Chemistry focuses on how substances interact with each other and with energy (for example heat and light).[3][4] The study of change of matter (chemical reactions) and synthesis lies at the heart of chemistry, and gives rise to concepts such as organic functional groups and rate laws for chemical reactions. Chemistry also studies the properties of matter at a larger scale (for example, astrochemistry) and the reactions of matter at a larger scale (for example, technical chemistry), but typically, explanations and predictions are related back to the underlying atomic structure, giving more emphasis on the methods for the identification of molecules and their mechanisms of transformation than any other science.