Question

Which physical change is endothermic?

Answer 1

Answer: The correct option is 1.

Explanation: Endothermic reactions are the reactions in which heat is provided to break down the reactant molecules.

In option 1:

The stronger intermolecular forces between the particles in solid molecule are broken down to convert into gaseous form. Hence, some energy in the form of heat is provided to move them far apart. Therefore, it is considered as an endothermic reaction.

In option 2, 3 and 4:

All the other processes involves the formation of bonds and thus there is no need to provide any energy.

Answer 2

The physical change that is endothermic is $\boxed{\left( 1 \right){\text{ C}}{{\text{O}}_{\text{2}}}\left( s \right) \to {\text{C}}{{\text{O}}_{\text{2}}}\left( g \right)}$.

Further explanation:

Changes are of two types:

(A) Physical changes:

It is the process in which the physical properties of the system are affected. These changes can also be reversed by physical methods. In these kinds of changes, the molecular composition of the substance remains the same. These are reversible in nature and no new substances are formed. For example, boiling of water, chopping of wood, melting of wax are physical changes.

(B) Chemical changes:

In this change, new substances are formed by the chemical combination of the previous substances. The chemical properties of substance changes when it undergoes a chemical change. These are irreversible in nature. For example, fermentation of grapes, burning of wood, rusting of iron are chemical changes.

Endothermic reactions are those in which more energy needs to be supplied to the system than that released by it.

Exothermic reactions are those in which more energy is released by the system than that supplied to it.

(1) ${\text{C}}{{\text{O}}_{\text{2}}}\left( s \right) \to {\text{C}}{{\text{O}}_{\text{2}}}\left( g \right)$

In this reaction, solid carbon dioxide is converted into gaseous carbon dioxide. The strong intermolecular force of attraction in solid needs to be broken down and energy is supplied for this purpose. Hence this is an endothermic process.

(2) ${\text{C}}{{\text{O}}_{\text{2}}}\left( l \right) \to {\text{C}}{{\text{O}}_{\text{2}}}\left( s \right)$

In this reaction, liquid carbon dioxide is converted into solid carbon dioxide. The intermolecular forces in liquid molecules are weaker than that present in solid molecules and are broken down easily so energy is released during the process. Hence this is an exothermic process.

(3) ${\text{C}}{{\text{O}}_{\text{2}}}\left( g \right) \to {\text{C}}{{\text{O}}_{\text{2}}}\left( l \right)$

In this reaction, gaseous carbon dioxide is converted into liquid carbon dioxide. The intermolecular forces in gas molecules are weaker than that present in liquid molecules and are broken down easily so energy is released during the process. Hence this is an exothermic process.

(4) ${\text{C}}{{\text{O}}_{\text{2}}}\left( g \right) \to {\text{C}}{{\text{O}}_{\text{2}}}\left( s \right)$

In this reaction, gaseous carbon dioxide is converted into solid carbon dioxide. The intermolecular forces in gas molecules are weaker than that present in solid molecules and are broken down easily so energy is released during the process. Hence this is an exothermic process.

Learn more:

1. Which of these is an extensive property? brainly.com/question/1398514

2. Which of the phase changes is an exothermic change? brainly.com/question/1875234

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Physical and chemical changes

Keywords: physical change, chemical change, CO2, endothermic, exothermic, solid, liquid, gaseous, intermolecular forces, strong, weaker.