Preparation of ethene in laboratory is as follows : -

At first take a hard glass test tube and in it put 3ml of melted wax and one tea spoon of sand. Then some porcelain is inserted in the front part of the test tube. The arrangement is made as shown in the following figure:

The test tube is then heated on a spirit lamp until the pieces of porcelain become red hot and then immediately heat the sand containing wax. Continue the heating process alternatively between the porcelain and the sand. When alkene vapours from wax pass through the heated porcelain ethane gas is liberated by cracking The gas is collected in a jar by downward displacement of water.