Test: The Hydrosphere - Class 7 MCQ

Water is very important for us to survive and live. We need water to drink, to clean ourselves and things, and to grow food. Just like how plants need water to grow, we need water to stay healthy and strong. So, water is essential for our bodies and helps us stay alive and well.

The hydrosphere includes all the water on Earth, such as in oceans, rivers, lakes, and even in the air as water vapor. It's like a big water family that takes care of the Earth and helps plants, animals, and people live happily.

• Most of the Earth's water is found in oceans and seas. Oceans and seas hold about 97% of all the water on Earth. This water is very salty, so we can't drink it.
• Only a small amount, about 2.5%, of the Earth's water is fresh water that we can use for drinking, and this fresh water is found in rivers, streams, ponds, underground sources, glaciers, and polar ice.

Oceans and seas hold approximately 97% of all water in the hydrosphere. This water is highly saline, containing a significant amount of salt, making it unsuitable for drinking.

So, the correct answer is (a) 97%.

When water vapor cools down, it changes back into liquid water and forms clouds. This process is known as condensation. Imagine a steamy bathroom mirror - the water vapor from your breath turns back into water droplets on the mirror when it cools down.

• Waves in the ocean are created when strong winds blow across the surface of the ocean.
• These winds make the water move and form waves. It's like when you blow air into your drink with a straw and see ripples on the water.
• This movement of water helps ships to sail and brings important things like fish closer to the shore for fishermen.
• Waves are like big helpers for sailors and fishermen!

• The rise and fall of ocean waters at coastal areas happen because the Moon and the Sun pull the water towards them.
• This pulling creates high tides and low tides.
• It's like how a magnet attracts metal.
• So, when the Moon and Sun pull on the water, it makes the water levels go up and down near the shores.
• This is why we see the water moving in and out along the beach.

When the Moon pulls on the water, it makes the water bulge, creating high tides. This happens because the Moon's gravity attracts the water, causing it to rise up. So, when you see the water rising high on the shore, it's because of the Moon's pull. Isn't that amazing?

When the Moon pulls on the water, it makes it rise up into a bulge. This rising of water is called high tide.

• During Full Moon and New Moon, high tides are higher and low tides are lower mainly because of the combined gravitational pull of the Sun and the Moon. This means that the Sun and the Moon work together to create these strong tides. It's like the Sun and the Moon are playing a big role in making the ocean water go up and down.

Tides help sailors and boats by guiding them safely into harbors. When the tide is high, it makes it easier for boats to enter the harbor without hitting rocks or getting stuck. This is like a helpful road map for boats on the water.

When tides are harnessed to produce electricity, it means that the energy from the moving water is used to create power that we can use in our homes and buildings. This is a good thing because it helps us have energy without harming the environment.

• An earthquake caused the destructive tsunamis in the Indian Ocean on December 26, 2004.
• When the earth shakes very strongly, it can make big waves in the ocean called tsunamis.
• These waves can be very tall and move very fast, causing a lot of damage.
• It's important for scientists to study earthquakes and tsunamis to keep people safe.

On December 26, 2004, one of the largest earthquakes ever recorded struck the Indian Ocean and surrounding areas. This event caused extremely destructive tsunamis in the region.

• Ocean currents help to regulate temperatures around the world. They act like giant rivers flowing in the ocean, carrying warm or cold water to different places.
• Just like how a fan cools you down when it's hot, ocean currents help to keep the Earth's temperature balanced.
• So, they are like nature's own air conditioner for the planet!