Earth's atmosphere

How was the Earth’s early atmosphere formed

• Volcanic activity

• Mainly CO2

• Nitrogen, water vapour, traces of methane and ammonia

• Volcanic activity released water vapour; condensed to form oceans; CO2 dissolved in oceans; carbonates produced sediments; carbon locked in sedimentary rocks; algae and plants evolved and absorbed CO2 by photosynthesis and released O2; carbon locked up in fossil fuels

• Now: Amount of CO2 increased due to burning lots of fossil fuels, Difficult to predict effects.

What are the economies of developed countries based on

Energy obtained from fossil fuels so changes cost money to implement

What is carbon footprint

Total amount of CO2 and other greenhouse gases emitter over a product or event’s full life cycle. Reduce it by carbon capture.

How is sulfur dioxide produced and what does it do

When sulfur impurities burnt in fuels. Forms acid rain. Can be removed before burning. Change conditions where hydrocarbons are burnt

What are some examples of natural resources

• Metal ores

• Crude oil

• Limestone

Why is the time left before fossil fuels run out only rough estimates

Uncertainties in calculations

What gases cause global dimming and respiratory problems and acid rain

carbon monoxide, sulfur dioxide, nitrogen oxides

What is potable water

water that is fit to drink

How to make potable water

1. Reservoir: As water enters water treatment. Metal bars catch large objects.

2. Settlement Tank: sand and soil settle out

3. Aluminium sulfate and lime added (small dirt particles clump together and sink to bottom). Sludge dumped in landfill site.

4. Passed through fine sand and gravel filter removing remaining mud particles

5. Chlorine added to kill bacteria. Ozone or UV light used

6. pH of water checked corrected to neutral

How do you purify salt water

1. Made pure by distillation. Expensive process. High energy costs in boiling.
   Flash distillation: boiling under reduced pressure

2. Desalination: converting salty water to potable

3. Reverse osmosis: membranes used to separate dissolved salts from salty water. Uses energy to make high pressures needed

how to make potable water from sewage water treatment

• Sewage sent to pumping station

• It is screened and large solid objects are removed. Same done in settlement tank

• Primary sedimentation - Large paddles rotation push solids (sludge) to centre of tank, through pipe to storage

• Secondary sedimentation - Biological treatment. Aerobic digestion through useful bacteria by feeding on remaining organic matter and breaking it down.

• Water is disinfected and sterilised by filtration, chlorine, ozone and UV light

• Useful bacteria recycled back to secondary sedimentation tank

• Water safe to drink

• Sewage sludge treatment- dried and used as fertiliser or source of renewable energy by digesting anaerobically to make biomethane gas

How is copper metal extracted from ore

• Sulfuric acid to make copper sulfate solution. Electrolysis

• Smelting - ore heated to high temp. in furnace to make impure copper. Then used as electrode in electrolysis for pure copper. Expensive and polluting

How is copper extracted from phytomining

• Use plants to extract copper from low grade ores

• Grow plants on land containing copper ores

• Plants burnt to produce ash

• Ash dissolved in acid to produce copper compound solution

• Electrolysis of solution

How does bioleaching work

• Plant material mixed with specific type of bacteria which oxidise copper compounds within plant material to produce copper ions.

• Copper ions are dissolved in solution to form copper sulfate solution and then electrolysis done

What is a Life cycle assessment and how is it done

• Cost, energy, material inputs and outputs, and effect on environment

• How to get raw materials and cost

• How to make it

• Can it be reused, recycled and cost

• Actual disposal

What is corrosion

Caused by chemical reactions between metal and substances in environment. For iron, called ‘rusting’.

What is rusted iron called

hydrated iron (III) Oxide

What is needed for iron to rust

air and water

How can you prevent iron and steel from rusting

• Paint

• Oil/grease

• Plastic

• Less/more reactive metal

What is sacrificial protection

iron is attached to more reactive metal so it doesn’t rust. Iron is ‘galvanised’

What is the iron rusting experiment

• Tube A - Calcium chloride (to absorb water), cotton wool, nail. Lid closed. → no rust

• Tube B - Nail, boiled water, oil (so no air enters), lid closed. → no rust

• Tube C - Water, nail, no lid. → rust

What are alloys

Mixture of metals. Harder than pure as regular layers in pure metal distorted by differently sized atoms.

What is bronze an alloy of

Copper and tin. Tough. Resist corrosion.

What is brass an alloy of

Copper and zinc. Musical instruments, taps. Harder

What is gold allowed with to make harder

Silver, copper, zinc

What is steel an alloy of

iron and specific amounts of non-metal carbon.

What is high carbon steel like

Hard and brittle. Make cutting tools.

What is low carbon steel like

Softer and more easily shaped

What is stainless steel an alloy of

Iron, carbon, nickel and chromium. Hard and resistant to corrosion

Why are aluminium alloys useful

Low density

What does the properties of a polymer depend on

• monomers used

• Conditions chosen to carry out reaction

How to form low density and high density polyethene

high pressures; catalyst with slightly raised pressure.

What are thermosoftening polymers like

soften or melt easily. Intermolecular forces relatively weak. Made up of individual polymer chains tangles together

What are thermosetting polymers like

Not soften. ‘Cross-linking’ so strong covalent bonds. Will eventually char if heated strongly.

Describe glass and its properties

• Made from sand, limestone and sodium carbonate. Heated at high temp. to form molten glass.

• Infinitively recyclable

• Sustainable

• withstand high temp.

• Aesthetically pleasing

• Brittle and fragile. Costly. High energy

Describe ceramics and its properties

-Heating mixtures of clay, powders and water and shaping. Heated in furnace. Covered in glazes (waterproof and shiny).

High energy to break.
Reusable
Good thermal insulator
long-lasting
brittle
Can’t be recycled

Describe polymers and its properties

• From crude oil

• Not biodegradable. Unsustainable

• Reused and recycled

• Cheap

• Doesn’t break easily

• Cracking and polymerisation → high energy

Describe composites

Made of 2 materials. One acts as binder for other, improving its properties → reinforcement

E.g. concrete, fibreglass, plywood

What is the equation for the haber process

Nitrogen(N2) + Hydrogen(3H2) →←(iron catalyst) Ammonia(2NH3)

Forward reaction exothermic

What are the conditions needed for the Haber process

• 200atm pressure

• 450C temp.

• iron catalyst

What is the process of the Haber Process

• Hydrogen and nitrogen gases pumped in

• Mixture compressed to 200atm pressure and heated to 450C

• Goes into reaction vessel with iron catalyst

• Mixture of gases cooled in cooling chamber. Ammonia liquefies and gets separated

• unreacted hydrogen and nitrogen returned to reaction vessel via compressor

How is nitrogen extracted from air

Fractional distillation of liquid air

How is hydrogen extracted

Reacting methane with steam

What are NPK fertilisers

Nitrogen, Phosphorus, Potassium

What is ammonia used for

Make nitric acid, which can be made into ammonium nitrate fertilisers.
Ammonia can be neutralised by sulfuric acid to make ammonium sulfate fertiliser or ammonium phosphate.
Can make potassium nitrate.

Making water potable practical

Experiment 1:

• Universal indicator in water sample in test tube for pH

• Weigh empty evaporating basin to 2d.p

• Pour 10cm3 water in evaporating basin

• Heat evaporating basin using bunsen burner till solid forms

• Weigh cooled evaporating basin and calculate mass of solids. Record in table.

• Increase in mass → has dissolved solids.

Experiment 2:

• Place water sample in conical flask and set distillation apparatus

• Heat water using bunsen burner till boils

• Distilled water collect in cooled test tube. Pass through pipe with condenser around with cool water

• Analyse distilled water by boiling point

What is carbon soot

Produced by burning fuels, especially coal. Cause global dimming and respiratory problems.

How to make ammonium sulfate in lab

Crystalisation of ammonia solution and sulfuric acid

Why is industrial process better than lab process

large scale, quicker, continuous process so economically better

Fertilisers are…

formulations with different required properties

What is the reaction when metal carbonate heated

decomposition

When saying why ores arent good, say…

conserves finite ores

Whenever saying why something is better, say…

more useful, used as fuels, are in greater demand

Do alkanes or alkenes produce more soot

alkenes due to incomplete combustion. Long-chained hydrocarbons produce more soot

Why are those conditions chosen in Haber process

Chosen is compromise to yield, safety and cost

What conditions do bacteria need in fermentation

anaerobic and warm

Why is methanoic acid stronger than ethanoic

Lower pH, more H+ ions, more frequent collisions, will reform less easily from ions