Chemical Reactions
1. What is a chemical reaction?

a chemical reaction is a process in which one or more substances, also called reactants, are converted to one or more different substances known as products. a chemical reaction rearranges the constituent atoms of the reactants to create different substances as products

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.