If the temperature of an iron sphere is increased

a) its mass will decrease.
b) its density will increase.
c) its density will decrease.
d) its density will remain unchanged.
e) its volume will decrease.

By increasing the temperature of the iron sphere, its volume will increase (due to the material of which it is composed), this is a phenomenon known as thermal dilation. However, the mass of the sphere will remain the same.

On the other hand, density is a characteristic property of substances and materials and is defined as the relationship between the mass and volume of a specific substance or material, as shown below:

This means density is inversely proportional to volume. Therefore, increasing the temperature of the iron sphere, its volume will be increased and its density will be decreased.