https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:chemical-energetics/x8bc8fb44369617ed:exothermic-and-endothermic-reactions/v/exothermic-and-endothermic-reactions-ur 2025-08-08T00:50:08.705567982Z Exothermic and endothermic reactions Created by Khan Academy video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Exothermic and endothermic reactions Created by Khan Academy https://cdn.kastatic.org/ka-youtube-converted/8bX9vw1-Ers.mp4/8bX9vw1-Ers.mp4 689 Exothermic and endothermic reactions https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:chemical-reactions/x2613d8165d88df5e:energy-of-chemical-reactions/v/endothermic-and-exothermic-reactions 2023-12-15T18:39:28.793791463Z Endothermic and exothermic reactions Chemical reactions can result in energy being released (exothermic) or energy being absorbed (endothermic). We can use the law of conservation of energy to determine how that energy is transferred between a system and its surroundings. Energy diagrams visually represent potential energy changes during a reaction, providing quantitative information about the bond-breaking and bond-forming process. Sal Khan video https://cdn.kastatic.org/ka_thumbnails_cache/766dc977-087f-4a15-bb65-66bf2cac51f9_1280_720_base.png Endothermic and exothermic reactions Chemical reactions can result in energy being released (exothermic) or energy being absorbed (endothermic). We can use the law of conservation of energy to determine how that energy is transferred between a system and its surroundings. Energy diagrams visually represent potential energy changes during a reaction, providing quantitative information about the bond-breaking and bond-forming process. https://cdn.kastatic.org/ka-youtube-converted/GSfwMq68Wt4.mp4/GSfwMq68Wt4.mp4 343 Exothermic and endothermic reactions https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:chemical-energetics/x8bc8fb44369617ed:exothermic-and-endothermic-reactions/a/endothermic-vs-exothermic-reactions-class-10-chemistry 2021-04-29T08:01:46Z Endothermic vs. exothermic reactions article https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:chemical-energetics/x8bc8fb44369617ed:exothermic-and-endothermic-reactions/e/exothermic-and-endothermic-reactions 2026-03-06T13:21:33.841038103Z Exothermic and endothermic reactions Let's practice problems involving exothermic and endothermic reactions. Chaitra exercise https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:chemical-energetics/x8bc8fb44369617ed:exothermic-and-endothermic-reactions/v/exothermic-and-endothermic-common-processes-and-solved-examples-ur 2025-08-08T00:50:08.705567982Z Exothermic and endothermic: Common processes and solved examples Created by Khan Academy video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Exothermic and endothermic: Common processes and solved examples Created by Khan Academy https://cdn.kastatic.org/ka-youtube-converted/Yh4PlT2jU2Y.mp4/Yh4PlT2jU2Y.mp4 371 Exothermic and endothermic reactions https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:thermodynamics/x2eef969c74e0d802:endothermic-and-exothermic-processes/v/endothermic-and-exothermic-processes 2022-10-05T02:43:18.611402953Z Endothermic and exothermic processes The first law of thermodynamics relates the change in the internal energy of a system (ΔE) to the heat transferred (q) and the work done (w). At constant pressure, q is equal to the change in enthalpy (ΔH) for a process. If ΔH is positive, the process absorbs heat from the surroundings and is said to be endothermic. If ΔH is negative, the process releases heat to the surroundings and is said to be exothermic. Phase changes, chemical reactions, and the formation of solutions are all examples of endothermic and exothermic processes. Jay video https://cdn.kastatic.org/ka_thumbnails_cache/505019ce-a6a7-4c2b-abe4-0a3431f5ee0a_1280_720_base.png Endothermic and exothermic processes The first law of thermodynamics relates the change in the internal energy of a system (ΔE) to the heat transferred (q) and the work done (w). At constant pressure, q is equal to the change in enthalpy (ΔH) for a process. If ΔH is positive, the process absorbs heat from the surroundings and is said to be endothermic. If ΔH is negative, the process releases heat to the surroundings and is said to be exothermic. Phase changes, chemical reactions, and the formation of solutions are all examples of endothermic and exothermic processes. https://cdn.kastatic.org/ka-youtube-converted/JPxTgtUx9sE.mp4/JPxTgtUx9sE.mp4 480 Exothermic and endothermic reactions https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:chemical-energetics/x8bc8fb44369617ed:exothermic-and-endothermic-reactions/v/enthalpy-1 2023-08-14T21:12:46.061619254Z Enthalpy Learn about enthalpy, a key term in understanding heat transfer in chemical reactions. Explore how reactions can either release or absorb energy, impacting the temperature of their surroundings. Uncover the significance of enthalpy in determining whether a reaction will occur and its role in the fascinating phenomena of endothermic and exothermic reactions. Jasmine Rana video https://cdn.kastatic.org/googleusercontent/YMQ8nha3lV2d6stAO63NB7-1fN20t3LXUI_K_zlVqbcLrrSd3bnAD4jkLqJjZB203aqWsU_U8nvyt84iL862x7fh Enthalpy Learn about enthalpy, a key term in understanding heat transfer in chemical reactions. Explore how reactions can either release or absorb energy, impacting the temperature of their surroundings. Uncover the significance of enthalpy in determining whether a reaction will occur and its role in the fascinating phenomena of endothermic and exothermic reactions. https://cdn.kastatic.org/ka-youtube-converted/AfjH7Xn8VB8.mp4/AfjH7Xn8VB8.mp4 514 Exothermic and endothermic reactions https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:chemical-reactions/x2613d8165d88df5e:energy-of-chemical-reactions/e/understand-energy-of-chemical-reactions 2026-04-28T11:00:37.315336883Z Understand: Energy of chemical reactions Check your understanding of energy changes in chemical reactions in this set of free practice questions. Fig exercise https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:thermodynamics/x2eef969c74e0d802:endothermic-and-exothermic-processes/v/representing-endothermic-and-exothermic-processes-using-energy-diagrams 2022-10-05T02:43:18.611402953Z Representing endothermic and exothermic processes using energy diagrams A physical or chemical process can be represented using an energy diagram, which shows how the potential energy of the initial state relates to the potential energy of the final state. If the initial state has a lower potential energy than the final state, the process is endothermic. If the initial state has a higher potential energy than the final state, the process is exothermic. Jay video https://cdn.kastatic.org/ka_thumbnails_cache/5d589c4c-d370-4a30-8219-4b4bad816d99_1280_720_base.png Representing endothermic and exothermic processes using energy diagrams A physical or chemical process can be represented using an energy diagram, which shows how the potential energy of the initial state relates to the potential energy of the final state. If the initial state has a lower potential energy than the final state, the process is endothermic. If the initial state has a higher potential energy than the final state, the process is exothermic. https://cdn.kastatic.org/ka-youtube-converted/LYrpdeXbvdk.mp4/LYrpdeXbvdk.mp4 305 Exothermic and endothermic reactions https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:thermodynamics/x2eef969c74e0d802:bond-enthalpies/v/bond-enthalpies-intro 2022-10-05T02:43:18.611402953Z Bond enthalpies The enthalpy of a bond is the enthalpy change that occurs when 1 mole of a particular bond is broken in the gas phase. Since energy is required to break a chemical bond, bond enthalpies are always reported as positive values. For any chemical reaction, the estimated change in enthalpy is the sum of the bond enthalpies of the bonds broken minus the sum of the bond enthalpies of the bonds formed. Jay video https://cdn.kastatic.org/ka_thumbnails_cache/d42cd120-5998-48d9-a93c-bd92757f4ecc_1280_720_base.png Bond enthalpies The enthalpy of a bond is the enthalpy change that occurs when 1 mole of a particular bond is broken in the gas phase. Since energy is required to break a chemical bond, bond enthalpies are always reported as positive values. For any chemical reaction, the estimated change in enthalpy is the sum of the bond enthalpies of the bonds broken minus the sum of the bond enthalpies of the bonds formed. https://cdn.kastatic.org/ka-youtube-converted/VxcqAIaO-cA.mp4/VxcqAIaO-cA.mp4 573 Exothermic and endothermic reactions https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:thermodynamics/x2eef969c74e0d802:bond-enthalpies/e/bond-enthalpies 2025-03-13T03:54:01.571704451Z Bond enthalpies Practice calculations involving bond enthalpies in this set of free questions designed for AP Chemistry students. exercise https://www.khanacademy.org/science/hs-bio/x230b3ff252126bb6:energy-and-matter-in-biological-systems/x230b3ff252126bb6:biomolecules-and-reactions/a/biomolecules-and-reactions 2026-04-28T11:00:37.315336883Z Learn: Biomolecules and reactions Learn about endothermic and exothermic chemical reactions, enzymes, and metabolism. article https://www.khanacademy.org/science/ap-biology/cellular-energetics/enzyme-structure-and-catalysis/a/activation-energy 2023-05-16T11:42:45.366417523Z Activation energy Activation energy, transition state, and reaction rate. article https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:reaction-rates-and-equilibrium/x2613d8165d88df5e:reaction-rates/v/collision-theory 2021-01-30T09:09:56Z Collision theory Collision theory states that molecules must collide to react. For most reactions, however, only a small fraction of collisions produce a reaction. In order for a collision to be successful, the reactant molecules must collide both with sufficient energy to overcome the activation energy barrier and in the proper orientation to form any new bonds in the products. Jay video https://cdn.kastatic.org/googleusercontent/KVNzRM6P5K59aYcHOyMgVFrq8GKsRUK3rh9_mblSqnd9RyYTNRU8NqV5R1gpqVQK05Dgl4z7KCfshabcgG_igWvr1A Collision theory Collision theory states that molecules must collide to react. For most reactions, however, only a small fraction of collisions produce a reaction. In order for a collision to be successful, the reactant molecules must collide both with sufficient energy to overcome the activation energy barrier and in the proper orientation to form any new bonds in the products. https://cdn.kastatic.org/ka-youtube-converted/1iAxhc6EflI.mp4/1iAxhc6EflI.mp4 528 Exothermic and endothermic reactions https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:chemical-energetics/x8bc8fb44369617ed:exothermic-and-endothermic-reactions/v/energy-changes-in-chemical-reactions-part-1 2025-03-21T20:29:57.678923887Z Energy changes in chemical reactions (part 1) Chemical reactions often involve energy changes. In exothermic processes, like combustion, energy is released to the surroundings, making them warmer. In endothermic processes, like photosynthesis, energy is absorbed, often from the sun. The law of conservation of energy states that energy is never created or destroyed—only transferred or stored in different forms. Mahesh Shenoy video https://cdn.kastatic.org/ka_thumbnails_cache/aa0b7cee-d09b-4345-ab05-5a9fabd4215d_1280_720_base.png Energy changes in chemical reactions (part 1) Chemical reactions often involve energy changes. In exothermic processes, like combustion, energy is released to the surroundings, making them warmer. In endothermic processes, like photosynthesis, energy is absorbed, often from the sun. The law of conservation of energy states that energy is never created or destroyed—only transferred or stored in different forms. https://cdn.kastatic.org/ka-youtube-converted/Xu8S3aC8YWk.mp4/Xu8S3aC8YWk.mp4 444 Exothermic and endothermic reactions https://www.khanacademy.org/science/cambridge-o-level-chemistry-cie/x8bc8fb44369617ed:chemical-energetics/x8bc8fb44369617ed:exothermic-and-endothermic-reactions/v/energy-changes-in-chemical-reactions-part-2 2025-03-21T20:29:57.678923887Z Energy changes in chemical reactions (part 2) Chemical reactions involve energy changes—some release energy (exothermic), while others absorb it (endothermic). The amount of energy transferred depends on the type and amount of reactants. The reaction rate can be increased by adding more reactants, raising the temperature, or improving particle distribution to encourage more collisions. Mahesh Shenoy video https://cdn.kastatic.org/ka_thumbnails_cache/815611d5-2408-4e22-aa17-e3cefeb1e8ea_1280_720_base.png Energy changes in chemical reactions (part 2) Chemical reactions involve energy changes—some release energy (exothermic), while others absorb it (endothermic). The amount of energy transferred depends on the type and amount of reactants. The reaction rate can be increased by adding more reactants, raising the temperature, or improving particle distribution to encourage more collisions. https://cdn.kastatic.org/ka-youtube-converted/ZCVcPikgki0.mp4/ZCVcPikgki0.mp4 466 Exothermic and endothermic reactions https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:reaction-rates-and-equilibrium/x2613d8165d88df5e:catalysts/v/catalysts_hs 2023-12-15T18:39:28.793791463Z Catalysts Catalysts are chemicals that help chemical reactions proceed faster rate. But the catalyst itself is not consumed in the reaction. There are a variety of ways that a catalyst causes the rate to increase. In all cases, the catalyst speeds up a reaction by lowering the activation energy. An enzyme is a substance produced by a living organism that acts a catalyst in biochemical reactions. Sal Khan video https://cdn.kastatic.org/ka_thumbnails_cache/52dfa5ef-31a8-4736-b81d-d9b89eef6e23_1280_720_base.png Catalysts Catalysts are chemicals that help chemical reactions proceed faster rate. But the catalyst itself is not consumed in the reaction. There are a variety of ways that a catalyst causes the rate to increase. In all cases, the catalyst speeds up a reaction by lowering the activation energy. An enzyme is a substance produced by a living organism that acts a catalyst in biochemical reactions. https://cdn.kastatic.org/ka-youtube-converted/8TuPmpNfoX8.mp4/8TuPmpNfoX8.mp4 303 Exothermic and endothermic reactions https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:kinetics/x2eef969c74e0d802:activation-energy-and-reaction-rate/e/activation-energy-and-reaction-rate 2023-08-07T17:25:22.494770007Z Activation energy and reaction rate Check your understanding of activation energy and reaction rate in this set of free practice questions designed for AP Chemistry students. exercise https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:thermodynamics/x2eef969c74e0d802:bond-enthalpies/v/worked-example-using-bond-enthalpies-to-calculate-enthalpy-of-reaction 2022-10-05T02:43:18.611402953Z Worked example: Using bond enthalpies to calculate enthalpy of reaction Bond enthalpies can be used to estimate the change in enthalpy for a chemical reaction. In this video, we'll use average bond enthalpies to calculate the enthalpy change for the gas-phase combustion of ethanol. Jay video https://cdn.kastatic.org/ka_thumbnails_cache/cd12a2be-ef51-4035-b10e-813f5774968e_1280_720_base.png Worked example: Using bond enthalpies to calculate enthalpy of reaction Bond enthalpies can be used to estimate the change in enthalpy for a chemical reaction. In this video, we'll use average bond enthalpies to calculate the enthalpy change for the gas-phase combustion of ethanol. https://cdn.kastatic.org/ka-youtube-converted/TdBY-so0H0Q.mp4/TdBY-so0H0Q.mp4 543 Exothermic and endothermic reactions https://www.khanacademy.org/science/hs-chemistry/x2613d8165d88df5e:chemical-reactions/x2613d8165d88df5e:energy-of-chemical-reactions/e/apply-energy-of-chemical-reactions 2026-04-29T07:20:45.495372596Z Apply: Energy of chemical reactions Apply your understanding of energy changes in chemical reactions in this set of free practice questions. Fig exercise