Chemistry Paper 1 & 2 Flashcards
1
Q
Element
A
substance made up of only 1 atom that all have same no. of protons
2,8,8,2
2
Q
Compound
A
Contain 2 or more elements chemically combined
3
Q
Mixture
A
Consists of 2 or more elements or compounds not
chemically combined together.
4
Q
Particles
A
Protons- mass: 1, charge: +1
Neutrons-mass:1, charge: 0
Electrons- mass: very small, charge: -1
5
Q
Mixtures can be separated by…
A
Filtration- separate insoluble solid from liquid.
Crystallization- separate soluble solid from liquid. water will evaporate.
Simple distillation- evaporate the liquid by heating, condense liquid back to a vapor by cooling
Fractional distillation- separate a mixture of different liquids, and they must have different boiling point.
evaporated solvent and collecting
Paper chromatography- different substances have different solubilities.
6
Q
Isotopes
A
Same no. of protons, different number of neutrons
7
Q
John Dalton
A
Solid sphere, can’t be created/ destroyed. Were arranged in atomic weight.
8
Q
JJ Thomson
A
Plum pudding model
Positively charged sphere
Negatively charged electron
Whole atoms is neutral
9
Q
Rutherford
A
Alpha particles went straight through gold foil, however some deflected (changed direction), reflected meaning atom wasn’t empty.
-The nucleus is surrounded by negatively charged electrons.
-nucleus is positively charged
-most of the atom was empty space.
-mass concentrated at the centre
10
Q
Niels Bohr
A
Electrons exist in shells, at specific distances.
11
Q
James Chadwick
A
Nucleus contains of neutrons and protons.
12
Q
Describe three other differences between the nuclear model of the atom and the plum pudding model.
A
-in nuclear, the atom is mostly empty space.
-the positive charge is all in the nucleus in nuclear, in the plum pudding model the atom is a ball of positive charge with embedded electrons.
-the mass is concentrated in the nucleus, in the plum pudding model the mass is spread out.
13
Q
Why is electrons with less shells less reactive?
A
Outer electrons are closer to nucleus
Greater attraction between nucleus and electrons
More energy needed to remove electrons, more difficult
14
Q
Groups ( 8 groups)
A
Rows , eg Li, Na, K.
No. of electrons outer shell
meaning similar chemical properties.
15
Q
Periods (7 periods)
A
Columns, eg, Li, Be, B, C
no. of shells
16
Q
Group names
A
Group 1- alkali , more reactive as they go down.
Group 2- alkaline
Middle- Transition metals
Group 7- Halogens, less reactive as you go down
Group 8- Noble gases, they are unreactive and do not easily form molecules because they have eight electrons in their outer shell, which are stable.
17
Q
Metals and Non metals
A
Metals always form positive ion.
18
Q
Group 0
A
Noble gases
Colorless gas! Non flammable.
They are unreactive as they have a full outer energy shell.
The boiling points of the noble gases increase with going down the group, as relative masses increase.
19
Q
Group 1
A
Alkali metals and have similar chemical properties, as they have single electron in their outer shell.
Low density, increases when going down.
In Group 1, the reactivity increases going down the group, loses its electron more easily, as its further away from nucleus.
React with water-> produces hydrogen gas, and form hydroxides that dissolve in water to give alkaline solutions
React with chlorine-> produces salt, form white salts, called sodium chloride.
React with oxygen-> metal oxides
Low density, soft
Low melting boiling points. Reactions are vigorous
20
Q
Group 7
A
Halogens
Colored vapours,
Fluorine is a very reactive, poisonous yellow gas.
Chlorine is a fairly reactive, poisonous dense green gas.
Bromine is a dense, poisonous, red-brown volatile liquid. lodine is a dark grey crystalline solid or a purple vapour.
In Group 7, the more down you go in group an element is the higher its relative mass (molecules get bigger), melting point and boiling point, increases.
Going down group 7:
the atoms become larger
the outer shell becomes further from the nucleus
the force of attraction between the nucleus and the outer shell decreases
an outer electron is gained less easily
the halogen becomes less reactive
Higher relative mass
flouride, chloride
21
Q
Oxidation and Reduction equations
A
Oxidation: Al–> Al3+ +3e-
Reduction: O + 2e- –> O2-
22
Q
Acids, neutral, Alkaline
A
Acids- 1-6, red, orange, yellow
Neutral- 7, dark green
Alkaline- 8-14, purple, blue
23
Q
Ions
A
Formed when atoms lose (positive ions) or gain electrons (negative ions)
24
Q
Ionic bonding
A
Oppositely charged ions
Held by electrostatic forces in a giant lattice.
Metals and non metals
High melting/boiling points
Only conduct electricity when dissolved in water, as ions are free to move.
25
Ionic compounds
An ionic compound forms giant structures, giant ionic lattice
Ionic compounds are held together by strong electrostatic forces of attraction between oppositely charged ions, high melting and boiling points.
26
Water, Methane, Ammonia
H20
CH4
NH3
27
Simple covalent bonding
Share pairs of electrons.
Non metals
Don't conduct electricity, as no ions.
Weak intermolecular forces , low melting/ boiling point. strong bonds
28
Metallic bonding
Share delocalised electrons.
Metals.
Strong forces, meaning high melting/boiling points, good conductors as they have delocalised electrons carrying charge
29
Small molecules
H2
Cl2
O2
Methane
Hydrogen chloride HCl
H2O
N2
Low melting points and boiling points. Need to break force not bond, so easily parted.
These substances have only weak forces between the molecules (intermolecular forces), strong covalent bonds.
Gases and liquids at room temperature.
The intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points.
These substances do not conduct electricity because the molecules do not have an overall electric charge.
30
Polymers
Polymers have very large molecules., made by joining of monomers
Single bonded
The atoms in the polymer molecules are linked to other atoms by strong covalent bonds.
The intermolecular forces between polymer molecules are strong and so these substances are solids at room temperature, but weaker than ionic or covalent bonds , lower boiling point than them
31
Properties of metals and alloys
Metals have giant structures of atoms with strong metallic bonding.
This means that most metals have high melting and boiling points.
In pure metals, atoms are arranged in layers, which allows metals to be bent and shaped.
Layers of atoms are able to slide over each other.
Pure metals are too soft for many uses and so are mixed with other metals to make alloys which are harder.
Alloys is a mixture of metals, the different sizes of atoms distort the layers, making it more difficult to slide over eachother, they are harder than pure metals.
32
Metal conductors
Metals are good conductors of electricity because the delocalised
electrons in the metal carry electrical charge through the metal.
Metals are good conductors of thermal energy because energy is
transferred by the delocalised electrons.
33
Giant covalent structures
strong bonds
high melting and boiling points
-diamond, made from carbon
-graphite, made from carbon
- silicon dioxide, silicon and oxygen
34
Diamond (see pictures)
each carbon atom bonds to 4 other carbon atoms by covalent bonds
Very hard , and melting points (strong bonds)
Don't conduct electricity, no electrons are free to move
35
Silicon dioxide
silicon and oxygen
In silicon dioxide, each silicon atom is bonded with 4 oxygen atoms.
has a high melting point, it is a giant structure, strong bonds, a lot of energy needed to break bonds
The word ‘nano’ means the wires are very thin. a layer a few hundred atoms thick
36
Graphite (see pictures) not a metal as formed by carbon
each carbon atom bonds to 3 other carbon atoms by covalent bonds
High melting point
Layers free slide as weak forces between layers. Soft
Conduct electricity.
contain sheets of hexagons.
37
Graphene
Single layer of graphite
good conductor
strong
light
high melting and boiling points. Graphene’s many covalent bonds are strong and need energy is needed to break them.
38
Solid, liquid and gas
Solid-Have strong intermolecular forces holding the particles together. The particles are very close together, stuck in fixed positions but vibrating on the spot.
Liquids-the forces of interaction between particles are weak. The particles are randomly arranged and move slowly past each other.
Gases- no forces of interaction between particles. The particles are randomly arranged and move quickly and randomly with lots of energy
39
Fullerenes (see pictures)
Hollow shaped molecules
Based on hexagonal rings of carbon atoms but they may also contain rings with 5 or 7 carbon atoms.
Form spheres and tubes.
Buckminsterfullerene C60 (SEE PIC)
First fullerene discovered.
Hollow sphere
6 or 5 carbon rings
Uses are catalysts, huge surface area, great lubricants.
Form nanotubes
40
Nanotubes (see pictures)
tiny carbon cylinders
Strong bonds
Conducts electricity and thermal energy.
don't break when stretched
Used in electronics or to strengthen materials without adding too much weight, like tennis racket frames.
41
In the reaction shown by the equation below, what mass of sulfur dioxide can be made from 16 g of sulfur? (Mr of SO2 = 64)
S(s) + O2(g) → SO2(g)
Amount of S= 16 / 32
= 0.5 mol
The equation shows that 1 mol of sulfur reacts with 1 mol of oxygen molecules to make 1 mol of sulfur dioxide. This means that 0.5 mol of sulfur makes 0.5 mol of sulfur dioxide.
mass of SO2 = relative formula mass × mol
= 64 × 0.5
= 32 g
42
Moles formula
Mass(g)= No. of moles (mol) x formula mass g/mol
43
Moles to balance equations
first, find no. of moles, and then divide by the smallest moles in all the atoms, and put in equation.
44
calculate the amount in moles of oxygen molecules that reacts with 2 mol of magnesium metal.
2Mg(s) + O2(g) → 2MgO(s)
The equation shows that 2 mol of magnesium metal reacts with 1 mol of oxygen molecules.
45
law of conservation of mass
The law of conservation of mass states that no atoms are lost or
made during a chemical reaction so the mass of the products
equals the mass of the reactants.
46
Limiting reactant
1) Mass of reactants is less than the mass of the products
- When reactant is gas, the gas will not be part of the unsealed reaction vessel.
The reactant that is completely used up is called the limiting reactant because it limits the amount of products.
47
Number of atoms
= Avogadro constant × the amount of substance in mol
Calculate the number of water molecules in 0.5 mol of water.
Number of water molecules = Avogadro constant x amount of substance in mol
= 6.02 × 1023 × 0.5
= 3.01 × 1023
48
Concentration formula
Mass = concentration g/dm3 x volume dm3
1 dm3 = 1000 cm3
49
Oxidation and Reduction (OIL)
Oxidation is loss of electrons
Reduction is gain of electrons
50
Acid
hydrochloric acid produces chloride.
nitric acid produces nitrates.
sulfuric acid produces sulfates.
51
The Ions for Acids
An acid is a substance that forms H+ ions when dissolved in water.
A more acidic solution will have a greater concentration of H+ ions.
As we move down the pH values by 1 for acids, the concentration of H+ ions increases by a factor of 10.
6pH to 4pH ----> 10 x 10
52
Ions for Bases
When alkalis dissolve in water, they produce OH- ions (negative hydroxide ions)
53
Measure pH of solution
If universal indicator is added to a solution it changes to a colour that shows the pH of the solution.
it will be green for neutral solutions.
orange/ red for acidic solutions.
blue/ purple for alkaline solutions.
A more accurate value can be obtained using a pH probe. We do this by placing the probe into the solution and looking at the digital screen to see the pH value.
54
Metals and acids
Metal + acid → salt + hydrogen
55
Reactions of metals with water
When a metal reacts with water, a metal hydroxide and hydrogen are formed. For example, sodium reacts rapidly with cold water:
Sodium + water → sodium hydroxide + hydrogen
56
Reactions of metals with dilute acids
When a metal reacts with a dilute
acid, a salt and hydrogen are formed. For example, magnesium reacts rapidly with dilute hydrochloric acid:
Magnesium + hydrochloric acid → magnesium chloride + hydrogen
Platinum will not react with dilute acids. Metals below hydrogen in the reactivity series do not react with dilute acids, and both gold and platinum are placed below hydrogen.
57
pH of alkaline solutions
The higher the concentration of OH- ions in an alkaline solution, the higher the pH.
A solution of 1 g/dm3 hydrochloric acid has a pH of 1.6. Predict its pH when it is diluted to 0.1 g/dm3.
The hydrogen ion concentration decreases by a factor of 10, so the pH increases by 1 from 1.6 to 2.6.
58
Neutralisation
Acid + Base---> Salt + Water
H+ + OH- ---> H20
The products of a neutralisation reaction are neutral
59
Metal carbonate and acid
Metal carbonate + acid ---> salt + water + carbon dioxide
60
Metal oxide and acid
Metal oxide + acid ----> salt + water
61
Bases & Alkali
base+ acid ----> salt + water
Bases neutralise acids.
A base can be a metal oxide or a metal hydroxide.
metal oxides
metal hydroxide
metal carbonate
Alkali is a base
Bases that dissolve in water are also known as alkalis.
A base that is insoluble in water is just a base and not an alkali.
62
Reactivity series
Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminum
Carbon
Zinc
Iron
Tin
Lead
Hydrogen
Copper
Silver
Gold
Platinum
63
Ores
compound of metal found in rocks, in Earth’s Crust
64
Strong and weak acids
A strong acid is completely ionised in aqueous solution. Examples
of strong acids are hydrochloric, nitric and sulfuric acids.
A weak acid is only partially ionised in aqueous solution. Examples
of weak acids are ethanoic, citric and carbonic acids.
65
More reactive than carbon- electrolysis
Less reactive than carbon- extracted using carbon
66
Electrolysis
Splitting of substances using electricity.
Passing an electric current through electrolytes causes the ions to move to the electrodes.
Positively charged ions move to the
negative electrode (the cathode), and negatively charged ions move to the positive electrode (the anode).
Ions are discharged at the
electrodes producing elements. This process is called electrolysis.
The metal (lead) is produced at the cathode and the non-metal (bromine) is produced at the
anode.
67
Electrode
made up of carbon/graphite, electric current passses through it
68
Suggest why the annual world production of iron is forty times greater than that of aluminium
* cheaper / costs less
* easier to extract
* iron has more uses
* more demand for iron
69
Why is mixture used as electrolyte?
A mixture is used as the electrolyte because a mixture of positive and negative ions are needed.
The electrolyte is a molten form of the ionic compound or the ionic compound dissolved in water (an aqueous solution).
The electrolyte needs to be molten or an aqueous solution so that the ions in the ionic compound are free to move and conduct electricity.
The electrolyte cannot be a solid ionic compound because the ions in a solid ionic compound are in their fixed positions and are unable to move, which means that they will not conduct electricity.
70
Water solution
H+ ions are attracted to the cathode, gain electrons and form hydrogen gas
OH- ions are attracted to the anode, lose electrons and form oxygen gas.
4OH- --> O2 + 2H2O + 4e-
the metal is produced at the cathode if it is less reactive than hydrogen.
hydrogen is produced at the cathode if the metal is more reactive than hydrogen
71
During electrolysis, at the cathode (negative electrode), positively
charged ions gain electrons and so the reactions are reductions.
At the anode (positive electrode), negatively charged ions lose
electrons and so the reactions are oxidations.
Reactions at electrodes can be represented by half equations, for
The electrodes are usually made of graphite, which is a giant covalent structure of carbon atoms. The electrodes are made of graphite because graphite has a very high melting point and is a very good conductor of electricity.
The electrodes are usually made of graphite, which is a giant covalent structure of carbon atoms.
The electrodes are made of graphite because graphite has a very high melting point and is a very good conductor of electricity.
72
Reduction and Oxidation half equations
Positive ions move to cathode and gain electrons to form atoms
Al3+ + 3e- ---> Al
This is reduction.
Negative ions move to anode and lose electrons to form atoms. Atoms join in pairs to form eg Cl2
2O2- ---> O2 + 4e-
Oxidation
73
percentage atom economy
product / reactant
74
Electrolysis in aqueous solutions
aqueous- dissolved in water
Water molecules split forming hydrogen ions( H+) and hydroxide ions (OH-).
Hydrogen is produced at the cathode if the metal is more reactive than hydrogen
if these ions are in (OH-), Fluoride (F), chloride (Cl), bromide (Br), iodide (I), and astatide (At) at anode
75
Electrolyte
liquid that conducts electricity.
76
Electrolysis
Anion (-), anode (+)
Cation (+), cathode(-)
77
Pairs
iodine, I2
bromine, Br2
chlorine, Cl2
fluorine, F2
oxygen, O2
nitrogen, N2
hydrogen, H2
I bring Clay For Our New House.
78
Endothermic and Exothermic
Endothermic- takes in heat from surroundings.
Exothermic- gives heat to surroundings.
79
Bioleaching and Phytomining
Bioleaching- use of bacteria to extract metal from ores, produces leachate solution
Phytomining- Plants absorb metal ions through their roots and burn and obtain metal from ash.
80
Making salts: Required Practical
Measure 20cm3 sulfuric acid and put in beaker
Heat using bunsen burner
Add coppy oxide in excess
Filter using filter paper and remove excess copper oxide
Pour solution to evaporating basic
Evaporate solution using water bath.
Leave for 24 hours
81
Electrolysis: Practical
Use a beaker and put electrolyte. Connect negative and positive electrode to power supply, on top of each electrode put a test tube.
Test any gas produced by holding a piece of blue litmus next to electrode.
Use different solutions.
82
Temperature changes: Practical
Place the polystyrene cup inside the glass beaker to make it more stable.
Measure an appropriate volume of each liquid, eg 25 cm3.
Check temperature
Add 5 ml of sodium hydroxide and check temperature
Add different amounts of sodium hydroxide and see temperature change.
83
Activation energy
Amount of energy needed for particles to react
84
Rate of reaction
=quantity of reactant used/
time taken
=quantity of product formed/
time taken
g/s, cm3/s
85
Collision theory
chemical reactions can only occur between particles when they collide. The collisions must have sufficient energy.
86
Factors affecting rate of reaction
Temperature
Surface area
Pressue/ Concentration
Catalyst
87
Temperature
As temp increases,
particles have more kinetic energy, move more quickly,
particles collide more
88
Surface area
If area increases,
More particles are exposed to other reactants
More collisions
89
Concentration/ Pressure
If increases,
Particles become more crowded,
more change of collisions,
Rate increases
90
Catalyst
Speeds up reaction without being used up.
Provides a different pathway, that has lower activation energy.
Saves money.
Reuse them again as not used up
91
Practical (To investigate the effect of changing the temperature on the rate of a reaction.)
-Add 50 cm3 of dilute sodium thiosulfate solution to a conical flask.
-Place the conical flask on a piece of paper with a black cross drawn on it.
-Add 10 cm3 of dilute hydrochloric acid to the conical flask. Immediately mix, and start a stop clock.
-Look down through the reaction mixture. When the cross can no longer be seen, record the time on the stop clock.
Measure and record the temperature of the reaction mixture.
Repeat steps 1 to 5 with different starting temperatures of sodium thiosulfate solution.
92
Practical ( To investigate the effect of changing the concentration on the rate of a reaction )
-Support a gas syringe with a stand, boss and clamp.
-Using a measuring cylinder, add 50 cm3 of dilute hydrochloric acid to a conical flask.
-Add 0.4 g of calcium carbonate to the flask. Immediately connect the gas syringe and start a stop clock.
Every 10 seconds, record the volume of gas produced.
-Repeat steps 1 to 5 with different concentrations of hydrochloric acid.
93
Reversible reactions
When products can react to form original reactants.
94
Example
( Blue )Hydrated copper sulfate ( reversible)—-> (white) anhydrous copper sulfate + water
Forward reaction is endothermic
95
Concentration and Reversible Reactions
96
Le Chatelier’s Principle
If a system is at equilibrium and the conditions change, the position of equilibrium moves to counteract the change.
97
Equilibrium is affected by:
Temperature
Concentration
Pressure
98
Temperature
Increase in temp- equilibrium moves to endothermic to reverse the change
Decrease in temp- equilibrium moves to exothermic to reverse the change
99
Pressure
-Increase in pressure causes the equilibrium position to
shift towards the side with the smaller number of molecules.
-Decrease in pressure causes the equilibrium position to shift
towards the side with the larger number of molecules .
To count molecules, only count big numbers, if no big numbers, count as one. ONLY BIG NUMBERS .
Negative kg mol, exothermic
100
Equillibruim
-Prevents the escape of reactants and products. In a closed system
-Equilibrium is reached when the forward and backward reactions occur at the same rate.
-concentration of reactants and products are constant
101
Concentration
-increase in concentration in left - equilibrium shifts to right to reduce effect of increasing concentration of reactant
-decrease in concentration in left-equilibrium shifts to the left to reduce the effect of decrease in reactant
102
Catalyst
No effect.
Speeds both, backward and forward reaction equally.
103
Crude oil
Formed from biomass/ plankton buried under mud for million years,compressed under heat and pressure.
will run out.
mixture of compounds, mostly hydrocarbon.
104
Hydrocarbon
Compound consisting of hydrogen and carbon atoms only
105
Alkanes
Saturated, as carbon atoms are fully bonded with hydrogen atoms single bonds.
CnH2n+2
n= carbon atoms
106
Physical properties of alkanes
Boiling points and viscosity(thickness), flow slowly increase as molecules get bigger.
Volatility decreases and less flammable, as molecules get bigger
107
Homologous series
Compounds with same chemical properties
108
Combustion of Hydrocarbons
hydrocarbon fuels release energy when they're combusted (burned)
Complete combustion=
hydrocarbon + oxygen (502)----> carbon dioxide (3CO2) + water (4H2O)
109
Incomplete combustion
Incomplete combustion=
Hydrocarbon + oxygen --> carbon monoxide + water + carbon dioxide
110
Alkanes (all are gases at room temp)
Methane CH4
Ethane C2H6
Propane C3H8
Butane C4H10
111
Alkenes
unsaturated, double bonds between carbon atoms.
CnH2n
More reactive than alkanes
if we add bromine water,
orange ---> colourless
Alkenes are used to make polymers
eg EthEne
112
Fractional distillation
In order for hydrocarbons in crude oil to be useful, we have to separate them.
113
Fractional distillation steps
Crude oil is evaporated, high temperatures.
Vapours are fed into fractionating column
Column is hot at bottom, cool on top
Gases condense, once they reach their boiling point, they turn to a liquid and are removed.
Long chained hydrocarbons have high boiling points, and are removed at the bottom.
Very short chained hydrocarbons, low boiling point, don't condense, and leave at top, as gases.j
114
Order of distillation
LPG (cooking)
Petrol (cars)
Kerosene (aircraft)
Diesel ( trains)
Heavy fuel oil ( ships)
Bitumen ( roofs)
115
Cracking
Thermal decomposition reaction, breaking down molecules by heating them.
116
Cracking purposes
There is a high demand for fuels with small molecules, as long chained molecules are not flammable.
Shorter- more useful
Convert long chained hydrocarbons into short chained hydrocarbon.
117
Catalytic cracking
Heat vaporises hydrocarbon
Vapours are passed over hot catalyst ( hot powdered aluminium oxide)
Comes into contact and splits.
Breaks into shorter chain alkane and an alkene
118
Steam cracking
Heat vaporises hydrocarbon
Vapours are mixed with steam, high temperature.
119
Formulation
a mixture that has been designed as a useful product
Examples- fuels, cleaning, medicines, fertilisers and foods.
120
Chromatography
Method of seperation and analysis of a mixture of soluble chemical substances, based on different solubilities.
121
Paper chromatography
A pure compound will produse a single spot in all solvents.
The compounds in a mixture may separate into different spots depending on the solvent.
More soluble substances travel further up the paper.
122
Mobile, stationary phase
Mobile- water that moves up
Stationary- paper, as it stays in same place
We use pencil, as pen would move up the paper with the solvent.
123
RF
Rf = distance moved by substance/
distance moved by solvent
124
Chromatography: Practical
Draw a pencil line across the chromatography paper, 1 - 2 cm from the bottom.
Use a pipette to add small spots of each ink to the line on the paper
Place the paper into a container with a suitable water in the bottom.
Allow the water to move through the paper, but remove the
chromatogram before it reaches the top.
Allow the chromatogram to dry, then measure the distance travelled by each spot and by water.
125
Test for hydrogen
Use a burning splint at the open end of a test tube of the gas.
A squeaky pop.
126
Test for oxygen
Use a glowing splint in mouth of test tube
Black/foamy
127
Test for carbon dioxide
Use lime water (aqeous solution of calcium hydroxide)
Turns milky/ cloudy
128
Test for chlorine
Use damp litmus paper.
The litmus paper is bleached and turns white.
129
For 200 million years, the proportions of different gases in the
atmosphere have been much the same as they are today:
*78% nitrogen
* 21% oxygen
* some, carbon
dioxide, water vapour and noble gases.
130
Earths early atmosphere
-Billion years ago, there was intense volcanic activity.
-Volcanic activity produced carbon dioxide, water vapor, and nitrogen, and small amounts of methane and ammonia.
-As the earth cooled the water vapor condensed to form the oceans
-when oceans formed , the carbon dioxide dissolved in the water, and carbonate were precipitated producing sediments .
-When plants died, the carbon they contained, became trapped in sedimentary rocks, and fossil fuels. Eg limestone
-Photosynthetic algae evolved in oceans, which produced oxygen, and took in carbon dioxide.
-Plants are now able to grow on the surface of the Earth.
-Carbon was trapped in fossil fuels.
131
Oxygen increased because of ...
Algae and plants
132
How did CO2 decrease?
- large amounts of CO2 dissolved in the oceans
-Animals fed on the plants which transferred carbon to their tissues including bones and shells
-When these organisms died, their remains formed sedimentary rocks
-Photosynthesis
-Formation of sedimentary rocks and fossil fuels that contain carbon.
133
-When the plants, plankton and animals died, they fell to the bottom of the seabed and got buried by layers of sediment (mud).
-Over millions of years, heat and pressure turned the dead material into fossil fuels (coal, crude oil and natural gas) or limestone.
134
Limestone
Limestone is formed from shells and skeletons of marine organisms.
135
Crude oil
-Crude oil and natural gas are made from deposits of plankton that have died and sunk to the bottom of the sea or the bottom of lakes.
-The plankton was then buried by layers of sediment, which prevented oxidation of the dead material due to a lack of oxygen.
-Over millions of years, the dead plankton has become crude oil and natural gas.
136
Coal
Coal is a fossil fuel which is formed from dead trees. The dead trees were buried by flooding, which prevented oxidation of the wood taking place due to a lack of oxygen. Over millions of years of compression and heat, the dead trees turned into coal.
137
Greenhouse gases have increased because of the following reasons:
Burning of fossil fuels –
the fossil fuels are oil, coal and natural gas. The burning of fossil fuels results in carbon dioxide being released into the atmosphere. We burn fossil fuels to heat homes and for transport (car, lorries, aeroplanes etc)
Farming –
the farming process emits carbon dioxide at every stage of production because each stage requires energy
Furthermore, the rearing of livestock, especially cattle, results in large quantities of methane, carbon dioxide and nitrous oxide being emitted into the atmosphere.
Deforestation --
When we cut forests down, carbon dioxide absorption stops as the trees are dead.
138
Describe the greenhouse effect in terms
of the interaction of short and long wavelength radiation with matter.
The short-wave radiation passes through the atmosphere and hits the earth.
Some of the energy that hits the earth is absorbed and the rest is re-emitted as longer wave radiation.
Some of the longer wave radiation goes into space and some is absorbed by the greenhouse gases.
The greenhouse gases that absorbed the long wave infrared radiation heat up and reradiate this thermal energy in all directions including back down towards earth, which heats the earth – this is the greenhouse effect.
As there are more greenhouse gases in the atmosphere, more of the long wave radiation that is being re-emitted from the earth is being absorbed and radiated back down to earth by the greenhouse gases.
This results in the temperature of earth rising, which is the enhanced greenhouse effect.
139
Greenhouse gases
Water vapour
Carbon dioxide
Methane
These keep earth warm, as they absorb heat energy and prevent it escaping to space
Too much will cause global warming,
140
Methane
Natural source- Decomposing plant material
Human made source- Rice paddy fields, cattle, coal mines
141
Water vapour
Natural source- Evaporation from oceans, lakes and rivers
Human made source- Burning hydrocarbon fuels
142
Evidence from climate change
Rising Sea Levels
The melting of the polar ice caps and glaciers is leading to rising sea levels
Animals die, can’t survive , extinct.
Frequent and intense drought
Crop failure and collapse of agricultural production, leading to hardship and starvation
Storms
The intensity of storms is increasing, more energetic and destructive
Extreme heat waves and rainfall
Great loss of life and destruction of infrastructure and ecosystems
Lack of reliable freshwater supplies results in economic and political instability as neighbouring countries compete for dwindling resources
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Carbon footprint
Total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event.
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Method of reducing carbon footprint
Methane is reduced- Eating less beef- Breed less cows, farm animals produce methane during digestion, and gets released to atmosphere.
Methane- Sending less waste to landfill by recycling more, meaning less wasteful to landfill
Carbon dioxide- Charging more tax on polluting vehicles, more expensive, less people will drive.
Carbon dioxide- Using biofuels, more plants, absorb more Carbon dioxide
Carbon dioxide- Capturing carbon dioxide produced in power stations and storing in rocks, not released to environment, less climate change. No holes in rocks, meaning they cant escape.
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Atmospheric pollutants
The combustion of fuels is a major source of atmospheric pollutants.
The gases released into the atmosphere when a fuel is burned may include carbon dioxide, water vapour, carbon monoxide, sulfur
dioxide and oxides of nitrogen.
Solid particles and unburned hydrocarbons may also be released that form particulates in the
atmosphere.
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Carbon dioxide
Burning fossil fuels, in power stations to make electricity and power cars.
hydrocarbon + oxygen --> carbon dioxide + water
Fossil fuels are hydrocarbons
Carbon dioxide is useful because plants use it for photosynthesis.
Chopping down trees, less photosynthesis, removes carbon dioxide
Too much is bad because it causes global warming.
Reduce by burning less fossil fuels, less electricity, less car journeys and flights.
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Carbon monoxide
Made when hydrocarbons burn in air, to make carbon dioxide, but when not enough oxygen, carbon monoxide is made.
hydrocarbon + oxygen (not enough oxygen) --> carbon monoxide + water
Toxic gas, colourless and odourless, hard to detect.
Binds to haemoglobin in red blood cells in place of oxygen, meaning less oxygen, less respiration, health problems.
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Reducing the Carbon footprint
Global climate change is a global issue
It is difficult to get all nations in the world to agree to make the major changes needed.
Science- dont have everything we need eg technology, hard for scientists to make models of what will happen.
Economics- make less money, economy may suffer, if prioritizing environment
Politics- not every countries will agree.
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Carbon dioxide and water vapour
Produced by complete combustion of hydrocarbon fuels
Methane + oxygen -> carbon dioxide + water
Greenhouse gases enhance the greenhouse effect, causes global warming, causes climate change.
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Sulfer dioxide (S02)
Sulfur reacts with oxygen during combustion to produce sulfur dioxide.
Causes respiratory problems and acid rain kills wildlife.
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Nitrogen oxides (NO)
The high temperature of engine causes the nitrogen in air to react with oxygen in air.
Causes acid rain, damages soil, no plants, respiratory problems.
Less catalytic converters
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Solid particulates fuels / soot (dusty powder carbon)
Solid carbon particles (or particulates) released from incomplete combustion clump together to form soot which gradually falls back to the ground
If they are inhaled they can damage the lungs and cause respiratory problems
They can cover buildings and statues, making them look unclean and accelerating corrosion
They can reflect sunlight back into space reducing the amount of light reaching the earth, this is called global dimming
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Climate change are effects of global warming
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Earths resources
Resources are needed for:
WARMTH
SHELTER
FOOD
TRANSPORT
Natural resources are materials that have been made from the formation of the earth.
Most of these natural resources can be used for human benefit and examples are fuels (petrol and diesel), building materials (wood and metals), materials for clothing (cotton), food and water etc.
Some natural products can be synthesised by scientists and chemists in a laboratory/ factory.
These synthesised products can be used to replace the natural products or to improve the natural products.
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Examples
For example, rubber can be made from the sap of trees.
Chemists can create synthetic rubber from man-made polymers, which can replace rubber made from tree sap.
Another example is fertilisers for crops. In the past, farmers spread manure on their crops (manure is animal faeces and dead plants). Chemists have created fertilisers that the majority of global farmers spread on their crops rather than using manure.
The main fertiliser that farmers use is ammonia, which is produced by the Haber process. The creation of ammonia in industry has increased yields from crops, which has led to intensive farming becoming widespread, thus allowing us to produce food in large enough quantities to support a growing population.
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There are two different types of natural resources;
Finite and Renewable Resources
Finite resources are also called non-renewables.
Finite resources are resources that will eventually run out. They will eventually run out because they are produced at a considerably slower rate than they are being used. eg crude oil, fossil fuels, (gas and coal), nuclear fuels
processed to provide energy and materials.
Renewable resources are resources that reform at a similar rate to/ faster than we use them.
Examples of renewable resources are food, fresh water, wind, solar and timber.
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Drinking water
Drinking water has have sufficiently low levels of dissolved salts such as sodium chloride
Drinking water cannot have high levels of microbes such as bacteria.
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Potable water
water which is safe to drink- potable water.
Pure water, does not have any dissolved substances, however potable does have dissolved substances like salt.
Rain water provides most of potable water as it contains low levels of dissolved substances .
Rainwater collects in the ground in aquifers and also in lakes rivers and in reservoirs
Potable water has a pH that is between 6.5 and 8.5. Water with a pH that is outside of this range is harmful for humans to drink.
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Treating Water from Surface or Ground Water
Fresh water from surface water or ground water still needs to be treated despite it being fresh water with low levels of dissolved substances. We treat fresh water to remove potential chemicals and pathogens.
The process in treating fresh water involves filtration and sterilisation.
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Filtration
The fresh water passes through a wire mesh, which is also known as a screen.
The mesh removes large pieces of debris in the water, such as twigs and weeds.
Filter through filter bed to remove insoluble particles .
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Sterilisation
To kill any harmful microorganisms like pathogens, bacteria or microbes, using chlorine, UV light
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For water to be potable, it must have...
-sufficiently LOW levels of dissolved salts and microbes
This is because dissolved salts can sometimes be harmful for humans
microbes can cause illnesses
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Water from Sea Water – Desalination
We can obtain potable water from sea water through a process known as desalination.
Desalination is a very expensive process because it uses lots of energy.
Therefore, a country would only obtain potable water from sea water if they had very little fresh water available to them.
We can obtain potable water from sea water by using either distillation or reverse osmosis
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One way of carrying out desalination is
Distillation- Sea water is heated until it boils. The salt remains in the liquid, and the steam is pure water. The steam is cooled and condensed to make potable water
Reverse osmosis- Water is put under high pressure and passed through a membrane which has tiny pores (holes) in it. The pores allow water molecules through, but prevent most
ions and molecules from passing through.
These reduce the levels of salt.
However both processes require very large amounts of energy which makes them very expensive.
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Waste water
Urban lifestyles and industrial processes produce large amounts of
waste water that require treatment before being released into the
environment.
Sewage and agricultural waste water- require removal
of organic matter and harmful microbes.
Industrial waste water- may require removal of organic matter and harmful chemicals.
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different wastes
human waste- contains harmful bacteria and high levels of nitrogen
compounds which can harm aquatic ecosystems.
industrial waste water- may contain harmful chemicals such as
toxic metal compounds.
agricultural waste water- may contain fertilisers or pesticides which can disrupt sensitive ecosystems.
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Sewage treatment involves the following steps:
-screening and grit removal to remove large particles.
-sedimentation produces sewage sludge and effluent (the liquid which remains on top)
-the sewage sludge is digested anaerobically by specific bacteria
-the effluent is treated with aerobic bacteria to reduce the volume of solid waste
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Alternative methods of extracting metals
The Earth’s resources of metal ores are limited.
One of the metals we are worried about is copper, as its ores are becoming limited.
Luckily new ways of extracting copper from low-grade ores have been developed. These include phytoming, and bioleaching.
No harmful gases are produced (e.g. sulfur dioxide) like in traditional mining.
Both methods cause less damage to the landscape than traditional mining, and both methods conserve supplies of high grade ores.
The main issue with these processes is that they're both very slow.
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Phytomining
Phytomining uses plants to absorb metal compounds.
The plants are harvested and then burned to produce ash that contains metal compounds.
Phytomining reduces the need for mining and reduces this damage.
Phytoextraction is slow, but it:
Growing plants is also dependent on weather condition.
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BIOLEACHING
Bioleaching uses bacteria to produce leachate solutions that contain metal compounds.
The metal compounds can be processed to obtain the metal
For example, copper can be obtained from solutions of copper compounds by displacement using scrap iron or by electrolysis
Bioleaching does not need high temperatures but it produces
toxic substances, including sulfuric acid, which damage the environment.
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Life cycle assessment stages (IMPACT ON ENVIRONMENT)
Extracting and processing raw materials
-using up limited resources ores and crude oil.
-damaging habitats, through quarrying, mining.
Manufacturing and packaging
-using up land for factories
-the use of machines and people
Use and operation during its lifetime
-cleaning
-repair
-using up limited resources, releasing pollutants.
Disposal at the end of its useful life
-using up land for landfill sites
-can all the product recycled or reused
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Life cycle assessment
Life cycle assessment Is used to assess the impact on the environment caused by manufacturing of products.
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Criticisms of LCAs
Criticisms of LCAs
It is sometimes easy to work out accurate numerical values for parts of a LCA.
For example, we can measure the amount of energy needed to manufacture a product, or the amount of carbon dioxide produced by transporting raw materials. However, some parts of a LCA require judgements, such as the effect of pollutants.
This means that completing a LCA is not a totally objective process, and different people might come up with different judgements.
It is important to consider who has completed the LCA and whether they have any bias
For example, if the LCA is completed by the company which is making and selling a product, they might only include some parts of the genuine environmental impact.
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PLASTIC AND PAPER BAGS
RAW MATERIALS:
Plastic- Crude oil is a finite resource; fractional distillation, cracking and polymerisation all require a lot of energy.
Paper- Can be made from recycled paper, or from trees. Making paper from trees requires more energy than recycling paper, but much less than making plastics.
MANUFACTURE:
Plastic- Cheaper to make large quantities of bags from plastic.
Paper-More expensive to make bags from paper because the handles must be glued on.
USE:
Plastic- Lower impact on the environment because plastic bags are usually stronger so they can be reused many times.
Paper- Relatively short lifetime; can only be reused a limited number of times.
DISPOSAL:
Plastic- Can sometimes be collected and recycled; if disposed of as litter, they do not biodegrade; in landfill, may take decades or centuries to degrade.
Paper- Can be recycled easily; if disposed of in landfill, they biodegrade quickly.
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Ways of reducing the use of resources
Metals, glass, building materials, clay ceramics and most plastics are made from limited natural resources.
Obtaining raw materials from the Earth by quarrying and mining causes environmental impacts
Some items made from these materials can be reused, and this saves the most energy and reduces the impact on the environment
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Examples
For example, glass bottles only need to be washed and sterilised before they can be filled again. Other products cannot be reused in this way, but they can be recycled
Metals can be recycled by melting and recasting or reforming into
different products.
The amount of separation required for recycling
depends on the material and the properties required of the final
product.
For example, some scrap steel can be added to iron from a
blast furnace to reduce the amount of iron that needs to be
extracted from iron ore.
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Reduce, Reuse and Recycle
End users must reduce material use: In order to keep developing sustainably, end users must reduce the amount of materials that they use. This can help to reduce the use of limited resources.
Users must reuse materials: Reusing materials reduces the amount new materials created. This in turn can reduce the amount of waste on earth.
Recycling materials saves energy: In comparison to creating new materials, recycling materials uses less energy. This means that we can also reduce the amount of waste and pollution.
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Advantages of recycling
-fewer quarries and mines are needed to extract finite reserves of metal ores
-less crude oil
-needs to be extracted from the crust as a raw material for making plastics.
-less energy is needed for recycling compared with making a new product from natural resources, so the emission of greenhouse gases is reduced.
-the amount of waste that is disposed of in landfill is reduced
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Disadvantages of recycling
-the collection and transport of used items needs organisation, workers, vehicles and fuel
-it can be difficult to sort different metals from one another.
-the sorted metal may need to be transported to where it can be turned into ingots
