Question

NCERT CLASS IX - Science Textbook
Chapter 1 - Matter in Our Surroundings

Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why.

Answer 1

Water is a special  substance regarding the density.


There are hydrogen oxygen bonds in water.  They are special.  Water molecules come closer as the temperature reduces to 4 deg. Centigrade and then again  below 4 deg. Centigrade the water molecules separate from each other.  Thus density is highest at 4 deg. Centigrade. 

Thus water molecules in crystal water ie., ice are arranged further away from each other.  This is due to the bonds, repulsions and attractions between hydrogen and oxygen among the neighbouring molecules.  The molecules are rigidly arranged in a crystalline form.

So ice is lighter than water.

Answer 2

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Liquid generally have lower density as compared to solids. But you must have observed that ice floats on water.Find out why?

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Density of ice is less than the density of water.The low density of ice can be attributed to the small pores it was which allows it to trap air.Hence ice floats on water.