Describe An experiment to show

1)gases have no definite volume 

2) gases have no definite shape              

Experiment to show

1)Gases have no definite volume .2)Gases have no definite shape.

  (Both shown in one experiment)

EXPERIMENT  take a coloured gas (like NO₂) in a test tube and cork its mouth. The gas spreads and takes the shape of the test tube. Then take another empty test tube and join both the test tubes by their mouths (open ends), remember to take out the cork of the first test tube which was used to close it.

you will notice that slowly the gas will spread in both the test tubes. And so its volume also changes as it mixes with the air that was present in the empty test tube.

This experiment can also be performed by using an incense stick. Light the incense stick and keep it in the test tube for some time. Take it out and then cork the test tube. 

CONCLUSION the volume and the shape of gases is not definite.

HOPE THIS HELPS