Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
The water cycle, also known as the hydrological cycle, is the continuous movement of water on, above, and below the surface of the Earth involving the change of state of .
Evaporation: The process by which water changes from a liquid state to a gaseous state (water vapor) due to the heat from the Sun. It occurs from the surface of water bodies like oceans, rivers, and lakes.
Transpiration: The biological process where plants lose water in the form of vapor through tiny pores called stomata on their leaves. This contributes significantly to the amount of vapor in the atmosphere.
Condensation: As water vapor rises, it cools down at higher altitudes where the temperature () is lower. The vapor changes back into tiny liquid droplets, which cluster together to form clouds.
Precipitation: When the water droplets in clouds become too heavy to stay suspended in the air, they fall back to Earth as rain, snow, hail, or sleet.
Infiltration and Runoff: Water that falls on land may soak into the ground (Infiltration) to form groundwater, or flow over the surface (Runoff) into rivers and oceans.
Groundwater: A portion of the that seeps through the soil and collects above impervious rocks, forming an important source of fresh water.
📐Formulae
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💡Examples
Problem 1:
Why do water droplets appear on the outer surface of a glass containing ice-cold water?
Solution:
This is due to the process of Condensation.
Explanation:
The water vapor present in the surrounding air comes into contact with the cold surface of the glass. The vapor loses heat energy, causing its temperature () to drop, and it changes state from gas to liquid droplets.
Problem 2:
A wet cloth is placed in the sun. After an hour, it becomes dry. Name the process and the energy source involved.
Solution:
The process is Evaporation and the energy source is Solar Energy (Sun's heat).
Explanation:
The heat from the sun increases the kinetic energy of the molecules in the wet cloth, allowing them to escape into the atmosphere as water vapor.
Problem 3:
Explain the role of plants in the water cycle.
Solution:
Plants contribute via Transpiration.
Explanation:
Plants absorb water from the soil through their roots. A large portion of this is released into the air as vapor through leaves, which eventually cools to form clouds.