chemistry c3 WJEC

Alkanes

• Alkanes are saterated hydrocarbons.
• Each carbon atom is bonded to 4 other atoms
• general formula for any alkane = CnH2n+n
• Alkanes with the same formula but different structures are called isomers

Alkenes

• all their names end in -ene
• they all contain a C=C double bond
• General formula= CnH2n
• Alkenes are extreamly reactive because the double bond can break open to allow other atoms to add on
• When an alkene is added to bromine water it turns colourless
• the double bond splits open and the bromine adds on, this is called an addition reaction
• the product is saturated

Enzymes

• Enzymes are biological catalysts
• Each enzyme has an optimum temperature and and optimum pH at which it works best at
• above the optimum temperature the activity begins to fall because the ebzyme is denatured

• Ethanol is made from sugars by fermentation
• enzymes in yeast change the sugar to ethanol and carbon-dioxide
• glucose = ethanol + carbondioxide
• C6H12O6 = 2C2H5OH + 2CO2
• ethanol can be obtained from the reaction mixture by distillation or fractional distillation
• Ethanol is used in alcholic drinks as a solvent and as a fuel
• Ethanol produces about 70% as much energy as petrol but it requires a large amount of sunlight and lots of land

Importance of ethanol

• small amounts of ethanol are thought to help against heart disease
• excessive alcohol intake may lead to liver damage or alcohol dependency
• increased cost to the NHS due to alcohol related incidents
• drink driving
• impact on families
• taxes on alcoholic drinks raise money for public spending

Ethanol and Ethanoic acid

• Ethanol when exposed to the air undergoes oxydation caused by microbes
• the microbes change the ethanol into ethanoic acid
• ethanoic caid is a member of the carboxylic acid family
• Ethanoic caid reacts with sodium carbonate to give off carbon dioxide gas. fizzing is seen
• this reaction can be used as a test for carboxylic acid