Surface tension permits an insect such as the water strider to “walk” on water.
Liquid is a form of matter between gas and a solid that has a definite volume, but no definite shape.
Liquids are made up of very small particles (atoms, molecules and or ions). Particles that make up the liquid are close together with no regular arrangement. These particles vibrate, move about, and slide past each other. The particles in a liquid have more kinetic energy than the particles in the corresponding solid.
Properties of Liquids:
- Surface tension
- Capillarity
- Viscosity
Water display a concave meniscus in a glass tube
because the adhesive (H–bond) forces between the H20 molecules and
the O–Si–O groups of the glass are stronger than the
cohesive (H–bond) forces within the water. Mercury displays
a convex meniscus in a glass tube because the cohesive (metallic
bonding) forces within the mercury are stronger than the adhesive
(dispersion) forces between the mercury and the glass.
Surface tension:
There is a force of attraction between molecules in liquids,
and liquids can flow until they take on the shape that maximizes
this force of attraction. Below the surface of the liquid, the force
of cohesion (literally, “sticking together”) between molecules is the
same in all directions. Molecules on the surface of the liquid, however,
feel a net force of attraction that pulls them back into the body of the liquid.
As a result, the liquid tries to take on the shape that has the smallest possible
surface area, the shape of a sphere. There is also a force of adhesion
(literally, “sticking”) between a liquid and the walls of the container.
The force of adhesion between paper and water combined with the force of
cohesion between water molecules explains why sheets of wet paper stick together.
The force of adhesion between water and wax is very small compared to the force of cohesion between water molecules. As a result, rain doesn't adhere to wax. It tends to form beads, or drops, with the smallest possible surface area, thereby maximizing the force of cohesion between the water molecules. The same thing happens when mercury is spilled on glass or poured into a narrow glass tube. The force of cohesion between mercury atoms is so much larger than the force of adhesion between mercury and glass that the area of contact between mercury and glass is kept to a minimum, with the net result being the meniscus shown in the adjacent figure.