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 Tamilnadu Samacheer Kalvi 8th Social Science Geography Solutions Term 1 Chapter 3 Hydrologic Cycle

Samacheer Kalvi 8th Social Science Hydrologic Cycle Textbook Evaluation

I. Choose the correct answer

Hydrological Cycle Questions And Answers Question 1.
The process in which the water moves between the oceans, atmosphere and land is called –
(a) River Cycle
(b) Hydrologic Cycle
(c) Rock Cycle
(d) Life Cycle
Answer:
(b) Hydrologic Cycle

Class 8 Samacheer Kalvi Question 2.
The percentage of fresh water on the earth is –
(a) 71
(b) 97
(c) 2.8
(d) 0.6
Answer:
(c) 2.8

Short Note On Hydrological Cycle Question 3.
The process of changing of water from gaseous to liquid form is known
as –
(a) Condensation
(b) Evaporation
(c) Sublimation
(d) Rainfall
Answer:
(a) Condensation

Question 4.
Water that flows in the sub – soil or through the ground into the streams, rivers, lakes and oceans is termed as –
(a) Condensation
(b) Evaporation
(c) Transpiration
(d) Runoff
Answer:
(d) Runoff

Question 5.
The evaporation of water from the leaves of plants is called –
(a) Transpiration
(b) Condensation
(c) Water vapour
(d) Precipitation
Answer:
(a) Transpiration

Question 6.
Water that is good enough to drink is called –
(a) Groundwater
(b) Surface water
(c) Potable water
(d) Artesian water
Answer:
(c) Potable water

II. Fill in the Blanks

  1. The degree of water vapour present in the atmosphere is known as ………………
  2. There are ……………… phases in the water cycle.
  3. The falling of water towards the earth surface from atmosphere in any form is known as ………………
  4. The precipitation with the rain drop size of 0.5mm in diameter is known as ………………
  5. Mist is lesser denser than ………………

Answer:

  1. Humidity
  2. Three
  3. Precipitation
  4. Drizzle
  5. Fog

III. Match the following

Hydrological Cycle Questions And Answers Samacheer Kalvi 8th Social Science Geography Solutions Term 1 Chapter 3
Answer:

  1. iv
  2. i
  3. ii
  4. iii

IV. Choose the correct statement

Question 1.
Evaporation refers to
I. The process in which the gaseous form of water changes in to liquid form.
II. It refers to the process in which the liquid form of water changes into gaseous form.
III. Water boils at 100°C temperature but, it actually begins to evaporate at 0°C.
IV. It is responsible for the formation of clouds.

(a) I, IV and V are correct
(b) II only correct
(c) II and III are correct
(d) All are correct
Answer:
(c) II and III are correct

V. State whether the following statements are True or False

Question 1.
Water boils at 212°F temperature but, it begins to evaporate at 32°F.
Answer:
True

Question 2.
Mist is not the tiny droplets of water hanging in the air.
Answer:
False
Correct statement:
Mist is the tiny droplets of water hanging in the air.

Question 3.
The sub – surface runoff is usually referred as interflow.
Answer:
True

VI. Answer in brief

Question 1.
Write a short note on aquifer.
Answer:
An aquifer is an underground layer of water – bearing rock.

Question 2.
Define “hydrological cycle”.
Answer:
Hydrologic cycle is a global sun – driven process where water is transported from oceans to atmosphere, from atmosphere to land and from land back to oceans.

Question 3.
How is the dew formation takes place?
Answer:
Dew is a water droplet formed by the condensation of water vapour on a relatively cold surface of an object. It forms when the temperature of an object drops below the dew point temperature.

Question 4.
Write a short note on surface run – off.
Answer:
Surface Runoff is the portion of rainfall, which enters the stream immediately after the rainfall. It occurs, when the rainfall is longer, heavier and exceeds the rate of infiltration. In this condition the excess water makes a head over the ground surface, which tends to move from one place to another following land gradient and is known as overland flow. When the overland flow joins the streams, channels or oceans, it is termed as surface runoff or surface flow.

VII. Give reasons

Question 1.
Infiltration of water is low in the region of non – porous soil.
Answer:
Water entering the soil at the surface of the ground is termed as infiltration. Infiltration allows the soil temporarily to store water, the rate of infiltration is influenced by the physical characteristics of the soil, vegetative cover, moisture content of the soil, soil temperature and rainfall intensity.

Question 2.
Fresh water is less on the earth.
Answer:
Most of the water on the earth is saline and is found in seas and oceans, which constitutes about 97.2%.

Question 3.
Snowfall is common in the polar region and mountainous regions.
Answer:

  1. The precipitation in the form of powdery mass of ice is known as snowfall.
  2. Often water vapour in a cloud is converted directly into snow pieces due to lowering of temperature.
  3. It is common in the polar and high mountainous regions.

VIII. Answer in a paragraph

Question 1.
Explain the different stages involved in the hydrological cycle.
Answer:
The three important phases of the hydrologic cycle are:

  • Evapotranspiration,
  • Precipitation and
  • Runoff.

1. Evapotranspiration:
It is defined as the total loss of water from the earth through evaporation from the surface water bodies and the transpiration from vegetation. In cropped area, it is difficult to determine the evaporation and transpiration separately. Therefore it is collectively called as evapotranspiration.

2. Precipitation:
It refers to all forms of water that fall from clouds and reaches the earth’s surface. For the occurrence of precipitation, cloud droplets or ice crystals must grow heavy enough to fall through the air. When the droplets grow large in size, they tend to all. While moving down, by collecting some small droplets, they become heavy enough to fall out of the cloud as raindrops.

3. Runoff:
Runoff is the water that is pulled by gravity across land’s surface. It replenishes groundwater and surface water as it percolates into an aquifer (it is an underground layer of water – bearing rock) or moves into a river, stream or watershed. It comes from unabsorbed water from rain, snowmelt, irrigation or other sources, comprising a significant element in the water cycle as well as the water supply when it drains into a watershed. Runoff is also a major contributor to the erosion which carves out canyons, gorges and related landforms.

Question 2.
Distinguish between evaporation and transpiration.
Answer:
Evaporation:

  • Process in which the liquid form of water changes into gaseous form.
  • Rate of evaporation is affected by temperature, Areal extent of surface water, wind and the atmospheric humidity.
  • 90% moisture in the atmosphere is contributed through evaporation.

Transpiration:

  • Process by which the water content in the plant is released into the atmosphere in the form of water vapour.
  • Rate of Transpiration is affected temperature, wind and humidity.
  • 10% moisture is contributed through Transpiration.

Question 3.
Give a detailed explanation on different forms of precipitation.
Answer:
Forms of Precipitation:
The form of precipitation in a region depends on the kind of weather or the climate of the region. Common types of precipitation include rain, sleet, freezing rain, hail and snow.

Rain:
The precipitation in the form of water droplets is called rain. The precipitation in which the size of rain drops are <0.5 mm in diameter is known as drizzle and the . rain drops with >0.5 mm in diameter is known as rain. Generally drizzle takes place from stratus clouds.

Sleet:
The precipitation which takes place in the form of mixture of water droplets and tiny particles of ice(5mm in diameter) is known as sleet. Sometimes raindrops fall through a layer of air below 0°C. As they fall, the raindrops freeze into solid particles of ice. So, the mixture of water droplets and ice particles would fall on the earth surface.

Freezing Rain:
At other times raindrops falling through cold air near the ground do not freeze in the air. Instead, the raindrops freeze when they touch a cold surface. This is called freezing rain.

Hail:
The precipitation which consists of round pellets of ice which are larger than 5 mm in diameter is called hail or hailstones. A hailstone starts as an ice pellet inside a cold region of a cloud.

Snow:
Often water vapour in a cloud is converted directly into snow pieces due to lowering of temperature. The precipitation in the form of powdery mass of ice is known as snowfall. It is common in the polar and high mountainous regions.

Question 4.
Explain the run – off and its types.
Answer:
Runoff is the water that is pulled by gravity across land’s surface. It replenishes groundwater and surface water as it percolates into an aquifer (it is an underground layer of water-bearing rock) or moves into a river, stream or watershed.

Types of Runoff:
Based on the time interval between the instance of rainfall and generation of runoff, the runoff may be classified into following three types

1. Surface Runoff:
It is the portion of rainfall, which enters the stream immediately after the rainfall. It occurs, when the rainfall is longer, heavier and exceeds the rate of infiltration. In this condition the excess water makes a head over the ground surface, which tends to move from one place to another following land gradient and is known as overland flow. When the overland flow joins the streams, channels or oceans, it is termed as surface runoff or surface flow.

2. Sub – Surface Runoff:
The water that has entered the subsoil and moves laterally without joining the water-table to the streams, rivers or oceans is known as sub- surface runoff. The sub – surface runoff is usually referred as interflow.

3. Base Flow:
It is a flow of underground water from a saturated ground water zone to a water channel. It usually appears at a downstream location where the channel elevation is lower than the groundwater table. Groundwater provides the stream flow during dry periods of small or no precipitation.

Activity
Find out the missing components of hydrologic cycle in the given diagram and fill it up appropriately.
Class 8 Samacheer Kalvi Social Science Geography Solutions Term 1 Chapter 3 Hydrologic Cycle
Answer:

  1. Evaporation
  2. Condensation
  3. Precipitation
  4. Transpiration
  5. Runoff
  6. Infiltration
  7. Ground water recharge (Percolation)

Samacheer Kalvi 8th Social Science Geography Hydrologic Cycle Additional Questions

I. Choose the correct answer

Question 1.
About …………….. of the earth’s surface is covered by water.
(a) 28%
(b) 71%
(c) 19%
(d) 50%
Answer:
(b) 71 %

Question 2.
……………. takes place from the surface water.
(a) Evaporation
(b) Transpiration
(c) Condensation
(d) Precipitation
Answer:
(a) Evaporation

Question 3.
The clouds melt and sometimes burst resulting in …………….
(a) Transpiration
(b) Evaporation
(c) Precipitation
(d) Condensation
Answer:
(c) Precipitation

Question 4.
Oceans, seas, lakes and rivers provide nearly ……………… of the moisture in the atmosphere.
(a) 30%
(b) 50%
(c) 70%
(d) 90%
Answer:
(d) 90%

Question 5.
Over the oceans ……………. is more prevalent than precipitation.
(a) Transpiration
(b) Evaporation
(c) Condensation
(d) Run – off
Answer:
(b) evaporation

Question 6.
The rate of evaporation is ……………… during the periods of calm winds.
(a) High
(b) Twice
(c) Low
(d) Three times
Answer:
(c) low

Question 7.
For aviation purpose, the criterion for fog is …………….. or less.
(a) 10 km
(b) 20 km
(c) 30 km
(d) 25 km
Answer:
(a) 10 km

Question 8.
……………… is formed by microscopic drops of water or by small ice crystals.
(a) Frost
(b) Cloud
(c) Fog
(d) Dew
Answer:
(b) Cloud

Question 9.
Generally drizzle takes place from ………….. clouds.
(a) Cirrus
(b) Cirrocumulus
(c) Cumulus
(d) Stratus
Answer:
(d) Stratus

Question 10.
………………. is the downward movement of infiltrated water through soil and rock layers.
(a) Transpiration
(b) Percolation
(c) Runoff
(d) Infiltration
Answer:
(b) Percolation

II. Fill in the blanks

  1. Only 0.25% of the available ground water can be economically extracted with ………………. technology.
  2. Transpiration takes place from ……………….
  3. When the air is ………………. evaporated water tends to stay close to the water body.
  4. ………………. is the tiny droplets of water hanging in the air.
  5. In freezing rain, the drops of water are usually greater than ………………. in diameter.
  6. Hail forms only in clouds during thunderstorms.
  7. ………………. appears like a powdery mass of ice.
  8. The percolation process represents the flow of water from ………………. zone to the ………………. zone.
  9. The sub – surface runoff is usually referred as ……………….
  10. Unit for measuring run off rate is ……………….

Answer:

  1. Drilling
  2. Plants
  3. calm
  4. Mist
  5. 0.5mm
  6. Cumulonimbus
  7. Snow
  8. Unsaturated, saturated
  9. Interflow
  10. Cubic feet per second

III. Match the following

Short Note On Hydrological Cycle Samacheer Kalvi 8th Social Science Geography Solutions Term 1 Chapter 3
Answer:

a. ii
b. iii
c. iv
d. i

IV. Choose the correct statement

Question 1.
Condensation is the in which
(1) The gaseous form of water changes into liquid form
(2) Excess water vapour condenses to form snow.
(3) Condensation is responsible for the formation of clouds.
(4) Evaporation is the route for water to return to the earth’s surface.

(a) 1 and 2 are correct.
(b) 1 and 3 are correct.
(c) 1,2 and 4 are correct.
(d) 2 and 4 are correct.
Answer:
(b) 1 and 3 are correct

V. Answer in brief

Question 1.
Mention some of the uses of water.
Answer:
All plants and animals need water for survival. Apart from drinking, water is required for domestic, agriculture, industrial purposes etc. Water is very essential for carrying out almost all economic activities.

Question 2.
What is Hydrology?
Answer:
1. Hydrology is the science which deals with the various aspects of water such as its occurrence, distribution, movement and properties on the planet earth. Availability of water on the earth is not uniform. Some places are very rich in water resources while some other places are poor in water resources.

2. Hydrologic cycle is a global sun-driven process where water is transported from oceans to atmosphere, from atmosphere to land and from land back to oceans.

Question 3.
Name the six main components in hydrological cycle.
Answer:

  1. Evapotranspiration
  2. Condensation
  3. Precipitation
  4. Infiltration
  5. Percolation
  6. Runoff.

Question 4.
When does the rate of evaporation increase?
Answer:
The rate of evaporation increases with

  1. Increase in wind speed
  2. Increase in temperature
  3. Decrease in humidity and
  4. Increase in areal extent of surface water bodies.

Question 5.
Define transpiration.
Answer:
Transpiration refers to the process by which the water content in the plants are released into the atmosphere in the form of water vapour.

Question 6.
What are the factors affecting the rate of transpiration?
Answer:
The rate of transpiration is also affected by the temperature, wind and humidity. The soil water content and the ability of the soil to conduct water to the roots, the nature of the plant parts including barks and leaves also determine the transpiration rate.

Question 7.
Where do condensation and saturation occur?
Answer:
Condensation occurs when the air get saturated.

  1. Warm air can hold more water vapour than the cool air.
  2. Saturation occurs when the temperature drops down.

Question 8.
How does the infiltrated water return to the surface?
Answer:
Some of the infiltrated water ultimately returns to the surface through springs or low spots down hills. Some of the water remains underground and is called groundwater.

Question 9.
Define Percolation.
Answer:
Percolation is the downward movement of infiltrated water through soil and rock layers.

Question 10.
How does percolation move the infiltrated water?
Answer:
Percolation moves the infiltrated water through the soil profile and rock layers which leads to the formation of ground water or become a part of sub – surface run – off – process.

VI. Give Reason for the following

Question 1.
The water cycle can be considered as a closed system for the earths.
Answer:
The water cycle can be considered as a closed system for the earth, as the quantity of water involved in the cycle is invariable, though its distribution varies over space and time.

VIII. Answer in Detail

Question 1.
Explain the three major forms of condensation.
Answer:
Dew, Fog and Clouds are the three major forms of condensation
(a) Dew:
It is a water droplet formed by the condensation of water vapour on a relatively cold surface of an object. It forms when the temperature of an object drops below the dew point temperature.

Frost:
The ice crystals formed by deposition of water vapour on a relatively cold surface of an object is known as frost.

(b) Fog:
Fog is the suspended tiny water droplets or ice crystals in an air layer next to the earth’s surface that reduces the visibility to 1,000 m or lower.

Mist:
Mist is the tiny droplets of water hanging in the air. These droplets form when the water vapour in the air is rapidly cooled, causing it to change from invisible gas to tiny visible water droplets.

(c) Clouds:
Clouds consist of tiny water droplets/ice particles which are so small and light in weight. Clouds are formed by microscopic drops of water or by small ice crystals.

 

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