10th/9th (Foundation) Physics, Chemistry, Math Forum

why??

why??

by meghna malik -
Number of replies: 1

1. when an ice block is put in water,after it melts there is no change in the water level.why does this happen?

2. also when a stone is thrown in water there is no change in the water level.why?

3.when water changes to ice the molecules come together then why does ice expand not contract?

In reply to meghna malik

Re: why??

by Manish Verma -
Let mass of ice be m.

Buoyant force = m.g

Let V be the volume of the immersed portion of the ice and hence volume of the water displaced.

Then buoyant force = d.V.g (d = density of water)

Hence, m.g = d.V.g

\(\Rightarrow V=\frac {m}{d}\)

Now, if the whole ice gets converted into water then the mass of water obtained would be same as the mass of the ice.

Mass of ice = m = Mass of water

Hence volume of this water = \(\frac {m}{d}\)

In both cases volume of the water is same.
I suppose that the second question refers to throwing stone in river. Well, to see any change in the level of the river one needs to throw the mountain instead..smile
Ice floats in water. The density of ice is less than that of water. Hence, when water changes to ice the molecules do not come closer. This has to do with the structure of ice. The following picure says it all:

Ice & Water Structures