List of top Science Questions

Which zone of a flame does a goldsmith use for melting gold and silver and why?

Fill in the blanks.
1. Microorganisms can be seen with the help of a ___.
2. Blue-green algae fix ___ directly from the air and enhance the fertility of the soil.
3. Alcohol is produced with the help of ___.
4. Cholera is caused by ___.

Complete the following word puzzle with the help of clues given below.
Down
1. Providing water to the crops.
2. Keeping crop grains for a long time under proper conditions.
5. Certain plants of the same kind grown on a large scale.
Across
3. A machine used for cutting the matured crop.
4. A rabi crop that is also one of the pulses.
6. A process of separating the grain from chaff.

Arrange the following boxes in proper order to make a flow chart of sugarcane crop production.

Explain how soil gets affected by the continuous plantation of crops in a field.

It is difficult to burn a heap of green leaves but dry leaves catch fire easily. Explain.

Explain how \(CO_2\) is able to control fires.

Name the unit in which the calorific value of a fuel is expressed.

Make a labelled diagram of a candle flame.

What is irrigation? Describe two methods of irrigation which conserve water.

Explain how fertilisers are different from manure.

Compare LPG and wood as fuels.

Explain how the use of CNG in automobiles has reduced pollution in our cities.

List conditions under which combustion can take place.

Identify the solutions among the following mixtures.

How do you differentiate between capture fishing, mariculture and aquaculture?

Soni says that the acceleration in an object could be zero even when several forces are acting on it. Do you agree with her? Why?

Explain how defects in a metal block can be detected using ultrasound.

How is ultrasound used for cleaning?

What is loudness of sound? What factors does it depend on?

What is reverberation? How can it be reduced?

A stone is dropped from the top of a tower 500 m high into a pond of water at the base of the tower. When is the splash heard at the top? 
Given, g = 10 ms^–2 and speed of sound = 340 ms^–1.

When a sound is reflected from a distant object, an echo is produced. Let the distance between the reflecting surface and the source of sound production remains the same. Do you hear echo sound on a hotter day?

Does sound follow the same laws of reflection as light does? Explain.

Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulum bob to one side and allow it to oscillate. Why does the bob eventually come to rest? What happens to its energy eventually? Is it a violation of the law of conservation of energy?