The Class 8 is an important year in a student’s life and Maharashtra State Board Social Science Grography is one of the subjects that require dedication, hard work, and practice. It’s a subject where you can score well if you are well-versed with the concepts, remember the important formulas and solving methods, and have done an ample amount of practice. Worry not! Home Revise is here to make your Class 8 journey even easier. It’s essential for students to have the right study material and notes to prepare for their board examinations, and through Home Revise, you can cover all the fundamental topics in the subject and the complete Maharashtra State Board Class 8 Social Science Grography Book syllabus.
Q 1. Match the column and complete the chain:
| A | B | C |
| Cirrus | Vertical extent in the sky | Roaring clouds |
| Cumulonimbus | higher altitude | Floating clouds |
| Nimbostratus | Medium altitude | continuous rainfall |
| Alto-cumulus | Low altitude | snowflake clouds |
Answer:
| A | B | C |
| Cirrus | Higher altitude | Snowflake clouds |
| Cumulonimbus | Vertical extent in the sky | Roaring clouds |
| Nimbostratus | Low altitude | Continuous rainfall |
| Alto-cumulus | Medium altitude | Floating clouds |
Q2. Choose the correct word from the brackets and complete the sentence:
(Cumulonimbus, Relative humidity, Absolute humidity, Condensation, Vapour-holding capacity)
(a) The ————of air is dependent on the temperature of air.
(b) The amount of vapour in 1 cu.m. of air shows the ———————–.
(c) As ——————–is less in desert areas, the air is dry there.
(d) —————–type of clouds are indicators of storm
(e) In a free environment, the —————of the vapour present in the atmosphere takes place around dust particles.
Answer a: The vapour-holding capacity of air is dependent on the temperature of air.
Answer b: The amount of vapour in 1 cu.m. of air shows the absolute humidity
Answer c: As relative humidity is less in desert areas, the air is dry there
Answer d: Cumulonimbus type of clouds are indicators of storm.
Answer e: In a free environment, the condensation of the vapour present in the atmosphere takes place around dust particles.
Q 3. Differentiate between:
(a) Humidity and clouds
(b) Relative humidity and Absolute humidity
(c) Cumulus clouds and cumulonimbus clouds
Answer:
| Humidity | Clouds |
| The proportion of water vapour in the air is called its humidity. | Clouds are a form of condensation at
higher elevation |
| Humidity help us to determine whether the air is dry or damp | Clouds form by the process of condensation |
| Humidity are of two types: Absolute Humidity and Relative Humidity | Clouds are divided into different types such as Cirrus, Alto-Stratus, Cumulus, etc |
Answer b:
| Relative Humidity | Absolute Humidity |
| The amount of water vapour present in
air can be expressed as a percentage of the amount needed for saturation at the same temperature and the same volume. | The amount of water vapour in 1 cu.m. of
air is the absolute humidity of the air. |
| Relative humidity is more in the mornings and nights. In the afternoon, as temperature increases, relative humidity decreases. | Absolute humidity is higher in the equatorial
areas while it reduces as we move towards the poles |
| It is expressed in percentage. | It is expressed in grams or kilograms per cubic metre |
| Near coastal areas, the relative humidity is more and so the air is moist. In desert areas, relative humidity is less. | The distribution of land and water on
earth and the seasons also affect absolute humidity. |
Answer c:
| Cumulus clouds | Cumulonimbus clouds |
| These clouds are formed extensively from 500 m to 6000 m altitude. | These are characteristic clouds which are indicators of thunderstorms. These look like huge mountains. |
| The vertical flow of the air adds to the formation of these clouds. These are huge and dome-shaped. | These are dense and dark in colour. There is
thunder accompanied by lightning. |
| Cumulus clouds are an indicator of pleasant weather. The vertical expanse of these clouds increases so much that they turn into cumulonimbus clouds and bring rain. | They bring rain with storm and may sometimes bring hailstones. But such a type of rain does not last long. |
Q 4. Answer the following questions:
(a) Why is the air in a region dry?
(b) How is humidity measured?
(c) What are the prerequisites for condensation?
(d) What is a cloud? Write its types.
(e) Which type of clouds give rain?
(f) On what does the percentage of relative humidity depend?
Answer a: The air in a place can be dry due to the minimum amount of water vapour present in the atmosphere due to less evaporation. For eg: Rajasthan lies in a region with dry and hot air. There is hardly any moisture in the air.
Answer b: Humidity of the air is measured in grams per cubic meter. When the humidity in the air is 0 gm/cu.m., the air is said to be dry. If the humidity in the air at 30° C temperature is 37 gms/ cu.m., then the air is said to be saturated.
Answer c: The process of changing water vapour in the air into water is called condensation. If the temperature of the air reduces, its vapour holding capacity also reduces. When relative humidity of the air becomes 100%, vapour starts condensing. At this time, the temperature of the air should be at dewpoint. It implies that for condensation, temperature should be low and relative humidity must be high. In the free environment, condensation of the vapour in the air occurs around fine particles (dust, salt, etc.) in the air. Dew, frost and fog are the forms of condensation at ground level while clouds are a form of condensation at higher elevation.
Answer d: Clouds are an important part of the earth’s weather and climate. Clouds form when water condenses in the sky. Clouds are visible accumulations of tiny water droplets or ice crystals in the Earth’s atmosphere. The different types of clouds are as follows:
| Classification of clouds | Types of clouds |
| High clouds | Cirrus
Cirrostratus Cirrocumulus |
| Middle clouds | Altostratus
Altocumulus |
| Low clouds | Stratocumulus
Nimbostratus |
| Clouds with extensive vertical development | Cumulus
Cumulonimbus |
Answer e: Nimbo-stratus clouds cause continuous rainfall and even snowfall. These low clouds have thick layers and are grey-ash in colour.
Answer f: Relative Humidity means the amount of water vapour present in air can be expressed as a percentage of the amount needed for saturation at the same temperature and the same volume. It is expressed in percentage.
Relative humidity (R.H.) (%) = Absolute humidity/Vapour Holding Capacity × 100
Q 5. Give geographical reasons:
(a) Clouds float in the sky.
(b) The proportion of relative humidity changes according to altitude.
(c) Air becomes saturated.
(d) Cumulus clouds change into cumulonimbus clouds
Answer a: Clouds are a form of condensation at higher elevation. Condensation occurs around minute particles in the atmosphere. Condensed water or snow particles in the clouds are very fine and almost weightless. So, clouds float in the air.
Answer b: The amount of water vapour changes according to difference in temperature. Similarly, relative humidity also changes. Generally, relative humidity is more in the mornings and nights. In the afternoon, as temperature increases, relative humidity decreases. Near coastal areas, the relative humidity is more and so the air is moist. In desert areas, relative humidity is less.
Answer c: Air at a certain temperature can hold a wide range of water vapor. When there is a lot of water vapor available the relative humidity rises. This is a reading of the moisture in the air compared to what it could hold, relative humidity. When the air can hold no more it is said to have reached its saturation point, or dew point.
Answer d: Cumulus clouds are formed extensively from 500 m to 6000 m altitude. The vertical flow of the air adds to the formation of these clouds. These are huge and dome-shaped. They are grey in colour. Cumulus clouds are an indicator of pleasant weather. The vertical expanse of these clouds increases so much that they turn into cumulonimbus clouds and bring rain.
Q 6. Solve the following:
(a) When the temperature of the air is 30° C, its vapour-holding capacity is 30.37 gms/ cu.m. If absolute humidity is 18 gms / cu.m. then what would be the relative humidity?
(b) What would be the absolute humidity of air if 1 cu.m. air contains 4.08 gms of vapour at 0°C temperature?.
Answer a: Given,
Temperature of Air = 30°C
Vapour holding capacity = 30.37 gms/cu.m.
Absolute Humidity = 18 gms/cu.m.
We can find the relative humidity by using the formula
Relative humidity = Absolute humidity/Vapour holding capacity × 100
= 18 × 100/30.37
= 59.27%
Answer b: The amount of water vapour in 1 cu.m. of air is the absolute humidity of the air.
Given, water vapour = 4.08 gms
Volume of air = 1cu.m
Thus, Absolute Humidity = Measure of water vapour/Volume of air
= 4.08/1
= 4.08gm/m3