CBSE Class 7 Social Science Chapter 5 Water NCERT Solutions

Solution:

(a) Precipitation is the process by which moisture falls from the atmosphere to the Earth's surface. This can occur in various forms, including rain, snow, fog, sleet, and hailstones.

(b) The water cycle, also known as the hydrologic cycle, is the continuous and dynamic process through which water circulates between the Earth's oceans, atmosphere, and land. It involves changes in the form of water (liquid, solid, gas) and its movement through evaporation, transpiration, condensation, precipitation, and collection.

(c) The height of ocean waves is primarily influenced by several factors. The most significant factor is the strength and duration of the wind blowing over the water surface; stronger and longer-lasting winds create larger waves. Additionally, underwater disturbances such as earthquakes, volcanic eruptions, or landslides can generate exceptionally large waves, often referred to as tsunamis.

(d) The movement of ocean water is affected by a combination of factors. These include the temperature of the water, prevailing winds, the gravitational pull exerted by the sun and the moon, and the presence of both warm and cold ocean currents, which create distinct patterns of water flow.

(e) Tides are the regular, rhythmic rise and fall of the ocean's water levels that occur approximately twice each day. They are primarily caused by the gravitational forces exerted by the Moon and, to a lesser extent, the Sun on the Earth's oceans. These forces create bulges of water on opposite sides of the Earth, leading to high and low tides.

(f) Ocean currents are continuous, directed movements of seawater that flow across the surface of the oceans. They act like vast rivers within the sea, transporting water, heat, and nutrients across large distances in predictable patterns.

Solution:

(a) Ocean water is salty because it contains a very large amount of dissolved salts. Rivers and streams carry minerals and salts from the land into the oceans. Over millions of years, this process has led to the accumulation of high concentrations of salts, with sodium chloride being the most abundant.

(b) The quality of water is deteriorating due to several human activities. Firstly, water resources are being used injudiciously and excessively. Secondly, the available potable water is often contaminated. This contamination occurs when industrial effluents, untreated sewage water, and waste from various human activities are discharged directly into rivers, lakes, and other water bodies. This pollution degrades the water quality, making it unsafe for consumption and harmful to aquatic life.

Solution:

(a) (i) Water cycle is the correct answer. This process accurately describes the continuous movement and transformation of water on Earth.

(b) (ii) Equator is the correct answer. Warm ocean currents typically originate in the warmer regions near the equator and flow towards the cooler polar regions.

(c) (i) Tide is the correct answer. Tides are defined as the rhythmic rise and fall of ocean water that occurs regularly, usually twice a day.

Solution:

The correct matching is as follows:

(a) Largest lake matches with (i) Caspian Sea. The Caspian Sea is the world's largest inland body of water.

(b) Periodic rise and fall of water matches with (ii) Tide. Tides are characterized by their regular, cyclical changes in sea level.

(c) Strong seismic waves matches with (iii) Tsunami. Tsunamis are powerful waves generated by seismic activity like earthquakes or volcanic eruptions under the sea.

(d) Streams of water moving along definite paths matches with (iv) Ocean currents. Ocean currents are defined by their continuous flow in specific directions.

(e) Water cycle is a fundamental process describing the continuous movement of water on, above, and below the surface of the Earth.

Solution:

This is a fun activity designed to test your observation skills! Here are the hidden river names:

(a) The hidden river name is Brahmaputra (another name for it is Tsangpo). The letters are found in 'bustee, stables where horses are housed, and the piles of wood'.

(b) The hidden river name is Padma. The letters are found in 'conference manager put pad, material'.

(c) The hidden river name is Orange. The letters are found in 'jealousy or anger'.

(d) The hidden river name is Niger. The letters are found in 'Bhavani germinated'.

(e) The hidden river name is Amazon. The letters are found in 'zonal champion'.

(f) The hidden river name is Indus. The letters are found in 'tiffin box rolled down and all the food fell in dusty potholes'.

(g) The hidden river name is Nile. The letters are found in 'Malini leaned against the pole'.

(h) The hidden river name is Thames. The letters are found in 'Samantha mesmerised'.

(i) The hidden river name is Yellow. The letters are found in 'neighbourhood, please don't yell! Owners'.

(j) The hidden river name is Congo. The letters are found in 'Write the following words', Marc! "On", "go", "in"......

This activity encourages you to look closely at words and identify hidden patterns, a useful skill for learning geographical names!

Carry on Detective

2. With the help of an atlas, draw each river which you discovered in For fun (Q.5), on an outline map of the world.

Solution: This is a practical exercise. You will need an atlas to locate these rivers on a world map and then draw them on an outline map. This will help you visualize their geographical locations and courses.

Solution: A terrarium is an artificial, enclosed environment created for keeping small houseplants. It typically consists of a transparent container, often made of glass, in which plants are grown, allowing for observation of their growth and the micro-ecosystem within.

Solution: Ocean bodies and seas contain salty water. This is due to the high concentration of dissolved salts, primarily sodium chloride, that have accumulated over geological time.

Solution: Salinity is a measure that indicates the amount of dissolved salts present in a body of water. Specifically, it is defined as the total amount of salts, in grams, that are dissolved in 1000 grams (or 1 kilogram) of water.

Solution: The average salinity of the world's oceans is approximately 35 parts per thousand. This means that, on average, there are 35 grams of dissolved salts in every 1000 grams of seawater.