Questions and Answers on Intermolecular Forces
Intermolecular forces written response Hexane and Water do not mix. When the two substances are combined they separate into layers in the same manner oil and water do. Explain why this is? Well to begin with this, these two things are very dissimilar. Water is considered polar and secondly hexane is considered non-polar. Polar and non-polar cannot mix together they are to different substances. Polar solutes will dissolve in polar solvents and non-polar solutes will dissolve in non-polar solvents, this is where the expression ‘like dissolves like’ comes from.
When theses two substances are combined they form different layers and this is because hexane is denser then water. Another very important reason to remember is that water is only soluble with nitrogen, fluorine, and oxygen. These two liquids are said to be immiscible. Water and oil will not mix for the same reason water is polar and oil is non-polar and for the same exact reason they are not mixable in a solution.
Methane, ammonia and water are chemically similar. Yet the three substances have very different boiling points. Explain why this is true? This is due to the bonding between the molecules.
The stronger they are the hotter you must make the liquid to cause it to boil. Intermolecular forces are the forces between the molecules of a substance. If a substance has very strong intermolecular forces, it is likely to be a solid, and if it has very weak intermolecular forces it is more likely to be a gas, and this is because there would be less attraction among the molecules (strong intermolecular force=more attraction between molecules). As you know, when you boil something, you are changing it from a liquid to a gas which means you would want to decrease the attraction among the molecules of the substance by adding energy.
If a substance has intermolecular forces that are stronger, you would need more energy to overcome the forces which means it would have a higher boiling point (higher boiling point=higher temperature=more heat=more energy). The opposite is also true. If a substance has weaker intermolecular forces, less energy is required to decrease the attraction among the molecules and therefore it would have a lower boiling point. Ammonia and water have higher boiling points due to hydrogen bonding. Methane has a low boiling point because it belongs to the weakest London dispersion forces.