Is photosynthesis considered a chemical reaction?

• A. Yes
• B. No
• C. Only in plants
• D. Not at all

Answer: (A)

Photosynthesis is a chemical reaction because it changes matter by rearranging atoms to form new substances. In this process, carbon dioxide and water are converted into glucose and oxygen, with energy from light driving the making and breaking of chemical bonds. The overall result is a new set of molecules with different properties than the starting ones, which is the essence of a chemical change. The big equation for the overall process captures this transformation: 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2. There are also redox steps involved—carbon dioxide is reduced to sugar and water is oxidized to oxygen—showing clear chemical rearrangements. This reaction isn’t limited to plants alone; algae and some bacteria perform photosynthesis as well. So the process is indeed a chemical reaction, not a purely physical change.