The two main branches of physical science are physics and chemistry. Physics primarily deals with forces and the interaction of matter and energy. Chemistry, on the other hand, studies how interaction alters the properties of atoms, molecules and substances.
Physics is the bedrock of all other sciences because it deals with how particles and objects move and transfer force. For example, the study of electromagnetism shows how electrical charges attract opposites and repel similar charges. This fundamental concept governs what types of atoms can undergo chemical reactions. Physics also deals with theoretical concepts such as what happens to objects as they move faster.
Chemistry, meanwhile, deals with the study of how matter's physical properties (the characteristics that make it unique) are affected during interaction with other matter or energy. Chemists work with a wide range of compounds and consult the periodic table of elements to determine what elements will interact and how they will behave. For example, the interaction of hydrogen and oxygen produces a molecule of water. Chemistry makes its way into almost every other scientific discipline and even culinary sciences. Heat, a form of energy, is applied to ingredients and causes the molecules to hopefully rearrange into a digestible and palatable form.