Question

Expansion and contractions of water?

Answer 1

All liquids expand when their temperature increases and contract when their temperature decreases.Their coefficients of volume or cubical expansion is about ten times greater than those of solids. A liquid has no definite shape.It always takes the shape of the container in which it is.So,in case of the liquid we consider only volume expansion. Water behaves unusually in case of liquids.When ice at about -5°C is heated it expands slightly up to 0°C,when it melts and forms water.When this water is heated it contracts from 0°C to 4°C which is unusual.Above 4°C, it expands, behaving like other liquids.When it changes into steam at 100°C, the volume increases 1600 times.The unusual behavior of water between 0°C and 4°C i.e., contraction of water when heated from 0°C to 4°C is known as the anomalous expansion of water.

The density is the mass per unit volume of a substance and that mass of a given quantity of a substance does not change.So when volume changes density changes.Since water contracts form 0°C to 4°C,its volume decreases and the density increases to reach the maximum value at 4°C.When water is cooled from 100°C it contracts till it reaches 4°C;then it expands.

Since water contracts on melting and on heating from 0°C to 4°C,it follows that it expands on freezing. Due to this,during frosty weather in cold countries,pipes sometimes burst.

Water has the smallest volume and the maximum density at 4°C.


Practical Applications:

The radiator of an automobile is not completely filled water.if it is filled completely,the expansion of water (when the radiator is hot) could lead to engine breakdown.
Liquids thermometers make use of the fact that liquids expand when heated.Alcohol and mercury are the two liquids commonly used in thermometers.