Test: Water - Class 7 MCQ

• Tides are the rise and fall of ocean water that happens twice a day. This movement is caused by the gravitational pull of the sun and the moon on the Earth's surface.
• When the water covers much of the shore by rising to its highest level, it is called high tide.
• Conversely, when the water falls to its lowest level and recedes from the shore, it is known as low tide.
• The gravitational forces of the sun and the moon are what create these tides.
• During full moon and new moon days, when the sun, the moon, and the Earth are in alignment, the tides are highest, known as spring tides.
• On the other hand, during the moon's first and last quarter, the gravitational pull of the sun and moon results in low tides, known as neap tides.

Topic in NCERT: Tides

Line in NCERT: "The rhythmic rise and fall of ocean water twice in a day is called a tide."

• Water changes into vapor through a process called evaporation when it gets heated up.
• As this water vapor cools down, it transforms back into liquid water through condensation.
• This continuous cycle of water changing its form and moving between the oceans, atmosphere, and land is known as the water cycle.
• It's like a natural recycling system for water on Earth, ensuring we have water to drink, for plants to grow, and for rain to fall.

Topic in NCERT: Water

Line in NCERT: "The sun's heat causes evaporation of water into vapour. When the water vapour cools down, it condenses and forms clouds."

Earthquakes: Most tsunamis are caused by earthquakes that occur beneath the ocean. The size of the tsunami is related to the size of the earthquake. Shallow focus earthquakes in subduction zones are the most destructive.

Strong winds only leads to high tides, not tsunami 

• The water cycle is the continuous movement of water on, above, and below the surface of the Earth.
• It involves processes such as evaporation, condensation, precipitation, and runoff, maintaining a balance of water across different parts of the planet.

Topic in NCERT: Water

Line in NCERT: "The process by which water continually changes its form and circulates between oceans, atmosphere and land is known as the water cycle."

• The Dead Sea is located in Israel. It is a landlocked salt lake bordered by Jordan to the east and Israel and the West Bank to the west.
• The high salinity of the Dead Sea prevents most aquatic life from thriving in its waters.

Topic in NCERT: Do you know ?

Line in NCERT: "Dead sea in Israel has salinity of 340 grams per litre of water."

• The tides in the ocean are caused by the gravitational pull of the sun and the moon.
• This means that the sun and the moon's gravity pulls on the water in the ocean, causing it to rise and fall in a regular pattern.
• This is why we have high tides and low tides during different times of the day.
• So, when you see the water level at the beach changing, it's because of the sun and the moon pulling on the water.

Topic in NCERT: Tides

Line in NCERT: "The strong gravitational pull exerted by the sun and the moon on the earth's surface causes the tides."

Salinity is measured by the amount of sodium chloride found in 1,000 grams of water, if there is 1 gram of sodium chloride in 1,000 grams of water solution it is 1 part per thousand.

Topic in NCERT: Do you know?

Line in NCERT: "Salinity is the amount of salt in grams present in 1000 grams of water."

The total volume of water on Earth is estimated at 1.386 billion km³ (333 million cubic miles), with 97.3% being salt water and 2.5% being fresh water. Of the fresh water, only 0.3% is in liquid form on the surface.

 The freshwater resources, such as water falling from the skies and moving into streams, rivers, lakes, and groundwater, provide people with the water they need every day to live.

Topic in NCERT: Distribution of Water Bodies

• In the ocean, when you see the water going up and down, that's what we call waves.
• So, when you're playing on the beach and you see the ball getting washed back to the shore by the waves, that's because the water on the surface of the ocean rises and falls alternately, just like a big blanket moving up and down gently.

Topic in NCERT: Waves

Line in NCERT: "When the water on the surface of the ocean rises and falls alternately, they are called waves."

Ocean water is saline because it contains a high concentration of dissolved salts, primarily sodium chloride​.