Science ObjectDigital resources are stored online in your NSTA Library.
Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach. This Science Object is the final of four Science Objects in the Chemical Reactions SciPack. It explains how different configurations of atoms and molecules are associated with different energy levels. Some changes of configuration among atoms and molecules require a net input of energy whereas others cause a net release. As a result, chemical reactions may release or consume energy. Some reactions such as the burning of fossil fuels release large amounts of energy by losing heat and by emitting light. Energy from light and other electromagnetic radiation can initiate many chemical reactions such as photosynthesis and the evolution of urban smog. The behavior of atoms in chemical reactions demonstrates the conservation of matter: When the number of atoms in a closed system stays the same, their total mass remains constant no matter how they are rearranged.