English Medium Class 9 - CBSE Question Bank Solutions for Science

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.

Sound travels in air :

The sound waves travel fastest :

State two observations which show that atom is not indivisible.

The velocities of sound waves in four media P, Q, R and S are 18,000 km/h, 900 km/h, 0 km/h and 1200 km/h respectively. Which medium could be a liquid substance?

State the law of conservation of mass. Give one example to illustrate this law.

Which postulate of Dalton's atomic theory can explain the law of conservation of mass ?

What is an atom ? How do atoms usually exist ?

The law of conservation of mass was given by :

One nm is equal to :

An atom of element E contains 3 protons, 3 electrons and 4 neutrons :
(a) What is its atomic number?
(b) What is its mass number?
(c) Write the electronic configuration of the element E.
(d) State whether element E is a metal or non-metal. Why?
(e) What type of ion, cation or anion, will be formed by an atom of element E? Why
(f) Write the symbol of the ion formed by an atom of element E.
(g) What could element X be?

An atom of an element X may be written as `""_9^4"X"`
(a) What does the figure 9 indicate?
(b) What does the figure 4 indicate?
(c) What is the number of protons in atom X?
(d) What is the number of neutrons in atom X?
(e) What is the number of electrons in atom X?
(f) How many electrons are there in the outermost shell of an atom of element X?
(g) Write the symbol of ion formed by an atom of element X.

The electronic configuration of an element Z is 2, 8, 8.
(a) What is the atomic number of the element?
(b) State whether element Z is a metal or a non-metal.
(c) What type of ion (if any) will be formed by an atom of element Z? Why?
(d) What is special about the outermost electron shell of the atom of this element?
(e) Give the name and symbol of element Z.
(f) Name the group of elements to which Z belongs.