sci_chem
Exothermic and Endothermic Reactions
Chapter summary, hard words and model exam answers for ICSE Class 10 Hindi.
Free online summary and notes (ICSE Class 10 Hindi). Read it here, no PDF download needed.
About the author
Chemistry · CBSE 10 · ICSE 10 · GCSE (AQA, Edexcel, OCR)
Summary
If the surroundings get hotter, energy left the reaction (exothermic). If they get colder, energy went into the reaction (endothermic).
If making the new bonds releases more than breaking the old ones used, the reaction is exothermic. If it releases less, it is endothermic.
Hand warmers and respiration release heat. Sports cold packs (dissolving ammonium nitrate) and heating limestone absorb heat.
Even a fire needs a spark to start. A catalyst makes the hill lower, so the reaction starts more easily.
Hard words & meanings
| exothermic | a reaction that releases heat to the surroundings, with a negative delta H |
| endothermic | a reaction that absorbs heat from the surroundings, with a positive delta H |
| enthalpy change (delta H) | the heat energy transferred during a reaction at constant pressure, in kJ/mol |
| activation energy | the minimum energy needed to start a reaction, shown as the peak on a profile |
| energy profile | a graph of energy against reaction progress showing reactants, peak and products |
| catalyst | a substance that speeds up a reaction by lowering the activation energy and is not used up |
| bond energy | the energy needed to break one mole of a particular bond |
| thermal decomposition | breaking a compound apart using heat; usually endothermic |
Model exam answers, grammar & audio
You have read the summary. The board-ready model answers, grammar notes, one-touch audio and writing practice for this chapter are part of Lipi©.
Sign in to unlockSee it, understand it, hear it read aloud, then write the exam answer with confidence, for a fraction of a tutor cost.