Cloud in a Bottle | English
Channel: IISER Pune Science Activity Centre
Date: 2018-09-25

In this well-known experiment, we will create a cloud in the bottle and learn what are the clouds made up of, how does it form inside the bottle and what is the scientific explanation of this process. This experiment also demonstrates an important idea in thermodynamics which will be discussed as well.

To create a cloud in the bottle, you need a clean transparent bottle which can be crushed easily. Take a small amount of water in the bottle and shake the bottle well. If you compress the bottle quickly you will see that bottle will turn translucent and something is formed inside the bottle. If you open the bottle and press it again, you’ll see the same material comes out of the bottle. Now take a small piece of paper and carefully light it on fire. Put the burning paper inside the bottle in such a way that it will get extinguished due to water. Remove the smoke from the burnt paper from the bottle by pressing it and now close the bottle cap. Now crush the bottle really hard and release it quickly. You will see the insides of the bottle will get foggy. Open the bottle and press it gently. You will see the cloud coming out of the bottle.

Why is this a cloud? Why not just smoke or water vapor? Because there is no smoke in the bottle as it was removed earlier and plain water vapor is not translucent when if diffuses in the air. This is a cloud or fog that is formed in the bottle. A cloud is made up of small droplets of water which are condensed on small dust particles. In this experiment, the water vapor inside the bottle condenses on the small particles generated from the burning paper and form the cloud. But how does this happen every time we crush the bottle and open it again? What exactly happens inside the bottle which creates more water vapors?
The process that results in generation of water vapors inside the bottle is called an adiabatic process. When the bottle is crushed, the air inside the bottle suddenly compresses. This is an adiabatic compression which results in heating of the system which produces more water vapor. As the bottle is released and comes to the original volume, the temperature is lowered and this newly formed water vapor condenses on the small particles. This creates the cloud inside the bottle every time the bottle is crushed and released.

This is a really fun experiment and can be done easily at home to understand what a cloud is and how it’s different from just water vapors. This also explain the concept of an adiabatic process as there is no transfer of mass or heat from the system to its surroundings.

Hope you learned something new today and understood the process pf convection currents. For more exciting experiments about math’s and science subscribe to or YouTube channel.
Thanks!

Team: Ashok Rupner, Chaitanya Mungi, Neha Apte, Sajeda Sayyad_Shaikh, Pinki Saha, Students of NCL School Pune, Dr. B N Das