Question

Define the various changes of state and which ones are endothermic and exothermic and why?

Answer 1

ANSWER -

The various changes of state are melting, freezing, evaporation (or vaporization), condensation, sublimation, and deposition.

Melting is the change from a solid to a liquid state, while freezing is the reverse process from a liquid to a solid state. These changes of state are endothermic because they require energy to break the intermolecular bonds between the particles of the substance, and the energy is absorbed from the surroundings.

Evaporation (or vaporization) is the change from a liquid to a gas state, while condensation is the reverse process from a gas to a liquid state. Evaporation is an endothermic process because it requires energy to break the intermolecular bonds between the particles of the liquid and convert them into the gaseous state, and this energy is absorbed from the surroundings. On the other hand, condensation is an exothermic process because it releases energy when the particles of the gas come together to form a liquid, and this energy is transferred to the surroundings.

Sublimation is the change from a solid directly to a gas, while deposition is the reverse process from a gas directly to a solid. Sublimation is an endothermic process because it requires energy to break the intermolecular bonds between the particles of the solid and convert them into the gaseous state, and this energy is absorbed from the surroundings. Deposition is an exothermic process because it releases energy when the particles of the gas come together to form a solid, and this energy is transferred to the surroundings.

Answer 2

Changes of state refer to the processes that occur when matter undergoes a transition from one physical state to another. There are several changes of state, and each involves a specific type of transition, which can be either endothermic or exothermic.

1. Melting: Melting is the process of changing a substance from a solid to a liquid state, and it is endothermic because energy is absorbed during the process.

2. Freezing: Freezing is the process of changing a substance from a liquid to a solid state, and it is exothermic because energy is released during the process.

3. Vaporization: Vaporization is the process of changing a substance from a liquid to a gas state, and it can be either endothermic or exothermic. If the vaporization occurs at a constant temperature, it is endothermic (e.g. boiling water). If the vaporization occurs at a constant pressure, it is exothermic (e.g. evaporation of sweat from our skin).

4. Condensation: Condensation is the process of changing a substance from a gas to a liquid state, and it is exothermic because energy is released during the process.

5. Sublimation: Sublimation is the process of changing a substance from a solid directly to a gas without passing through a liquid state, and it is endothermic because energy is absorbed during the process.

6. Deposition: Deposition is the process of changing a substance from a gas directly to a solid without passing through a liquid state, and it is exothermic because energy is released during the process.

The endothermic or exothermic nature of a change of state depends on the amount of energy required to break the intermolecular forces between the particles. For example, melting requires energy to break the intermolecular bonds between particles, and this makes it an endothermic process. On the other hand, freezing releases energy as particles come together to form a solid, and this makes it an exothermic process. Similarly, vaporization is endothermic because energy is required to break the bonds between the particles in the liquid, whereas condensation is exothermic because energy is released as particles come together to form a liquid.