krypton, xenon and radon)
TRANSITION METALS - The block of metal elements
found between Groups 2 and 3 in the Periodic Table (e.g.
iron, copper, gold, silver)
NUCLEUS - the small centre of every atom. The nucleus
contains the positive protons and the neutral neutrons.
Virtually all of the mass of the atom is found here.
ATOMIC NUMBER - the number of protons in an atom
(also equal to the number of electrons in the atom).
Atomic number determines where the element is found
in the table.
MASS NUMBER - The sum of the protons added to the
neutrons.
ISOTOPES - Atoms with the same atomic number but
with a different mass number (Atoms of the same
element with a different number of neutrons)
IONS - these are atoms after the atom has either lost an
electron (or electrons) or gained an electron (or
electrons)
Topic 4
BOND - the attraction that holds atoms together
MOLECULE - a small group of atoms joined together (by
covalent bonding)
DIATOMIC - contains two atoms e.g. O2, CO, N2, Cl2
COVALENT BOND - where two atoms share electrons
SINGLE COVALENT BOND - where two electrons are
shared
DOUBLE COVALENT BOND - where four electrons
are shared
TRIPLE COVALENT BOND - where six electrons are
shared
CHEMICAL FORMULA - this gives the number of
atoms of each element present in a substance e.g. H2O,
C12H22 O11
Topic 5
FUEL - a substance which burns releasing energy
COMBUSTION - a reaction of a substance with oxygen,
giving out energy
EXOTHERMIC - a reaction in which energy is released
POLLUTION - substances which damage the
environment
FRACTIONAL DISTILLATION - separation of a
mixture of substances into parts or fractions based the
fact that they have different boiling points
FLAMMABILITY - refers to how easily a substance
burns e.g. a flammable substance burns easily
VISCOSITY - describes the thickness of a liquid e.g. a
viscous liquid does not run easily.
HYDROCARBONS - compounds containing carbon and
hydrogen only
INCOMPLETE COMBUSTION - when there is
insufficient oxygen for a fuel to burn completely.
CATALYTIC CONVERTER - a device on cars,
containing a transition metal such as platinum, which
converts harmful gases such as carbon monoxide and
nitrogen oxides into less harmful gases.
LEAN BURN ENGINE - one which uses more air and
less fuel than non-lean burn engines
Topic 6 (I)
ALKANE - a member of the family of hydrocarbons of
general formula CnH2n+2
HOMOLOGOUS SERIES - a family of compounds with
similar chemical properties. All members of the family fit
the same general formula e.g. the ALKANES are a
homologous series with the general formula CnH2n+2
CYCLOALKANES - a homologous series of
hydrocarbons of general formula CnH2n where the
carbon atoms are joined into a circular arrangement
ISOMERS - compounds with the same molecular formula
but with a different structural formula
ALKENES - a homologous series of hydrocarbons of
general formula CnH2n where there is a double bond
between two of the carbon atoms
Topic 6 (II)
SATURATED - where the carbon atoms are only joined
by single covalent bonds e.g. alkanes
UNSATURATED - where two of the carbon atoms are
joined by a double covalent bond e.g. alkenes
ADDITION REACTION - a reaction where a substance
adds onto an unsaturated compound to give only one
product. If the starting substance is an alkene, the
product will be saturated.
CRACKING - where a long chain alkane is broken into a
mixture of a short chain alkane and an alkene. These
molecules are smaller and more useful. A catalyst is
needed to speed up the reaction and reduce the heat
required.
Topic 7
METAL ELEMENTS - conduct electricity when solid
and when molten. The type of charged particle which
carries the current in a metal is called an electron.
NON-METAL ELEMENTS - do not conduct electricity,
with the exception of solid carbon in the form of
graphite.
Compounds containing metals are called ionic
compounds. Ionic compounds do not conduct
electricity when solid because the ions are not free to
move
Ionic compounds conduct electricity when their ions are
free to move about (molten or in solution).
Such compounds are called electrolytes (contain ions
which can move about).
The purpose of an electrolyte is to complete the circuit.
COVALENT MOLECULES – small group of non-metal
atoms with low melting/boiling points.
COVALENT NETWORKS - very high melting/boiling
point network of non-metal atoms.
ELECTROLYSIS – using electricity to split up an ionic
compound.
D.C SUPPLY – is used so that the products at each
electrode can be identified.
Topic 8
NON METAL ELEMENTS - can react with air or
oxygen to form compounds called oxides.
NON-METAL OXIDES - dissolve in water produce acids
e.g. CO2, NO2, SO2, SO3.
SO2 and NO2 react with water to form acid rain.
Oxides of non-metals which do not dissolve do not
affect the pH.
OXIDES OF METALS OR HYDROXIDES of metals
which dissolve in water produce alkaline solutions. The
data book gives information about which ones dissolve or
react.
The oxides of Group 1 metals and some of some Group 2
metals produce alkaline solutions with water.
ACIDS have a pH of less than 7. (pH<7)
ALKALIS have a pH of more than 7. (pH>7)
Pure water and neutral solutions have a pH equal to 7.
(pH=7)
All acid solutions contain HYDROGEN IONS (H+ (aq))
and have pH values < 7. If an electric current is passed
through any acid solution, the H+ ions are changed into
hydrogen gas at the negative electrode. Hydrogen gas
burns with a pop.
Topic 8
All alkaline solutions contain HYDROXIDE IONS
(aq)) and have pH values > 7
(OH-
Water has a very low concentration of ions
In water and any neutral solution, the concentration of
H+ ions and OH- ions is the same and this gives a pH = 7
(neutral).
In an acid solution the concentration of hydrogen ions
(H+(aq)) is more than that in pure water.
In an alkaline solution the concentration of hydroxide
ions (OH-(aq)) is more than that in pure water.
DILUTING ACIDS AND ALKALIS
Adding more water to an acid increases the pH of
the solution towards 7 making it less acidic. (The
acidity decreases and the pH value increases).
Adding more water to an alkali decreases the pH of
the solution towards 7 making it less alkaline. (The
alkalinity decreases and the pH value decreases).
NB In both cases, the pH number moves towards 7
Diluting an acid decreases the concentration H+(aq)
ions.
Diluting an alkali decreases the concentration OH(aq) ions.
Topic 9
NEUTRALISATION is the reaction of acids with
neutralisers and at the same time the pH value moves
towards 7.
REACTIONS OF ACIDS WITH NEUTRALISERS
(EXAMPLES OF NEUTRALISATION)
Acid + Alkali
--------------> Salt + Water
Acid + Metal Oxide ---------> Salt + Water
Acid + Metal Carbonate -> Salt + Water +
Acid + Metal
Carbon dioxide
---------------> Salt + Hydrogen
Some metals such as copper, silver and gold do not
react with dilute acids.
WHAT IS A SALT?
A salt is a substance in which the hydrogen ion of an
acid has been replaced by a metal ion (or the
ammonium ion).
When an acid is neutralised by an alkali, H+ ions from
the acid join with OH- from the alkali to form water.
A BASE is a substance which neutralises an acid. This
means that alkalis (metal hydroxides), metal oxides,
metal carbonates and metals are all examples of bases.
An alkali is made if the base dissolves in water.
Topic 9
NAMING SALTS
Hydrochloric acid (HCl) always makes CHLORIDE salts
Nitric acid (HNO3) always makes NITRATE salts
Sulphuric acid (H2SO4) always makes SULPHATE salts
SOLUBLE SALTS - add excess of an insoluble metal
oxide or metal carbonate to an acid, and remove the
unreacted substance by filtration, followed by
evaporation of the filtrate to obtain the salt.
INSOLUBLE SALTS - can be formed by precipitation.
To make insoluble lead (II) iodide, mix together two
separate solutions of soluble salts one containing lead (II)
ions and the other containing iodide ions e.g. lead (II)
nitrate solution and sodium iodide solution.
Pb(NO3)2(aq) + 2NaI(aq) -------> PbI2(s) + 2NaNO3(aq)
Lead iodide is formed as a yellow precipitate which can
be removed easily by filtering
PRECIPITATION is the reaction of two solutions to
form an insoluble product called a precipitate. The
data book indicates the solubility of many substances.
Topic 10
BATTERY - a device containing chemicals that react to
produce electricity. Advantage of battery over mains is
it is safer and portable. A disadvantage is that it is more
expensive than mains electricity. A battery runs out
because the chemical reaction stops/chemicals are used
up.
CELL - the correct term for devices called batteries.
ELECTROLYTE - a substance that contains ions which
can move (either molten ionic compounds or ionic
compounds in solution or a watery paste as in a dry cell).
RECHARGEABLE b - a cell in which electricity can
regenerate chemicals to allow the cell to produce
electricity many times.
VOLTAGE - a measure of the push of electrons between
two reactions.
ELECTROCHEMICAL SERIES - a list of reactions in
the data book (page 7) which can be used to determine
which reaction of a pair is better at pushing electrons
onto the other reaction. Electrons flow from the higher
equation to the lower equation. The further the
equations from each other the higher the voltage.
Topic 10
DISPLACEMENT REACTION - where one metal
higher in the electrochemical series displaces (pushes
out) another metal from a solution of the other metal.
ION BRIDGE – (salt bridge) a link containing ions
which completes a circuit.
OXIDATION - the reaction of a metal element to
form a compound.
OXIDATION - the loss of electrons by a reactant in
any reaction.
REDUCTION - the reaction of a compound to form a
metal.
REDUCTION - the gain of electrons by a reactant in
any reaction.
REDOX REACTION - a reaction in which reduction
and oxidation occur together.
OILRIG - This will help you remember oxidation and
reduction.
OIL stands for Oxidation Is the Loss (of electrons).
RIG stands for Reduction Is the Gain (of electrons).
Topic 11
DENSITY - the mass of a metal divided by the space it
takes up. A metal is dense because the atoms are packed
closely together and take up little space.
MALLEABILITY - the ability of a metal to be beaten
into shape.
CONDUCTIVITY - the ability of a substance to let heat
or electricity through it.
ORE - a naturally-occurring compound of metals.
ELECTROLYSIS - splitting an ionic substance into its
elements using electricity.
REDUCTION - a reaction is which a metal is obtained
from a compound.
ALLOY - a mixture of metals with non-metals.
Topic 12
CORROSION - the changing of the surface of a metal
when it loses electrons.
RUSTING - the special name for the corrosion of iron
FERROXYL INDICATOR - turns blue in the presence of
iron(II) ions Fe2+(aq)
FERROXYL INDICATOR - turns pink in the presence of
hydroxide ions
PHYSICAL PROTECTION - stopping corrosion by
keeping out air and/or water
CHEMICAL PROTECTION - using more reactive metals
to push electrons onto iron
GALVANISING - coating iron with a layer of zinc
TIN PLATING - coating iron with a layer of tin
ELECTROPLATING - coating a metal with a layer of
another metal using electricity
SACRIFICIAL PROTECTION - where a more reactive
metal sacrifices itself to protect the less reactive metal
Topic 13
PLASTICS - a wide variety of large molecules made from
products from crude oil distillation
SYNTHETIC – made by the chemical industry
FIBRE - a large molecule which is made into long threads
NATURAL - occurring in nature
BIODEGRADABLE - broken down into smaller pieces by
living organisms
TOXIC - harmful
THERMOPLASTIC - a plastic that can be re-softened
by heating e.g. poly(ethene)
THERMOSETTING - a plastic that cannot be resoftened by heating e.g. bakelite
MONOMER - small units that join together to give a very
big molecule
POLYMERS - very big units made when many monomer
molecules join together
POLYMERISATION - the process in which monomers
join to give a polymer
CRACKING - a reaction in which long-chain
hydrocarbons are converted into unsaturated
hydrocarbons
ADDITION POLYMERISATION - the making of a
polymer by a series of addition reactions
Topic 14
NUTRIENTS - soluble compounds containing nitrogen,
phosphorus and potassium which are absorbed by
roots.
NPK FERTILISERS - those containing Nitrogen,
Phosphorus and Potassium
NITRIFYING BACTERIA - bacteria living in swellings
on the roots of pea and bean plants (legumes) that can
take nitrogen out of the air and give this to plants.
FIXING NITROGEN - taking nitrogen out of the air
and changing it into useful compounds for plants e.g.
nitrates.
DENITRIFYING BACTERIA - taking nitrates out of
soil and changing it nitrogen.
HABER PROCESS - the joining of nitrogen and
hydrogen gases to make ammonia gas using an iron
catalyst.
OSTWALD PROCESS - the oxidation of ammonia with
oxygen to make nitrogen dioxide using a platinum
catalyst. The nitrogen dioxide dissolves in water to
produce nitric acid. The industrial manufacture of
nitric acid. The Ostwald process is exothermic.
EXOTHERMIC REACTION - a reaction which gives
out energy.
Topic 15 I
PHOTOSYNTHESIS - a process in plants in which
carbon dioxide and water are changed into
carbohydrates and oxygen with the help of sunlight and
chlorophyll.
CARBOHYDRATE - a compound containing carbon,
hydrogen and oxygen in which the ratio of
hydrogen:oxygen is the same as in water i.e. 2:1
ENDOTHERMIC - a reaction in which energy is
absorbed (or taken in).
CHLOROPHYLL - a green chemical in the leaves of
plants which is able to trap the energy of the sun and
use this energy to make carbohydrates.
RESPIRATION - a process in living things where oxygen
is used to break up food and produce water, carbon
dioxide and energy
ISOMERS - compounds with the same molecular formula
but with a different structural formula.
MONSACCHARIDE - single sugar molecules such as
glucose or fructose (C6H12O6)
DISACCHARIDE - two sugar molecules joined together
as in sucrose or maltose (C12H22O11)
Topic 15 - II
CONDENSATION - the joining of sugar molecules with
the elimination of water molecules.
POLYMERISATION - the joining of many sugar
molecules together e.g. when glucose is changed into
starch.
DIGESTION - a process in living things where large
molecules are broken into smaller molecules with the
help of enzymes.
ENZYMES - biological catalysts which are used to help
reactions such as photosynthesis and digestion in living
things.
HYDROLYSIS - the breakdown of molecules by splitting
them with water e.g. sucrose into molecules of glucose
and fructose.
FERMENTATION - a reaction between sugars and
enzymes in yeast which produces alcohol and carbon
dioxide.
ALKANOL (alcohol) - a compound made by the
fermentation of a carbohydrate (e.g. ethanol).
ETHANOL - a member of the alkanol family with
formula C2H5OH.
Chemical Tests
CARBON DIOXIDE –turns lime water milky
HYDROGEN GAS – burns with a pop
OXYGEN GAS – relights a glowing splint
ALKENES C=C – decolourises Bromine solution
GLUCOSE/FRUCTOSE/MALTOSE – turn Benedict’s
solution brick red
STARCH – turns iodine solution blue/black
IRON (ll) IONS Fe2+ - turn ferroxyl solution blue
ACIDS – turn universal indicator red/orange pH less
than 7
ALKALIS – turn universal indicator blue/purple pH
greater than 7
NEUTRAL SOLUTIONS – turn universal indicator
green pH = 7
AMMONIA – turns pH paper/universal indicator
blue/pH greater than 7/alkaline.