Question

(c) There are two theories used to explain why graphite can act as a solid lubricant.
Theory a The forces of attraction between the layers are weak,
allowing the layers to slide over one another.
Theory B Gas molecules are trapped between the layers
allowing the layers to slide over one another.
The table shows the ability of graphite to act as a lubricant in different locations.
Ability to act as a lubricant
Location
Earth's surface
good
high altitude
average
outer space
very poor
Suggest which theory is supported by the evidence in the table.
Give a reason for your choice.

Answer 1

Answer:

The theory supported by the evidence in the table is,

Theory B, Gas molecules are trapped between the layers allowing the layers to slide over one another  

Explanation:

The table showing the ability of graphite to act as a lubricant in different locations is given as follows;

Ability to act as a lubricant     ${}$        Location

Earth's surface                          ${}$       Good

High altitude          ${}$                          Average

Outer space           ${}$                          Very poor

The crystals of graphite are made up of graphenes which are rings of atoms of carbon atoms arranged in parallel planes. The bonds between graphene planes are Van der Waals forces, such that under appropriate conditions, the planes easily slide relative to one another which partly gives graphite its lubricating property when used in air

When adsorbed on the surface of the graphite, molecules of water reduces the force bonding the planes of the graphenes further such that the graphite's lubricating property is related to the availability of water vapor

Therefore, given that the lubricity of graphite is highly dependent on the availability of water vapor, and that the availability of water vapor which is a gas, is reduced with increasing altitude, to being absent in outer space, the theory supported by the evidence in the table is Theory B, which states that  gas molecules are trapped between the layers allowing the layers to slide over one another.