Question

A liquid surface behaves like a stretched

elastic membrane.

a) Name the liquid property for the

above behaviour.

b) Define angle of contact. What is its

value for pure water with glass?

Answer 1

The liquid properties due to which this behavious occur are,

1) Adhession
2)Cohession.

Angle of contact is the angle between the liquid curface and the container wall.

Pure water and glass )))------>> 90°

Answer 2

a) The liquid property for the above behaviour is Surface tension.

b) The angle of contact is the angle which the tangent makes to the free surface of the liquid at the point of contact with the walls of the vessel inside the liquid.

The angle of contact is the angle which the tangent makes to the free surface of the liquid at the point of contact with the walls of the vessel inside the liquid. The angle of contact for pure water and glass is zero.

Explanation:

• The liquid property for the liquid surface behaves like a stretched elastic membrane is Surface tension.
• Surface tension is the tension of the surface film of a liquid which is caused by the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize the surface area.
• The angle which is subtended between the tangents drawn at the liquid surface and the solid surface inside the liquid at the point of contact is known as the angle of contact.
• The angle of contact for pure water and glass is zero.

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