Question

A piece of ice is floating in a beaker containing water. When ice melts, the temperature falls from $20^\circ$ to $4^\circ$ and the level of water
A) Remains unchanged
B) Falls
C) Rises
D) Change erratically

Answer 1

Recall the concept of density. Basically density shows how tightly or how loose are the particles arranged in a given area. It shows the compactness of the mass of a substance. It can be calculated by dividing the mass of any object per unit volume. It is denoted by the symbol Rho $\rho$.

Complete step by step answer:
Step I:
Given that the ice in the beaker is melting and the temperature is falling from ${20^ \circ }C$ to ${4^ \circ }C$.
Water has maximum density at a temperature of ${4^ \circ }C$. Density can be written as
$\rho = \dfrac{{Mass}}{{Volume}}$
At ${4^ \circ }C$ density of water is maximum.
Step II:
Since density is inversely proportional to the volume, therefore, if density is maximum at ${4^ \circ }C$ then volume will be minimum at ${4^ \circ }C$ .
Step III:
Volume of any object is the product of its height and the total area of the object.
$Volume = Height \times Area$
$V = H \times A$
$V$ is the volume
$H$ is the height
$A$ is the area
Now the area will be constant. Therefore, if volume is minimum then it’s height will also decrease.

Therefore if ice melts and the temperature falls, then the level of water will also fall. Hence Option B is the right answer.

Note:
It is to be noted that density is of great importance. It helps in knowing whether an object will sink or float when placed on the surface of a liquid. If the density of the object is more than that of water then it will sink. But if the object has density less than that of water then the object will float.