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GCSE Chemistry > Chemistry Paper 2 > Flashcards

Chemistry Paper 2 Flashcards

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1
Q

Pure Substance

A

Single element or single compound.

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2
Q

Alkanes

A

CnH2n+2

  • if we know the number of carbon atoms (n) we can calculate the number of hydrogen atoms
  • multiply by two and then add two
  • saturated molecules, carbon atoms are fully bonded to hydrogen atoms
  • only have single covalent bonds between the carbon atoms
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3
Q

Hydrocarbons

A

Methane
CH4

Ethane
C2H6

Propane
C3H8

Butane
C4H10

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4
Q

Alkene

A
  • have double covalent bond between two carbon atoms
  • more reactive then alkanes

Test For Alkene
- Shake with orange bromine water should turn transparent

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5
Q

Catalysts

A

Increase rate of reaction without being used up

Provide different pathway for reaction that requires lower activation energy.

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6
Q

Copper Sulphate Reaction

A

Hydrated Copper sulphate (Blue) is heated to form
- anhydrous copper sulphate (white)
- water
add water back to form Hydrated Copper Sulphate (blue)

forward reaction is endothermic (putting heat in)
backwards reaction is exothermic (energy is released, the reactions get hot)

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7
Q

Equilibrium

A

Sealed Container, no reactants or products can escape

Equilibrium - forward and reverse reactions occur at the same rate in a sealed container

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8
Q

Extracting Metals

A

Phyto mining
Plants absorb metal compound and are burned.
Ash contains high level of metal compound.

Bioleaching
Bacteria mixed with ore carry out chemical reactions and produce solution called leachate.

Use displacement or electrolysis to extract metal from metal compound.

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9
Q

Atmosphere

A

Atmosphere Today
21% Oxygen
78% Nitrogen
1% Other Gases

Volcanoes
- released water vapour, condensed and formed oceans

  • released carbon dioxide, early atmosphere was mainly carbon dioxide with little or no oxygen, similar to Mars or Venus. Carbon dioxide dissolved in water to make weak acid, reacted with minerals to form
    precipitates and gradually carbonate rocks.
    some carbon dioxide was used to make shells and corals for organisms like mussels, and when they died they formed limestone (this removed carbon from atmosphere)
  • released nitrogen gradually
  • released small amounts of methane and ammonia
  • Photosynthetic algae first formed in the oceans, this released oxygen.

Early Atmosphere

  • large amounts of carbon dioxide
  • little oxygen
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10
Q

Fossil Fuels

A

Coal
- formed when ferns and Tress. If these die in wet marshy land they do not decompose (lack of oxygen or acidic conditions, Prevent bacteria from carrying out decomposition) Over time they are covered with sediment and compressed, high temperature and pressure creates Coal.

Crude Oil
- formed from plankton
Plankton - tiny plants and animals found in sea.
when they die they settle in mud on sea beds, if oxygen is not present they do not decompose. Over time they are compressed by sediment, heat and pressure convert them into crude oil.

Natural Gas

  • Natural Gas is often the hydrocarbon methane
  • found near deposits of oil because natural gas is also formed from plankton in a similar way to oil.
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11
Q

Greenhouse Effect

A

Energy from sun travels to the earth as short length radiation (visible light). Most passes through easily some reflects back. Earth radiates back the energy as long wavelength (infra-red), and is absorbed by the molecules of gas in the atmosphere.

short length radiation does not interact strongly with gas molecules in the atmosphere

longwave length radiation interacts with the gas molecules in the atmosphere and is absorbed

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12
Q

Rate of Chemical Reaction

A

Rate of Chemical Reaction - determined by the frequency of successful collisions

  • reactions are rapid initially because we have a large number of reactant molecules, this means we have a large number of collisions per second
  • Overtime reactions slow down because the number of reactant molecules is running out, smaller number of collisions per second
  • finally the reaction stops because all of the reactant molecules have run out, collisions per second is zero
  • rate is proportional to the concentration
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13
Q

Effect of Surface Area on Rate

A

Effect of Surface Area on Rate

  • particles can only react with particles on the surface of the solid
  • Two blocks from the same block (cutting in half) have more surface area then one block, more particles to react means faster reaction
  • Smaller sized blocks of solid reactants have a greater surface area to volume ratio than larger blocks
  • This means that they have more particles on the surface so there are more collisions per second, this increases rate of reaction
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14
Q

Catalysts

A

Catalysts

  • increase rate of reaction without being used up
  • allow us to quickly carry out reactions without needing to increase temperature. This saves money
  • increase rate by providing a different pathway for reaction that has a lower activation energy
  • Different reactions need different catalysts
  • enzymes act as catalysts in living organisms
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15
Q

Hydrated Copper Sulphate (Blue) Reversible Reaction

A
  • if we heat Hydrated Copper Sulphate (endothermic), we produce anhydrous copper sulphate (white) + water
  • If we add the water back then the reaction reverses, energy is released (exothermic) and we get Hydrated Copper Sulphate (Blue)
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16
Q

Equilibrium

A

Equilibrium

  • reaction is taking place in a sealed container
  • container prevents any reactants or products from escaping
  • At some point the forward and the reverse reactions will take place at the exact same rate (equilibrium)

Le Chatelier’s Principle
- if reaction is at equilibrium and a change is made to the conditions, then the reaction responds to counteract the change

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17
Q

Pressure and Reversible Reactions

A

Pressure and Reversible Reactions

  • if we increase the pressure on a reversible reaction at equilibrium, the position of the molecule shifts to the side with the smaller number of molecules
  • if we reduce the pressure, the position shifts to the side with larger number of molecules
18
Q

Crude Oil

A

Crude Oil

  • Crude Oil is a finite resource (will run out one day)
  • Formed over millions of years from the remains of tiny sea creatures called plankton which were berried in mud
  • Crude oil is a mixture of molecules called hydrocarbons
19
Q

Hydrocarbons

A

Hydrocarbons are molecules made up of hydrogen and carbon atoms only

20
Q

Properties of Hydrocarbons

A
  • fluids with a high viscosity flow slowly (tells us the thickness of a fluid)
  • as the size of the hydrocarbon molecules increases, the molecules get more viscous
  • as the size of the hydrocarbon molecules increases, the molecules get less flammable
  • as the size of the hydrocarbon molecules increases, the boiling point also increases
21
Q

Combustion of Hydrocarbons

A

During Combustion of Hydrocarbons the carbon and hydrocarbon atoms react with oxygen and become oxidised to release energy
- if oxygen is unlimited this reaction produces carbon dioxide and water (complete combustion)

22
Q

Fractional Distillation of Crude Oil

A

Fractional Distillation

  • in order for hydrocarbons to be useful we have to sperate them
  • crude oil is separated into fractions. Fractions contain hydrocarbons with similar number of carbon atoms
  • crude oil is heated, all of the hydrocarbons evaporate and turn into a gas.
  • all of the vapour is fed into a fractional distillation column, the column is hotter at the bottom and cooler at the top
  • Hydrocarbons condense when they reach there boiling point, the liquid fractions are then removed
  • The remaining hydrocarbons continue moving up the column, these now condense when they reach there boiling points
  • Very long chain hydrocarbons have high boiling points, these hydrocarbons are removed from the bottom of the column
  • Very short chain hydrocarbons have got very low boiling points and these do not condense, they are removed form the top of the column as gases
  • some fractions are used as fuel
  • some are used as feedstock (chemical used to make other chemicals)
23
Q

Cracking

A

Cracking

  • long chain hydrocarbons are not flammable, they do not make good fuel (need to be cracked into smaller hydrocarbons)
  • when we crack long chain hydrocarbons we produce short chain hydrocarbons + alkene’s
24
Q

Catalytic Cracking

A

Catalytic Cracking

  • use high temperature and a catalyst
  • catalyst is used to speed up reaction
25
Q

Steam Cracking

A

Steam Cracking

- use high temperature and steam

26
Q

Paper Chromatography

A

Paper Chromatography

  • 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 vey far
  • Chemicals that are weakly attracted will move further up the paper
  • A pure chemical will produce a single spot in all solvents
  • The chemicals in a mixture may separate into different spots depending on the solvent
27
Q

The Atmosphere of the Earth Today

A

The Atmosphere of The Earth Today
- 78% nitrogen
- 21% oxygen
- small proportion of other gases such as:
carbon dioxide, water vapour and noble gases

28
Q

The Atmosphere Volcanic Activity

A
  • volcanic activity released the gases that formed the atmosphere (water vapour)
  • as the earth cooled the water vapour condensed into oceans
  • released huge amounts of carbon dioxide, the Earths atmosphere mainly consisted of carbon dioxide with little or no oxygen (like Mars and Venus)
  • volcanoes also released other gases (nitrogen, methane and ammonia)
29
Q

The Early Atomosphere

A

The Early Atmosphere

  • mainly carbon dioxide
  • little but increasing amount of nitrogen
30
Q

The Atmosphere Changes

A

The Atmosphere Changes

  • water vapour condensed to form oceans
  • some carbon dioxide dissolved in water to form a weak acid
  • this reacted with minerals in the sea to form precipitates, this formed sediments carbonate rock on sea bed
  • some carbon dioxide in sea was used to make corals and shells of organisms such as mussels
  • photosynthetic algae began to evolve in the oceans and introduced oxygen into the atmosphere
  • plants also evolved increasing oxygen and decreasing carbon dioxide through photosynthesis
  • at some point the levels of oxygen reached a point where animals could evolve
31
Q

Coal

A

Coal

  • is formed from the remains of ferns and trees
  • if these die in marshy wetlands they do not decompose due to lack of oxygen or acidic conditions, prevent bacteria from carrying out decomposition
  • over time the remains are covered with sediments and compressed, high temperature and pressure creates coal
32
Q

Oil

A

Oil

  • crude oil is formed from plankton which are tiny plants and animals found in the sea
  • when these die they settle in mud on the sea-bed
  • if oxygen is not present they do not decompose
  • over time they are compressed by sediment
  • heat and pressure convert them into crude oil
33
Q

Natural Gas

A

Natural Gas

  • Natural Gas is mainly the hydrocarbon methane
  • often found near deposits of oil, because it is formed form plankton in a similar way to oil
34
Q

Potable Water (Rain Water UK)

A

Potable Water (Rain Water UK)

  • rain contains low levels of dissolved substances
  • rain water collects in the ground in aquifers and in lakes, rivers and reservoirs
  • pass the water through filter beds to remove suspended materials
  • The water is sterilised to kill microbes, in the UK chlorine is used
  • In other parts of the world ozone or ultraviolet light is used instead to sterilise water
35
Q

Potable Salty water (Sea water)

A

Salty Water (desalination)

  • reduces amount of dissolved minerals down to an acceptable level for potable water
  • to carry out desalination you could use distillation or reverse osmosis (passing water though membranes)
  • require very large amounts of energy (expensive)
36
Q

Waste Water Treatment

A

Waste Water Treatment

  • sewage is screened by passing through a mesh, removes solids
  • sewage is allowed to settle in large sedimentation tanks, this produces liquid effluent (liquid waste) and a semi-sloid sludge which sinks
  • sludge is taken away and digested by anaerobic bacteria (in absence of oxygen, these bacteria produce biogas which can be burned for electricity)
  • digested sludge can be used as fertilisers for farming
  • liquid effluent contains large amounts of organic molecules and harmful microorganisms
  • air is bubbled through liquid effluent, this allows aerobic bacteria to multiply, in the presence of oxygen they digest organic molecules and harmful bacteria
  • liquid effluent can be safely discharged into nearby rivers or sea
  • chemical waste, any harmful chemicals first have to be removed before it can be treated like waste
37
Q

Potable Water (comparison)

A

Potable Water

  • easiest way is to use ground water from aquifers, safe to drink once treated with chlorine
  • can make potable water from waste water, however takes many purification steps, only done in places where water is scarce
  • salt water needs to be desalinated, requires lot of energy and is expensive
38
Q

Alternative methods of extracting Metals

A

Alternative methods of extracting Metals

  • A metal ore contains enough metal to make it economical to extract the metal
  • Ore’s are becoming scarce, this means we are going to have to extract metals from low-grade ores (contain only small amount of metal)
  • Harder to extract metal economically
  • To extract in an economical way we can use Phytomining and Bioleaching
  • These methods do not involve digging, transporting and disposing of large amounts of rock
39
Q

Phytomining

A

Phytomining

  • Plants are grown on land containing metal compound
  • Plants absorb metal compound
  • Plants are then harvested and burned
  • Ash contains high concentration of metal compound
  • We now need to extract the metal from the compound
  • In the case of copper compounds we can displace the copper using iron (scrap iron, cheap)
  • We can also use electrolysis
40
Q

Bioleaching

A

Bioleaching

  • bacteria are mixed with low grade ore
  • bacteria carry out chemical reactions and produce a solution called leachate
  • leachate contains the metal compound that we want
  • We now need to extract the metal from the compound
  • In the case of copper compounds we can displace the copper using iron (scrap iron, cheap)
  • We can also use electrolysis

GCSE Chemistry (2 decks)

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