CLASS 4

 ASSESSMENT 3

A. Choose the correct answer:

1. A ______ is a huge ball of burning gases.
   c. stars

2. The large-scale cutting down of trees is known as ______.
   b. deforestation

3. Moving air is called ______.
   b. wind

4. Cooling a liquid can change it into a ______.
   b. solid

5. A bow uses ______ force of the bowstring to shoot an arrow.
   c. elastic

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B. Fill in the blanks using the words given in the box:

1. Venus is the second planet from the Sun.
2. Dry and wet waste must be separated.
3. When the sun heats up the air, the air gets lighter and rises up.
4. There are large spaces between the molecules of a gas.
5. A knife is a wedge, while a hammer is a lever.

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C. State TRUE or FALSE:

1. The Indian name of Uranus is Arun.
   True

2. We should use plastic bags as they are environment-friendly.
   False

3. Cholera is a water-borne disease.
   True

4. A screw is a special form of an inclined plane.
   True

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D. Answer the following questions:

1. Explain how a volcano is formed.
   A volcano forms when magma from beneath the Earth's crust escapes to the surface. This occurs due to pressure buildup within the Earth's mantle, causing the molten rock to rise through cracks or weak spots in the crust. The magma erupts as lava, ash, and gases, creating a volcanic structure.

2. What are the causes of land pollution?

   • Dumping of non-biodegradable waste like plastic and metal.
   • Overuse of chemical fertilizers and pesticides.
   • Deforestation leading to soil erosion.
   • Industrial and mining activities that degrade the land.

3. Explain what causes the blowing of sea breeze during the day.
   During the day, the land heats up faster than the sea. The warm air above the land rises, creating a low-pressure zone. Cooler air from the sea, which has higher pressure, moves toward the land to fill this gap, causing a sea breeze.

4. What is the difference between condensation and sublimation?

   Condensation	Sublimation
   Conversion of gas into liquid.	Direct conversion of solid into gas without becoming a liquid.
   Example: Formation of dew.	Example: Dry ice turning into carbon dioxide gas.

5. Why do we need the force of friction?

   • Friction helps in walking by providing grip.
   • It allows vehicles to stop or slow down.
   • It enables objects to stay in place and not slide unnecessarily.
   • It is necessary for many daily activities like writing, holding objects, and operating machines.