krit.club logo

Air, Water, and Weather - The Water Cycle and Evaporation

Grade 4CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

•

Water exists in three states on Earth: Solid (ice), Liquid (water), and Gas (water vapor). The chemical formula for water is H2OH_2O.

•

Evaporation is the process by which water changes from a liquid state to a gaseous state (water vapor) due to an increase in temperature.

•

Factors that increase the rate of evaporation include: High temperature, large surface area, strong wind, and low humidity (dry air).

•

Condensation is the process where water vapor (H2OH_2O gas) cools down and changes back into liquid water droplets. This process is responsible for the formation of clouds.

•

The Water Cycle is the continuous journey of water from the Earth's surface to the atmosphere and back again through the stages of Evaporation, Condensation, Precipitation, and Collection.

•

Precipitation occurs when water droplets in clouds become too heavy and fall back to Earth as rain, snow, sleet, or hail.

📐Formulae

Liquid Water+Heat→EvaporationWater Vapor\text{Liquid Water} + \text{Heat} \xrightarrow{\text{Evaporation}} \text{Water Vapor}

Water Vapor−Heat→CondensationLiquid Water\text{Water Vapor} - \text{Heat} \xrightarrow{\text{Condensation}} \text{Liquid Water}

Rate of Evaporation∝Temperature\text{Rate of Evaporation} \propto \text{Temperature}

Rate of Evaporation∝Surface Area\text{Rate of Evaporation} \propto \text{Surface Area}

💡Examples

Problem 1:

Why do wet clothes dry faster on a windy day compared to a calm day?

Solution:

Wind increases the rate of evaporation.

Explanation:

Moving air (wind) carries away the water vapor molecules (H2OH_2O) as soon as they escape from the surface of the clothes. This allows more water molecules to evaporate quickly, shortening the drying time.

Problem 2:

If you pour 100100 ml of water into a wide plate and 100100 ml of water into a narrow glass, which one will evaporate first?

Solution:

The water in the wide plate will evaporate first.

Explanation:

Evaporation is a surface phenomenon. The wide plate has a larger surface area exposed to the air, allowing more H2OH_2O molecules to escape into the atmosphere simultaneously compared to the narrow glass.

Problem 3:

Explain why you see water droplets on the outer surface of a glass containing ice-cold juice.

Solution:

This is due to the process of Condensation.

Explanation:

The air around the glass contains water vapor (H2OH_2O in gas form). When this warm vapor touches the cold surface of the glass, it loses heat and turns back into liquid water droplets.