Water is a molecule with the chemical formula H2O, consisting of two hydrogen atoms and one oxygen atom. It is a polar molecule, with a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms, making it highly cohesive and adhesive. Water is essential for all life on Earth, as well as many industrial processes. It is also a powerful solvent due to its polar nature. The three states of water (solid, liquid, gas) are due to differences in temperature and pressure. The specific properties of water make it an incredibly important substance to understand in fields ranging from chemistry to biology to geology.