This is a simple but nevertheless a very dramatic experiment which demonstrates the expansion of air. You will require a glass bottle, a coin and some water to perform it. First, pour some cold water in the bottle. Rinse the bottle with cold water and then throw away the water. This makes the bottle “cool”. Now dip the coin in water and place this wet coin on the mouth of the bottle. The wet coin ensures that the mouth of the bottle is sealed. Then rub your hands together to warm them up. Cup the bottle with your warm hands. After some time the air inside the bottle will expand and will be expelled out. At that moment the coin will “lift” a little bit and let out the excess air. The coin acts like a valve in a pressure cooker. Once the pressure in the bottle increases the coin like a valve lifts to release the extra “steam”. This experiment costs nothing but still is a very dramatic experiment to demonstrate the expansion of air.
This work is supported by IUCAA (www.iucaa.in) and TATA Trust (www.tata.com/aboutus/sub_index/Tata-trusts)
Credits:,Ashok Rupner, Manish Jain, Pradnya Pujari, Shivaji Mane, Jyoti Hiremath, Arvind Gupta, Vidula Mhaiskar
Dubbed in Urdu by Ishrat Shaik from Pratham’s Science Learning Program
source
