Understanding Endothermic Processes

An endothermic process is a process that absorbs energy from its surroundings. This energy is typically absorbed in the form of heat, causing the temperature of the surroundings to decrease. In contrast, an exothermic process releases energy into the surroundings, usually as heat, causing the surrounding temperature to increase.

The question asks us to identify which of the given processes is an endothermic process. Let's analyze each option:

Analyzing the Options

• Sublimation of dry ice: Dry ice is solid carbon dioxide (\(\text{CO}_2\)). Sublimation is the phase transition from a solid directly to a gas, without passing through the liquid phase. For this transition to occur, energy is required to overcome the intermolecular forces holding the molecules together in the solid state. This energy is absorbed from the surroundings, making sublimation an endothermic process. Think about how dry ice is used to create a cold environment; it absorbs heat from the air to sublime.
• Dilution of sulphuric acid: When concentrated sulphuric acid is diluted with water, a significant amount of heat is typically released. This is because the hydration of sulphuric acid ions is a highly exothermic process. Therefore, the dilution of sulphuric acid is an exothermic process.
• Evaporation of water: Evaporation is the phase transition from liquid water to water vapor (gas). Like sublimation, evaporation requires energy input to break the intermolecular bonds between water molecules in the liquid state so they can escape into the gaseous phase. This energy is absorbed from the surroundings (e.g., your skin feels cooler when sweat evaporates), making evaporation an endothermic process.
• Both Sublimation of dry ice and Evaporation of water: Based on the analysis above, both the sublimation of dry ice and the evaporation of water are processes that absorb heat from the surroundings, defining them as endothermic processes.

Conclusion on Endothermic Processes

We have determined that both the sublimation of dry ice and the evaporation of water require energy input and are thus endothermic processes. The dilution of sulphuric acid, on the other hand, releases energy and is exothermic.

Therefore, the option that correctly identifies endothermic processes from the given list is "Both Sublimation of dry ice and Evaporation of water".

Revision Table: Comparing Energy Changes

Additional Information: Phase Transitions and Energy

Phase transitions, also known as changes of state, often involve significant energy changes. Moving from a more ordered state (solid, liquid) to a less ordered state (liquid, gas) requires energy input to overcome intermolecular forces. This energy is absorbed from the surroundings, making these transitions endothermic. Examples include melting (solid to liquid), boiling/evaporation (liquid to gas), and sublimation (solid to gas).

Conversely, moving from a less ordered state to a more ordered state releases energy as intermolecular forces are formed or strengthened. These transitions are exothermic. Examples include freezing (liquid to solid), condensation (gas to liquid), and deposition (gas to solid).

Chemical reactions can also be endothermic or exothermic depending on the balance of energy absorbed to break bonds and energy released when new bonds are formed. In endothermic reactions, more energy is absorbed than released overall.