Water in the Atmosphere
EXERCISES
1. Multiple choice questions.
(i) Which one of the following is the most important constituent of the atmosphere for human beings?
(a) Water vapour (c) Dust particle
(b) Nitrogen (d) Oxygen
Ans: (d) Oxygen.
(ii) Which one of the following process is responsible for transforming liquid into vapour?
(a) Condensation (c) Evaporation
(b) Transpiration (d) Precipitation
Ans: (c) Evaporation.
(iii) The air that contains moisture to its full capacity :
(a) Relative humidity (c) Absolute humidity
(b) Specific humidity (d) Saturated air
Ans: (d) Saturated air.
(iv) Which one of the following is the highest cloud in the sky?
(a) Cirrus (c) Nimbus
(b) Stratus (d) Cumulus
Ans: (a) Cirrus.
2. Answer the following questions in about 30 words.
(i) Name the three types of precipitation.
Ans: There are actually many more than three types of precipitation, but here are three of the most common:
*Rain: Liquid water droplets falling from clouds.
(ii) Explain relative humidity.
Ans: It's like a sponge: how full is the air with moisture compared to its max at that temperature? 100% = maxed out, feels muggy. ️%
(iii) Why does the amount of water vapour decreases rapidly with altitude?
Ans: Two main reasons explain why the amount of water vapor decreases rapidly with altitude:
1. Colder Temperatures: As you go higher, the temperature drops, making it harder for water molecules to stay in their gaseous state (vapor) and easier for them to condense into liquid (clouds or precipitation). Think of it like a cold drink sweating on a hot day – the colder surface condenses the water vapor in the air around it.
2. Lower Air Pressure: Air pressure also decreases with altitude. This means there are fewer air molecules per unit volume to hold onto water vapor. With fewer "hands" to grab onto, water molecules are more likely to escape into space or condense into droplets.
Imagine a crowded party where everyone is holding balloons (water vapor molecules). If the party moves to a bigger room (lower air pressure), it's easier for some balloons to float away (condense or escape).
These two factors combined create a rapid decrease in water vapor with altitude, resulting in drier air at higher levels.
(iv) How are clouds formed? Classify them.
Ans: Clouds form when warm, moist air rises and cools, causing water vapor to condense into tiny droplets or ice crystals.
Classification:
*Altitude: High (Cirrus), Middle (Alto-), Low (Stratus, Nimbus), Vertical (Cumulus)
*Appearance: Layered (Stratus), Fluffy (Cumulus), Wispy (Cirrus), Rainy (Nimbus)
Remember, clouds are constantly changing, so these are just general categories!
3. Answer the following questions in about 150 words.
(i) Discuss the salient features of the world distribution of precipitation.
Ans:
World Distribution of Precipitation: A Glimpse
The world's precipitation paints a fascinating and uneven picture, shaped by a complex interplay of factors like temperature, air pressure, and geography. Here are some key features:
Latitudinal Variation:
Abundant near the equator: Warm temperatures and rising air lead to heavy rainfall around the equator, with the Intertropical Convergence Zone (ITCZ) marking the wettest belt.
Drier in the subtropics: Descending air and high pressure create vast deserts between 20° and 30° north and south latitudes.
(ii) What are forms of condensation? Describe the process of dew and frost formation.
Ans: Condensation happens when warm, moist air cools and releases water vapor as tiny droplets or ice crystals. Here are some common forms:
Dew: Tiny water droplets that form on cool surfaces like grass or leaves when the air temperature reaches the dew point (the temperature at which condensation starts). Think of a cold glass sweating on a hot day.
Frost: Ice crystals that form on surfaces when the dew point is below freezing. The water vapor bypasses the liquid stage and directly condenses as ice. This often happens on clear nights when heat radiates easily from the ground, causing temperatures to plummet.
Fog: Tiny water droplets suspended close to the ground, formed when air cools below its dew point. Imagine steam rising from a hot cup of tea in a cold room.
Clouds: Masses of water droplets or ice crystals suspended in the atmosphere, formed when rising air cools and condenses. Think of fluffy cotton candy floating in the sky.
Here's a helpful tip to remember the difference between dew and frost:
*Dew: Think of "dew drops," like little jewels sparkling on cool surfaces.
*Frost: Think of "frosty," like a white, icy coating on objects.
These are just a few examples, and condensation plays a crucial role in various weather phenomena like rain, snow, and hail. So next time you see glistening dew or sparkling frost, remember the fascinating science of water vapor transforming into its many forms!
Answer Type By: Himashree Bora.