Answer:

1.As a result, when you add oil to a cup of water the two don't mix with each other. Because oil is less dense than water, it will always float on top of water, creating a surface layer of oil. You might have seen this on streets after a heavy rain—some water puddles will have a coating of oil floating on them.

2.When we mix sand and water,no reaction takes place. The sand simply settles down at the bottom of the water container.In comparison,if we mix something like salt or sugar in water,they will react and make the water salty or sweet. sand therefore does not dissolve in water and is insoluble.

3.When water is added to paper, the hydrogen bonds holding the cellulose fibers begin to break down. This is because water molecules consist of oxygen and hydrogen atoms, which form hydrogen bonds with cellulose fibers, thus weakening their own hydrogen bonds in the process.