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Chemistry science with hazel
Chemistry (Swans International School)
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The Perfect Answer
Revision Guide To…
Chemistry
CIE IGCSE
9-1 / A*-U
1st Edition
Copyright © Hazel Lindsey, Caroline Gillespie 2018
Hazel Lindsey, Dr. Caroline Gillespie
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1. The particulate nature of matter ................................................................................. 3
2. Experimental techniques ............................................................................................5
3. Atoms, elements and compounds .............................................................................7
4. Stoichiometry ...........................................................................................................10
5. Electricity and chemistry ..........................................................................................12
6. Chemical energetics ................................................................................................. 15
7. Chemical reactions ................................................................................................... 16
8. Acids, bases and salts.............................................................................................. 19
9. The periodic table .....................................................................................................23
10. Metals .......................................................................................................................24
11. Air and water ............................................................................................................27
12. Sulfur ........................................................................................................................30
13. Carbonates ............................................................................................................... 31
14. Organic chemistry .................................................................................................... 32
Copyright © Hazel Lindsey, Caroline Gillespie 2018. All rights reserved.
No part of this publication may be reproduced or transmitted in any form or by any means without prior permission from Science with Hazel Ltd
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NOTE: Standard black text is core content (grades 1-5). Supplement content is in italics (grades
5-9)
NB. A copy of the periodic table will be available in papers 1, 2, 3 and 4
Core content will be examined in papers 1 (MC) and 3. Supplement AND Core content will be
examined in papers 2 (MC) and 4
1. The particulate nature of matter
Properties
Structure
Solid
• Holds a fixed shape
• Doesn’t flow
• Regular structure (lattice)
• Fixed positions
• Vibrate in position
Liquid
• Flows easily
• Fixed volume but shape changes
• No lattice
• Weaker forces between particles
• Move freely, slide past each other
Gas
• No fixed volume or shape
• Lighter than same volume of solid or
liquid
• No forces between particles
• Move quickly, can hit each other
What is melting?
• A solid is heated and turns to liquid
• Particles have more kinetic energy
• Substance expands as particles vibrate more
• Particles can break from fixed positions to move more freely
What is boiling?
• A liquid when heated turning to gas
• Particles have more kinetic energy
• Particles break away from position to escape from liquid
What is evaporation?
• Particles in liquid at different temperatures
• Some liquid turns to gas
• Some particles have enough kinetic energy to turn to gas
What is freezing?
• The opposite of melting
• Liquid turns solid
• Particles lose kinetic energy and move more slowly
• Particles get closer together and forces of attraction take over
What is condensation?
• The opposite of evaporation
• Gas turns to liquid
• Particles lose energy and come closer together
• Forces of attraction take over and particles stay together
What is sublimation?
• Solid turns straight to gas
What happens when you heat a gas?
• Particles gain energy and move faster
• Hit the walls more often with more force
• Pressure increases
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What happens when you compress a gas?
• Its pressure increases
• Particles in smaller space hit walls more often
What is Brownian motion?
• Random movement of particles in suspension
• Causes random molecular bombardment
• Seen in air when dust dances
• Diffusion is evidence e.g. food smells spreading through air
What is diffusion?
• Movement of particles
• From an area of high concentration to low
• Rate of diffusion depends on molecular mass
• The lower the mass of its particles, the faster a gas diffuses
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2. Experimental techniques
Apparatus
Purpose
Burette
Pipette
Measuring cylinder
Measurement of volume
Scales
Mass
Stopwatch
Time
Thermometer
Temperature
What is paper chromatography used for?
• To separate a mixture and identify its components
How to carry out chromatography:
• use a pencil line as reference line (pencil doesn’t move)
• add dots of ink
• dip filter paper in water
• furthest dot has the greatest solubility
How do you calculate the Rf value?
•
Rf = distance travelled by component
distance travelled by solvent
How can you separate colourless substances?
• Use a locating agent
• Apply to chromatogram
Why is purity important?
• Prevent contamination
• Needed for food
• Safety of drugs
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Describe methods of purification
Method
Purpose
Description
Filtration
• Separate solid from
liquid
• Solid is caught by filter
• Liquid passes through
Crystallisation
• Separate solid
dissolved in liquid
• Heat until saturated
• Cool so crystals form
• Filter solvent out
Evaporation
• For solids that don’t
• Keep heating solution
crystallise, dissolved in • Heat carefully until dry
liquids
Simple distillation
• Extract solvent from
solution
•
•
•
•
Heat solution in flask
Solvent evaporates
Taken to condenser
Purified solvent condenses
Fractional
distillation
e.g. petroleum,
ethanol
• Separate mixture of
liquids
• Using fractionating
column
•
•
•
•
•
Heat mixture in flask
Liquids have different boiling points
Lower boiling point liquid turns to gas
Taken to condenser
Liquid condenses
Paper
chromatography
• Separate mixture of
substances
• Mixture placed in centre of paper
• Water dropped on top
• Different substances diffuse at different rates
Electrolysis
• Purify more reactive
metals
• Ores more difficult to
decompose
•
•
•
•
•
Heating with
carbon
• Purify zinc, iron, lead
• Heat with carbon in blast furnace
• Metal oxides are reduced to give pure metal
• Limestone reacts with sand in the ore,
making slag
Using electrolysis tank
Metal dissolved in solution
Reduced (gain electrons) at cathode
Molten metal made
Oxygen gains electrons at anode and
bubbles off
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3. Atoms, elements and compounds
Proton
Neutron
Electron
Relative charge
1
0
-1
Relative mass
1
1
1/1836
What is the proton number (atomic number) of an atom?
• Number of protons in nucleus of atom
Define nucleon number (mass number)?
• Total number of protons and neutrons in nucleus
How is the periodic table arranged?
• Arranged in order of proton number
• Period number (across) shows how many electron shells
• Group number (down) shows number of electrons in outer shell
What is an isotope?
• Atoms of same element with same proton number
• Different nucleon (mass) number
• Either radioactive or non-radioactive
• Isotopes of same element have same properties
o Have same number of electrons in outer shell
Give two uses of radioactive isotopes
• Carbon dating using carbon-14
o Carbon-14 taken in during life
o Radioactive decay shows age of artefacts
• Treating cancer (radiotherapy) with cobalt-60
o Radiation from isotope kills cancer cells faster than healthy ones
Describe the arrangement of electrons around the nucleus
• 1st shell can accept 2 electrons
• 2nd shell can accept 8
• Shells are filled from 1st shell outwards
• Number of outer shell electrons dictates properties of atom
• Noble gases have full outer shell and very stable
What is an element?
• Contains only one type of atom
What is a mixture?
• Contains more than one element or compound not bonded together
What is a compound?
• Made of atoms of different elements bonded together
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Compare the properties of metals and non-metals
Metals
Non-metals
On the left of the periodic table
On the right of the periodic table
Good conductors of electricity and heat
Do not conduct
High melting and boiling points
Lower melting and boiling
Hard, strong, don’t shatter
Shatter, brittle
High density, malleable and ductile
Low density when solid
Form positive ions when they react
Form negative ions
Oxides are bases (alkali)
Oxides are acidic
What is an alloy (e.g. brass)?
• Mixture of a metal with other elements
How is an ion made?
• By gain or loss of electrons
What is an ionic bond?
• When a metal and a non metal form an ionic compound
• Bond formed between ions of opposite charge
How is an ionic bond made between elements in groups 1 and 7?
• Group 1 elements lose an electron to gain stable outer shell
o Become positively charged
• Group 7 elements gain electrons
o Become negatively charged
• Opposing charges attracted together to form bond
What is a lattice structure?
• Ionic compounds arranged regularly
• Alternating positive and negative charges
• Forms giant 3d structure
How is a covalent bond made?
• Pairs of electrons are shared
• Giving noble gas configuration (full outer shell)
• Occurs in H2 Cl2 H2O NH3 HCl
Describe electron arrangement in N2
• Nitrogen has 5 outer electrons
• Needs to share 3 more
• 3 pairs of electrons are shared in an N2 molecule
Compare ionic and covalent bonds
• Ionic compounds have higher melting and boiling points
• Ionic bonds are very strong, take a lot of heat to break bonds
• Ionic compound usually soluble in water
• Water molecules able to separate in to ions, making it soluble
• Ionic compounds conduct electricity when melted or dissolved
• Ions free to move so can conduct electricity
• Covalent compounds are more volatile
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Describe a giant covalent compound
• A macromolecule
• All atoms held together with covalent bonds
Describe the structure of silicon (IV) oxide (silicon dioxide)
• Each silicon atom bonds covalently to 4 oxygen atoms
• Each oxygen atom bonds to 2 silicon atoms
• Giant structure
What are the similarities between diamond and graphite?
• Very high melting point
• Hard structure
• Both are giant covalent macromolecules
• Each atom held in place by covalent bonds
Relate the structure of graphite to its uses
• Lubricant and conductor
• Formed of sheets - slide over each other easily (lubricant)
• Free electron per atom so carries charge (conducts)
Relate use of diamond to structure
• Used for cutting tools
• Hardest substance on earth
• Every atom bonded to surrounding atoms by four strong covalent bonds
• No free electrons and no ions
Describe metallic bonding
• Lattice of positive ions
• In a ‘sea of electrons’
Why are metals malleable and able to conduct electric current?
• Layers of ions can slide over one another
• Electrons free to move so can carry current
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4. Stoichiometry
Write the formula for water
• H 2O
Write the balanced equation for Hydrogen and Oxygen forming water
• 2H2 + O2 —> 2H2O
What is the formula for a compound made of Cl- and Ca2+
• CaCl2
Calcium is a solid, Cl2 is a gas and they react to make calcium chloride, a solid. Write the equation
• Ca(s) + Cl2(g) —> CaCl2(s)
What are the state symbols?
• Gas = (g)
• Liquid = (l)
• Solid = (s)
• Aqueous/in water = (aq)
How do you balance an equation?
• The same number of atoms of each element both sides
• To multiply the number of atoms, place a number in front of the element
Define relative atomic mass (Ar)
• Average mass of naturally occurring atoms of an element
• On a scale where 12 C has mass 12
Define relative molecular mass (Mr)
• Sum of relative atomic masses
Define the mole
• Amount of a substance that contains same number of units as the number of carbon atoms
in 12g of carbon-12
What is the Avogadro constant?
• The number of elements/molecules in a mole
• 6.02 x 1023
How do you calculate the number of moles in a given mass?
• Number of moles = mass / mass of 1 mole (Mr)
What volume does 0.5 moles of a gas occupy at RTP?
• 1 mole takes up 24 dm3
• So 0.5 x 24 = 12 dm3
What is an empirical formula?
• A formula that gives the simplest whole-number ratio of atoms in a compound
How is % purity calculated?
• % Purity = (mass of pure product / mass of impure product) x 100%
How is % yield calculated?
• % Yield= (actual mass obtained / calculated mass) x 100%
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Example questions using moles, mass and Mr
1. Find the Mr of MgCO3
=24+12+(3x16)
= 84
2. Find the mass of 0.2 moles of CaCO3
mass = Mr x moles
mass = 0.2 x (40+12+(3x16)
=20g
3. Find the number of moles in 54g of H2O
number of moles = Mass/Mr
moles = 54/18
moles = 3
4. Find the empirical formula of a compound which contained 5.85g K, 2.10g N and 4.8g O
K
N
O
5.85
2.1
4.8
39
14
16
0.15
0.15
0.3
0.15/0.15 = 1
0.15/0.15 = 1
0.3/0.15 = 2
1
1
2
Mass
Mr
Moles
divide by smallest
number
ratio
Answer = KNO2
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5. Electricity and chemistry
Define electrolysis
• Breakdown of a molten or aqueous ionic compound by electricity
Common electrolysis experiments:
Compound
Product at anode Product at cathode
(+)
(-)
Observations
Molten lead (II) bromide
Bromine
Lead
Lead collects on
cathode and drips off
Bromine gas at anode
bubbles off
Concentrated
hydrochloric acid
Chlorine
Hydrogen
Hydrogen and chlorine
gas bubbles off
Concentrated aqueous
sodium chloride
Chlorine
Hydrogen
Hydrogen and chlorine
gas bubbles off
Dilute sulphuric acid
Oxygen
Hydrogen
Hydrogen and oxygen
gas bubble off
Carbon electrode
Carry current but
unchanged during
reaction
Platinum electrode
Carry current but
unchanged during
reaction
Describe the principles of electrolysis
• Metals or hydrogen are formed at negative electrode (cathode)
• Non metals are formed at positive electrode (anode)
• Metal ions receive electrons (reduced) at cathode
• The non metal loses electrons (oxidised) at the anode
• Overall is a redox reaction – reduction at cathode, oxidation at anode
Remember OIL RIG!
• Oxidation Is Loss
• Reduction is Gain
• (of electrons)
What would the electrolysis products from CaF2 (calcium fluoride)
• Fluorine gas at anode
• Calcium at cathode
Describe the process of electroplating using a metal
• Use the metal as anode
• Item to be plated used as cathode
• Electrolyte is solution of soluble compound of the metal
• Metal ions reduced at cathode
• Cathode is plated with metal
List uses for electroplating
• Coating steel cans with tin
• Coating steel car bumpers with chromium
• Coating jewellery with silver
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Relate electrolysis to copper refining
• Anode of impure copper
• Electrolyte is copper (II) sulphate
• Cathode is pure copper
• Copper ions in solution reduced at cathode
• Copper from impure anode dissolves to replenish solution
• Impurities from anode drop to bottom
What happens to copper (II) sulphate with inert electrodes?
• Copper ions reduced at cathode
• Cathode becomes coated with copper
• Solution loses blue colour as copper ions reduced
What is a half equation?
• The reaction that occurs at each electrode
What are the half equations for electrolysis of molten lead bromide?
• Cathode: Pb2+ + 2e- —> Pb
• Anode: 2Br- —> Br2 + 2eList the uses of common metals and insulators
Material
Use
Reason
Copper
Electric wiring- at home, in cars
Very good conductor
Steel cored aluminium
Electric cables – around the country
Very good conductor, very
strong
Plastics
Insulation around electric
components – plugs, casings
Insulator
Ceramics
Discs to support large electric cables Insulator, tough
How is charge transferred during electrolysis?
• Negatively charged electrons move from negative terminal towards positive
• New electrons added to circuit at the cathode
• Electrons removed at anode
• Ions transfer charge in electrolyte to electrode of opposite charge
• Positive ions move to cathode
• Negative ions move to anode
Describe production of electrical energy in a simple cell
• Simple cell is two metals and electrolyte
• The redox reactions form a current
• More reactive metal is negative pole
• Negative pole produces electrons
• Electrons flow along wire forming current
• If ions in solution are less reactive than the anode, they accept electrons
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Outline manufacture of aluminium oxide
• Aluminium oxide is dissolved in molten cryolite
• Cryolite has a lower melting point
• Ore/cryolite at 950 C
• Inert carbon electrodes
• Cathode: 4Al3+ + 12e- —> 4Al (reduction)
• Anode: 6O2- —> 3O2 + 12eOutline manufacture of chlorine, hydrogen and sodium hydroxide from NaCl
• Concentrated aqueous sodium chloride used (brine)
• Chlorine gas made at anode: 2Cl- —> Cl2 +2e• Hydrogen gas made at cathode: 2H+ + 2e- —> H2
• Na+ and OH- left in solution – sodium hydroxide solution
• Sodium hydroxide solid extracted by evaporation
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6. Chemical energetics
What does exothermic mean?
• A reaction that causes release of heat energy
• Bond forming is exothermic
What does endothermic mean?
• Reaction uses heat
• Bond breaking is endothermic
e.g. CH4 + 2O2 —> CO2 + 2H2O forward reaction exothermic
• More energy released by making bonds made than energy used to break bonds S
• Supplement – you would be required to draw this and label it from data given
How is the energy of a reaction calculated?
• Identify the bonds present
• Calculate the energy needed to break the bonds (energy of bond x number)
• Calculate the energy released by making the bonds in the products
• Subtract the energy released from the energy needed
Describe release of heat energy by burning fuels
• Fuels are substances used to provide energy
• Chemical energy in fuel converted to another type (e.g. heat energy)
• Most fuels burned to make heat energy
What gas can be used as a fuel without making pollutants?
• Hydrogen
How is hydrogen used as a fuel?
• Hydrogen and oxygen combine to form water without burning
• Use a hydrogen fuel cell
• Overall equation: 2H2 + O2 —> 2H2O
• Hydrogen is oxidised at the negative pole
• Oxygen is reduced at the positive pole
How are radioactive isotopes used as fuel?
• Break down naturally, giving out radiation and energy
• Forced to break down faster in nuclear power stations
• Uranium-235 often used
• Energy released used to make steam, driving turbines
• Turbines generate electricity
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7. Chemical reactions
What is the difference between a chemical and a physical change?
• Physical changes don’t make new chemical substances
• Chemical changes take in or give out energy
• Chemical changes are harder to reverse
• Examples of physical changes: mixing, dissolving
• Example of chemical changes: burning gas
Factor
Effect on rate of
reaction
Explanation
Concentration
Increasing
Higher concentration
concentration of
= more particles to
reactant increases rate react
Particle size
Smaller particle sizes
create faster reactions
More surface area
available to react
Catalysts
Adding catalyst
increases rate
Catalysts let reaction
happen in way that
uses less energy
Temperature
Increased temperature
increases rate
Particles move faster,
have more energy
Explanation using
collision theory
Increased collision rate
More particles in a given
area more likely to collide
Increased collision rate
Molecules have more
kinetic energy so move
faster
More molecules have
enough energy (exceed
the activation energy) to
react
Investigate effect of different variables on rate of reaction
• Take a chemical reaction e.g. HCl reacting with zinc
• Keep 3 variables the same e.g. particle size, temperature, catalyst
• Alter the 4th variable e.g. concentration of HCl
• Measure speed of reaction by measuring volume of gas produced
Why are fine powders an explosion risk in industry?
• E.g. In flour mills
• Flour particles are very small – very large surface area
• Flour particles flammable
• Rate of reaction if catch fire is dangerously fast
Why are gases an explosion risk in coal mines?
• Methane and flammable gases in air
• Form explosive mix in air
• Spark can ignite a dangerously fast reaction
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What is the effect of light on the rate of photochemical reactions?
• Increased light intensity = Increased rate of reaction
• Light provides the energy for reaction
• Increasing light intensity speeds up the rate of reaction
Describe use of silver salts in photography
• Silver bromide decomposes where light strikes
• Causes reduction of silver ions to silver
• Silver stays on the film, giving a darker area
• Where brighter light strikes, decomposition is faster
Describe the photochemical reaction in photosynthesis
• Reaction between carbon dioxide and water
• In presence of chlorophyll and sunlight
• Producing glucose and oxygen
What does this
arrow represent?
• Reaction is reversible
What is a reversible reaction?
• Chemical reaction that occurs both forwards and backwards simultaneously
Describe what happens in a reaction at equilibrium
• In a closed system the reaction reaches equilibrium
• At equilibrium, the net amount of product and reactant stays same
• If change is made, system reacts to oppose the change
• Equilibrium is restored
What happens when you heat hydrated copper (II) sulphate?
• Blue powder (copper (II) sulphate) turns white (anhydrous copper (II) sulphate)
What happens when you add water to anhydrous copper (II) sulphate?
• White powder (anhydrous copper (II) sulphate) gets hot and turns blue (copper (II)
sulphate)
How do different factors affect reversible reactions?
Factor
Effect
Temperature
If forward reaction is exothermic:
Increasing temp = reduced yield of products
Concentration
If fewer molecules on right of the equation:
Increased concentration = increased yield of products
Pressure
If fewer molecules on right of the equation:
Increased pressure = increased yield of products
Define oxidation
• Loss of electrons
• Oxidation state used to name ions e.g. copper (II) sulphate
Define Reduction
• Gain of electrons
• Lowers oxidation state
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Define redox reaction
• Electron transfer between molecules
• Combination of reduction and oxidation
• If oxidation states change during a reaction, it is a redox reaction
Define oxidising agent
• Substances which oxidises another during redox reaction
Define reducing agent
• Substance that reduces another during redox reaction
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8. Acids, bases and salts
What are characteristic properties of acids?
• Turns litmus paper red
• React with metals to make a salt and hydrogen
• React with bases to make a salt and water
• React with carbonates to make a salt, water and carbon dioxide
• Turns methyl orange red
• Donates protons in aqueous solution
What are characteristic properties of bases?
• Turns litmus paper blue
• Turns methyl orange yellow
• React with acids to make a salt and water
• React with ammonium salts to drive out ammonia
• An alkali is a soluble base
• Accept protons in aqueous solution
What is the difference between a weak and a strong acid?
• Molecules of strong acids in solution all become ions
• Only some molecules in a weak acid become ions
• Strong acids carry more current
• Strong acids have lower pH
What is the difference between a strong and a weak base?
• Strong base in solution all become ions
• Only some molecules in a weak base become ions
• Strong base carry more current
• Strong base have higher pH
How is acidity and alkalinity measured?
• pH scale
• Neutral is pH7
• Acids have pH less than 7
• Bases have pH greater 7
• Universal indicator paper shows pH through colour
Why is soil pH important?
• Crops grow best when soil pH close to 7
• Acidic soil makes crops grow badly / not at all
• Soil can be treated with alkali to increase the pH
What is an acidic oxide?
• In general non metals react with oxygen to make acidic oxides
• E.g. carbon burns in oxygen to make carbon dioxide
• Carbon dioxide dissolves in water to make carbonic acid
What is a basic oxide?
• Most metals react with oxygen to make basic oxides
• Basic oxides can neutralise acid
• E.g. copper (II) oxide
What is an amphoteric oxide?
• Can be both acidic and basic
• Will react with both acids and bases
• E.g. aluminium oxide
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What is a neutral oxide?
• Is neither acidic nor basic
• Will not react with either acid or base
• E.g. carbon monoxide
How is a salt made?
• Mixing acid with either metals, soluble or insoluble bases or carbonates
Metal + acid —> salt + hydrogen
•
E.g. magnesium + hydrochloric acid —> magnesium chloride + hydrogen
Metal hydroxide + acid —> salt + water
•
E.g. Sodium hydroxide + hydrochloric acid --> sodium chloride + water
Metal oxide + acid —> salt + water
•
E.g. magnesium oxide + hydrochloric acid —> magnesium chloride + water
Metal carbonate + acid —> salt + water + carbon dioxide
•
E.g. potassium carbonate + nitric acid —> potassium nitrate + water + CO2
Making salts table
Example process
Examples
Metal
Dissolve metal in dilute acid
Remove excess by filtering
Evaporate and cool to crystallise
Magnesium
Aluminium
Zinc
Iron
Insoluble base
Add to dilute acid and heat
Keep adding base until no more dissolves
Evaporate and cool to crystallise
Copper (II) oxide
Copper (II) carbonate
Soluble base
Mix two solutions together
Determine where neutral is by titration
Use indicator to show where neutral is
Evaporate and cool to crystallise
Sodium hydroxide
Potassium hydroxide
ammonia
How do you make insoluble salts?
• By precipitation
• Some ions are spectators – do not take part
• Two solutions mixed together
• Insoluble salt forms as precipitate
• Use filtration to separate from solution
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What tests are used to identify aqueous cations?
Ion
Add aqueous sodium hydroxide
Add aqueous ammonia
Aluminium
White precipitate forms
Precipitate dissolves if more added
White precipitate forms
Adding more has no effect
Ammonium
Ammonia gas given off
No reaction
Calcium
White precipitate forms
Adding more has no effect
No precipitate, or very slight
white one
Chromium (III)
Grey-green precipitate
Dissolves if add more- grey-green
solution
Grey-green precipitate forms
Adding more gives purple
solution
Copper (II)
Pale blue precipitate
Adding more has no effect
Pale blue precipitate
Dissolves if add more- deep blue
solution
Iron (II)
Pale green precipitate
Pale green precipitate
Iron (III)
Red-brown precipitate
Red-brown precipitate
Zinc
White precipitate
Dissolves if add more
White precipitate
Dissolves if add more
What is the flame test?
• Used to determine non-aqueous cations
• Burn solid salt in blue flame
• Lithium ion burns red
• Sodium ion burns yellow
• Potassium ion burns lilac
• Copper ion burns blue-green
How do you detect anions?
Ions
Test
Result
Halides (chloride, bromide,
iodide)
Equal volume dilute nitric acid
Add aqueous silver nitrate
White = chloride
Cream = bromide
Yellow = iodide
Sulfate (SO42-)
Equal volume dilute HCl
Add barium nitrate
If sulphate present – white
precipitate forms
Sulfite (SO32-)
Add equal volume dilute HCl
Heat gently
Sulfur dioxide given off
(Potassium manganate turns
from purple to colourless)
Nitrate (NO3-)
Add small amount dilute
sodium hydroxide
Add aluminium foil
Heat gently
Ammonia gas given off if
nitrate present
Carbonate ions (CO32-)
Add dilute HCl
Mixture bubbles and gives off
CO2
CO2 turns limewater milky
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How do you identify ammonia gas?
• Colourless alkaline gas
• Strong smell
• Hold damp red litmus paper in gas
• Paper turns blue
How do you identify carbon dioxide?
• Bubble through limewater
• Limewater turns milky
How do you identify chlorine gas?
• Green poisonous gas
• Hold damp indicator paper in gas (use fume cupboard!)
• Paper turns white
How do you identify hydrogen gas?
• Colourless gas, reacts violently with oxygen when lit
• Collect gas in tube, hold lighted split to it
• Burns with squeaky pop
How do you identify oxygen?
• Colourless gas
• Collect gas in tube
• Hold glowing splint to it
• Splint re ignites
How do you identify sulphur dioxide?
• Colourless, poisonous acidic gas
• Soak filter paper in acidified aqueous potassium manganate (VII)
• Paper goes from purple to colourless
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9. The periodic table
What is the periodic table?
• Method of classifying elements
• Can be used to predict properties of elements
Describe the change from metallic to non-metallic elements across a period?
• Metals lie to the left
• Non metals lie on the right
• Transition elements are in the middle
What is valency?
• Valency = number of outer shell electrons
How does group number relate to the element’s character?
• All elements in the same group have same valency
• Elements with same group share similar characteristics
• Number of outer shell electrons dictates whether metallic or non metallic
Describe elements in group I
• Contains lithium, sodium and potassium
• Alkali metals
• Soft metals - increasing softness down the group
• Density increases down the group
• Melting point decreases down the group
• Rate of reaction with water increases down the group
Describe the elements in group VII
• Halogens – e.g. chlorine, bromine, iodine
• Diatomic non-metals
• Trend in colour – gets deeper down group
• Trend in density – increases down group
• Reactivity decreases down the group - more reactive halogens will displace a less reactive
halogen from a solution of halide
What are the transition elements?
• Metals with high densities, high melting points
• Form coloured compounds
• Often act as catalysts
• Have variable oxidation states
What are the noble gases?
• In group VIII (also known as group 0)
• Unreactive
• Monoatomic
• Gases
• Have full outer shell of electrons
• No need to gain or lose electrons
What are noble gases used for?
• Providing inert atmosphere
• Argon in lamps
• Helium in balloons
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10. Metals
What are the general physical properties of metals?
• Ductile
• Malleable
• Conduct electricity and heat
• High melting points
• High density
What are the general chemical properties of metals?
• Less reactive than group I
• No clear trend in reactivity
• Most form coloured compounds
• Most can form ions with different charges
• Can form more than one compound with another element
• Can form complex ions
• Oxides/hydroxides react with dilute acids to form a salt
• React with oxygen to form basic oxides
Why are alloys used instead of pure metals?
• Alloy = mixture of metal with small amounts of other substances
• Improve properties of original
• E.g. stainless steel = chromium and nickel mixed with iron
The reactivity series (reactivity decreases downwards)
Metal
Reaction with water / steam
Reaction with HCl
Potassium
Very violent with water
Explosively fast
Sodium
Violent with water
Explosively fast
Calcium
Less violent with cold water
Very vigorous
Magnesium
Very slow with cold water,
vigorous with steam
Vigorous
Zinc
Quite slow with steam
Quite slow
Iron
Slow with steam
Slow
Lead
Slow, only if acid concentrated
Copper
No reaction
No reaction
Silver
“
“
Gold
“
“
How does reaction with carbon show reactivity?
• Carbon is more reactive than some metals
• Carbon reduces their oxides to the metal
How does reaction with another metal oxide show reactivity?
• If more reactive, the metal reacts with oxygen to form oxide
• A metal will reduce the oxide of a less reactive metal
How does reaction with ions of other metals in solution show reactivity?
• A metal displaces a less reactive metal
• From solutions of its compounds
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What is the effect of heat on hydroxides of a metal?
• Hydroxides except sodium and potassium decompose
• Produce oxides and water
What is the effect of heat on carbonates of a metal?
• Carbonates except sodium and potassium decompose
• Produce oxide and carbon dioxide
What is the effect of heat on nitrates of a metal?
• Except sodium and potassium nitrate
• Decompose to oxide, nitrogen dioxide and oxygen
• Nitrates of sodium and potassium form nitrites and oxygen
Why is aluminium apparently unreactive?
• Reacts rapidly with oxygen
• Thin coat of aluminium oxide
• Forms a barrier against further corrosion
How are different metals extracted from their ores?
• Most reactive metals extracted by electrolysis
• Least reactive metals occur naturally as pure element
• Metals in the mid range can be heated with carbon or carbon monoxide
• Carbon reacts with oxides of metal less reactive than itself, leaving metal
What are the essential reactions to extract iron from hematite?
• C + O2 —> CO2 produces heat
• C + CO2 —> 2CO makes carbon monoxide
• Fe2O3 + 3CO —> 2Fe + 3CO2 iron oxide reduced to iron
• CaCO3 —> CaO + CO2 limestone produces calcium oxide to remove sand from ore
• CaO + SiO2 —> CaSiO3 calcium silicate floats on iron – molten slag
How is iron converted to steel?
• Molten iron from blast furnace poured into furnace
• Oxygen added, which reacts with carbon, sulphur and phosphorous impurities in iron
o Carbon dioxide and sulphur dioxide released as gases
o Phosphorous (V) oxide is a solid
• Calcium oxide added
• Reacts with silicon dioxide and phosphorous oxide impurities
• Creates a slag that is skimmed off
• Carbon added to increase strength
How is aluminium extracted?
• From bauxite ore
• By electrolysis
• Aluminium ore dissolved in molten cryolite
• Reaction at cathode: 4Al3+ + 12e- —> 4Al (reduction)
• Anode: 6O2- —> 3O2 + 12e- (oxidation)
What are advantages and disadvantages of recycling metals?
Metal
Advantages
Iron/steel
Can be recycled as new steel
Aluminium
New aluminium expensive to extract
Disadvantages
Many different alloys, difficult to recycle
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How is zinc extracted?
• Zinc blende is mainly zinc sulphide ZnS
• Roasted in air to give zinc oxide and sulphur dioxide
• Reduced with carbon monoxide in a furnace
• ZnO + CO —> Zn + CO2
• Mixture separated by fractional distillation
• OR using electrolysis giving a purer product
What is aluminium used for?
• Aircraft manufacture due to strength and low density
• Food containers due to corrosion resistance, non toxic
What are the uses of copper?
• Electrical wiring – excellent conductor
• Cooking utensils – excellent heat conductor
What is mild steel used for?
• Car bodies
• Machinery
• Hard and strong
What is stainless steel used for?
• Chemical plant
• Cutlery
• Hard and rustproof
What is zinc used for?
• Galvanising – coating iron to protect from corrosion
• Making brass – as alloy with copper. Is hard, strong and shiny
• Brass used for door locks, keys, musical instruments
How can properties of iron be changed?
• Controlled use of additives
• Form different steel alloys with different properties
• Depending on requirements
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11. Air and water
What are the chemical tests for water?
• Turns white anhydrous copper (II) sulphate blue
• Turns blue cobalt (II) chloride paper pink
• Both changes can be reversed by heating
How is water supply treated?
• Find a clean source, screen used to trap large particles
• Coagulant added to make particles stick together
• Flotation tanks make particles float so can be skimmed off
• Filtered to remove smaller particles and smells
• Chlorine added to kill bacteria
• Stored
What is water used for?
• Home use – drinking, cooking, washing
• Farms – animals and watering crops
• Power stations – heated to make steam to drive turbines
• Industry – solvent, washing, cooling hot reaction tanks
What are consequences of inadequate water supply?
• Infections from dirty water – diarrhoea, cholera, typhoid
• Poverty and starvation – can’t water crops
What is the composition of air?
• Approx. 78% nitrogen
• 21% Oxygen
• Remainder is mixture of noble gases and carbon dioxide
What are common air pollutants?
Pollutant
Source
Effect
Carbon monoxide
Incomplete combustion of carbon
Poisoning – death from
oxygen starvation
Sulphur dioxide
Sulfur-containing fossil fuel
combustion
Respiratory problems
Acid rain
Oxides of nitrogen
Car engines
Respiratory problems
Acid rain
Lead compounds
Leaded petrol
Damage to children’s brains
Kidney and nerve damage
Why is acid rain a concern?
• Destruction to buildings
• Erodes stone
• Damages forests
What conditions cause iron to rust?
• Oxygen
• Water
• Salt speeds up the process
How can rusting be prevented?
• Keep oxygen out with paint
• Grease
• Coat with another metal e.g. galvanising
• Sacrificial protection
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How are oxygen and nitrogen separated from liquid air?
• Cooled to liquid
• Carbon dioxide and water vapour removed
• Fractional distillation
• Gases boil and taken off at different temperatures
What happens to oxides of nitrogen from car engines?
• Produced when petrol burned
• Reduced in catalytic converter
• Example: 2NO —> N2 + O2
Describe and explain sacrificial protection
• More reactive metal attached to metal to be protected
• Oxidises preferentially
Describe and explain galvanising
• Coat a metal with zinc
• Resists corrosion
• Offers sacrificial protection if coating cracks
Why is nitrogen needed in fertilisers?
• Plants require it to produce chlorophyll and proteins
Why is phosphorous needed in fertilisers?
• Root growth
• Ripening of crops
Why is potassium needed in fertilisers?
• Produce proteins
• Disease resistance
How is ammonia displaced from its salts?
• Heat any ammonia compound
• With a strong base
• Base displaces ammonia from compound
What are the essential conditions for ammonia manufacture (in the Haber process)?
• Nitrogen from air
• Hydrogen from cracking hydrocarbons or reacting methane with steam
• Reversible reaction so yield can be altered
• Pressure at 200 atm for good yield but safe conditions
• Iron catalyst – speeds up rate, doesn’t increase yield
• 450 celsius high enough for good rate, low enough for good yield
What are greenhouse gases?
• Carbon dioxide and methane
• Can contribute to climate change
• Increase amount of reflected sunlight within the atmosphere
How is carbon dioxide formed?
• Product of complete combustion of carbon containing substances
• Product of respiration
• Product of reaction between acid and carbonate
• Thermal decomposition of a carbonate
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Name two sources of methane
• Decomposition of vegetation
• Waste gases from animal digestion
Describe the carbon cycle
• Combustion of fuels, bacteria and respiration release CO2 in to the air
• CO2 in the air taken up by photosynthesis, forms part of plants
• Plants eaten by animals, which respire
• When plants die, carbon stored as fossil fuels within earth
• CO2 in air dissolves in to ocean
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12. Sulfur
List the sources of sulphur
• Around rims of volcanoes
• Underground beds in Mexico, Poland and USA
• In metal ore ‘galena’
• Sulfur compounds in fossil fuels
List the uses of sulphur
• Manufacture of sulphuric acid
• Vulcanising (toughening) rubber
• In dyes, cosmetics, dugs, pesticides, matches, shampoo, lotions
• Added to cement to make sulphur concrete – acid resistant
• Bleach for wood pulp to make paper
• Food preservative (by killing bacteria)
How is sulphuric acid manufactured?
• By the contact process
• Using sulphur (OR sulphur dioxide), air and water
• 1st sulphur burned in oxygen S + O2 —> SO2
• Mixed with more air
• Passed over catalyst vanadium (V) oxide at 450 degrees
• Makes sulphur trioxide 2SO2 + O2 —> 2SO3 (reversible)
• Dissolved in concentrated sulphuric acid
• Thick fuming liquid – oleum
• Mixed with water
• Concentrated sulphuric acid H2O + SO2 —> H2SO4
Name properties of sulphuric acid
• Concentrated sulphuric acid is a dehydrating agent
• Gives out lots of heat when mixed with water
Name uses of sulphuric acid
• Car batteries
• Fertilisers
• Paints, pigments and dyes
• Fibres, plastics
• Soaps, detergents
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13. Carbonates
How is lime (calcium oxide) manufactured?
• Limestone (calcium carbonate) heated
• CaCO3 —> CaO + CO2
• Called thermal decomposition
• Reversible reaction
List the uses of lime (calcium oxide) and slaked lime (calcium hydroxide)
• Neutralise acidity in lakes and soils
• Remove sulphur from waste gases at power plants (flue gas desulfurisation)
• Ca(OH)2 + SO2 —> CaSO3 + H2O
List the uses of calcium carbonate
• Making iron by reacting with sand in iron ore to make slag
• Mixed with clay, heated and ground to make cement
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14. Organic chemistry
Name beginning
Number of carbons
meth-
1
eth-
2
prop-
3
but-
4
pent-
5
hex-
6
Name ending
Type of molecule
-ane
Alkane
-ene
Alkene
-ol
Alcohol
-oic acid
Carboxylic acid
Draw the structure of basic alkanes
Alkanes. Number Name
of Carbon Atoms
Displayed Formula
1 methane
2 ethane
3 propane
4 butane
5 pentane
Draw the structure of basic alkenes
Alkenes. Number Name
of Carbon Atoms
Displayed Formula
1 n/a
2 ethene
3 propene
4 butene
5 pentene
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Draw the structure of basic alcohols
Alcohols. Number of
Carbon Atoms
Name
Displayed
Formula
1 methanol
2 ethanol
3 propanol
Draw the structure of basic carboxylic acids
Carboxylic acids. Number
of Carbon Atoms
Name
Displayed
Formula
1 methanoic acid
2 ethanoic acid
3 propanoic acid
Name the fossil fuels
• Coal
• Natural gas
• Petroleum
What is the main part of natural gas?
• Methane
What is petroleum?
• Mixture of hydrocarbons
• Can be separated by fractional distillation
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Name the fractions of petroleum
• Refinery gas for cooking and heating
• Gasoline/petrol for cars
• Naptha for making chemicals
• Parrafin for jet fuel
• Diesel oil/gas for diesel engines
• Fuel oil for ships and home heating
• Lubricant for lubrication, waxes and polishes
• Bitumen for road making
What happens to the properties, as molecules get larger?
• Boiling points increase
• Viscosity increases
• Become less flammable
What is a homologous series?
• Family of similar compounds
• Similar chemical properties
• Same functional group
• Have same general formula
What is structural isomerism?
• Compounds with same formula but different structure
• Have slightly different properties
• The more carbons, the more isomers are possible
What is an alkane?
• Hydrocarbon containing carbon-carbon single bonds
• Names end in –ane (e.g. ethane)
• General formula CnH2n+2
What are the properties of alkanes?
• Boiling point increases with chain length
• Saturated = all single bonds
• Generally unreactive, except for burning
• Used as fuels, burn easily in oxygen releasing heat
• Produce carbon monoxide when burned without enough oxygen
Describe substitution reactions of alkanes and chlorine
• Chlorine atoms take place of a hydrogen
• With enough chlorine, all hydrogen atoms will be replaced
• Requires light to break bonds - a photochemical reaction
What is an alkene?
• Hydrocarbon containing carbon-carbon double bonds
• Names end in –ene ( e.g. ethene)
• Double bond is functional group
• Have the general formula CnH2n
What are the properties of alkenes?
• Can be manufactured by cracking
• Are unsaturated due to double bonds
• More reactive than alkanes
What is cracking?
• Alkenes are made from alkanes by cracking
• Releases hydrogen
• E.g. ethane —> ethene + Hydrogen
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What is a test for unsaturation?
• Add bromine water (orange)
• If a C=C bond is present, turns colourless
Describe addition polymerisation
• Addition reactions of alkenes
• Add on to each other
• Make carbon compounds with very long chains
How is poly(ethene) made?
• Example of addition polymerisation
• Ethene molecules are monomers
• Undergo addition reaction to make a polymer
Describe the reactivity of alkenes
• More reactive than alkanes due to double bond
• Undergo addition reactions
• Double bond breaks and atoms can be added
• Addition reaction turns unsaturated alkene in to saturated compound
How do alkenes react with bromine?
• Addition reaction
How do alkenes react with hydrogen?
• Addition reaction
How do alkenes react with steam (water)
• Addition reaction
What is an alcohol?
• Contain an –OH group
• -OH is the functional group
• Names end in –ol (e.g. ethanol)
• Is not a hydrocarbon
• Have the general formula CnH2n+1OH
How is ethanol manufactured?
• By fermentation using yeast (anaerobic respiration)
• By hydration of ethene through addition reaction
Compare manufacture methods of ethanol
• Fermentation uses renewable resources
• But needs a lot of material and is slow
• Fermentation requires fractional distillation to separate
• Hydration is fast and can run continuously
• Hydration produces pure ethanol
• But uses ethene from oil – non renewable
What is ethanol used for?
• Solvent e.g. for glues, perfumes, inks
• Fuel e.g. for car engines
What is a carboxylic acid?
• Contain a –COOH group
• -COOH is functional group
• Names end in –oic acid (e.g. ethanoic acid)
• Have general formula CnH2nO2
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What are the properties of ethanoic acid?
• Acidic – turns litmus red
• Reacts with metals, bases and carbonates to form salts
• Weak acid - partially dissociates in water
• Reacts with alcohols to form esters
• Through a condensation reaction
• A weak acid
How is ethanoic acid made?
• By oxidation of ethanol
• By fermentation
• By using an oxidising agent e.g. potassium manganate (VII)
How does a carboxylic acid react with an alcohol?
• Produces compounds called esters
• Two molecules join to make larger molecule, releasing water
• Called a condensation reaction
• Requires a catalyst
What is a polymer?
• Large molecule built up from small units (monomers)
• Different polymers have different units and/or linkages
Name some typical uses of plastics
• Drinks bottles
• Bags
• Packaging
• Pipes/hoses
• Insulation for electrical wires
Name some uses of Nylon
• Ropes
• Fishing net
• Tents
• Curtains and carpets
• Parachutes
• Seat belts
Name some uses of Terylene
• Clothing
• Thread
How do non-biodegradable plastics cause pollution problems?
• Don’t break down or rot
• The pile of waste grows as more is made and thrown away
• Fill up landfill
• Birds, fish and mammals choked if try to eat them
• Cannot be digested so sit in stomach of animals - leads to starvation
• Clog up drains and sewers, causing flooding
• Collect in rivers and harm fish
• Unsightly in environment and discourage tourism
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Describe the difference between condensation and addition polymerisation
Condensation
Addition
Starting monomers
Two types, not with C=C
bonds
One type with C=C bonds
Bond made
Between functional groups at
each end of molecule
C-C between monomers
Products of reaction
Polymer and one another
Polymer only
How to deduce a monomer from an addition polymer
• Identify the repeating unit with two carbon atoms side by side
• Draw the unit out separately
• Place a double bond between the carbon atoms
• This is the monomer
How is Nylon made?
• Condensation polymerisation
• One monomer has an NH2 group at each end
• One monomer has a COCl group at each end
• The N atom and the C atom form an amide bond at one end each
• HCl is eliminated
• The reaction then occurs at the other end of each molecule
• Forming a polymer – a polyamide
How is Terylene made?
• Condensation polymerisation
• One monomer has a carboxyl (COOH) group at each end
• One monomer has an alcohol (OH) group at each end
• A carbon atom and an oxygen atom from an ester linkage
• A water molecule is eliminated
• Polymer is formed – a polyester
Name two natural polymers found in food
• Proteins
• Carbohydrates
What is the main similarity and main difference between proteins and nylon?
• Similarity - Same amide linkage
• Difference - Made from different units
Draw the basic structure of proteins
• Amino acids
• Amide linkages
Describe hydrolysis of proteins
• Proteins broken down in to amino acids
• Catalysed by proteases
Describe a complex carbohydrate
• Large number of sugar units
• Joined by condensation polymerisation
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Describe the hydrolysis of complex carbohydrates
• Hydrolysis by acids or enzymes
• Gives simple sugars
• E.g. starch broken down with amylase as catalyst
Describe the fermentation of simple sugars
• Breakdown of glucose
• Requires enzyme catalyst
• Produces ethanol and carbon dioxide
How is chromatography used to separate hydrolysis products?
• Can show which amino acids were in a protein or which sugars were in a carbohydrate
• Amino acids and sugars are colourless
• Need locating agents
• Can use enzymes, at body temperature and pH
• Or heated with acid
• Drop on to chromatography paper
• Compare products with known substances
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