Exploring the concepts of exothermic and endothermic reactions, this overview delves into the energy changes in chemical processes. It explains how exothermic reactions release energy, making the environment warmer, while endothermic reactions absorb energy, resulting in a cooler environment. The text also covers reaction profiles, the calculation of enthalpy changes, and the role of batteries in energy transfer, highlighting the practical applications of these chemical principles in everyday technology.
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Exothermic reactions release energy to the surroundings, typically as heat, and sometimes as light, resulting in an increase in temperature
Endothermic reactions absorb energy from their surroundings, causing a decrease in temperature
Reaction profiles, also known as energy diagrams, are graphical representations that illustrate the energy changes during chemical reactions
For an exothermic reaction, the profile shows a downward curve, with the reactants at a higher energy level than the products, reflecting the net release of energy
In contrast, the profile for an endothermic reaction slopes upward, with the reactants at a lower energy level than the products, indicating the net absorption of energy
The enthalpy change (ΔH) of a reaction can be calculated using Hess's law or by employing bond enthalpies
Bond enthalpies are the average energies required to break or form chemical bonds in gaseous molecules, measured in kilojoules per mole (kJ/mol)
The calculation of enthalpy change allows chemists to predict the heat exchange associated with a reaction and to determine whether a reaction is exothermic or endothermic
Batteries store chemical energy and convert it into electrical energy through electrochemical reactions
Fuel cells continuously convert the chemical energy of a fuel and an oxidant into electricity through redox reactions, with water often being the only byproduct
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Definition of chemical reaction
Process where atoms rearrange, breaking/forming bonds, transforming substances.
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Exothermic reaction characteristics
Releases energy, often as heat/light, increases environment temperature.
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Endothermic reaction characteristics
Absorbs energy, causing temperature decrease, products have higher enthalpy.
