National Chemistry

These notes are for the Scottish National Chemistry course taught in fourth year in most Scottish schools.

The notes available here are concise notes. They are NOT to be considered as material to learn from - they are for revision.

 The notes are arranged under the following topics

National 3 Unit 1
Unit 2
Unit 3

National 4 and 5 Unit 1 Rates of Reaction
Atomic Structure
Bonding and Properties
Acids and bases

National 4 and 5 Unit 2 Fuels and Homologous Series
Consumer Products
Carbohydrates

National 4 and 5 Unit 3 Metals
Plastics
Fertilisers
Nuclear Chemistry
Chemical analysis

.

National 4 Carbohydrates

Carbohydrates

Photosynthesis is when green plants (caused by CHLOROPHYLL) light energy (absorbed by chlorophyll) take in water and carbon dioxide to make carbohydrates (food for animals) and oxygen gas (breathed in by animals) (song)

  carbon dioxide + water -----light----&------> glucose + oxygen
  6CO2 + H2O ---chlorophyl------> C6H12O6 + 6O2

  Respiration is the process by which animals and plants breakdown carbohydrates using oxygen to produce energy and release carbon dioxide and water.

  glucose + oxygen----------> carbon dioxide + water
  C6H12O6 + 6O2 ----------> 6CO2 + 6H2O
 
Animals use this energy for movement and growth.

About a hundred of glucose molecules react together to form starch and water. The formation of water by an organic reaction is termed CONDENSATION.

  n x glucose ---------------> starch + n x water
  n x C6H12O6 ----------------> (C6H10O5)n + n H2O

(n=big number; approximately a 100 for starch)

In the carbon cycle animals and plants take in oxygen and put out carbon dioxide while plants also take in carbon dioxide and water and release oxygen thus balancing the oxygen and carbon dioxide in the air.
  Destruction of plants - e.g. clearing rain forests could reduce the amount of carbon dioxide taken in and oxygen released.

 Carbohydrates like glucose, sucrose and starch contain the elements carbon, hydrogen and oxygen. When burned they release a lot energy producing carbon dioxide and water.
Respiration and combustion of carbohydrates produce carbon dioxide and water because a carbohydrate contains Carbon and Hydrogen

  Fructose C6H12O6 monosaccharide turns hot blue Benedict's brick red
  Glucose C6H12O6 monosaccharide turns hot blue Benedict's brick red

  Maltose C12H22O11 disaccharide turns hot blue Benedict's brick red
  Sucrose C12H22O11 disaccharide no test
 
  Starch (C6H10O5)n poloysaccharidde  turns iodine blue-black

Two momosaccharides reract together to make one disaccharide and water - a CONDENSATION reaction

  C6H12O6 + C6H12O6 -----> C12H22O11

Glucose, C6H12O6 , is sweet and dissolves in water. It is a reducing sugar - it turns blue Benedicts reagent orange.
Photosynthesis produces glucose which then builds up a polymer (by condensation polymerisation) called starch.

 
Starch is not sweet and does not dissolve well in water - a beam of light will show up starch particles in a starch solution (does not happen with glucose). Starch does not affect blue benedicts but does turn iodine blue black.

  Fructose C6H12O6 monosaccharide turns hot blue Benedict's brick red
  Glucose C6H12O6 monosaccharide turns hot blue Benedict's brick red

  Maltose C12H22O11 disaccharide turns hot blue Benedict's brick red
  Sucrose C12H22O11 disaccharide no test
 
  Starch (C6H10O5)n poloysaccharidde turns iodine blue-black

testing for a reducing sugar
 
During digestion starch molecules are broken down in the body by enzymes - biological catalysts - into small glucose molecules which can pass through the gut wall.
This is called hydrolysis. Glucose then reacts with Oxygen in the body to produce
energy, water and carbon dioxide - this is called respiration.

  starch + water ----enzyme-----> glucose
  (C6H10O5)n + H2O ----enzyme-----> n x C6H12O6

Disaccharides can also be broken down by hydrolysis

  disaccharide monosaccharide monosaccharide
  maltose glucose fructose

  C12H22O11 -----> C6H12O6 + C6H12O6
 

Alcoholic drinks can be made from any fruit or vegetable which is a source of starch
or sugar.

e.g. barley = beer, lager
 whisky grapes = wine, brandy

The fermentation of glucose - using the biological catalyst (enzyme) yeast produces the alcohol (ethanol) and carbon dioxide.

  glucose ---enzyme in yeast--------> ethanol + carbon dioxide

  C6H12O6 2C2H5OH + 2CO2

Ethanol, C2H5OH, is a member of the alkanol family (another homologous series).

Distillation increases the concentration of alcohol in the liquid from fermentation.
Alcohol and water can be separated by distillation because they have different boiling points.

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