Define displacement and double displacement reaction with example.

The reaction in which one element takes the place of another element in a compound, are known as displacement reactions. Example: When iron nails are dipped in copper sulphate solution, iron being more reactive than copper displaces copper from its solution and forms iron sulphate and copper. Fe s + CuSO 4 aq → FeSO 4 aq + Cu s The reactions in which two compounds react by an exchange of ions to form two new compounds are called double displacement reactions. For example- When silver nitrate solution is added to sodium chloride solution, then a white precipitate of silver chloride is formed along with sodium nitrate solution. In this reaction, nitrate ion and chloride ion exchange their places. AgNO 3 aq + NaCl aq → AgCl + NaNO 3

Define exothermic reaction and endothermic reaction with example.

Exothermic Reactions – Exothermic reactions are those reactions in which heat is released. Reactants → products + heat For example- Neutralization, burning a substance, reactions of fuels, rusting of iron, respiration, etc. Endothermic Reactions- These are those reactions in which heat is absorbed. Reactants + heat → products For example- Melting ice, evaporation, cooking, photosynthesis, etc.

Rancidity can be defined as the chemical decomposition of oils and fats when exposed to air, light, moisture, and bacterial activity in food and other products making them undesirable for consumption. It can be prevented by the following methods: The packing of food materials should replace the air with Nitrogen. The food materials should be placed at very low temperatures. The addition of antioxidants also prevents rancidity process.