chemical analysis - C8 Flashcards
what is a pure substance
a substance that contains only one type of element or compound
what is the difference of the boiling points of pure and impure substances
pure substances boil at specific temperatures
impure substances boil over a range of temperatures
us checking for boiling point a physical or chemical test
physical
what is formulation?
-they are mixtures that have a specific formula
-a mixture made suing precise amounts of different components, each having a specific purpose
give examples of formulations
paint, medicines , cleaning agents, fertilisers, alloys, some food and drinks
what is chemical analysis
the instruments and methods we use to identify, separate and quantify different substances.
what are the precautions to take when testing for chlorine gas
-wear a gas mask
- do it in a fume cupboard
how do we test for carbonate ions?
when a carbonate reacts with an acid it forms a salt, carbon dioxide and water
-so add dilute HCL
-collect any gas and bubble it through lime water
-if it turns cloudy then carbonates were present
how do we test for sulfate ions
-add dilute HCL to get rid of any carbonates
-add barium chloride
-if a white precipitate forms, barium sulfate has formed which means sulfate ions are present
how do we test for halides
-add dilute nitric acids to get rid of any impurities
-then add silver nitrate
-if it forms a white precipitate = chloride ions
-cream precipitate = bromide ions
-yellow precipitate = iodide ions
how can we test for cations
flame tests and sodium hydroxide tests
how do you carry out a flame test
-dip a nichrome wire in some HCL, then rinse it off with water and put it over a bunsen burner flame to clean it
-the dip the nichrome wire loop in the compound you want to test
-put it in the blue part of the flame
what flame do sodium ions give
yellow
what flame do potassium ions give?
lilac
what flame do lithium ions give
crimson
what flame do copper ions give
green
what flame do calcium ions give
orange-red
how do the sodium hydroxide test work
when a metal ion reacts with sodium hydroxide it forms a precipitate which makes the solution a certain colour
what precipitate do copper ions give
blue precipitate
what precipitate do calcium ions give
white
what precipitate do iron 2 ions give
green
what precipitate do iron 3 ions give
brown
what precipitate do magnesium ions give
white
what precipitate do aluminium ions give
white but if excess sodium hydroxide is added it turns colourless
how does flame emission spectroscopy work
-metal ion is heated until it emits light
-the light is detected by a spectroscope which can detect the different wavelengths of light
-each cation produces a unique combination of wavelengths and will put these onto a unique spectrum
-then we can identify the cation
what does the intensity of the lines mean
the concentration of the metal ions
what happens if there is more than one ion
the different wavelengths are put onto a single spectrum
what is flame emission spectroscopy an example of
an instrumental method
what are the benefits of using instrumental methods
more accurate, more sensitive, more quick
what are ceramics
brittle hard materials that are heat resistant and corrosion resistant
what are the two types of ceramics
clay ceramics and glass
how are clay ceramics formed
-shaping clay then heating it until it becomes hard
-they have high compressive strength so can be used in bricks
-also includes china and porcerlain
how is glass formed
soda-lime glass
-melting sand, sodium carbonate and limestone
-moulding it then allowing it to solidify
borosilicate glass
- with melting boron trioxide and sand
-a lot higher melting point than soda lime
-is strong, hard and good thermal insulator so can be uses in windows
what are composites
substances with two or more materials with different properties that are combines to get a product with desirable properties
what are composites made of
reinforcement - long solid fibres/fragments
matrix- what holds fibres together , usually soft then goes hard
what are polymers
large molecules with high relative mass made by joining smaller monomers together
what is low density polyethene
made in- moderate temperatures, high pressures, catalyst
-flexible but weak
-used in carrier bags
what is high density polyethene
made with- low temperatures and pressures with catalyst
-rigid but strong
-used in drainage pipes
what properties to polymers usually have
flexible, easily shaped, good conductors of heat and electricity
what are thermosoftening polymers
layers of polymers held together by weak intermolecular forces
-when heated it melts the forces break so they can be changed shape
what are thermosetting polymers
layers of polymers held by strong intermolecular forces so when heated they don’t break so they are hard strong and rigid
what is corrosion
when metals slowly break down due to reacting with substances in their environment
how does iron rust
by being exposed to water and oxygen
in a rusting reaction, what is oxidised and what is reduced
iron oxidised
oxygen reduced
if there are 3 test tube
-with water and a layer of oil
-with air and just calcium chloride
-with just water
which one will the nail rust in?
the one with just water
the layer of oil blocks oxygen from dissolving in the water
the calcium chloride removes all water vapour from the air
how can we avoid rust
barrier methods and sacrificial methods
what is a barrier method
blocking oxygen and water from coming in contact with metal
-coating with paint
-oiling and greasing
-electroplating
what is a sacrificial method
adding a more reactive metal to the iron so that the oxygen reacts with that metal
give an example of a method that is both barrier and sacrificial
coating in zinc
why doesn’t aluminium rust the same way iron does
because when the aluminium rust with the air it forms a protective layer so the air can’t reach the rest of the metal
what is sustainable development
an approach to human and economic growth to make substances that meet the needs of current generations and won’t compromise the chance to meet the needs of future generations
what is reusing
using a material again either for the same or different purposes
what is recycling
collecting and processing materials that would have been thrown away and turning them into new products
what is the benefit of using recycled aluminium
-wont have to dig to get its ore
wont have to use electrolysis to separate it them
what are the purpose of life cycle assessments
to see the effect a product has on the evironment
what are the steps to looking at a life cycle assesment
extracting and processing raw materials
-manufacturing and processing them
-using them
-disposing of them
what are things that aren’t good for the environment
pollutants, energy usage, landfills, mines, cutting down trees
What are the 3 things needed for water to be potable
Low amount of dissolved substances
-no microorganisms
-pH between 6.5 and 8.5
Where do we get potable water from
Fresh water = water exposed to air = rivers, lakes and resouvairs
Ground water = aquifers
How do we make water potable
- Pass though wire mesh to remove big things
2.pass through sand and gravel mixture to remove small things
3.steralise it
How can we steralise water
Pumping chlorine gas through it . Exposing it to ozone of ultraviolet radiation
How do countries with low rainfall get potable Water
Desalination
What are the two ways to do desalination
Simple distillation and reverse osmosis
What are the ways waste water is created
Domestic, agricultural and industry
How is waste water treated
- Screening - passed though mesh to filter large items
- Sedimentation - sits in tank so heavier atoms go to the bottom as sludge, the top is effluent .
3.effluent is aerobically digested by microorganisms
4.sludge is anaerobically digested to produce methane
Sludge left over can be used as fertiliser
Why is the Haber process important
The ammonia is urself for fertilisers
How does the haber process work
Nitrogen and ammonia are fed though to the left side of the chamber with and iron catalyst. here is is 450 degrees and pressure is 200 . Some will join together to form ammonia others won’t . So the gas is fed through to a cooler part and ammonia condenses first as it has a higher boiling point that nitrogen and ammonia
Why do plants need npk fertilisers
To absorb the nutrients
Describe the nitrogen part of npk
Nitrogen is needed to make amino acids for proteins for growth
Nitrogen comes from ammonia
Ammonia can react with nitric acid to make ammonium salts. Can react with oxygen and water to make nitric acid
Describe the phosphorus part of npk
Phosphate can be
mined as cphosphate rock but
the salts in it are insoluble so plants can’t use them so the phosphate rocks react with acid to make soluble salts
Nitric acid - make phosphoric acid and calcium nitrate
Sulphuric acid - makes calcium sulphate and calcium nitrate = single superphosphate
Phosphoric acid - makes calcium phosphate = triple superphosphate
