When elements combine to form compounds what happens to the properties of the original elements?

The properties of the original elements are completely changed.

For example, in the compound called "iron(II) sulphide", it is composed of iron and sulphur, that are chemically combined together. The element iron is attracted to magnets. Meanwhile, iron(II) sulphide is not attracted to magnets. 

Another example is where sulphur has a yellow colour, but iron(II) sulphide has a brownish colour. As we can see, even the physical properties (colours) are completely different.

Therefore, the properties of the original elements are completely changed when they're combined into compounds.

By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.