Studied by 1 person
How to test for carbonate ions?
Add dilute acid
Bubbles should form
To test bubbles are carbon dioxide, test with limewater
Solution should turn milky/cloudy
How to test for hydroxide precipitates?
Add dilute sodium hydroxide solution
Observe and record colour of precipitate formed
What is the corresponding hydroxide precipitate colour for the following metal ions: Aluminium, Calcium, Magnesium, Copper, Iron(II), Iron(III)
Aluminium - White (though dissolves/loses colour in excess)
Calcium - White
Magnesium - White
Copper - Blue
Iron(II) - Green
Iron(III) - Brown
How to test for sulfate ions?
Add a few drops of dilute hydrochloric acid
Add a few drops of dilute barium chloride
If sulfate ions are present, white precipitate should form (barium sulfate)
Why is HCl added first in test for sulfate ions?
To remove any carbonate ions which may be present
Carbonate ions also produce a white precipitate when reacted with barium chloride solution
How to test for halide ions?
Add dilute nitric acid
Add dilute silver nitrate
Observe colour of precipitate formed- this corresponds with type of halide
Why is nitric acid added in first in test for halide ions?
Removes carbonate ions which may be present
Carbonate ions also produce a white precipitate when reacted with silver nitrate solution
What is the corresponding precipitate colour for each halide?
Chloride - White
Bromide - Cream
Iodide - Yellow
How to do flame test?
Place wire loop in HCl to clean
Check wire is clean by placing in blue flame- wire is only clean if there is no colour produced
Dip loop into solid sample and place in blue flame
Observe and record colour produced
What are the colours produced in flame test for each of following metal ions: Lithium, Sodium, Potassium, Calcium, Copper
Lithium - Crimson
Sodium - Yellow
Potassium - Lilac
Calcium - Orange-red
Copper - Green
What will happen if a mixture undergoes a flame test?
As each ion produces an individual colour, some flame colours may not be clearly visible and may be hidden by other colours
What is sustainable development?
Development which meets need of current generations without compromising needs of future generations.
What is potable water? Why is it impure?
Water that is safe to drink, containing low levels of dissolved substances. It cannot be pure due to these dissolved substances.
In the UK, how is potable water produced?
Choosing source of freshwater
Passing through filter beds
Sterilisation using UV beds, chlorine, ozone
Explain desalination by reverse osmosis
Water, at a high pressure, is passed through membranes which allow water molecules in, but not other ions
This leaves behind lots of waste water and so is largely inefficient
Membranes are expensive and process requires lots of energy
Explain desalination through distillation
Water is heated so that steam is produced to be condensed- this is potable water
The waste water left behind is very salty and difficult to dispose of without damaging marine ecosystems
Process requires lots of energy- both for evaporating and condensing
How can corrosion be stopped?
Coating- applying coating that acts as a barrier (greasing, painting, electroplating). If damaged, metal will become corroded
Sacrificial method- a more reactive metal covers the less reactive method
Galvanising- metal is sprayed with more reactive metal which initially acts as a barrier but if damaged, will act as a sacrificial metal.
What two things are necessary for rusting?
Water
Oxygen
Bronze and brass: Alloys of _________ and uses
Bronze: copper and tin
Used to make statues, bells, coins
Brass: copper and zinc
Used to make musical instruments, doorknobs, locks, taps
Gold: Properties
Very soft, malleable
Unreactive
Resists corrosion
Alloy steels: Elements, properties, uses
High carbon steel
Contains carbon
Strong, brittle
Used in construction
Low carbon steel
Contains carbon
Softer, easily shaped
Used in car body panels
Stainless steel
Contains chromium and nickel
Hard, resistant to rusting
Used in cutlery
Glass: Soda-lime and Borosilicate
Soda-lime glass: made in heating a mixture of sand, sodium carbonate, and limestone.
Borosilicate glass: made from sand and boron trioxide
What two things do properties of polymers depend on?
The monomers they are made from
The conditions under which they are made
Polymers: Properties, Structure and Uses
Low density Poly(ethene)
Flexible, unreactive, can be made into film
Molecules are arranged randomly, polymer chains are branched
Used for bubble wrap and carrier bags
High density Poly(ethene)
Strong, flexible, resists shattering, resists chemical attack
Molecules are lined up more closely, less branching
Used for plastic bottles, pipes, buckets
Thermosoftening and Thermosetting plastics
Thermosoftening
Melt when heated
Used in most everyday plastics
Can be recycled
Does not have any covalent bonds
Thermosetting
Do not melt when heated
Used to make electric plugs
Has covalent bonds
Composite materials, Reinforcement and Matrix: Definitions
Composite - a material made from two or more materials
Reinforcement - The material making up the bulk of a composite
Matrix - What binds the reinforcement together
Composite Materials: reinforcements and matrices
Reinforcement concrete
Reinforcement: Steel
Matrix: Concrete
Fibreglass
Reinforcement: Glass fibres
Matrix: Polymer resin
Carbon fibre reinforced polymer
Reinforcement: Carbon fibres
Matrix: Polymer resin
Chipboard
Reinforcement: Wood chips
Matrix: Resin glue
Fibreglass and carbon fibre reinforced polymer: Properties
Fibres are
low density
strong in tension
flexible
Resin is
stiff
Composites are
strong
stiff
lightweight
Reinforced concrete: Properties
Strong in tension
Strong in compression
Flexible
Glass ceramics: Properties
Transparent
High melting point
Stiff and brittle
Poor electrical conductivity
Poor heat conductivity
Relatively poor strength
Clay ceramics: Properties
Opaque
High melting point
Stiff and brittle
Poor electrical conductivity
Poor heat conductivity
High strength under compression
Metals: Properties
Shiny
High melting point
Malleable
Good electrical conductivity
Good heat conductivity
High strength
Plastics: Properties
Various appearances
Low melting point
Usually flexible
Poor electrical conductivity
Poor heat conductivity
Relativity low strength
Composites: Properties
Usually opaque
High melting point
Usually stiff and brittle
Poor electrical conductivity
Poor heat conductivity
Usually very high strength
Where can hydrogen and nitrogen be sourced from?
Nitrogen is found from the air
Hydrogen is found in natural gas
Haber process: Ideal conditions
Temperature: 450°C
Catalyst: Iron
Pressure: 200atmospheres
What fertilisers can ammonia make?
When involved in neutralisation reactions, produces ammonium ion
When oxidised, makes nitric acid
When neutralised by nitric acid, forms ammonium nitrate
Raw materials that can be mined for fertilisers
Potassium sulfate
Potassium chloride
Phosphate rock- can be used to make fertilisers but is insoluble so cannot be used directly
Reactions of phosphate rock for formation of fertilisers
With nitric acid, produces calcium nitrate and phosphoric acid
With sulfuric acid, produces single superphosphate
With phosphoric acid, produces triple superphosphate
What is the proportion of gases in our atmosphere?
78% Nitrogen
21% Oxygen
1% Argon
0.03-0.04% Carbon dioxide
How did the proportion of oxygen in the atmosphere increase and carbon dioxide decrease?
Photosynthesis of algae and plants reduced CO2 levels and increased O2 levels
Formation of sedimentary rocks and fossil fuels reduced amount of carbon in atmosphere
Explain the greenhouse effect
Solar radiation passes through atmosphere to be absorbed by the Earth, which reflects infrared radiation.
Some of this radiation returns to space, but some is absorbed by greenhouse gases, which in trapping the heat, warm up the Earth
The increase in greenhouse gases in our atmosphere increases this effect.
Which human activities increase the amount of greenhouse gases in the atmosphere?
Deforestation- reduces intake of CO2 in photosynthesis and burning releases CO2
Burning fossil fuels- combustion releases CO2 as product
Farming cattle and rice releases methane
Name some effects of global warming
Melting of icecaps and glaciers
Sea level rise
Habitat change
Rainfall patterns changing
Species distribution and migration patterns changing
Actions to take to reduce carbon footprint
Individual: using public transport, boycotting unsustainable brands, recycling, install solar panels
Local: petitioning and writing letters to council, car sharing, support local farmers by buying only locally-sourced produce
Why might actions to reduce your carbon footprint be difficult to take?
Cost
Convenience
Accessibility
Changes to lifestyle
What are the properties and effects of atmospheric pollutants?
Carbon monoxide: toxic, colourless, odourless
Sulfur dioxides and oxides of nitrogen: cause acid rain and respiratory problems in humans
Particulates: cause global dimming and respiratory problems in humans
What is the difference between a chemical pure substance and a pure substance in everyday speak?
A chemical pure substance is a single element or compound
An everyday pure substance is one that is in its natural state, and contains no additives
What is a formulation? Name some examples
A formulation is a mixture that has been designed as a useful product
Examples include fuels, cleaning products, paints, alloys, fertilisers, foods, and medicines.
How would you carry out a chromaography practical?
Draw a pencil line on filter paper and place spot of mixture on line
Lower paper into solvent and wait for it to travel up the paper
Analyse chromatogram- mixture should separate out into different substance spots
What is the mobile and stationary phase and how does it affect how far the solvent will travel?
The mobile phase is the solvent (water or ethanol)
The stationary phase is the filter paper
If the substance spends more time in the mobile phase/is more soluble, it will be carried farther up the paper
How can you calculate the Rf value?
Rf = distance travelled by substance / distance travelled by solvent
How to test for common gases: oxygen, hydrogen, carbon dioxide, chlorine
Hydrogen: Place burning splint into tube, should produce squeaky pop sound
Carbon dioxide: Bubble through limewater, mixture should turn milky/cloudy
Oxygen: Place glowing splint into tube, should relight
Chlorine: Bleaches damp litmus paper white
Alkanes: General formula and first four in series
Cn H2n+2
Methane
Ethane
Propane
Butane
With increasing molecular size, how do boiling points, viscosity, and flammability change?
Higher boiling points
More viscous
Less volatile
Less flammable
Darker colour
Fractional distillation: Explain the process
Mixture is evaporated and is passed into fractionating column where it is hottest at bottom and grows cooler the further up you go
Hydrocarbons condense as soon as they reach a temperature lower than their boiling point, at which they will be collected
Therefore hydrocarbons with the highest boiling points condense first and are collected near the bottom, grouped with other hydrocarbons with similar boiling points
Cracking Conditions: Steam and Catalytic
Catalytic: turned into gas, passed over hot, powdered, aluminium oxide catalyst, temperatures of 550°C
Steam: turned into gas and mixed with steam, temperatures of over 850°C
Alkenes: General formula and first four in series
Cn H2n
Ethene
Propene
Butene
Pentene
Reaction with bromine water: Results
Alkenes turn bromine water colourless- they are more reactive due to their double bond
Alkanes have no effect on colour of bromine water- they are less reactive due to being saturated
Cracking: Product use
Useful as fuels
Alkenes can act as a starting material for other chemicals and produce polymers
Reaction of alkenes with oxygen
Reacts the same way that all hydrocarbons do but tends to burn with a smoky flame due to incomplete combustion
Hydrogenation: Conditions and reaction
Alkene + hydrogen → alkane
Requires a catalyst
Hydration: Conditions and reaction
Alkene + water (steam) → alcohol
Temperature of approximately 300°C
Requires catalyst
Alkene and halogen reaction
Alkene + halogen → halogenoalkene
Spontaneous
Alcohols: Functional group and first four in series (+ uses)
All have functional group -OH
Methanol - used as chemical feedstock
Ethanol - fuel, solvent, alcohol in drinks
Propanol - solvent/fuel
Butanol - solvent/fuel
Fermentation: Reaction and conditions
Glucose → ethanol + carbon dioxide
Catalyst - enzymes within yeast
Sugars dissolved in water and mixed with yeast (provides glucose)
Warm temperatures (25-35°C)
Air lock so that air cannot get in (anaerobic process) but CO2 can leave
Alcohols: Reaction with sodium
Sodium + *ethanol → sodium ethoxide (salt) + hydrogen
*Although ethanol is used here, other alcohols undergo similar reactions
Bubbles of hydrogen gas are produced and the liquid contains sodium ethoxide
Alcohols: Solubility in water
Mix easily to produce a solution
However, solubility decreases as length of alcohol increases
Alcohols: Oxidation
ethanol + oxidising agent → ethanoic acid + water
*Although ethanol is used here, other alcohols undergo similar reactions
Alcohols: Combustion
alcohol + oxygen → carbon dioxide + water
Undergo complete combustion
Carboxylic Acids: functional group and first four in series
Functional group of -COOH
Methanoic acid
Ethanoic acid
Propanoic acid
Butanoic acid
Carboxylic acids: Reactions
Solubility in water
Reaction with metals
Reaction with bases
Reaction with carbonates
Reaction with alcohols
Solubility in water
Dissolves to form acidic solutions
Reaction with metals
carboxylic acid + metal → salt + hydrogen
Reaction with bases
carboxylic acid + base → salt + water
Reaction with carbonates
carboxylic acid + carbonate → salt + water + carbon dioxide
Reaction with alcohols
carboxylic acid + alcohol → ester + water
Why are carboxylic acids called “weak acids”?
They only partially ionise in an aqueous solution
Esters: Formation equation, properties
carboxylic acid + alcohol → ester + water
EX: ethanoic acid + ethanol → ethyl ethanoate + water
They have fruity smells and can be used as solvents
What are the differences between addition and condensation polymerisation?
Addition polymerisation involves monomer molecules combining to form larger polymer molecules- this requires a C=C double bond
Condensation polymerisation involves monomers combining to form a polymer and a small molecule such as water- this requires two functional groups.
Amino acids: Definition, functional groups
Amino acids are molecules which have at least two functional groups
They have the the carboxylic acid group -COOH and -NH2
Name some naturally occuring polymers
DNA
Starch
Cellulose
Proteins
How would you calculate the mean rate of reaction?
Quantity of product formed or reactant used up/time
Which factors affect the rate of chemical change? And how?
Concentration (more reactant particles means more collisions)
Pressure (more particles within given volume, increased number of collisions)
Temperature (increased energy particles collide with and increased speed means more collisions)
Surface area (more surface particles can collide over)
Presence of catalyst (lowers activation energy, provides alternative reaction pathway)
Required practical for rate of reaction: Turbidity/colour change
Add 10cm³ of sodium thiosulfate solution, ensure concentration is known, to a conical flask atop a black cross
Add 10cm³ of hydrochloric acid
Swirl flask gently and start stopwatch. Stop the watch after cross can no longer be seen.
Repeat process with different concentrations of sodium thiosulfate solution
Define collision and activation theory
Collision theory - Chemical reactions can occur only when reacting particles collide with each other and with sufficient energy.
Activation energy - The minimum amount of energy required for reaction to take place
Define equilibrium and Le Chatelier’s Principle
Equilibrium - When the forward and backward reaction occur at the exact same rate
Le Chatelier’s Principle - When a change is made to a system at equilibrium, the system moves to counteract that change
What happens if you change the concentration (providing the system is at equilibrium)?
If the concentration of reactants is increased, more products will be formed
If the concentration of products is decreased, more reactants will react
What happens if you change the temperature (providing the system is at equilibrium)?
An increase in temperature means the endothermic reaction will be favoured.
A decrease in temperature means the exothermic reaction will be favoured.
What happens if you change pressure (providing the system is at equilibrium)?
An increase in pressure favours the side with the least amount of moles
A decrease in pressure favours the side with the most amount of moles
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Flashcard (34)