Science, Tech, Math › Science Is Energy Released When Chemical Bonds Are Broken or Formed? Share Flipboard Email Print Hero Images / Getty Images Science Chemistry Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated July 17, 2019 One of the biggest challenges for chemistry students is understanding whether energy is required or released when chemical bonds are broken and formed. One reason this can be confusing is that a complete chemical reaction can go either way. Exothermic reactions release energy in the form of heat, so the sum of the energy released exceeds the amount required. Endothermic reactions absorb energy, so the sum of the energy required exceeds the amount that is released. In all types of chemical reactions, bonds are broken and reassembled to form new products. However, in exothermic, endothermic, and all chemical reactions, it takes energy to break the existing chemical bonds and energy is released when the new bonds form. Breaking Bonds → Energy Absorbed Forming Bonds → Energy Released Breaking Bonds Requires Energy You have to put energy into a molecule to break its chemical bonds. The amount needed is called the bond energy. After all, molecules don't spontaneously break. For example, when is the last time you saw a pile of wood spontaneously burst into flames or a bucket of water turn into hydrogen and oxygen? Energy must be applied for these reactions to occur. Forming Bonds Releases Energy Energy is released when bonds form. Bond formation represents a stable configuration for atoms, sort of like relaxing into a comfy chair. You release all your extra energy when you sink into the chair and it takes more energy to get you back up again.