20 BREAKDOWN OF ETHANOL TO ETHENE ETHYLENE Absorb ethanol on to cotton wool or asbestos wool and push this to the bottom of a hard glass testtube In the middle of the testtube pack small pieces of unglazed porcelain Fit a delivery tube to collect ethene gas over water Have 3 testtubes ready to collect ethene First heat the porous pot strongly and then gently warm the cotton wool to produce ethanol vapour This vapour will break down over the hot porous pot to produce ethene gas and water vapour The ethene is insoluble in water unlike ethanol and will collect in the testtubes Test the 3 samples by a burning ethene b shaking with a few drops of dilute potassium permanganate solution made alkaline with sodium carbonate solution the colour should disappear c shaking with a little bromine water the colour again disappears Disconnect the delivery tube when you stop heating to avoid a suck back of water onto the hot porous pot