Water is a polar molecule. The oxygen end has a slightly negative charge and the hydrogen end has a slightly positive charge. The positive end of a water molecule is attracted to the negative end of another water molecule. Other molecules which are polar are attracted to the ends of water molecules. Two properties of water are explained by its polar nature.
Cohesion is the property of water where water sticks to water.
There are two types of pure substances. Elements are substances made of only one kind of atom. Oxygen, carbon, iron, potassium, aluminum, and helium are all examples of elements. There are 92 naturally occurring elements. Compounds are substances which are made from chemical combinations of two or more kinds of elements combined in definite amounts.