8/14/2019 Chemistry 4 Notes

http://slidepdf.com/reader/full/chemistry-4-notes 1/5

C4A – Acids and Bases

•Sulphuric acid is used to clean metal plates

• The pH scale

Red – Strong Acid

 Yellow/Orange – Weak Acid

Green – Neutral

Blue/Purple – Weak Alkali

Purple – Alkali

•Neutralisation

A base is a solid that reacts with acids

acid + base → salt + water

H2SO4 (Sulphuric Acid) + 2NaOH (Sodium Hydroxide) → Na2SO4 (Sodium Sulphate) + 2H2O (Water)

All acids in solution with water contain hydrogen ions (H+)

All alkalis in solution with water contain hydroxide ions (OH-)

•

More on basesMetal oxides and hydroxides are always bases

Hydrochloric acid + Copper (II) hydroxide → Copper(II) chloride + Water

Ammonia is also a base

Carbonates can also neutralise acids, but carbon dioxide is also madeHydrochloric acid + Calcium carbonate → Calcium Chloride + Carbon Dioxide + Water

C4B – Reacting Masses

•No mass is lost in any chemical reaction

•In a candle, mass is changed into water (hydrogen+oxygen) and carbondioxide (carbon+oxygen)

• This can be tested with soda lime as these elements are trapped in it and the

total mass of the candle and soda lime will always be equal

• The mass of products is always equal to the mass of reactants

•Relative formula mass

 The bottom number on the periodic table is the atomic number

 The top number is the relative atomic mass

We can work out the relative formula mass from the relative atomic mass

• Yield

Predicted Yield is the maximum possible amount of yieldActual Yield is the actual yield

Percentage Yield = Actual Yield/Predicted Yield x 100

C4C – Fertilisers and Crop Yield

•Fertilisers are used to replace essential elements removed by previous crops

•Overuse of nitrogen-containing fertilisers causes eutrophication

Rain water causes fertiliser to run into rivers

Nitrate/Phosphate concentration in the water increases

Microscopic water plants (Algae) grow at an accelerated rate (Algal Bloom)Dense algae prevents sunlight reaching underwater plants and they die, alsokilling the nutrients of the algae

8/14/2019 Chemistry 4 Notes

http://slidepdf.com/reader/full/chemistry-4-notes 2/5

8/14/2019 Chemistry 4 Notes

http://slidepdf.com/reader/full/chemistry-4-notes 3/5

•Washing powders are a complex mixture of ingredients

 The active detergent does all the cleaning and are often made by aneutralisation

Some use soap which is less damaging to delicate fibres

Some use synthetic detergents (soap-less) and are better at cleaning

•Detergent molecules

Have charge hydrophilic heads

Have uncharged hydrophobic tails

 The hydrophobic tails link to the stain and then pull them towards the water

•Soap is made by the neutralisation of fatty acids and alkalis

 The acids have long chains of hydrogen and carbon and form the hydrophobictail

Saponification - When a fatty acid with glycerol (triglyceride) reacts withsodium hydroxide, a sodium salt is formed (soap)

 The charged sodium adds to the hydrophilic head

Synthetic detergents are made by neutralising a synthetic acid with an alkalito form a molecule similar to soap, but with stronger detergent properties

•Other ingredients

Water softeners for hard water areas – Stops clothes being covered in scumand means less detergent is used

Bleach can be used to remove coloured stains

Optical brighteners make clothes very bright

Bio detergents are detergents with enzymes (biological catalysts) that breakdown the stains

 They will denature at high temperatures

C4F – Batch or Continuous?

•Developing a pharmaceutical drug or medicine is a long, costly process

•It can take £300,000,000 and 15 years to develop•Discovery→Phase 1: Test on Animals→Phase 2 : Test on human volunteers→Phase 3 : Clinical

 Trial→Marketing

•Drugs must be legalised and must be marketed which also costs

•Many drugs cannot be automated in production, which can cost

•Manufacture can require a lot of energy

•Extracting chemicals

Extraction from plants has many stagesCrush Plants

Mix with solvent

Filter

Purify

Evaporate Solvent

DRUG

Use chromatography to test for impurities

•Decisions to be made before producing the drug

Cost of research and development

 Time taken to reach legal requirements

Demand for the product

8/14/2019 Chemistry 4 Notes

http://slidepdf.com/reader/full/chemistry-4-notes 4/5

How long will it take for profits to repay the investment

•Batch or Continuous

 The Haber process is continuous

Continuous processes are used when there is a constant demand and arecalled bulk chemicals

Many products are made by batch and are called speciality chemicals

C4G – Nano chemistry

•Different forms of carbon such as graphite and diamond are called 'allotropes'

•Diamond – Transparent, very hard, very high melting point, insulator, lustrouswith a brilliant shine

•Graphite – Opaque and black, soft and slippery, high melting point, conductselectricity, lustrous

•Structures

Diamond

All carbon atoms are joined to four others by strong covalent bonds

 There are no ions or free electrons

Graphite

Atoms are in layers

Strong bonds within layers

Weak bonds between layers

Electrons are delocalised so it can conduct electricity

Buckminsterfullerene

Made of 60 carbon atoms joined together

Each molecule is called a “Bucky” ballOther fullerenes have been discovered since

Nanotubes

Fullerenes joined together make tube shapes called nanotubes in a new areaof study called nanotechnology

 They are very strong and can conduct electricity

•Semiconductors in electrical circuits

•Industrial Catalysts

•A reinforcement for tennis racquets

 They have a large surface area so they are good for attaching catalysts

•Nanochemistry was born with nanotubesIt works with materials at an atomic level and works with small particles called

nanoparticles

 They are the only particle that can act as a true metallic conductor

 The spacing and size of nanotubes can make them act like semiconductorssuch as silicon

•Caging molecules

It is possible to trap molecules or cage them inside nanotubes

 They could be used to inject into the bloodstream to prevent cancer asmedicine

•Making molecules could be done (molecular manufacture) by using nanotubesto precisely position parts (positional chemistry)

8/14/2019 Chemistry 4 Notes

http://slidepdf.com/reader/full/chemistry-4-notes 5/5

C4H – How pure is our water?

• Tap water is impure, but the chemicals are harmless to us

•Water pollutants include:

Nitrate Residues – Get in the water when rain dissolves fertilisers into rivers

Lead compounds - Can dissolve into water from lead pipes

Pesticide residues – From farmers spraying too close to rivers and lakes

•In developing nations where water is not purified, it contains disease-causingmicrobes

•Water is used as:

A cheap raw material for manufacture

A coolant

A solvent

•Purification is important to remove:

Microbes

Dissolved salt and mineralsPollutants

Insoluble materials

•Purification process

Water goes to the sedimentation tank to allow large materials to settle

 Then it goes to filtration which traps finer materials

Finally it goes through chlorination where microbes are killed

Not all impurities are gone, but most are harmless and at low concentration

•Seawater is often distilled for homes and is 3% salt

Distilled water is tasteless as it is pure

Distillation costs a lot•Water is often tested for chemicals by precipitation

•A precipitate will make the water cloudy if there is an impurity

 Three halides form precipitates with different colours

Silver Chloride – White

Silver Bromide – Cream

Silver Iodide – Yellow

•An example reaction

Sodium Chloride + Silver Nitrate → Sodium Nitrate + Silver Chloride