alcohols

Question 1

why are the properties of alcohols different to alkanes?

Answer 1

• alkanes have non-polar bonds because the electronegativity of hydrogen and carbon are very similar
• alkanes are non- polar
• alkanes have very weak London forces
• alcohols have a large difference in electronegativity of the O and H atoms
• alcohols are polar
• alcohols have weak London forces and stronger hydrogen bonds

Question 2

properties of alcohols compared to alkanes

Answer 2

• less volatile
• higher melting points
• greater water solubility
• differences become much smaller as the length of the carbon chain increases

Question 3

volatility and boiling points

Answer 3

in liquid state, intermolecular hydrogen bonds hold the alcohol molecules together

• thee bonds must be broken in order to change from liquid to gas
• more energy needed that overcoming the weaker London forces in alkanes
• alcohols have lower volatility than the alkanes

Question 4

solubility in water

Answer 4

• alcohols are soluble in water as they can form hydrogen bonds with water
• alkanes are non- polar so cannot
• as the chain length of alcohols increase, the solubility decreases as the influence of the O-H group decreases

Question 5

combustion of alcohols

Answer 5

• reaction is exothermic, releasing a large quantity of energy in the form of heat
• as the chain length increases, an increase in heat released per mole

Question 6

what is the colour change when compounds are oxidised

Answer 6

orange to green

Question 7

dehydration definition

Answer 7

reaction in which water molecules is removed from the starting material