Illustrated Glossary of Organic Chemistry

Reaction rate: The speed at which a reaction consumes starting material or produces products. Expressed mathematically as a rate equation such as rate = k [CH₃I] [HO^-].

Some metals react quickly with water, while others are essentially inert. There is no visible reaction between zinc metal and water at room temperature: Zn + H₂O ---> NR (left beaker). On the other hand, the reaction of calcium metal with water is vigorous, producing hydrogen gas bubbles and a murky calcium hydroxide precipitate: Ca + 2 H₂O ---> Ca(OH)₂ + H₂ (right beaker). Click the image to watch the video. The zinc/water reaction rate is slower (is less than) the calcium/water reaction rate.