National Chemistry

 

 

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.

drink aware

National 4

Carbohydrates

 

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

 

 

 

 

 

 

 

 

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