lastmin Flashcards
1
Q
Fractional Distillation stages
A
1-Crude Oil is heated to a very high temperature causing the crude oil to boil so all the Hydrocarbons evaporate and turn into a gas
2-Crude Oil Vapour is then fed into the fractional distillation column , the column is hotter at the bottom and cooler at the top .
3- Hydrocarbon vapours now rise up the column, the hydrocarbons condense when they reach their boiling point and then the liquid fractions are removed. The remaining hydrocarbons continue moving up the column and these condense when they reach their boiling point.
2
Q
Fractions contain hydrocarbons with a similar number if carbon atoms. Some fractions are used as fuels. What is petrol and diesel use to do
A
fuel cars
3
Q
Fractions contain hydrocarbons with a similar number if carbon atoms. Some fractions are used as fuels. What is kerosene used as
A
jet fuel
4
Q
Fractions contain hydrocarbons with a similar number if carbon atoms. Some fractions are used as fuels. What is heavy fuel oil
A
to power
5
Q
Fractions contain hydrocarbons with a similar number if carbon atoms. Some fractions are used as fuels. What is liquified petroleum gases used in
A
camping stoves
6
Q
Some fractions are used as Feedstock for the petrochemical industry. What chemicals are feedstock used to make?…(4)
A
Solvents
Lubricants
Detergents
Polymers
7
Q
What is cracking
A
Cracking is a process in which long chain alkanes are broken down (cracked) to produce smaller, more useful molecules
8
Q
Long chain Hydrocarbons are not very flammable and this is one reason why they do not make good fuels. Why is this a problem
A
Because there is a high demand for short-chain hydrocarbons to be used as fuels
9
Q
name the two ways to carry out cracking
A
Catalytic Cracking and Stream Cracking
10
Q
what we use in catalytic cracking
A
We use high temperatures and a catalyst.
11
Q
what we use in steam cracking
A
We use high temperature and steam
12
Q
what does cracking make
A
Cracking makes hydrocarbons called alkenes
13
Q
Alkenes are very useful molecules, why?
A
Used to make chemicals called polymers
also used as the starting material for other useful chemicals as well
14
Q
Well, alkenes are MORE reactive than alkanes and we can use this idea to test for alkenes…how do you test for alkenes?
A
We test for alkenes using bromine water which is orange. If we shake our alkene with bromine water then bromine water turns colourless
15
Q
how to calculate the mean rate of reaction
A
mean rate of reaction = quantity of product formed/time taken
16
Q
what is a pure substance
A
A pure substance is a substance not mixed with any other substance
17
Q
what is the simplest way to determine if a substance is pure or not
A
To simply measure its melting point and boiling point.
A pure substance melts at a specific fixed temperature.
A pure substance also has a specific fixed boiling point.
Impure substances melt and boil over a range of temperatures.
18
Q
What is a formulation
A
A formulation is a complex mixture that has been designed as a useful product
In a formulation, the quantity of each component is carefully measured so that the product has the properties we need.
19
Q
Formulations include…(name 7)
A
FUELS CLEANING PRODUCTS PAINTS MEDICINES ALLOYS FERTILISERS FOODS
20
Q
What are 4 ways to separate mixtures/physical separation techniques
A
FILTRATION
CRYSTALLISATION
DISTILLATION
CHROMATOGRAPHY
21
Q
Gases in the atmosphere?
A
78 percent nitrogen
21 percent oxygen
small proportions of other gases eg carbon dioxide, water vapour and noble gases such as argon
22
Q
what is carbon footprint
A
The total amount of C02 and other greenhouse gases emitted over the full life cycle of a product, service or event
23
Q
what do we use resources for
A
For warmth, shelter, food and transport.
In many cases these resources are produced by agriculture (farming) eg cotton is produced from a plants
24
Q
what i s Potable water
A
Potable water is water that is safe to drink
25
why is potable water not the same as pure water?
Because pure water in the chemical sense contains no dissolved substances at all but potable. water dies - but in small amounts
26
where crude oil found
in rocks
27
what kind of resource is crude oil
finite
28
what is crude oil
a mixture of molecules called hydrocarbons
29
what are hydrocarbons
molecules made of hydrogen and carbon atoms only
30
alkanes
hydrocarbons with the general formula C2H2n+2
31
List Alkanes in order
Methane
Ethane
Propane
Butane
MEPB
32
What are alkanes and why
plus ps what does saturated mean
Alkanes are saturated molecules because the carbon atoms are fully bonded to hydrogen atoms
Because the carbon atoms are fully bonded to the hydrogen atoms
Saturated on general means something has bonded as many times as possible aka no more (C-C can be made)
In specific here, saturated means the carbons atoms are fully bonded to the hydrogen
33
3 properties of hydrocarbons
Viscosity - tells us thickness of a fluid
Size of HC molecules increases, Viscosity increase
Flammability - tells us how easily a hydrocarbon combusts
Increases decreases
Boiling point - the temperature at which a liquid turns to a gas
Increases increases
34
Examples of where hydrocarbons can be used as fules
ships
planes
cars
these all run on Hydrocarbon fules
35
when do Hydrocarbons release energy and how
When combusted (burnt).
During combustion, Carbon and Hydrogen atoms in fuel react with oxygen . The carbon and hydrogen are oxidised.
If oxygen is unlimited, the reaction produces carbon dioxide and water - this is Complete combustion.
Complete combustion =
Hydrocarbon + oxygen ----> carbon dioxide + water
36
for hydrocarbons in crude oil ( a naturally occurring petroleum product) to be useful, what must we do?
Separate them - to do that we use a technique called fractional distillation
In Fractional distillation, crude oil is separated into fractions. Fractions contain hydrocarbons with a similar number of carbon atoms.
Fractional distillation separates crude oil into simpler, more useful mixtures. The method can be used because different hydrocarbons have different boiling points.
37
long chain hydrocarbons have long chain boiling points. Where are these removed in fractional distillation?
From the bottom of the column.
38
Very short chain hydrocarbons have low boiling points and these do not condense - they are removed from where as what in fractional distillation?
Removed from the top of the column as gases
39
some fractions are used as feedstock for the petrochemical industry, what is a feedstock?
A chemical that is used to make other chemicals
40
to solve the problem of a demand of shorter chained hydrocarbons, what do we do?
We use cracking!!!
41
what does cracking make
Hydrocarbons called alkenes
42
alkanes have a single bond between two carbon atoms, what do alkenes have?
A double bond between two carbon atoms
43
what is petrochemical
a substance made from crude oil using chemical reactions
44
When we plot quantity of product formed (grams) on y axis and time in x axis, initially the reaction is fast why?
Because we are making a lot of product in a short amount of time. That is because we have a large number of reactant molecules so lots of them are reacting and forming products.
45
When we plot quantity of product formed (grams) on y axis and time in x axis, gradually, the slope of the line becomes less steep, telling us that the reaction is slowing down. Why
Because the rate of reaction is decreasing, meaning a lot of the reactants have turned into product, meaning there are fewer reactant molecules available to react.
46
When we plot quantity of product formed (grams) on y axis and time in x axis, at the end of the line, the slope of the line is now zero - the line is flat so the reaction has stopped... Why?
Because all the reactant molecules have already reacted.
47
how to calculate mean rate of reaction?
Mean rate of reaction = quantity of product formed / time taken
48
what does a forward reaction tell us
that the product will not turn back to form the reactants.
49
what does shift mean
moving
50
what is a reversible reaction
when the products can reform to original reactants
51
how can we change the direction of reversible reactions
by changing the conditions
52
magnesium +oxygen ---> magnesium oxide (a compound) talk about this
Arrow points in one direction only
telling. us reaction only goes forward
magnesium oxide will not turn back to form magnesium and oxygen again
53
ammonium chloride -------> ammonia + hydrogen chloride
| meant to be another arrow
When we heat compound ammonium chloride, it reacts to form ammonia and hydrogen chloride....
If we take the products (ammonia and hydrogen chloride) and cool them down, they now react together to reform ammonium chloride
It is a reversible reaction
We can change the direction of the reaction by changing the conditions and in this case we made the reaction go forwards by heating it and backwards by cooling but every reaction is different.
54
Energy changes taking place in a reversible reaction
endothermic/heat
hydrated copper sulfate (blue) --------> hydrous copper sulfate (white)+water
meant to be another arrow
If we heat anhydrous copper sulfate then it reacts to form anhydrous copper sulfate which is white and also produces water
Because we are heating we are putting energy in so the forward reaction is endothermic
If we take our anhydrous copper sulfate and add the water back the reaction reverses and in the reversible reaction the energy os released and the reaction gets hot telling us the reversible reaction is exothermic
If a reversible reaction is exothermic in one direction it is endothermic in the other direction and the same. amount of energy is transferred each time.
55
Equilibrium in a reversible reaction plus example
ammonium chloride -------> ammonia + hydrogen chloride
meant to be another arrow
Imagine we are carrying out this reaction in a sealed container and it stops anyr eactants or products from escaping. At some point, the forward and reverse reactions will take place at the exact same rate - at equilibrium
56
equilibrium definition
Equilibrium is when we carry out a reversible reaction in a sealed container none of the reactants or products can escape and when at some point the forward and reverse reactions occur at the same rate. - this point is called equilibrium.
57
what are the effects of changing conditions on equilibrium
If a system is at equilibrium and a change is made to the conditions, then the system responds to counteract the change.
This is called Le Chatelier's Principle
(We use the word system here just to say reaction)
58
what happens if we change the concentration of products plus reaction to remember
At equilibrium, the system will counteract any changes we make.
So if we change the concentration of the reactants or products, then the system is no longer at equilibrium.
In other words, the forwards and reverse reactions are not taking place at the same rate.
This means that the concentrations of all the substances will change until equilibrium is reached.
so in this case, because we have increased the concentration of the products , more of the reactants will be formed until equilibrium is reached again.
Example =
2N02 arrows N2O4
59
what happens if we make a change 'to the temp
like we said before if we make any change to a system at equilibrium then the system counteracts the change. So if we increase the temperature of this system then the equilibrium shifts to the left to reduce the temperature
Example =
2N02 arrows N2O4
That is because the reversible reaction is endothermic soo the amount of N2O4 would decrease
If we were to decrease the temperature of this system, equilibrium shifts to the right to increase the temperature that is because forward reactions exothermic so energy is released causing the temperature to increase. So in this case the amount of N2O4 would increase and the amount of NO2 would decrease.
60
Pressure and rate of reactions
Pressure affects reactions involving gases
The pressure of a gas depends on the number of molecules
but also other factors too but for gcse we will just look at number of molecules
Nitrogen + hydrogen reverse arrows ammonia
N2 +3H2 goes to RR 2NH3
Rules
If we increase pressure on a rr at equilibrium, the position of equilibrium shifts to the side with the smaller number of molecules
and if we reduce the pressure then the position of the equilibrium shifts to the side with the larger number of molecules
If the number of molecules is the same on both sides then changing the pressure would have no effect of the position of equilibrium
61
REQUIRED PRACTICAL - THE RATE AND EXTENT OF CHEMICAL CHANGE
EFFECT OF CONCENTRATION ON RATE OF REACTIONS
There are 2 different methods and we should know both..
First tell me about the disappearing cross experiment. Use it to explore the effect of concentration on rates of reactions.
Sodium thiosulfate solution + hydrochloric acid -----> Sulfur (solid)
If we react those reactants then one of the products is sulfur and sulfur is a solid.
The sulfur makes the solution go cloudy and scientists call this cloudiness TURBIDITY and we can use this to see how long the reaction takes to finish. Here is the method:
1)use measuring cylinder to put 10cm3 of sodium thiosulfate solution into a conical flask
and place a conical flask onto a printed black cross and add 10cm3 of hydrochloric acid into the conical flask
2) swirl the solution and start a stopwatch
and look down through the top of the flask
because After a certain time the solution will turn cloudy so Stop the clock when we no longer see the cross
3) Carry out experiment again using lower concentrations of sodium thiosulfate solution
and repeat whole experiment and calculate mean values for each concentration of sodium thiosulfate solution
Remember not to calculate any anomalous results when calculating a mean
One important idea linked to this practical is reproducibility.
Both this and the second experiment show us that the greater the concentration of a chemical reaction, the faster the reaction takes place
so because this result is shown by two different experiments, we can say that the finding is reproducible
62
what is a hypothesis
a proposal that could explain a fact or observation
| In science, a hypothesis must be testable
63
REQUIRED PRACTICAL - THE RATE AND EXTENT OF CHEMICAL CHANGE
EFFECT OF CONCENTRATION ON RATE OF REACTIONS
There are 2 different methods and we should know both..
First tell me about the disappearing cross experiment. Use it to explore the effect of concentration on rates of reactions.
One important idea linked to this practical is reproducibility. when is a measurement reproducible and what is the problem with the disappearing cross experiment
A measurement is reproducible if it can be repeated by another person or using a different technique or equipment and still get the same result
The problem with the disappearing cross experiment is that different people have different eyesights meaning some can see the cross for longer than others so they may not get the same results
However, because all the students use the same size printed cross, hopefully, this problem may not be too great.
64
REQUIRED PRACTICAL - THE RATE AND EXTENT OF CHEMICAL CHANGE
EFFECT OF CONCENTRATION ON RATE OF REACTIONS
There are 2 different methods and we should know both..
Tell me about the 2nd method - measuring the volume of a gas produced by a reaction
Take a look at this reaction :
Magnesium + hydrochloric acid ---> magnesium chloride + hydrogen
This reaction produces hydrogen gas
here we are reacting magnesium with hydrochloric acid
This reaction produces hydrogen gas and this allows us to measure the volume of hydrogen gas produced
Method :
1-Use a measuring cylinder to place 50cm3 of hydrochloric acid into a conical flask and Attach the conical flask to a bung and delivery tube
2-Place the delivery tube into a container filled with water and Then place an upturned measuring cylinder also filled with water over the delivery tube
3-Add a 3cm strip of magnesium to the hydrochloric acid and start a stopwatch and The reaction produces hydrogen gas which is trapped in the measuring cylinder
4-Every 10 seconds we measure the volume of hydrogen gas in the measuring cylinder and we continue until no more hydrogen is given off an we should Repeat the experiment using different concentrations of hydrochloric acid
Both this and the first experiment show us that the greater the concentration of a chemical reaction, the faster the reaction takes place
so because this result is shown by two different experiments, we can say that the finding is reproducible
65
All separation techniques including paper chromatography are physical processes meaning what
meaning that they do not involve chemical reactions and no new substances are made.
66
What does paper chromatography allow us to do
separate substances based on their solubilities
67
what is solubility
the degree to which a substance dissolves in a solvent to make a solution
68
what is a solvent
Just like an ordinary liquid in which another substance dissolves in to make a solution
69
what do we call paper in paper chromatography and why
the stationary phase because it does not move.
70
what do we call the solvent and why in paper chromatography
the mobile phase because it does move
71
why does paper chromatography work
because each chemical in the mixture will be attracted to the stationary phase (the paper) to a different extent
Chemicals that are strongly attracted to the stationary phase will not move very far but chemicals that are only weakly attracted will move further up the paper
72
in paper chromatography, what will a pure chemical produce but what will chemicals in a mixture produce
a pure chemical will produce a single spot in all solvents but the chemicals in a mixture may separate into different spots depending on teh solvent.
73
why do we draw our starting line in pencil for paper chromatography?
Because if we drew the line in pen then the pen ink would move up the paper with the solvent
74
Paper chromatography required practical - we have a sample of food colouring which is a mixture of chemicals and we'll call it U for unknown.
We also have four known food colourings that it could contain and we are going to label these A-D
1-First use a ruler to draw a horizontal pencil line on the chromatography paper around 2 cm from the bottom of the paper and Mark five pencil spots at equal spaces across the line, leaving at least 1 cm clear at each side
2- Use a capillary tube to put a small spot of each of the known food colours and the unknown colour on the pencil spots and It is important that we keep the spots relatively small as this prevents the colours from spreading onto each other later
3-Now pour water into a beaker to a depth of 1 cm (water is the solvent in this case) and Attach the paper to a glass rod using tape and lower the paper into the beaker
pencil line with the spots of ink must be above the surface of the water otherwise the water will wash the ink off the line.
The sides of the paper must not touch the side walls of the beaker, if that happens then it will interfere with the way that the water moves
We usually put a lid on the beaker to reduce evaporation of the solvent
4-At this stage, the water will move up the paper and the colours will be carried up, during this time, we need to be careful not to move the beaker but Remove the paper when the water has travelled around three quarters up
and Here use a pencil. to mark the point where the water has reached then finally hang the paper to dry
75
what should we do in paper chromatography if we want to identify the chemicals in the colours
calculate the RF value
76
how to calculate the RF value
RF value = distance moved by chemical / distance moved by solvent
ANSWER SHOULD ALWAYS BE LESS THAN 1
77
Gases in the atmosphere have stayed pretty constant for the last 200 million years but before that there were huge changes:
First billion years was intense volcanic activity
volcanoes releases the gases that formed the atmosphere, one of these was water vapour
As earth cooled, water vapour condensed to form oceans
volcanoes also released huge amounts of carbon dioxide
so in this early stage, the earth's atmosphere consisted mainly of carbon dioxide with little or no oxygen - very much like Mars/Venus atmosphere today, volcanoes also released other gases including nitrogen which gradually built up in the atmosphere eg small amounts of methane and ammonia
Water vapour from volcanoes condensed to form the oceans
Some of the CO2 dissolved in the oceans to form a weak acid
These reacted with minerals in the sea to form precipitates
Over time, this formed sediments of carbonate rock on the sea bed
Some of the CO2 in the sea was used to make corals and shells of organisms eg mussels
When these died they formed sedimentary rock limestone, this removed CO2 from the atmosphere
Also photosynthetic algae first evolved in the oceans and photosynthesis produced oxygen which entered the atmosphere
Over following billion years, plants evolved, increasing amount of oxygen in the atmosphere and at some point , the level of oxygen reached the point where animals could evolve.
As well as producing oxygen, photosynthesis also takes in carbon dioxide
The carbon dioxide can be trapped in fossil fuels and again that caused the level of CO2 in atmosphere to fall
78
fossil fuels definition plus examples
non renewable resource formed over millions of years
coal
oil
gas
All fossil fuels contain trapped carbon
That carbon is part of the carbon dioxide taken in by photosynthesis
79
how coal formed
from remains of ferns and trees
if these die in marshy wetlands then they do not decompose and that can be due to lack of oxygen or acidic conditions these both prevent bacteria from carrying out decomposition
Over time the plant remains are covered with sediment and compressed
High temp and pressure creates coal
80
how oil formed
crude oil formed from plankton
when they died they settle in mud near sea bed
if oxygen is not present then they do not decompose and over time are compressed by sediment
Heat and pressure then convert them to crude oil
81
how natural gas formed
Mainly in the hydrocarbon methane
| Often find near deposits of oil because natrual gas is formed from plankton in a similar way to oil
82
greenhouse gases
water vapour
co2
methane
83
greenhouse effect
1- energy from sun travels to earth as short wavelength radiation eg ultraviolet // uv and visible light
some reflects back to space but most passes easily through atmosphere because short wavelength radiation does not interact strongly with the gas molecules in the atmosphere; the energy of the radiation is absorbed when it reaches the surface of the earth
surface of earth the radiates as long wavelength radiation eg infrared
some long wavelength radiation interacts with the greenhouse gas molecules in the atmosphere ie the energy in the long wavelength radiation is absorbed because energy is trapped, temp increases
Greenhouse effect keeps warmth for life, without, would be too cold for most organisms to survive.
84
Resources - modern agriculture lets us do what
to grow enough cotton to meet the needs of the world
Also agriculture helps us use Earths resources more efficiently
85
resources - humans plant trees which can be used for what
for timber or fuel eg powerstations run on biofuels like woodhsip
86
In some cases, chemistry has let us replace natural resources with a synthetic alternative eg rubber talk about rubber
natural rubber comes from tree sap
| Synthetic rubber is produced from crude oil
87
what resource is metal
finite
88
what resource is wood
renewable
89
important that out activities are sustainable what does this mean
we can meet our needs without preventing future generations from meeting theirs
90
chemistry is important for how we use resources give examples
eg artificial fertilisers allow us to grow more food with the land available
Chemistry also helps provide water safe to drink
Processes like phytomining and bioleaching help us extract metals more efficiently
91
humans do not just drink any water....water must be sufficiently low in levels of dissolved salt like what?////
drinking water cannot have high levels of microbes eg what?
sodium chloride
| bacteria
92
in UK what provides most of our potable water
rain water - it contains low levels of dissolved substances
| we collect it in the ground in aquifers and in lakes rivers and reservoirs, all these are good sources of freshwater
93
to produce potable water steps
first choose a good source of fresh water eg river
Then pass the water through filter beds to remove materials like leaves or suspended particles
Finally water is sterilised to kill microbes. In UK we use chlorine to sterilise potable water but some parts of the world ozone or UV light is used instead.
94
In UK there is a huge access to fresh water eg rivers and we already know they have low levels of dissolved minerals but in other places, fresh water is scarce eg too salty to drink like sea water which has high levels of dissolved minerals. In this case, potable water is produced by desalination. whAT DOES THIS MEAN?
It means reducing the levels of dissolved minerals down to an acceptable level for potable water
95
what are the two ways of doing desalination
to use distillation
to pass water through membranes, this is called reversible osmosis
Both these reduce levels of dissolved minerals but both require great energy so are expensive.
96
how we use a great deal of water and only a bit to drink ie what else do we use for
personal hygene - baths and showers
flush toilets, wash clothes
for agriculture
97
why does all waster water have to be carefully treated before being released back to environement
because all the waste contains large amounts of organic molecules eg urine and faeces and harmful microorganisms like bacteria.
98
how to treat water stages
1' - sewage is screened by passing through a mesh which removes solids and pieces of grit
2-Sewage is allowed to settle in large sedimentation tanks producing a liquid effluent and a semi solid sludge which sinks
3-Sludge is taken away and digested by anaerobic bacteria
In absence of oxygen, these bacteria produce biogas which can be burned for electricity
4-At the end, the digested sludge can be used as fertilisers for farming
99
what is liquid effluent
liquid waste
100
talk about treatment of liquid effluent
liquid effluent contains a large amount of organic molecules and harmful microorganisms that both must be reduced before returning to the environment.
So air is bubbles through the liquid effluent allowing anaerobic bacteria to multiply.
In presence of oxygen, anaerobic bacteria digest the organic molecules and harmful microorganisms
After this, the liquid effluent can be safely discharged into nearby rivers or the sea .
101
a lot of water is used by industry give two examples
in making paper and chemicals
102
when water is treated before water can safely enter the general sewage system, what needs to happen?
any harmful chemicals first need tobe removed
103
In some parts of the world, treated sewage is used directly to produce potable water but not in where
not in UK
104
Comment on how potable water can be produced (not in UK) 3 ways - compare
easiest way to produce potable water is to use ground 3 other ways :
1) From aquifers :
water from aquifers- usually this is safe to drink once it has been treated with chlorine
Can sometimes be polluted with fertilizer from farms though so the water from aquifers needs to be tested carefully
2)Directly from wastewater :
We can make potable water directly from waste water eg sewage but this takes many purification steps so only happens when water is scarce
3)Salt water:
salt water needs to be desalinated to produce potable water it required much energy and is expensive
105
most metals are found where
in earths crust and already reacted with otehr elements eg oxygen
106
worldwide demand for metals is going up...what is a really important metal and what is it used in
copper, used in electronic equipment such as phones
107
Each year millions of tons of metal are extracted from Earth's crust in where
in mines
108
what is a metal ore
a metal ore contains enough metal to make it economical to extract the metal
109
problem is that unlike a metal ore usually is, copper ores are becoming scarce so we will need to extract from low-grade ores containing a small amount of copper and so it is harder to extract the copper economically from the ores. How this is done (2 methods plus explain them)
PHYTOMINING - plants are grown on land containing the metal compound we want
plants absorb the metal compound and concentrate it in their tissue
plants are then harvested and burned
at end, the ash contains a high concentration of metal compound
BIOLEACHING- uses bacteria as bacteria are mixed with the low grade ore. Bacteria carry out chemical reactions and produce a solution called leachate (which contains the metal copper we want)
At the end of both these the metal cccccoper we wanted has been extracted from the low grade ore.
110
After extracting from ore we want to extract metal from copper....explain how to do that 2 ways and the goods about them
We can displace the copper using iron. iron is more reactive than copper. We usually use scrap iron which is more reactive than copper and is usually cheap. We can also extract the copper using electrolysis.
1-both allow us to economically extract metals from low grade ores - important since earth's resources of metal ores are limited
2-these methods do not involve digging transporting and disposing of large amounts of rock unlike in traditional mining.
111
why do scientists believe climate change is real
due to evidence for it being shared between scientists can then criticise the evidence and decide if it is valid , this is then peer reviewed and allows scientists to detect false claims eg based on poor evidence or bias
112
why is it hard understanding climate change
since climate change is complex
since. climate change is difficult to model - at times we hear stories about it in media that are simplified or bias or speculation absed on only parts of the evidence
113
why are there uncertainties with climate change
since we cannot predict with certainty how much temperature of the atmosphere will increase - this can lead to speculation in the media.
114
talk about the combustion of the hydrocarbon methane
methane + oxygen ----> carbon dioxide + water
CH4 + 2O2. CO2 +2H2O
methane is. found in natural gas and is used to heat homes
carbon atom in methane molecule has been oxidised to form gas CO2 and hydrocarbon oxidised to form water vapour
this process is complete combustion and we can tell that because we have made co2
FOR COMPLETE COMBUSTION TO HAPPEN WE NEED PLENTY OF oxygen
CO2 is a greenhouse gas so when we burn fuels and release CO2 it contributes to climate change
115
iF THE amount of oxygen is reduced from combustion of the hydrocarbon methane, we can make carbon monoxide instead of dioxide....describe it
toxic gas
no colour
no smell
so have many detectors at home
116
3 products of combustion summary
co2, water vapour, carbon monoxide
