Chemistry C4

Chemistry - How Pure Is Our Water?

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  • Created by: Khadijah
  • Created on: 25-03-11 14:07

How Pure Is Our Water

The 4 Main Sources:

  • Seas
  • Lakes
  • Resevoirs
  • Aquifers (wells and bore holes)

Water is important for the chemical industry because it is used for cooling, as a solvent. It is a raw material.

Some parts of Britain has a higher demand for water than supply

The World Health Organisation estimates that 2 million people die from water-bourne diseases (cholera). Almost 20% of the world's population has no access to clean water.

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Water Treatment

Water is treated to purify the water. It needs to be safe to drink, because untreated water may contain:

  • Insoluble particles
  • Pollution
  • Microorganisms
  • Dissolved salts and minerals.

Water Treatment Process:

Untreated Water --> Sedimentation --> Filtration --> Cholorination --> Pure Water

  • Sedimentation - the water settles to allow the insoluble particle to sink
  • Filtration - to remove the very fine particles
  • Chlorination - to kill the microorganisms
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Pollution In Water

  • Nitrates - surface run off from fertilizers
  • Lead compounds - old pipes in the plumbing
  • Pesticides - spraying crops near the water supply

Dissolved Ions

Dissolved Ions are easy to detect as they have undergone precipitation. It is made when two solution mixed together create a solid.

Sulfates can be detected using Barium Chloride solution because a white precipitate of barium sulfate forms.

Silver nitrate can be used to detect Halide ions.
 Chlorides form a white precipitate
- Bromides form a cream precipitate
Iodides form a pale yellow precipitate

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Water Purification

  • Tap water is not pure
  • Extra steps taken to purify tap water
  • There is possibility of poisonous materials
  • Therefore, they DISTILL it.

Distillation ensures that water is absolutley pure. However, this uses alot of energy and therefore is expensive.

Huge amounts of water is needed to distill sea water because it is very corrosive. Therefore it is very expensive to purify sea water.

- We are prevented from drinking sea water because it is too expensive

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Nanochemistry - Carbon

There are three allotropes* of Carbon:
*different forms of the same element, but arranged differently

  • Diamond
  • Buckminister Fullerene
  • Graphite


  •  Nanotubes made by joining fullerens together.
  • Graphite hexagon curled over in a tube
  • They conduct electricity
  • Very strong
  • Used to reinforce graphite tennis rackets
  • Make connectors and semi conductors in modern computers
  • develop new effective catalysts.
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More on Nanochemistry

  • Fullerenes and Nanotubes can cage other molecules because they have the perfect shape to trap other substances.
  • drugs;major new HIV treatment uses. BUCKYBALLS were introduced
  • catalysts; attaching catalyst material to a nanotube maximised the surface area. Increased efficiency.

- BUCKYBALLS; by burning the soot of hydrocarbon.

- LASERS; used to vapourise Carbon which deposit to leave a molecule

- MATTER can be removed from a big structure to produce nanoscale features

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Allotrope of Carbon - DIAMOND



doesnt conduct electricity
insoluble in water
transparent and lustrous
used as a cutting tool because in cut glass
high melting and boiling point
bonded to 4 other carbon atoms, (strong covalent)
No free electrons (therefore doesnt conduct electricity)

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Allotrope of Carbon - GRAPHITE


  • Insoluble in water
  • is black, (used in pencils)
  • lustrous and opaque (light cannot get thru)
  • conducts electricity
  • hight melting point
  • slippery, therefore used in lubricants.
  • Layered structure
  • Bonded to three other carbon atoms
  • Held by weak intermolecular forces; this allows the layers to slide easilly.
  • Free delocalised electrons - conducts electricity(has covalent bonds also)
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- Consists of 60 carbon atoms arranged in a sphere

- It is a black solid

- Makes a red solution when dissolved in petrol

- It has strong covalent bonds

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Batch or Continuous

BATCH:Where reactants are put in to a reactor, then reaction creates product. Medicines and pharmaceuticals are often made in batches BECAUSE:

  • Product made on demand
  • Production can be small scale
  • Can be used to make a variety of products
  • More labour intensive; because reactor is cleaned, emptied and filled. 

CONTINUOUS:Where reactants are constantly being added to a reactor, and product is continually being made.

  • operates all the time
  • make product on large scale
  • dedicated to just one product
  • runs automatically
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Making Medicines

Materials to create medicines can be manufactured or extracted from natural resources (plants).


1) CRUSHING - the plant is crushed using mortar and pestle

2) DISSOLVING - a suitable solvent is added to dissolve the material

3) CHROMATOGRAPHY - a concentrated solution of the material is spotted on to chromatography paper and allowed to separate.

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Developing Medicines

  • Research needs to take place. Therefore labour costs will be high
  • Further research to develop the drug before it is tested.
  • It needs to be tested because we need to see if it works properly, its safe to use and there are no serious side-effects.
  • The medicine has to be approved in order for it be consumed
  • Medicines are made of raw materials, which can be expensive. 
  • Medicine is made through batches, therefore labour, energy and staff costs are high.
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A detergent molecule is non-polar. This means that is has an overall balanced charge. 

  • The tail is non-polar and is not attracted to water. Therefore (hydrophobic)
  • The head is negatively charged, it has an electrical charge. It is attracted to water. Therefore (hydrophilic) 


1) The hydrophobic tail is repelled by water, causing it to stick on the dirt/oil droplet

2) As more and more detergent molecules attach themselves to the dirt/oil the it will eventually be lifted off.

3) When it is totally surrounded, the oil droplet can be washed away. 

Molecules held by weak intermolecular forces dissolve in the dry cleaning solvent.

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  • Detergent - to do the cleaning
  • Water - to dissolve and dilute the detergent, so it pours out of a bottle
  • Water Softener - to soften hard water
  • Rinse Agent - to help the water drain off the crockery 
  • Colour and Fragrance - makes the product more attractive to buy 

Detergent is usually a salt made by neutralizing a complicated organic aci with an alkali


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  • Detergent - to do the cleaning
  • Bleach - removes coloured stains
  • Water Softener - softens hard water
  • Optical brightener - makes white appear brighter
  • Enzymes - break up food and protein stains in low-temp wash

Low temperature is used to wash delicate fabrics. This is because some may shrink at higher temperatures and bio washing powder's enzymes may denature. This can save energy and money :) 

some stains will not dissolve in water; dry cleaning solvents are used when stains are insoluble in water. 

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Again, THANK YOU!!

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