 Water's ability to act as a solvent for a great many substances is one of the properties which makes water so important to life. For example, the polarity of water contributes to its ability to dissolve salt, such as the sodium chloride depicted here, and to keeping substances dissolved. The salt crystals are made up of positive and negative ions. The water molecules have portions that are partially positive, the hydrogen atoms, and portions that are partially negative, the oxygen atom. The water molecules surround the ions from the salt and orient themselves so that the opposite charges attract. This allows many different substances to be dissolved in water and to remain dissolved. This is important to life because water acts as a transport medium for nutrients and other substances that cells need in order for life to persist.