Chapter 5 - Water
Question 1: Define the following.
a) Evaporation
b) Condensation
c) Precipitation
d) Transpiration
e) Terrarium
f) Water cycle
g) Salinity
h) Waves
i) Tsunami
Answer:
a) A process through which water turns into vapour.
b) When water vapour cools down, it condenses and forms cloud.
c) Precipitation is any liquid or frozen water that forms in the atmosphere and falls back to the earth. It comes in many forms like rain sleet and snow.
d) Transpiration is the process of water movement through a plant and its evaporation from aerial parts such as leaves, stems, flowers.
e) It is an artificial enclosure for keeping small house plants.
f) The process by which water continuously changes its form and circulates between oceans, atmosphere and land is known as water cycle.
g) Salinity is the amount of salt in grams present in 1000 grams of water. The average salinity of ocean is 35 parts per thousand.
h) When the water on the surface of the ocean rise and fall alternatively, they are called waves.
i) A Tsunami is a series of waves caused by earthquake or undersea volcanic eruptions.
Question 2: Explain water cycle.
Answer: The sun's heat causes evaporation of water into vapour. When the water vapour cool down, it condenses and forms cloud. From there it may fall on the land or sea in form of rain, snow or sleet. It is the process by which water continuously changes its form and circulates between oceans, atmosphere and land.
Question 3: Give reason:
a) Ocean water is salty.
b) The quality of water is deteriorating.
Answer:
a) Ocean water is salty because it contains a large amount of salt dissolved in it. The salt present in ocean water is mostly sodium chloride or the common salt.
b) The quality of water is deteriorating in following ways:
• Mixing of sewerage water into the river, ocean etc.
• Excessive use of water causing scarcity.
• Mixing of industrial effluent and untreated water of industries into the stream, river and even oceans.
Question 4: How are Spring and Neap Tides formed?
Answer:
• Spring Tides: The sun and the moon are in the same line, their combined gravitational pull causes very high tides, which are known as Spring Tides.
• Neap Tides: Neap Tides are low tides created when the sun and the moon are at right angle to each other.
Question 5: Write a brief note on Tsunami.
Answer: Tsunami is the Japanese word that means Harbour waves as the Harbors get destroyed whenever there is a Tsunami. Tsunami can be high as 15m. The largest Tsunami was 150 metres height. These waves travel at the speed of more than 700 km per hour. In 2004, the Tsunami caused damage to Indira Point in Andaman Nicobar Islands.
Question 6: How do we classify ocean movement? Explain.
Answer: We can classify ocean movements as follows:
1. When the water on the surface of the ocean rises and falls alternatively, they are called waves. The stronger the wind blows the bigger the waves become.
2. The rythmic rise and fall of ocean water twice in a day is known as tide. Tides may be high or low. It is high tide when water covers much of the shore by rising to its highest level. It is low tide when waterfalls to its lowest level and recedes from the shore. Tides are caused due to the strong gravitational pull exerted by the sun and moon on the Earth's surface.
3. Ocean current are stream of water flowing constantly on ocean surface in definite direction. There are two types of ocean currents:
• Cold current - Labrador Ocean Current
• Warm current - Gulf Stream Current
Question 7: How are high tides important?
Answer: High Tides are important in following ways:
• They help in navigation.
• They raise the water level close to the shores. This helps the ship to arrive at the harbour easily.
• They also help in fishing.
• They help to generate electricity.
Question 8: What are the factors affecting the height of the waves?
Answer: Winds, earthquakes, volcanic eruptions or underwater landslides are the factors affecting the height of the waves. The stronger the wind blows the bigger the waves become.
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