Answer:- 
Explanations:- Alkanes are non polar molecules as these only have carbons and hydrogens. Electron negativity difference of C and H is very low and it makes them non polar. These have weaker London dispersion forces.
The forces of attraction becomes stronger in alkanes as the number of carbon increases because the surface area as well as molecular weight of the alkanes increases with an increase in number of carbons.
Butane has four carbons, propane has three carbons, ethane has two and methane has only one carbon, So, the strongest to weakest order of inter molecular forces is butane > propane > ethane > methane .
Answer: The answer to the first one is the second option and the answer for the second one is the first option.
Explanation:
Answer: 15.3 carbon atoms
Evaporating.
This is because evaporation occurs for things such as water coming in contact with a heat source that cause molecules to run crazy and begin to go farther and farther apart, becoming steam and evaporation in the air.
Therefore, during the process of evaporation, molecules become less condensed.
Hope this helps!