Hydrocarbons Flashcards
What are hydrocarbons
Molecular compounds that only contain hydrogen and carbon
What is the general formula that all alkanes have
[the stuff in brackets is the small numbers] C(n)H(2n+2)
What is a homologous series
A series of molecules that have a general formula and vary in a single feature (such as carbon chain length)
When are the molecules saturated?
When all the carbon-carbon bonds are singular
Are alkanes saturated or unsaturated
Saturated
What is the name for 1, 2, 3 and 4 carbons in the chain
1 - meth
2 - eth
3 - prop
4 - but
When are hydrocarbons unsaturated
When there is one or more double covalent bond between adjacent carbon atoms
What is the general formula for alkenes
C(n)H(2n)
What is a functional group and an example of one
The carbon-carbon double bond is an example and it is a group of atoms that is mainly responsible for the molecule’s chemical properties
What is an isomer?
Molecules with the same molecular formula but different arrangements of atoms
How many isomers does butane have and what do the numbers in the name show
2
the 1 shows that the C=C bond starts at the end of the molecule
the 2 shows that the C=C bond is in the middle
When does complete combustion occur
When all the atoms from the hydrocarbon are used up
What colour is bromine water
Orange-brown
What is the test that distinguishes between alkanes and alkenes and why is this
Alkanes do not form colourless solutions when mixed with bromine water but alkenes do because of the double carbon bond
What do the numbers in the product 1,2dibromoethane mean
They show that there are two bromine atoms and they’re attached to different carbon atoms- if it was 1,1 then they would only be attached to one carbon atom
What is an addition reaction?
Where the reactants combine to form one large product molecule and no other product
What is the formula for ethanol
C2H5OH
What is the ethanol in alcoholic drinks made of?
Sugars broken down from starch and seeds are germinated before using them to make ethanol as the enzymes in the seeds naturally break down the starch
What is the plant source of beer and whisky
barley seeds
What is the plant source of wine
grapes
What is the plant source of vodka
wheat seeds
What is fermentation
When the enzymes in the yeast (which is mixed with the water and plant sugars) turns the sugars into ethanol and carbon dioxide
Why is an air lock necessary when fermenting ethanol
The air lock in the neck of the jar allows CO2 out whilst still keeping air out as fermentation is a form of anaerobic respiration and only works without the presence of oxygen
What percentage of alcohol concentration does fermentation produce
No more than 15% otherwise it will kill the yeast cells
How are more concentrated alcohols made
Through fractional distillation as ethanol’s boiling point is lower than the boiling point of water
What do organic compounds consist of?
A central framework of carbon atoms onto which hydrogen and other atoms are attached
What do all alcohols, alkenes and alkanes’ names end in?
alcohols -anol
alkenes -ene
alkanes -ane
Give examples of common alcohol chemical properties
- production of carbon dioxide and water in complete combustion
- can be oxidised to form compounds called carboxylic acids
- they react with reactive metals such as sodium, forming hydrogen gas as one of the products
Give some examples of uses of alcohols
- many used in solvents for cosmetics and medical drugs
- methanol and ethanol are used as fuels and can be made from renewable sources
- scientists are now working on developing butanol and propanol fuels from renewable resources
Which fuel has the most and least amount of energy stored?
Petrol and methanol
How do you compare the energy given out by different alcohols in combustion?
- measure the mass of the alcohol bottle and cap and record the mass
- place the bottle in the middle of a mat and use a measuring cylinder to add 100cm3 water into a conical flask
- measure the initial temperature of the water
- light the wick of the bottle and allow the water to get to around 40 degrees
- measure the mass of the burner after placing the cap
- calculate the mass of the alcohol burned to produce a 1 degree increase in temperature
What happens to wine/beer/cider if it is left open?
It turns into vinegar due to a reaction between ethanol and oxygen - the product is a ethanoic acid
What homologous group does ethanoic acid belong to?
Carboxylic acids
What is the general formula for carboxylic acids
C(n)H(2n+1)COOH
How are carboxylic acids formed
Usually through gentle oxidation of alcohols using oxidising agents such as hot copper oxide
Give the properties of carboxylic acids
- form solutions with a pH less than 7 (if soluble)
- react with metals to form a salt and hydrogen
- react with bases to form a salt and water
- react with carbonates to form a salt, water and carbon dioxide
Why do carboxylic acids have acidic properties
Due to the -COOH presence which in solution forms a hydrogen ion while the rest of the molecule forms the negative ion that makes salt
What can vinegar be used for?
To test for carbonate rocks like chalk and limestone - the ethanoic acid ‘fizzes’ producing carbon dioxide gas
What are plastics made of?
Polymers
What is a polymer?
A large molecule made from lots of small molecules called monomers joined together - the process in which the monomers join together is called polymerisation
What kind of average relative molecular mass does a polymer have?
A high relative molecular mass (anything from tens to thousands of millions) - as the polymer molecules can be any lengths, they cannot be given a specific relative mass
What is addition polymerisation
Monomers react to form a polymer without the formation of by-products
How do ethene molecules form poly(ethene)
- Ethene molecules have a double covalent bond between the carbon atoms
- One of the bonds in the double bond breaks open and another ethene molecule is added on
- This happens again and again forming a long chain
What does a repeating unit in a polymerisation equation show
It shows how the monomer has changed and how it repeats throughout the polymer chain
What is a synthetic polymer and give an example
It is a polymer that is manufactured in a lab or factory and polythene is an example
Give examples of some naturally occurring polymers
DNA, starch and proteins
What is the name of a polymer based on?
Its the term poly- followed by the name of the monomer in brackets … e.g poly(styrene)
PLEASE LOOK AT PAGE 186 IN THE CHEM BOOK FOR THE GENERAL FORMULA FOR THE ADDITION POLYMERISATION
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Give some properties and uses of poly(ethene)
properties - flexible, cheap and good insulators
uses- plastic bags, plastic bottles, cling film
Give some properties and uses of poly(propene)
properties- flexible, does not shatter
uses - buckets, bowls, crates, ropes and carpets
Give some properties and uses of poly(chloroethene)
properties- tough, good insulator, either hard ot flexible
uses- window frames, gutters, pipes and insulation for wiring
Give some properties and uses of poly(tetrafluoroethylene)
properties- tough and slippery
uses- non-stick coatings for frying pans, burette taps, stain-proofing clothing
What type of polymers is polyester and what process is it made by
A synthetic polymer
It is made by condensation polymerisation
What is the compound for -esters
-COO- (look at a picture of an ester compound)
When are esters formed?
When carboxylic acid reacts with alcohol in presence of a catalyst - its a condensation reaction as water is also produced
What functional groups form a polyester chain
The monomers that make up polyester contain alcohol and carboxylic acid functional groups
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Define biodegradable
The materials (such as wood and paper) rot because microbes can feed on them and break them down
Are synthetic polymers biodegradable?
No - it means they last for a long time but they do not rot when they are thrown away
What happens to the non-biodegradable rubbish?
Some of it is incinerated (burned) and the energy released can be used in electricity but can produce carbon dioxide and possibly toxic substances which can be removed from the waste gases but forms toxic ash which must be disposed of safely
How can we reduce the amount of waste that goes into landfills or incinerators?
Reduce the amounts of materials we use and also by reusing materials - if an item can be reused any more, it may be possible to recycle it by processing it to make a new item and this will also help to conserve crude oil
How much of the UK’s rubbish goes into landfills?
Over half
State the steps in recycling polymers and making them into new products
- collect the waste
- sort the waste into different types of polymer (usually done by hand - time consuming)
- dispose of waste that connot be recycled in a landfill site
- clean the polymers and grind them into chippings
- purify the chippings
- melt the chippings then process them into a new product
What system is in place to help with the sorting of polymers?
They have codes and symbols on plastic items to show what they are made of
