Substances such as liquids, gases and solids are generally categorized into soluble and insoluble. A soluble substance will breakdown when combined with another substance, whereas an insoluble substance will not. Many substances that are said to dissolve are actually soluble and breakdown and combine with other substances. One of the most common examples of this reaction is when salt dissolves in water.
Why does salt dissolve in water?
Salt is a soluble solid that will breakdown when combined with water. Salt dissolves in water because of the properties of both substances. Salt is made up of a sodium molecules and chlorine molecules. These two molecules are held together by ionic bonds. This means that one molecule steals and electron from the other. This makes the sodium molecules positively charged and the chlorine molecules negatively charged. When salt comes into contact with water the ionic bonds that hold the sodium and chlorine molecules together are pulled apart. This happens due to the molecular structure of water. Water is made up of an oxygen molecule and two hydrogen molecules. The oxygen molecule in water is negatively charged and the hydrogen molecules are positively charged. When salt is added to water the oxygen molecules attract the negatively charged chlorine molecules and the hydrogen molecules attract the positively charged sodium molecules and this breaks the bonds between the salt molecules causing them to dissolve.
The following video explains this process: