Physics
Skating on ice is possible because

The pressure on the ice due to skate raises its melting point
The pressure on the ice due to skate melts the ice by lowering its melting point forming a thin film of water
The surface of ice is smooth
Ice is cold

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Physics
Water pipes in hilly areas often burst on a cold frosty night, because

Water in the pipes freezes and on freezing water expands, so pipes break
Frost makes the pipes rusty, so they break
None of these
The material of which pipes are made contracts due to cold and so breaks

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