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A WALK ON LAKE

 


 Water is a peculiar liquid.  But it is very essential for the life to beat. 

      When liquids are cooled down, they contract and become solid.  Water also contracts and become ice.  But it contracts up to 4 degree c only.  It expands from 4 degree c to 0 degree c due to water molecule bonding.  That is, its density decreases.  That is why ice floats on water.  

      In a water body like a lake, cooled water comes to the top because it is less denser.  Then the top surface first freezes over.  Since ice and water is poor conductor of heat, the liquid water remains intact below the friezed surface.  Hence the aquatic life can continue to live in the lake in winter also.  Men can walk and play on the lake during winter.  Even truck can move on it, if ice is sufficiently thick.

      Iceberg is a ice mountain which has broken away  from glacier and floats on ocean.  1/10 of iceberg  is visible above the surface of ocean.  90 % of the iceberg  remain immersed in ocean due to Archimedes principle. SONAR (SOUND WAVES NAVIGATION AND RANGING)  is used to detect icebergs by ships and submarines. 

      Snow flake takes interesting shapes in winter as shown in figure
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AT 0.1 degree c temperature and 0.006 atmospheric pressure; liquid water, solid ice and water vapour can co-exist.  This is called triple point of water.

 Fire from ice: If ice is shaped into lens, it can focus sun's rays and start a fire.  How strange?  
   
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