C6.2 And C6.3 Flashcards
What is a hydrocarbon
A compound which only contains hydrogen and carbon
What is a homologous series
Organic compounds with the same functional group and general formula
Similar chemical reactions and physical properties
What is a functional group
An atom / group of atoms, or a type of bond which determined the chemical reactions of an organic compound
What is a general formula
Chemical formula showing the relative number of atoms of each element in a compound
What does saying ‘Alkanes are saturated’ mean
Their carbon atoms are joined by single bonds
What is the general formula for alkanes
C(n) H(2n+2)
What is an alkane
A hydrocarbon with the functional group of single carbon bonds
How many atoms are joined to one carbon atom
4
How do you model alkanes and alkenes
Using the displayed formula
Methane would be
H H-C-H H
What does it mean if an alkene is described as unsaturated
It has a double bonded carbon atoms
How does the size of alkanes (small and big) affect these properties
Boiling point
Flammability
Cleanliness of flame
Viscosity
Small:
Low boiling
Very flammable
Clean flame
Low viscosity
Big:
High boiling
Harder to burn
Dirty sooty flame
High viscosity
What is complete combustion
Burning in a plentiful supply of oxygen
What is incomplete compustion
Burning in a limited supply of oxygen
What equation shows the complete combustion of an alkane (methane)
CH4 + 2 02 → CO2 + H20
What happens in the complete combustion of an alkane
Carbon atoms are oxidised to form carbon dioxide
Hydrogen atoms are oxidised to form water
What happens in the incomplete combustion of an alkane
Water is formed (hydrogen is oxidised)
Carbon cannot be fully oxidised to form carbon dioxide
Carbon monoxide is formed instead
Equation for incomplete combustion of an alkane (methane)
CH4 + 3/2 O2 → CO + 2 H2O
Or
2CH4 + 3O² → 2CO + 4H²O
What are alkenes
Alkenes are hydrocarbons with the functional group of double carbon bonds (unsaturated)
What is the general formula for alkenes
C(n)H(2n)
What are the first six prefixes for alkenes, alkanes, alcohols (etc)
Meth-
Eth-
Prop-
But-
Pent-
Hex-
What is an addition reaction
Reaction where an atom (or group of atoms) combines with a molecule to form a larger molecule with no other product
What is an addition polymer
Substance consisting of molecules made from many repeating units, formed by addition reactions
What happens to alkenes in addition reactions
The double carbon bond breaks and forms a single carbon bond
(At the end of the reaction there will still be 4 things bonded to each carbon atom)
Whay are alkenes reactive
Due to the carbon double bond which undergoes additions reactions
How can alkanes be formed from alkenes
A nickel catalyst is required
Alkene + hydrogen → alkane
E.g
Ethene + hydrogen → ethane
How can addition reactions be used to test for an alkene
Alkenes react with bromine to form a colourless compound called diobromethane
Bromine water (bromine dissolved in water) is brown, but this reaction with alkenes turns it colourless
The reaction does not work with alkanes
What happens in the hydration of an alkene
Adding water to an alkene makes it an alcohol
Ethene + water → ethanol
What is an alcohol
All alcohols are part of a homologous series
As they contain oxygen they are not hydrocarbons
They have a functional group of OH
What is the functional group of alcohols
OH
What is the general formula of alcohols
C(n)H(2n+1)OH
What happens in the complete combustion of an alcohol
Water vapour and carbon dioxide are produced
What happens in the incomplete combustion of an alcohol
Water vapour and carbon monoxide are produced
How are carboxylic acids made
By reacting alcohol with oxidising agents (e.g potassium manganate solution)
What is a carboxylic acid
An acid in a part of a homologous series
It has the functional group
COOH
What is the general formula for carboxylic acids
C(n)H(n+1)COOH
What are the main reactions of carboxylic acids
Metal + carboxylic acids → slat + hydrogen
Carboxylic acid + alkali → salt + water
Carboxylic acid + carbonate → salt + water + carbon dioxide
How can you test for an alcohol
Adding an oxidising agent such as potassium manganate will turn it onto a carboxylic acid
In this reaction there would be a colour change to clear
When doing this experiment wear gloves / eye protection as the reaction is violent
What is crude oil
A complex mixture of hydrocarbons (mostly alkanes) formed from the remains of dead organisms over millions of years
What is a finite resource
A resource which will run out eventually
What are fossil fuels
Fuels such as crude oil, natural gases and coal
They are formed from the remains of microorganisms over millions of years
How is crude oil useful
Using fractional distillation, different alkanes can be separated from crude oil.
These alkanes all have different uses (e.g petrol)
The fractionating column is hottest at the base
How are different fractions of crude oil colleceted
As the hydrocarbons have different boiling points they will travel different distances up the fractionating column.
They will then fall into trays (condense) and leave the column.
Lowest boiling point to highest
LPG
Petrol
Paraffin
Diesel
Heating oil
Fuel oil
Bitumen
What is cracking
Process of separating larger alkanes into smaller alkanes and alkenes through the use of high temperatures and a catalyst
What temperatures and catalysts are used in cracking
600 to 700°C
Hot catalyst of alumina or silica
How does cracking create a smaller alkane and an alkene
Covalent bonds between carbon atoms are broken at one point in the alkane
This leaves a smaller alkane and the additional polymer forms double carbon bonds (making an alkene)
Why is cracking done
Smaller alkanes are more useful than larger ones, as they can ignite easier and flow better (making them better fuels)
Cracking allows oil refineries to produce enough small alkanes to match the demand for them
Alkenes are also produced and they can be used for making polymers
Why is crude oil important
90% of it is used to produce fuels that are needed everyday (e.g petrol)
What are addition reactions
Reactions where an atom / group of atoms combines with a molecule to form a larger molecule and NO other product
What are addition polymers
A substance consisting of molecules made from many repeating units, formed by addition reactions
What are repeating units
A section of a polymer that is repeated many times in the molecule
What are polymerization reactions
A reaction where small monomers molecules join to make larger polymer molecules
Why can alkenes be used in addition reactions and alkanes cannot
As the double carbon bond breaks and attaches to another carbon molecule
How would you model propene being polymerised to poly propene (/ displayed formula
Propene is
H H H H
H-C-C=C Or C=C
H H H H CH3
[ H H ]
[ -C-C- ]
[ H CH3 ]
———– n
The letter n stands for how many repeating units there are
What is DNA like
DNA is made of monomers called nucleotides
Contains a phosphate group
Sugar (deoxyribose)
An organic group ( nitrogenous base)
The bases are Adenine, thymine, cytosine, guanine
How is DNA formed from nucleotides
The deoxyribose of one nucleotide binds with the phosphate of another to form a sugar phosphate backbone
Hydrogen bonds (intermolecular forces) form between opposite bases holding the stands together
How are proteins formed
Proteins are polymers made from amino acids (20 amino acids)
Each amino acid has a reactive functional group at each end so they can join to form long protein molecules
What are carbohydrates made of
They are compounds of carbon hydrogen and oxygen
They include simple sugars such as deoxyribose and sucrose and complex sugars such as starch.
Sucrose is made from two simple sugars, glucose and fructose
Starch is made of many simple sugar molecules joined together
What is a condensation reaction
A reaction where two molecules join together to form a larger molecule and a smaller molecule (usually water or hydrogen chloride)
What are condensation polymers
Substance with molecules made from many repeating units formed by condensation reactions
What happens when a carboxylic acid an alcohol react
An ester and water is formed
What is an ester
Organic molecules used for food flavourings
Often sweet smelling substances
What are polyesters
Condensation polymers made of a carboxylic acid with two carboxyl groups and an alcohol with two hydroxyl groups
They contain many ester groups (COO)
What are polyamides
Polymers made from a carboxylic acid with two carboxyl groups and an ‘amine’ with two amino groups
They contain many amide groups (CONH)
What is needed for condensation polymerisation to occur
It can happen without a catalyst and at room temperature and standard pressure
What is an amino functional group group
NH2
What are chemical cells
Stores of chemical energy
They undergo exothermic reactions to produce P.D
When connected to a circuit current can flow
(Continues until reactants are used up)
What are chemical cells made of
They are made of lithium
This material is expensive
What are hydrogen fuel cells
A fuel cells that uses hydrogen.
Hydrogen reacts with oxygen to produce water vapour.
This is an exothermic reaction and electricity is produced
2H² (g)+ O²(g) → 2H²O(g)
What are the environmental effects of chemical and fuel cells
Both require combustion of fossil fuels in their production
-chemical cells require heavy mining of rare metals
-Fuel cells require a toxic catalyst which is hard to dispose of
Benefits of fuel and chemical cells
They produce less greenhouse gasses than using petrol or diesel
What happens in a hydrogen fuel cell
Hydrogen enters the cell and loses an electron to the anode making it positive.
The hydrogen ions are small enough to pass through the proton exchange membrane
The electrons lost by the hydrogen travel through the external circuit
Hydrogen ions combine with oxygen and electrons at the other side (past the cathode) to form water vapour.
There is a catalyst in the proton exchange membrane
Why is the proton exchange membrane called that
It is used to transfer (exchange) H+ ions
H+ ions are protons
What are the ionic equations that occur in a fuel cell
2H² -4e- → 4H+(aq)
4H+(aq) + O²(g) → 2H²O
What 3 gases make up 99.9% of the earth’s atmosphere
Nitrogen (78%)
Oxygen (21%)
Argon (0.9%)
How was the earth’s atmosphere originally formed / what was it originally made of
Its believed to have been formed by volcanic activity
Volcanoes release a huge amount of carbon dioxide and water vapour.
As the earth cooled water vapour condensed to form oceans
This left am atmosphere predominantly made from burning fossil fuels
How did the atmosphere change overtime /why
The amount of oxygen increased and carbon dioxide decreased due to photosynthesis completed by plants and algae.
This intially cause the oxidation of metals, but eventually lead to oxygen being released into the atmosphere
What are pollutants
Substances released into the environment that may damage living things
What are pollutants
Substance released into the environment that may cause harm to living things
How do most atmospheric pollutants enter the air
By the burning of fossil fuels
Why is carbon monoxide a pollutant
It is released through the incomplete combustion of coal / wood / natural gases
When breathed in it binds to haemoglobin in red blood cells reducing oxygen in your blood stream.
Carbon monoxide poisoning causes drowsiness, difficulty breathing and death
What are particulates
Small particles (mostly carbon) formed by incomplete combustion
What problems do particulate caused
When breathed in they settle deep in the lungs.
This can cause bronchitis and other breathing problems + increases heart disease
Why di acidic oxides (e.g nitrogen dioxide) cause problems (+sulfur dioxide)
They dissolve into the moisture in clouds and fall as acidic rain
Acid rain corrodes stonework and corrodes metals
It can kill trees and living things in rivers
Sulfur dioxide is formed when sulfur reacts with oxygen when fossil fuels are combusted
They can cause acid rain
What is the greenhouse effect
The interaction of infrared radiation in the air and molecules in the atmosphere reducing the transfer of energy to space
What are greenhouse gases
Gas in the atmosphere that reduces the transfer of energy to space by infrared radiation
What is global warming
Worldwide increase in temperature over time
Examples of greenhouse gasses
Water vapour
Carbon dioxide
Methane
How does the greenhouse effect work
Energy transferred by radiation reaches the sun
The radiation increases the earths temperature
Infrared radiation is emitted by the earth, some goes into space and some is absorbed by greenhouse gas molecules in the atmosphere
Infrared radiation is emitted by greenhouse gas particles in all directions, warming the surface of the earth
How are greenhouse gasses released into the air by human activities
Carbon dioxide - combustion of fossil fuels
Methane - rice paddy fields, cattle, landfill sites, use of natural gas
What is the advanced greenhouse effect
By releasing greenhouse gases into the atmosphere we are increasing the concentration of them in the atmosphere
This leads to earth’s temperatures increasing further
What is climate change
Long - term change in climate patterns
What will global warming do to the earth
Results in an increased temperature
Altered weather patterns cause flooding and problems of disease / pests
Ice caps melt and rising sea levels
How are greenhouse emissions reduced
Consumption of fossil fuels is reduced by using biofuels
Renewable energy resources are used to generate electricity
Carbon dioxide is prevented from entering the atmosphere using carbon capture and storgae
Why are the emissions of water vapour not seen as an issue
As it has a very low effect on warming the earth + lots of it falls back as rain
Where does most drinking water come from
Lakes reservoirs and aquifers
What is an aquifer
Layer of rock that stores water underground
What is potable water
Water that is safe to drink
What is desalinisation
Process of removing dissolved salts from water
How is small scale and large scale desalinisation doen
Large - using distillation
Small - ‘reverse osmosis’ to filter out the salts
Why is desalinisation not used in the uk
As supplies of freshwater are not limited and the cost
How is water usually treated
1) water is ‘screened’ (passed through close bars of metal) to remove large objects such as leaves and branches.
2) (clarification) Settlement tanks are used to remove soil and sand, aluminum sulfate and like are also added to remove silt and sludge (they clump the particles together - sink to the bottom)
3) (Filtering) Dirty water is passed through a filter trapping undissolved solids (gravel beds or sand are often used to filter)
4) Bacteria is finally killed by adding small amounts of chlorine
Why is Fluoride added to water (in some areas)
It strengthens teeth preventing cavity loss
Combats tooth decay in children
Negatives of fluoridation (adding fluoride to water)
Causes discolouring of teeth ( yellow teeth )
Causes damage to soft tissue such as gums
How can hydrogen be made from alkanes
Alkane + water → carbon monoxide + hydrogen
What happens in the comete and incomplete combustion of alkenes
Complete
Alkene + oxygen → carbon dioxide and water (same reaction as alkanes)
Incomplete
Alkene + oxygen → carbon + carbon monoxide + water (different to alkanes)
