Chemical Bonds and Balancing Equations EQ: Why do chemicals react? What is the difference between compounds, mixtures, and solutions? Important Terms Molecule- is two or more atoms combined and are physically attached Compound- is when two or more elements are combined by chemical bonds (NaCl, Sugar..ect) and is a solid Solution- is when two or more elements are combined by chemical bonds and are in a liquid state. (every drop is the same concentration HCL, Vinegar)