ANS:A - exothermic

An exothermic reaction is a chemical reaction that releases energy in the form of heat to its surroundings. Here's a breakdown of what happens during an exothermic reaction:

1. Energy Release: In an exothermic reaction, the total energy of the products is lower than the total energy of the reactants. This energy difference is released as heat during the reaction. Essentially, the chemical bonds in the reactants are stronger than those in the products, and the excess energy is released to the surroundings.
2. Temperature Increase: Since heat is released, the temperature of the surroundings tends to increase during an exothermic reaction. This increase in temperature is often noticeable and can sometimes be significant, especially in highly exothermic reactions.
3. Enthalpy Change: Exothermic reactions have a negative enthalpy change (Δ𝐻<0ΔH<0), indicating that the overall change in heat content of the system is negative. This means that the system loses heat to the surroundings during the reaction.
4. Examples: Exothermic reactions are common in various chemical processes, including combustion reactions (such as burning wood or gasoline), neutralization reactions (such as the reaction between an acid and a base to form water and a salt), and many types of chemical reactions used in industry and everyday life.

In summary, an exothermic reaction is characterized by the release of heat to the surroundings, resulting in a temperature increase and a negative enthalpy change. This release of energy is a fundamental aspect of many chemical reactions and has important implications in various fields, including chemistry, engineering, and environmental science.