Chemistry Articles

Elements and compounds can move from one physical state to another and not change. Oxygen (O2) as a gas still has the same properties as liquid oxygen. The liquid state is colder and denser but the molecules are still the same. Water is another example. The compound water is made up of two hydrogen (H) atoms and one oxygen (O) atom. It has the same molecular structure whether it is a gas, liquid, or solid. Although its physical state may change, its chemical state remains the same. So you ask, "What is a chemical state?" If the formula of water were to change, that would be a chemical change. If you added another oxygen atom, you would make hydrogen peroxide (H2O2). Its molecules would not be water anymore. Changing states of matter is about changing densities, pressures, temperatures, and other physical properties. The basic chemical structure does not change.