Question

For tap water and clean glass, the angle of contact is
A. \[0^\circ \]
B. \[90^\circ \]
C. \[140^\circ \]
D. \[8^\circ \]

Answer 1

Hint: The above problem can be resolved using the concept of cohesiveness and adhesiveness for a specific liquid and the container's wall, in which the liquid is kept. The angle of contact depends on the composition of the ions in the liquid and the magnitude of cohesive force and the adhesive force.


Complete step by step answer
The angle of contact is determined as the calculated value of the angle that is observed to form within the meniscus of the liquid and the walls of columns containing the liquid.
For tap water to be enclosed in a clean glass, the angle of contact will be zero degrees, and this is due to the reason because of the cohesive and adhesive force. The cohesive force and the adhesive
Forces are observed to be equal in this case, which becomes a necessary condition for the angle of contact to be zero degrees.
Therefore, for tap water and clean glass, the angle of contact is zero degree and the option A is correct.


Note: Try to understand the cohesive force and adhesive force concept, along with its significance with the angle of contact. The cohesive force arises when an interaction between the molecules itself and adhesive forces occurs due to interaction within the molecules of different materials. The angle of contact will be zero only when the practical value for the cohesive force and the adhesive force become similar.