Chemistry·Chemical reactions · NSSCO 6.2
Energetics — exothermic & endothermic reactions
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Every reaction takes in or gives out energy. Learn what exothermic and endothermic mean, read energy-level diagrams with activation energy, see why breaking bonds costs energy and making bonds releases it, and calculate energy changes with q = mcΔT and with bond energies.
What you'll learn in this lesson
By the end you should be able to (NSSCO Chemistry 6.2):
- Explain the meanings of exothermic and endothermic
- Describe enthalpy change ΔH: exothermic (ΔH negative) and endothermic (ΔH positive), using labelled energy-level diagrams showing energy change and activation energy
- Describe bond breaking as endothermic and bond forming as exothermic
- Calculate energy changes using simple calorimetry, q = mcΔT
- Calculate energy changes for simple reactions using bond energies
- State that light can provide the energy for a reaction (photosynthesis; silver from silver chloride)
- State that photosynthesis makes glucose from CO₂ and water with chlorophyll and sunlight
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