Chemistry

Polyethene uses and properties

Properties:

• flexible

• cheap

• electrically insulating

Uses:

• plastic bags

• plastic bottles

Polypropene uses and properties

Properties:

• flexible

• strong

Uses:

• food packaging

• ropes

• carpets

Polychloroethene (PVC) uses and properties

Properties:

• long-lasting

• tough

• cheap

Uses:

• plastic sheets

• artificial leather

• drainpipes and gutters

• insulation on wires

PTFE (polytetrafluoroethylene) uses and properties

Properties:

• very tough

• non stick

• resistant to high temperatures

Uses:

• cookware

• pipes

Are nitrates soluble? Exceptions?

All nitrates are soluble

Which three elements are always soluble in compounds

Sodium, potassium, ammonium

Are chlorides soluble? Exceptions?

Most chlorides are soluble apart from silver and lead (II)

Are sulfates soluble? Exceptions?

Most sulfates are soluble apart from barium, calcium and lead (II)

Are carbonates soluble? Exceptions?

Most carbonates are insoluble apart from SPA

Are hydroxides soluble? Exceptions?

Most hydroxides are insoluble apart from SPA

Sulfate ion

SO₄²⁻

Nitrate ion

NO₃⁻

Carbonate ion

CO₃²⁻

Recycling advantages and disadvantages

Advantages:

• reduces need for mining and quarrying which damages habitats

• uses less energy than extracting new materials

• reduces how quickly non-renewable resources are used up

Disadvantages:

• difficult to collect and process materials to be recycled

• limits product e.g. can only be certain colours

• (expensive)

Describe haber process

Stage 1: H2 and N2 are obtained from natural gas and the air respectively and are pumped into the compressor through pipe
Stage 2: the gases are compressed to about 200 atmospheres inside the compressor
Stage 3: the pressurised gases are pumped into a tank containing layers of catalytic iron beds at a temperature of 450°C. Some of the hydrogen and nitrogen react to form ammonia:
N2 (g) + 3H2 (g) ⇌ 2NH3 (g)
Stage 4: unreacted H2 and N2 and product ammonia pass into a cooling tank. The ammonia is liquefied and removed to pressurised storage vessels
Stage 5: the unreacted H2 and N2 gases are recycled back into the system and start over again

Group 1 physical and chemical properties

Physical:

• soft

• low density

• low melting point

• reactive

As you go down the group:

• density increases

• melting point decreases

Noble gases:

• uses of helium, argon and neon

• properties

• as you go down group

• Helium is used for filling balloons and weather balloons as it is less dense than air and does not burn.

• Argon is used to provide an inert atmosphere for welding and to fill electric light bulbs

• neon, argon, xenon in advertising signs

• low melting point

As you go down group:

• boiling point increases (due to larger molecules)

• density increases

Exothermic

• definition

• types of reaction

• uses

• In exothermic reactions energy is given out to the surroundings so the temperature of the surroundings increases

• Combustion, oxidation, and neutralisation reactions

• Hand warmers and self heating food/drink cans

Endothermic

• definition

• types of reaction

• uses

• In endothermic reactions energy is taken in from the surroundings so the temperature of the surroundings decreases
  -Electrolysis, thermal decomposition reactions and the first stages of photosynthesis

• ice packs

Is bond breaking exothermic or endothermic and does it use more or less energy

Endothermic -
More energy is required to break the bonds than that gained from making the new bonds
has a positive change in energy as products have more energy than reactants

Is bond making exothermic or endothermic and does it use more or less energy

Exothermic - More energy is released when new bonds are formed than energy required to break the bonds in the reactants
So more energy is released than absorbed
Therefore an exothermic reaction has a negative change in energy as products have less energy than reactants

What is the order of crude oil from the bottom and give uses of each one

bitumen - surfacing roads and rooves
fuel oil - ships and power stations
diesel oil - diesel engines
kerosene - jet fuel
petrol - fuels for cars
gases - domestic heating and cooking

As you go down the crude oil tube fractionating collumn what happens to number of atoms in molecules, boiling point, ease of ignition and viscosity

number of atoms in molecules - decreases
boiling point - decreases
ease of ignition - decreases
viscosity - increases

Describe the history of the atmosphere

1. volcanic activity
   Gases produced by volcanoes formed early atmosphere
   There was little or no oxygen
   Lots of CO2, water vapour and some other gases
   The Earth was incredibly hot and molten until some slowly solidified into volcano land masses

2. Water vapour condenses
   Gradually, the Earth cooled enough for the water vapor to condense forming oceans
   CO2 is a very soluble gas so it dissolved into the oceans lowering levels in the atmosphere
   There was still little or no oxygen

3. Cyanobacteria
   Primitive plants called cyanobacteria grew
   Can photosynthesize converting CO2 and water into glucose and O2
   Oxygen in atmosphere increases
   CO2 in atmosphere decreases

Test for carbonate ion

Add dilute acid and bubble the gas produced through limewater. If the limewater turns cloudy due to calcium carbonate precipitate, then carbonate ions were present

Test for sulfate ion

Add dilute hydrochloric acid and aqueous barium chloride, if present a white precipitate of barium chloride is formed

Test for halide ion

Add dilute nitric acid and silver nitrate solution forming a precipitate of silver halide.
Silver chloride = white
Silver bromide = cream
Silver iodide = yellow

How to test for cations

When in aqueous solution, add sodium hydroxide and the precipitate they form has different colours

What colour precipitate do the ions make