Question

Raincoats are made water proof by coating it with a material, which
A) Absorb water
B) Increase surface tension of water
C) Increase the angle of contact
D) Decreases the density of water

Answer 1

Hint: Cohesion, also known as cohesive attraction or cohesive force, is the action or attribute of similar molecules attracting one other. It's an inherent feature of a material created by the shape and structure of its molecules, which causes an uneven distribution of surrounding electrons when molecules approach close to one another, resulting in electrical attraction that may keep a tiny structure like a water drop in place.

Complete answer:
Now, any surface that does not allow water to pass through it is considered to be waterproof. As a result, when we look at the raincoat, we can see that it essentially prevents water from passing through. To put it another way, it does not exhibit the attribute of getting wet. That does not rule out the possibility of water collecting on the raincoat's exterior surface. When we consider the properties of water, we know that it has the ability to moisten whatever surface it comes into touch with. One of the reasons why water wets the glass's surface is because of this. This has a straightforward scientific explanation.
When it comes to water molecules, there is a significant attraction between them. Water molecules are attracted to the molecules of other surfaces when they come into touch with them.
This is best described as a combination of cohesive and adhesive forces.
The cohesive force is the force that causes water molecules to cling together, whereas the adhesive force is the force that causes water molecules to adhere to the surface of other substance molecules. In the case of a raincoat, the cohesive force in water molecules is obviously far larger than the adhesive force, therefore water does not attach to the raincoat surface.
The angle of contact between the water and material of the raincoat is obtuse. So the rainy water does not wet the raincoat.
Hence option (C) is correct.

Note:
A raincoat, sometimes known as a slicker, is a raincoat or slicker that is used to shield the body from rain. Raincoats that are waist length are sometimes referred to as rain jackets. A rain suit can be made by combining a rain jacket with a pair of rain trousers; a rain suit can also be made in one piece, similar to a boilersuit. Modern raincoats are frequently made of permeable waterproof materials like Gore-Tex or Tyvek, as well as coated nylons. These materials let water vapour flow through, allowing the garment to 'breathe' and enable the wearer's perspiration to leave. The quantity of rain that a raincoat can withstand is frequently expressed in millimetres, or water gauge.