Question

If you pour a few drops of petrol on your palm, it will feel cool as the petrol evaporates. This change is a/an-
A.Endothermic reaction
B.Exothermic reaction
C.Chemical reaction
D.Slow reaction

Answer 1

Hint: Petrol is a derivative of petroleum obtained through petroleum distillation. It is used as a fuel as it is volatile in nature and releases its energy completely on burning.

Complete step by step answer:
Petrol is a mixture of flammable and volatile hydrocarbons in the range of $C_4-C_{10}$. It easily vaporizes at room temperature on coming in contact with a larger surface. It is a fast reaction.Since petrol evaporates easily it needs latent heat of vaporization so it absorbs the heat energy from our palm and we feel the cooling sensation. Latent heat of vaporization is the heat absorbed when a substance changes its state from liquid to gas. Since heat is required during evaporation of the substance, it is an endothermic reaction.
Exothermic reaction is the reaction in which an amount of energy is released during a chemical reaction. Chemical reaction is a reaction in which a new substance is formed and the physical and chemical properties of the substance are different from the reactants used.
Slow reaction is such a reaction whose rate of reaction is very slow. In other words, the reaction which occurs at a very slow rate is a slow reaction.

Hence the correct answer is option A.

Note:
Acetone and alcohol also show this volatile property. When they are rubbed in hand they also give a cooling sensation as they too absorb the heat from our palm to vaporize. Petrol is also called gasoline and it is used as-
-A solvent to dissolve oils and fats.
-Aviation fuel and automobile fuel.