Class 7 Geography Chapter 5 Question Answers - Water

Short Question Answer:

Q1: Define salinity.
Ans: Salinity is the amount of salt in grams present in 1000 gm of water. The average salinity of the ocean is 35 parts per thousand. Salinity is expressed in parts per thousand (ppt).

Q2: Define the vertical distribution of seawater.
Ans: When surface water gets heated by the sun, water evaporates and increases the concentration of salts. Surface water becomes denser and sinks and sub-surface water rises. Thus, the salinity of seawater causes vertical circulation.

Q3: What is an ocean wave?
Ans:  When the water on the surface of the ocean rises and falls alternatively they are called waves.

Q4: What is flood tide and ebb tide?
Ans:  The rise of sea level is called the flood tide and the fall is called the ebb tide. These are influenced by the gravitational pull of the moon and the sun

Q5: Why do ocean bodies and seas contain salty water?
Ans: Because it contains a large amount of dissolved salts. Most of the salt is sodium chloride.

Q6: Name the factors which are responsible for the movement of oceanic water.
Ans:  The factors are-

• Winds
• Temperature
• Coriolis effect
• The attraction of the moon and the sun depends upon its distances.

Q7: Name the two types of current and their movement on Earth.
Ans: Ocean currents are broadly of two types of warm and cold currents. The warm currents flow from low latitudes in tropical zones towards the high latitudes in the temperate and sub-polar zones. The cold current flows from high latitudes to low latitudes.

Q8: How tides are formed?
Ans: Tides are periodic rises and falls in the level of water in seas and oceans caused by the attraction of the moon and the sun. Twice a day, about every 12 hours and 26 minutes, the sea level rises and falls.

Q9: What is an ocean current?
Ans: Ocean currents are stream of water flowing constantly on the ocean surface in definite direction.

Q10: Why is our earth like a terrarium?
Ans: Our earth is like a terrarium. The same water that existed centuries ago still exists today. The water used to irrigate a field in Haryana may have flowed down the Amazon River a hundred years ago.

 Long Question Answers:

Q1: Our unique planet Earth is covered by different categories of water. Give the distribution of water in percentage.
Ans:  The distribution of water in percentage is as follows:

• Oceans (97%): Almost all of Earth’s water is found in its oceans, which are vast, salty bodies of water covering most of the planet’s surface and hosting countless marine creatures.
• Ice Caps (2.0%): The coldest regions, like the North and South Poles, are covered by ice caps, which act as frozen reservoirs of water.
• Groundwater (0.68%): Deep beneath the Earth’s surface lies groundwater, a hidden resource stored in layers of soil and rock, waiting to be accessed.
• Freshwater (0.01%): This is the water we drink and use for various purposes, found in rivers, lakes, and underground reservoirs. It’s precious due to its scarcity compared to saltwater.
• Inland Seas and Salt Lakes (0.009%): These are smaller, salty bodies of water, unique ecosystems that exist in certain regions.
• Atmosphere (0.0019%): The atmosphere contains tiny water vapor droplets, essential for cloud formation and precipitation.

Q2: Why are tides important to us?
Ans: Tides are important to us because:

• High tides help in navigation.
• They raise the water level close to the shores. This helps the ships to arrive at the harbor more easily.
• 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.
• The rise and fall of water due to tides is being used to generate electricity in some places.

Q3: Why the quality of water is deteriorating?
Ans: The quality of water is deteriorating because:

• Only about 33,400 kilometers of water are allocated for drinking, agriculture, domestic, and industrial purposes.
• Water misuse and pollution are widespread issues.
• The quality of drinking water is deteriorating due to excessive use of pesticides, insecticides, hazardous waste, and organic decay.
• Industries discharge chemicals and untreated wastewater into nearby water bodies, contributing significantly to water pollution.
• Sewage also adds to the contamination and Consequently, water quality continues to decline.
• Nitrogen presence in water is linked to shortened lifespans.
• Water salinity reduces agricultural fertility.

Q4: Write a short note on the Tsunami.
Ans:  Tsunami is a Japanese word that means “Harbour waves” as the harbors get destroyed whenever there is a tsunami.

• An earthquake, a volcanic eruption or underwater landslides can shift large amounts of ocean water.
• As a result a huge tidal wave called a tsunami, which may be as high as 15m., is formed. The largest tsunami ever measured was 150m. high. These waves travel at a speed of more than 700 km. per hour.
• The tsunami of 2004 caused widespread damage in the coastal areas of India. The Indira Point in the Andaman and Nicobar Islands got submerged after the tsunami.

Q5: What are the major movements of ocean water?
Ans: The movements that occur in oceans can be broadly categorized as waves, tides, and currents.

• Waves: When the water on the surface of the ocean rises and falls alternately, they are called waves. Waves are formed when winds scrape across the ocean surface. The stronger the wind blows, the bigger the wave becomes.
• Tides: The rhythmic rise and fall of ocean water twice in a day is called a tide. It is high tide when water covers much of the shore by rising to its highest level. It is low tide when water falls to its lowest level and recede from the shore. The strong gravitational pull exerted by the sun and the moon on the earth’s surface causes the tides.
• Ocean Currents: Ocean currents are streams of water flowing constantly on the ocean surface in definite directions. The ocean currents may be warm or cold. Generally, the warm ocean currents originate near the equator and move toward the poles. The cold currents carry water from polar or higher latitudes to tropical or lower latitudes. The Labrador current is a cold current while the Gulf Stream is a warm current.