Question

 ______ has no definite shape but has a definite volume.
A. Helium
B. Mercury
C. Oxygen
D. Carbon

Answer 1

Hint: The substance which has a definite shape and definite volume is said to exist in a solid state. A substance which has a definite volume but no definite shape is said to exist in liquid state. A substance which has neither a definite shape nor a definite volume is said to exist in a gaseous state.

Complete step by step answer:

The solid substances have a definite shape and a definite volume because of the presence of strong intermolecular forces of attraction between the molecules inside them and due to which very small intermolecular spaces persist between the molecules. In case of a liquid, they have a definite volume but not a definite shape because of the presence of weak intermolecular force of attraction among the molecules and due to which the intermolecular spaces are more than that of solids. In the case of gases, they neither have a definite shape nor a definite volume because of the presence of weakest intermolecular forces of attraction and due to which, is the intermolecular space very large among the molecules and which helps the gases to diffuse easily.
Thus, as per the question, the substance that has no definite shape but has a definite volume should be the one that exists as a liquid at room temperature. Mercury exists as a liquid at room temperature.
Hence, the correct option is B i.e. Mercury.

Note:
Helium is a noble gas and is very stable due to a completely filled valence shell electronic configuration (complete octet). Oxygen also exists in a gaseous phase and is non-metal. Carbon is also a non-metal that exists in solid state due to strong intermolecular forces present among the atoms.