Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Water exists in three distinct physical states: Solid (ice), Liquid (water), and Gas (water vapor).
Evaporation: The process of conversion of liquid water into water vapor. This is the 'disappearing act' often observed when puddles dry up or wet clothes dry in the sun.
Condensation: The process where water vapor loses heat and converts back into liquid water. This is seen when water droplets form on the outer surface of a glass containing ice-cold water.
Transpiration: The process by which plants release water vapor into the air through tiny pores in their leaves called stomata.
Precipitation: When water droplets in clouds become too heavy to remain suspended, they fall back to Earth as rain, snow, or hail.
Water Cycle: The continuous movement of water from the Earth's surface to the atmosphere (via evaporation and transpiration) and back to the surface (via condensation and precipitation).
Factors affecting evaporation: Rate of evaporation increases with an increase in temperature, increase in surface area, and increase in wind speed.
📐Formulae
💡Examples
Problem 1:
During an experiment, a student spreads of water on a plate and another of water in a narrow glass. Both are kept under the sun. Which one will dry faster?
Solution:
The water in the plate will dry faster.
Explanation:
Evaporation is a surface phenomenon. Since the plate has a larger surface area than the narrow glass, the water molecules have more space to escape into the air. Therefore, the rate of evaporation is higher in the plate.
Problem 2:
Why do we see water droplets on the outside of a glass filled with ice-cold water?
Solution:
This is due to the process of condensation.
Explanation:
The air surrounding the glass contains water vapor. When this vapor comes into contact with the cold surface of the glass, it loses heat energy. This causes the gaseous water molecules to slow down and cluster together, turning back into liquid water droplets.
Problem 3:
Explain the role of the sun in the 'Disappearing Act' of water.
Solution:
The sun provides the necessary heat energy for evaporation.
Explanation:
The sun heats the water in oceans, rivers, and lakes. As the temperature increases, the kinetic energy of water molecules increases, allowing them to break free from the liquid state and enter the atmosphere as water vapor.