CBSE NCERT Class VII (7th) | Social Studies | Geography
Chapter : WATER
CBSE NCERT Solved Question Answer
Q1 Explain the process of water cycle.
The sun’s heat causes evaporation of water vapour. When the water vapour cools down, it condenses and forms clouds. From there it may fall on the land or sea in the form of rain, snow or sleet. The process by which water continually changes its form and circulates between oceans, atmosphere and land is known as the water cycle.
Q2 What is a terrarium and why is our earth compared to a terrarium?
Terrarium: It is an artificial enclosure for keeping small house plants. In this the water that evaporates from the leaves and soil condenses and falls back as forms of water drops. Our earth is like a terrarium. The same water that existed centuries ago still exists today.
The major sources of fresh water are the rivers, ponds, springs and glaciers.
Q4 What is salinity?
Salinity is the amount of salt in grams present in 1000 grams of water.
Q5 Why is sea water saline?
The ocean bodies and the seas contain salty water. The water of the oceans is salty or saline as it contains large amount of dissolved salts.
Q6 Name the three types of movements of the water.
a) Waves b) Tides c) Ocean Currents
Q7 What are waves? How are they formed?
When the water on the surface of the ocean rises and falls alternately, they are called waves. Waves are formed when gentle winds scrape across the ocean surface. The stronger the wind blows, the bigger the wave becomes.
Q8 What are tides?
The rhythmic rise and fall of ocean water twice in a day is called a tide.
Q9 What causes tides on the earth’s surface?
The strong gravitational pull exerted by the sun and the moon on the earth’s surface causes the tides.
Q10 What are the two types of tides?
There are two types of tides: Spring tides and Neap tides
Spring Tides: During the full moon and new moon days, the sun, the moon and the earth are in the same line and the tides are highest. These tides are called spring tides.
Neap Tides: When the moon is in its first and last quarter, the ocean waters get drawn
in diagonally opposite directions by the gravitational pull of sun and earth resulting in low tides. These tides are called neap tides.
Q11 How are the tides useful to us?
1) High tides help in navigation. They raise the water level close to the shores. This helps the ships to arrive at the harbour more easily.
2) The high tides also help in fishing. Many more fish come closer to the shore during the high tide. This enables fishermen to get a plentiful catch.
3) The rise and fall of water due to tides is being used to generate electricity in some places.
Q12 What are ocean currents?
Ocean currents are streams of water flowing constantly on the ocean surface in definite directions.
Q13 What are the types of ocean currents?
There are two types of ocean currents: warm and cold.
Generally, the warm ocean currents originate near the equator and move towards the poles. The cold currents carry water from polar or higher latitudes to tropical or lower latitudes.
Q14 How does the Ocean current influence the climate?
The ocean current influence the temperature conditions of the area. Warm currents bring about warm temperature over the land surface.
Q15 What happens when the warm and cold ocean currents meet?
The areas where the warm and cold currents meet provide the best fishing grounds of the world. The areas where a warm and cold current meet also experience foggy weather making it difficult for navigation.
Q16 Give any one example of warm and cold ocean currents.
Warm Ocean Current: Gulf Stream
Cold Ocean Current: Labrador Ocean current