English Medium Class 9 - CBSE Question Bank Solutions for Science

What are the building blocks of matter ?

How is the size of an atom indicated ?

Name the unit in which the radius of an atom is usually expressed.

Write the relation between nanometre and metre.

Why is it not possible to see an atom even with the most powerful microscope ?

When we open a gas tap of a few seconds, the sound of escaping gas is heard first but the smell of gas comes later. Why?

Fill in the following blanks with suitable words :

In water, the proportion of oxygen and hydrogen is .............. by mass.

Describe an experiment to show that sound cannot pass through vacuum.

How many times is a proton heavier than an electron?

An electric bell is suspended by thin wires in a glass vessel and set ringing. Describe and explain what happens if the air is gradually pumped out of the glass vessel.

Why cannot a sound be heard on the moon? How do astronauts talk to one another on the surface of moon?

What value has been given to the mass of this reference atom ?

Define the terms 'frequency', 'wavelength' and 'velocity' of a sound wave. What is the relation between them?

A body vibrating with a time-period of `1/256` s produces a sound wave which travels in air with a velocity of 350 m/s. Calculate the wavelength.

Dalton's atomic theory says that atoms are indivisible. Is this statement still valid ? Give reasons for your answer.

Is it possible to see atoms these days ? Explain your answer.

Fill in the blank with suitable word.
Sound cannot travel through ____________.

Through which of the following materials can sound travel? wood, air, water, steam, ice, hydrogen, steel, diamond.