English Medium Class 9 - CBSE Question Bank Solutions for Science

(a) What is the nucleus of an atom and what is the nature of charge on it?

(b) Name the scientist who discovered the nucleus of atom.

Name the particles used by Rutherford in his experiment on the discovery of nucleus. Also state the charge on these particles.

What is reverberation ? What will happen if the reverberation time in a big hall is too long ?

Describe the Rutherford's model of an atom. State one drawback of Rutherford's model of the atom.

Rutherford's alpha particle scattering experiment led to the discovery of :

What is a molecule ? Explain with an example.

Consider the following sound waves marked A, B, C and D.

(a) Which two waves represent sounds of the same loudness but different pitch ?
(b) Which two waves represent sounds of the same frequency but different loudness ?
(c) State whether all these sound waves have been produced by the same vibrating body or different vibrating bodies ?
(d) Which vibrating body/bodies could have generated the sound waves shown here ?

In hydrogen peroxide (H2O2), the proportion of hydrogen and oxygen by mass is :

Write the cations and anions present, if any, in the following : 

1. CH₃COONa 
2. NaCl
3. H₂
4. NH₄NO3

Fill in the following blanks :

1 mole contains .............. atoms, molecules or ions of a substance.

If one mole of nitrogen molecules weighs 28 g, calculate the mass of one molecule of nitrogen in grams.

Calculate the number of molecules present in a drop of chloroform (CHCl3) weighing 0.0239 g.

(Atomic masses : C = 12 u ; H = 1 u ; Cl = 35.5 u)

If 1 gram of sulphur dioxide contains x molecules, how many molecules will be present in 1 gram of oxygen ?

(S = 32 u ; O = 16 u)

Which contains more molecules, 10 g of sulphur dioxide (SO2) or 10 g of oxygen (O2) ?

(Atomic masses : S = 32 u ; O = 16 u)

How many atoms are present in a PO₄ ^3– ion?

How many atoms are present in a `PO_4^(3-)` ion?