Experiments with very cold Liquid nitrogen

Описание: Liquid nitrogen(LN) boils at -196 degrees C (-320.8 degrees F). It turns straight into very cold gaseous nitrogen when it is decanted into a warm beaker. The smokes/clouds seen here are actually condensed water vapor from the humid surroundings.
The water that condensed on the outer surface of the beaker became very cold frost which 'bites' skin as the latter shrinks.
The flexible rubber of the balloon shrinks and shrivels when LN is poured over it. This is because the air in the balloon cools and contracts. Flexible rubber stiffens and becomes brittle after it is dipped into very cold LN. It can therefore be crushed into small pieces.
LN is used in cryogenics (low temperature Physics) and also by the sperm banks to freeze sperms.
When LN is poured onto the palm, the latter should be flipped over to drain the very cold liquid off it.
It will not bite the skin as there is a layer of gaseous nitrogen that insulates the skin. This gaseous layer prevents drastic heat loss from the warm palm to the cold LN. This insulating effect is known as Leidenfrost Effect.
When one bites the LN-cooled biscuits, the water vapor/vapour condenses into 'smoke/cloud' which can be seen coming out of the nostrils of the students.
When the ping pong ball with 2 holes punctured at glancing angles, is dipped into LN, the air inside the ball cools and LN is forced into the ping pong ball. When it is taken out to let the LN vaporize, the 2 streams of gaseous nitrogen will then spin it around horizontally on a vertical axis - based on Newton's 3rd Law of Motion and Principle of Moments.
View this YouTube video which has more than 2 million hits.
   • #petersplimln  Liquid Nitrogen and the spi...  
For more Science videos, do kindly visit this website: www.PLchemPHY.com.sg