The Central Board of Secondary Education (CBSE) is one of the renowned educational boards in India. CBSE conducts Class 10 board exams every year, mostly in the month of March. The main aim of the board is to provide the best education to all its learners so that they can excel in their academic careers.

Class 9 is a very crucial stage in a student’s life. All the basic concepts and fundamentals for the Class 10 board exam are taught in this class. And science is a subject that is filled with various theories and principles. Students are advised to learn the concept of science properly in order to score well in their exams. Practising important marks-wise questions is one of the best ways to prepare for the Class 9 examination. The important 5 marks question for Class 9 science is given here so that students can prepare more effectively.

Solving the questions on a regular basis will give students an idea about the question pattern and the difficulty level of the questions. The questions are designed by subject experts following the latest CBSE Class 9 Science syllabus.

The important 5-mark questions for Class 9 science is given below.

Question 1- The atomic number of chlorine is 17 and mass number is 35.

(a) What could be electronic configuration of a negatively charged chloride ion

\(\begin{array}{l}Cl^{-1}\end{array} \)

(b) What would be the atomic number and mass number of

\(\begin{array}{l}Cl^{-1}\end{array} \)

(c) Define valence and calculate the valence of

\(\begin{array}{l}Cl^{-1}\end{array} \)

Question 2- (a) Calculate the power of an engine which can lift 200 kg of water to store in a tank at a height of 10 m in 4.9 sec. Also express in horsepower (given g = 9.8m/s2)

(b) What type of energy is stored in the spring of a watch?

(c) What is the work done by the tension in the string of a simple pendulum.

Question 3- (a) Describe the oxygen cycle in nature.

(b) What is the importance of carbon cycle in nature?

(c) List any two consequences of global warming.

Question 4- The relative atomic mass of Boron is 10.8. Calculate the percentage of its isotopes

\(\begin{array}{l}^{10}_{5}B\end{array} \)
\(\begin{array}{l}^{11}_{5}B\end{array} \)
, occuring in nature.

Question 5- (a) What happens to the kinetic energy when:

(i) The mass of the body is doubled at constant velocity?

(ii) The velocity of the body is doubled at constant mass?

(iii) The mass of the body is doubled but the velocity is reduced to half?

(b) Two bodies of equal masses move with the uniform velocities v and 3v respectively. Find the ratio if their kinetic energies.

Question 6- (a) Certain force acting on a 20 kg mass changes its velocity from 5 m/s to 2 m/s. Calculate the work done by the force.

(b) State two possible conditions under which the work done would be zero.

(c) If the kinetic energy of the body is increased by 300%, then determine the percentage increase in the moment.

Question 7- (a) What is the amount of work done:

(i) By an electron revolving in a circular orbit of radius r rounds a nucleus?

(ii) By an electron moving with half the speed of light in empty space free of all forces?

(b) An electric pump is used to pump water from an underground sump to the overhead tank situated 20 m above. It transfers 2000 kg of water to overhead tank in 15 minutes. Calculate the power of pump.

(c) What do you mean by instantaneous power of a device?

Question 8- (a) Explain the work done by the person in the following conditions:

(i) When he is standing at a place holding a suitcase in his hand.

(ii) When he is moving holding the suitcase in his hands.

(b) A certain household has consumed 250 units of energy during a month. How much energy is this in Joules?

Question 9- (a) In Rutherford’s experiment, how was it shown that an atom has a lot of empty space within it?

(b) Why is the nucleus of an atom positively charged?

(c) Calculate the valency of chlorine, sulphur and magnesium? Atomic number of chlorine = 17, sulphur = 16, and magnesium = 12.

Question 10- (i) Why denitrification of nitrogen compounds is necessary?

(ii) What is biomass?

(iii) What is humification? Why it is important?

Question 11- (a) Oxygen has three isotopes of atomic masses 16, 17 and 18 respectively.

(i) Oxygen has three isotopes of atomic masses 16,17 and 18 respectively.

(ii) They have same chemical properties

(iii) They are all electrically neutral.

(b) Name the isotopes of hydrogen.

(c) Give one point of similarity and one point of difference between isotopes

\(\begin{array}{l}^{14}_{6}C\end{array} \)
\(\begin{array}{l}^{12}_{6}C\end{array} \)

Question 12- (a) Define soil pollution.

(b) Name any two methods to prevent the loss of topsoil.
(c) How is acid rain formed?

Question 13- (a) Define the water cycle.

(b) Draw the water cycle in nature, giving a neat and labelled diagram.

(c) (i) What is nitrogen fixation?

(ii) What is the effect of oxygen on nitrogen?

Question 14- (a) Why is helium inert?

(b) Why Na atom gets

\(\begin{array}{l}1+\end{array} \)
charge when it loses one electron?

(c) What are the limitations of Rutherford’s model of the atom?

(d) Name the particle which determines the mass of an atom.

Question 15- (a) What would be the impact of the increase in the concentration of carbon dioxide in the atmosphere?

(b) (i) What do you mean by biogeochemical cycle? Name any two of the Biogeochemical cycles.

(ii) Nitrogen cycle is called a perfect cycle in nature. Explain.

Question 16- (a) The average atomic mass of a sample of an element X is 16.2 u. What are the percentages of isotopes

\(\begin{array}{l}^{16}_{8}X\end{array} \)
\(\begin{array}{l}^{18}_{8}X\end{array} \)
in the sample?

(b) Complete the following table

Element Atomic Number Mass Number Protone Neurons Electrons
A 11 12
B 35 17
C 9 10
D 20 10

Question 17- (a) (i) Name two agents of soil erosion.

(ii) Write any two steps used to control soil erosion.

(b) A forest area has been cleaned by cutting trees for industrialisation purposes. List any two changes that will be brought into the water cycle of that area.

Question 18-

(a) How are electrons arranged around the nucleus in an atom?

(b) If an atom of an element has atomic number 11 and mass number 24, find the number of protons, electrons and neutrons in its atoms.

Question 19- (a) Chlorine occurs in nature in two isotopic forms with masses 35 u and 37 u in the ratio 3:1. Calculate the average atomic mass of chlorine atom on the basis of this data.

(b) Give any three uses of three isotopes.

Question 20- Define the following terms:

(i) Ammonification

(ii) Nitrification

(iii) Denitrification

(b) State any two applications of the greenhouse effect.


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