Chemistry P2 Flashcards
What are addition polymers made from?
Alkenes or alkanes? Why?
Unsaturated monomers
Alkenes = double covalent bond - can open double bonds and join together to form polymer chains (addition polymers)
What is needed for monomers to join together to create a polymer?
Pressure
Catalyst
Naturally occuring polymers?
DNA
Starch
Proteins
(DNA from 4 different monomers)
(Starch = polymer of glucose)
(Proteins = polymer of amino acids)
What is the polymer - poly(ethene) used for?
Properties?
Properties:
- flexible
- electrical insulator
- cheap
Uses:
- plastic bags
- bottles
- wire insulation
What is the polymer - poly(propene) used for?
Properties?
Properties:
- flexible
- strong
- tough
- malleable
Uses:
- crates
- furniture
- ropes
What is the polymer - poly(chlroroethene) used for?
Properties?
Properties:
- tough
- cheap
Uses:
- window frames
- water pipes
What is the polymer - poly(tetrafluroethene) used for?
Properties?
Properties:
- unreactive
- tough
- non-stick
Uses:
- non-stick pans
- waterproof clothing
What are the advantages and disadvantages of recycling polymers?
Advantages:
- Reduces amount of non-biodegradable waste in landfill
- Decreases emissions released from burning polymers
- Recycling uses less water and energy resources than new ones
- Decreases amount of crude oil needed to produce more plastics
- Saves money + new jobs
Disadvantages:
- Must be separated by type before melted and reformed into new product (difficult and £££)
- If mixed = quality decreases and strength decreases
- Melting polymers can release dangerous gases that harm plants and animals
Why is it important to find environmental way to dispose of polymers?
Landfill sites:
- lots of plastic dumped in landfill
- usually when polymers are too difficult or £££ to recycle
- lots of valuable used for landfill
- most polymers = biodegradable
Combustion:
- Burning plastics produces a lot of energy - can be used to generate electricity BUT:
- if not carefully controlled = toxic gases released from combustion of plastics (e.g PVC burned = HCI - has to be removed)
- Carbon dioxide produced = global warming
Polymers are made from….
Can be separated by……… which is then …….. and………and…….to be used as useful chemicals
Crude Oil
Fractional Distillation
Further purified
Cracked
Refined
In order to carry out a flame test:
- Light a Bunsen burner to produce a hot…..
- Pick up a small sample of………… using a …….. ………………, cleaned in…..
- Hold sample in….. of flame and observe flame colour
- …blue flame
- solid salt - PLATINUM WIRE LOOP, … cleaned in HYDROCHLORIC ACID
- …in edge of flame
What is the positive flame test colour for a LITHIUM metal ION?
RED
What is the positive flame test colour for a SODIUM metal ION?
YELLOW
What is the positive flame test colour for a POTASSIUM metal ION?
LILAC
What is the positive flame test colour for a CALCIUM metal ION?
ORANGE/RED
What is the positive flame test colour for a COPPER metal ION?
BLUE/GREEN
In order to carry out the hydroxide precipitate test for metal cations:
- Dissolve a little …………….. in a test tube using ………….
- Add a few drops of ………………………..solution, 1 drop at a time.
- Record colour of any precipitate formed.
- If a ……… precipitate forms, add ……………………………………..solution to see if it will disappear to leave a ……………..solution.
- Solid salt -….distilled water
- Dilute sodium hydroxide solution
- EXCESS dilute sodium hydroxide to leave a CLEAR/COLOURLESS solution.
Test for ammonium ions:
- Dissolve a little …………. in a test tube using …………….
- Add………………………..solution and warm gently with Bunsen burner flame.
- Remove from flame. Hold a piece of……………………………near mouth of test tube. If ammonia present, turns…..
- Solid salt -….. distilled water
- DILUTE SODIUM HYDROXIDE
- DAMP RED LITMUS PAPER - turns BLUE
Hydroxide Precipitate Test for Metal Cations:
What colour does Iron(2) ION turn with dilute SODIUM HYDROXIDE?
GREEN
Hydroxide Precipitate Test for Metal Cations:
What colour does Iron(3) ION turn with dilute SODIUM HYDROXIDE?
BROWN
Hydroxide Precipitate Test for Metal Cations:
What colour does Copper ION turn with dilute SODIUM HYDROXIDE?
BLUE
Hydroxide Precipitate Test for Metal Cations:
What colour does Calcium ION turn with dilute SODIUM HYDROXIDE?
WHITE
Hydroxide Precipitate Test for Metal Cations:
What colour does Aluminium ION turn with dilute SODIUM HYDROXIDE?
WHITE - excess NaOH = COLOURLESSsolution
Test for Carbonate ions:
- Put a little ……………. in a test tube and add a few drops of ………………
- Record whether any ……………. occurs.
- Use …………… to check that any ……………. contain carbon dioxide.
- Solid salt ….. dilute hydrochloric acid
- Effervescence
- Limewater ….. bubbles
Test for sulfate ions:
- Dissolve a little ……… in a test tube using ……………..
- Add a few drops of …………………………, (removes carbonate ions that may give a precipitate), then add a few drops of ………………………….
- Record whether a …………………. precipitate forms.
- Solid salt …distilled water
- Dilute hydrochloric acid….. barium chloride solution
- WHITE ppt
Testing for halide ions:
- Dissolve a little ……………… in a test tube using …………………
- Add a few drops of …………………, (removes carbonate ions), then a few drops of …………………….
- Record the colour of any precipitate formed.
- Solid salt …distilled water
- Dilute nitric acid …. silver nitrate solution
What are alkanes?
Double or single bonds?
A group of hydrocarbon molecules based on a chain of carbon atoms.
Single
Are alkanes saturated or unsaturated?
Saturated
What is the general formula for Alkanes?
Cn H2n+2
What is a homologous series?
A group of chemicals that have a similar chemical structure.
Alkanes = homologous series of hydrocarbons.
What are alkenes?
Double or single bond?
Hydrocarbons with at least 1 double covalent bond between carbon atoms that are unsaturated.
Are alkenes saturated or unsaturated?
Unsaturated hydrocarbons - can make more hydrocarbons
What is a functional group?
A group of atoms that determine how a molecule reacts.
What are alkenes functional group?
Cn H2n (twice as many hydrogens as carbons)
What is the order for Alkenes and Alkanes?
Monsters
Eat
People’s
Buts ———–> alkenes = But-1-ene + But-2-ene (2nd/3rd carbon along = double bond)
How to test for an alkene?
Bromine water
When shaken together, an alkene will decolourise bromine water = orange to colourless
Because an ADDITION REACTION - takes place where bromine is added across alkene in double bond.
Add excess bromine water = orange –> colourless –> orange
Alkanes and alkenes burn in oxygen in combustion reactions.
What are the products of complete combustion?
Products of incomplete combustion?
Complete combustion = carbon dioxide + water
Incomplete combustion = carbon dioxide + water + carbon (soot) + carbon monoxide (toxic gas)
What is the test for water?
Using ANHYDROUS copper sulfate in a U-shaped tube = turns blue colour.
What are the problems of incomplete combustion?
- Carbon monoxide = toxic gas - combines with haemoglobin in red blood cells - preventing oxygen binding properly - fainting, tiredness or death. (Hence carbon monoxide alarms needed).
- Some carbon atoms in hydrocarbon may still be fully oxidised to carbon dioxide - but some only partially oxidised to carbon dioxide:
Some carbon atoms released as smoke + soot –> can block pipes carrying waste gases and cause breathing problems.
What causes acid rain? (pH less than 5.2)
Sulfur dioxide.
- Fossil fuels burned - release mostly CO2 + other harmful gases - sulfur dioxide + various nitrogen oxides.
- Sulfur dioxides comes from sulfur impurities in fossil fuels.
- Sulfur dioxide mixes with clouds = dilute sulfuric acid = acid rain.
What are the pros and cons of hydrogen being used as a clean, renewable fuel?
Pros:
- Can be used to power vehicles + for fuel cells.
- Clean fuel - hydrogen combines with oxygen to produce energy - only waste product = water.
- Hydrogen’s obtained from water - renewable source + can be obtained by water produced by fuel cell itself.
Cons:
- Need special, expensive engine.
- Hydrogen gas needs to be manufactured = £££ + uses energy from another source - fossil fuels! (Pollutants)
- Hydrogen = hard to store + not widely available.
Process for practical - combustion of alcohols:
- Measure mass of an alcohol burner + cap + record mass of named alcohol.
- Place alcohol burner in centre of heat-resistant mat.
- Using a measuring cylinder, add 100cm3 of cold water to conical flask.
- Measure + record initial temp of water + clamp flask above alcohol burner.
- Light wick of burner and allow water to heat up by 40 degrees celcius.
- Replace cap on burner and measure and record final temp of water.
- Measure mass of alcohol burner and cap again + record mass.
- Calculate mass of alcohol burned to produce a 1 degree rise in temp.
- Repeat steps with fresh, cold water and different alcohol.
Less alcohol burned = better fuel.
What is the functional group for carboxylic acids?
-COOH
What is alcohol functional group?
-OH
What was the first stage of Earth’s atmosphere?
- Earth’s surface cooled and crust formed - volcanoes kept erupting and releasing gases from inside Earth. This ‘de-gassing’ released mainly carbon dioxide but also steam, methane and ammonia + water vapour (the gases that formed the Earth’s atmosphere).
- When things settled down, early atmosphere = mostly carbon dioxide + water vapour - little oxygen.
- As Earth cooled, water vapour condensed to form oceans.
What was the 2nd stage of the Earth’s atmosphere?
Green plants evolved and produced oxygen:
- A lot of early carbon dioxide dissolved in the oceans to to form a weak acid –> reacted with minerals in sea to form precipitates - formed sediments of carbonate rock on seabed. Some carbon dioxide in sea = made corals + shells of organisms (mussels) - when dead to form sedimentary rock limestone - also removed carbon dioxide.
- Nitrogen gas was then put in atmosphere in 2 ways:
- formed by ammonia reacting with oxygen
- was released by denitrifying bacteria
(Nitrogen wasn’t very reactive so amount in atmosphere increased - being made - not broken down).
- Green plants - PHOTOSYNTHETIC ORGANISMS evolved over most of Earth. Produced oxygen which entered atmosphere.
Animals could now evolve.
- Due to plants, carbon dioxide increased and much of carbon dioxide got locked up in fossil fuels and sedimentary rocks.
What was phase 3 of the Earth’s atmosphere?
- Build up of oxygen in atmosphere killed off early organisms that couldn’t tolerate it.
- Allowed evolution of more complex organisms that made use of oxygen.
- Oxygen created ‘O-Zone’ Layer = blocked harmful, rays from sun + enabled even more complex organisms to evolve.
- Virtually no carbon dioxide left now.
State 2 ways in which oxygen is important.
(21% of Earth’s atmosphere today).
- combustion
- aerobic respiration
Pure oxygen will re-light lit splint - test for oxygen.
