Write a chot not on the following 1.exothemic reaction 2.endothemic reaction 3. Crocking 4.isomesm

Here are short notes on the terms you provided:

1. Exothermic reaction: An exothermic reaction is a chemical reaction that releases energy, typically in the form of heat or light, into its surroundings. This causes the temperature of the surroundings to increase. An example is the combustion of fuels.

2. Endothermic reaction: An endothermic reaction is a chemical reaction that absorbs energy, typically in the form of heat, from its surroundings. This causes the temperature of the surroundings to decrease. An example is the dissolution of ammonium nitrate in water.

3. Cracking: Cracking is a process in petroleum refining where large, complex hydrocarbon molecules are broken down into smaller, simpler, and more valuable hydrocarbon molecules. This is typically achieved using heat and/or catalysts, producing substances like gasoline and alkenes from heavier crude oil fractions.

4. Isomerism: Isomerism is a phenomenon where two or more compounds have the same molecular formula but different structural arrangements of atoms. These compounds, called isomers, often exhibit different physical and chemical properties due to their distinct structures.