Question
Water spreads over a clean glass plate but mercury does not. Why?
Solution
Water spreads over a clean glass plate but mercury does not. In case of water, the surface tension force between glass plate and air is greater than the surface tension between liquid and solid. Therefore, angle of contact is less than 90o. Hemce, it will spread over the glass plate.
In case of mercury, the surface tension force between glass plate and mercury is less than the surface tension between liquid and solid. Therefore, angle of contact is greater than 90o. Hence, mercury will not spread over the glass plate.
In case of mercury, the surface tension force between glass plate and mercury is less than the surface tension between liquid and solid. Therefore, angle of contact is greater than 90o. Hence, mercury will not spread over the glass plate.
