fuels and heats - ethene experiment

experiment set up

ethanol

ethanol is poured into a boiling tube and glass wool is added

glass wool soaks up the ethanol and holds it in place at the end of the tube

aluminium oxide

a small amount of aluminium oxide is placed half way along the tube

the aluminium oxide is gently heated using a bunsen burner

observation

• bubbles of gas are seen to collect in the test tube

  as the ethanol is heated it turns to vapour and pass over aluminium oxide to form ethene.

experiment is done

five test tubes of gas are collected and stoppered.

the first test tube is mainly of air from the apparatus

safety precautions

when experiment is done - the apparatus is raised so that the delivery tibe is no longer dipping into the water

then the bunsen burner is turned off (to avoid suck back)

dangers

if the delivery tube were left in the water trough after turning off bunsen burner, a suck back would occur. - the cold water would cause the hot boiling tube to crack

tests on ethene

combustion

stopper is removed and a lighted wax taper is put into the test tube

when the gas has stopped burning, lime water is added and it is shaken and stoppered

observation: gas burns with a yellow luminous flame

addition of bromine

bromine water is added to test tube, stoppered and shaken

observation: bromine water changes from red to colourless - test fir unsaturation in a compound

addition of acidified potassium permanganate

dilute, acidified KMnO₄ is added to the test tube of ethene. stoppered and shaken

colour changes from purple to colourless