when you fill a cylinder with liquid why is it concave when you fill it and convex when you get to the top?

Answer 1

There are two types of forces namely; Cohesive and Adhesive Forces; these are weak forces of attraction

Cohesive forces are weak forces of attraction between the particles of a (same) substance.

Adhesive forces are weak forces of attraction between the particles of one substance and another.

The answer to your question is mainly due to the adhesive forces.

Surface tension is due to the cohesive forces and it is the secondary reason.

Due to cohesive forces the surface of any liquid acts like a stretched membrane; and is under tension.

When the cylinder (say glass cylinder) is partly filled up with the liquid, the liquid surface is in contact with glass along a circle. At each point of contact the glass pulls the liquid at angle ‘A’ to the vertical, due to the resultant of adhesive force and cohesive forces.

This angle is called the angle of contact. If this angle is 90 degree the surface of liquid is horizontal (not concave). For silver and pure water this angle is 90 degree.

If the angle is below 90 degree, the surface is concave, (water and glass)

If the angle is above 90 degree, the surface is convex, (mercury and glass)

In the case of water and glass, when water is filled up to the brim, there is no glass on the side to pull the surface of the liquid at that angle; now the brim of the glass cylinder is horizontal; and the angle of pulling is tilted down ward pointing the ground, and hence the surface is little convex in shape.

The shape of the surface depends on how the cylinder top is curved or turned to the vertical at its top.

Answer 2

No glass or plastic is perfect the liquid wants to stick to the sides so it forms a convex pattern. When you fill the cylinder all the way up, and a little more the surface tension of the liquid keeps it together. You have over filled the container, but just before it reaches the point of failure the attraction between the molecules is strong enough to form a convex bulge.

Answer 3

Two types of forces are responsible for this phenomenon. One is ADHESION and other is COHESION. This is totally called surface tension. Adhesion is the attraction between the liquid molecules and the wall of cylindrical container. Cohesion is the attraction between the liquid molecules. Before reaching the brim of the container, the surface of the liquid is concave. This is because, very great affinity due to Adhesion force. The centre of the surface is slightly lowered due to gravitational force. Thus you get the concave. After reaching the brim of the cylinder, the centre of the surface become slightly rised and the peripheral area is restricted by the brim of the cylinder due to the force, Adhesion. Once if the excess liquid is poured into the cylinder, this will create the additional force greater than the Adhesive force and the liquid comes out of the cylinder.

If you pour mercury, the surface is convex even before the reach to brim. After reaching the brim, the surface is in concave shape. This is due to very high surface tension of the mercury.

Answer 4

Initially it is concave because of the adhesive force between the liquid and the container walls... the liquid around the periphery "sticks" to the container a little better than it "sticks" to itself, so it's a little higher right at the liquid/container interface.

Once you have no more container edge to stick to - and you keep filling, the profile becomes convex due to surface tension of the liquid (the liquid "sticks" to itself as best as it can until it collapses under its own weight).

Answer 5

Surface tension of the liquid.
Try adding a drop of detergent to a water-filled topped cylinder.
You'll break the surface tension and make the water spill over the sides.

Answer 6

Surface tension is primary function of intermolecular forces and gravity...water and most liquids behave as yoiu described...there are others such as Hg that behave otherwise...

Answer 7

surface tension