CBSE Class 10 Science Exam 2020: Important 1 Mark Questions with Solutions

Here we are providing some important 'very short answer type questions' for CBSE Class 10 Science Board Exam 2020. These questions will be asked in 1 markers set in exam paper.

Nov 18, 2019 16:53 IST
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Important Very Short Answer Type Questions
Important Very Short Answer Type Questions

To help students acquaint with important topic and questions to be prepared for upcoming board exam, we present here a set of important very short answer type questions for CBSE Class 10 Science Exam 2020.

In CBSE class 10 Science Question Paper 2020, question no. 1-14 comprising Section-A will carry one mark each. These questions will be designed in different formats like MCQs, very short answer type questions, assertion-reason type questions, etc. To prepare for all such questions, students just need to be good at the basic concepts and aware of all important facts and principles in explained in class 10 Science.

Questions and answers provided by jagranjosh will help you recall and retain all the important information which can make you able to answer different objective type questions in Class 10 Science Exam 2020.

Given below are some very important 1 mark questions for class 10 Science exam 2020:

1. Explain why a ray of light passing through the centre of curvature of concave minor gets reflected along the same path. 


The light falling on the centre of curvature is reflected back along the same path because

incident ray falls on the mirror along the normal to the reflecting surface.

CBSE Class 10 Science Previous Years' Solved Question Papers

2. What is the important function of presence of ozone in earth’s atmosphere?


Ozone is the Earth’s natural process for all life forms. It shields our planet from the UV radiations, as these ultraviolet rays are harmful for all the living things. Therefore, any change in the size of this layer will automatically affect the life of people, plants and animals living on earth. 

3. Dark reaction of photosynthesis does not need light. Do plants undergo dark reaction at night? Explain.


Dark reaction does not mean that it occurs in the absence of light i.e., at night. Infact, it is the reaction occuring simultaneously with light reaction. It a chemical process occurring independent of light. This reaction is completely based on enzymes.

4. What is a solenoid? Draw the pattern of magnetic Field lines of a solenoid through which a steady current flows. What does the pattern of field lines‟? Inside the solenoid indicate? 


Solenoid can be defined as a coil of many circular turn of insulated copper wire wrapped in cylindrical structure.

Following diagram shows the pattern of magnetic Field lines of a solenoid through which a steady current flows:

current carrying solenoid

5. What is meant by acquired and inherited traits? Explain with one example each.


Acquired Trait: A trait or characteristic of an organism which is not inherited but develops in response to the environment is called an acquired trait. Example: The cut tail of the mouse which has been brought about by some agents in its environment is an acquired trait.

Inherited Trait: A trait or characteristic of an organism which is caused by a change in its genes is called an inherited trait. Example: The characteristics received by a child from its parents like the son inherits his father’s red hair.

CBSE Class 10 Science Solved Sample Paper 2019

6. Write the molecular formula of first two members of homologous series having functional group – OH.  


The general formula for the homologous series of functional group −OH is CnH2n+1OH.

The two consecutive members of this series are: 

a. CH3OH(Methanol)

b. CH3CH2OH (Ethanol)

where n is 1 and 2 respectively

The molecular formula for both of them are CH4O and C2H6O.

7. How is menarche different from menopause?


The first occurrence of menstruation at the age of 12 in females is called menarche. Menarche is the beginning of the reproductive life of a girl. Menstruation stops when a woman reaches the age of 50 approx. At this age she loses her ability to bear child in her womb, i.e., she becomes infertile. This stage of permanent stoppage of menstruation is called the menopause. Thus, reproductive life of a woman starts at menarche and ends at menopause.

8. What kind of combustion is observed in alkanes? Why do air holes of a gas burner have to be adjusted when vessel being heated gets blackened by the flame?


Alkanes are saturated hydrocarbons and generally burn in air with a blue, non-sooty flame.

If the bottoms of the cooking vessels in our homes are getting blackened, it shows that the air holes of the gas stove are getting blocked and the fuel is not burning completely.

9. A concave mirror of focal length 15 cm can form a magnified, erect as well as inverted image of an object placed in front of it." Justify this statement stating the position of the object with respect to the pole of the mirror in both the cases  for obtaining the images.


For magnified and erect image the object is placed between pole P and focus F. For magnified and inverted image the object is placed either at focus or anywhere between F and C.

10. "Energy flow in a food chain is unidirectional" Justify this statement.


The flow of energy in the ecosystem is said to be unidirectional because the energy lost as heat from the living organisms of a food chain cannot be reused by plants in photosynthesis.

NCERT Exemplar Problems and Solutions Class 10 Science: All Chapters

11. What is the effect of DNA copying, which is not perfectly accurate, on the reproduction process?


The DNA copying which is not perfectly accurate in the reproduction process results in variations in

12. What is the function of retina in human eye. 


The retina acts as a screen on which the image is formed in the eye. The retina has a large number of light-sensitive cells. When the image falls on the retina then these light-sensitive cells get activated and generate electrical signals. 

13. (a) If a normal human cell has 46 chromosomes, how many chromosomes will be there in a human:

(i) Sperm

(ii) Zygote

(b) Name an animal in which individuals can change sex. What does this indicate?


(a) A normal human being has 46 chromosomes in which 23 chromosomes come from males and 23 chromosomes come from female.

(i) Sperms coming from males have 23 chromosomes.

(ii) Zygote forming in the womb of a woman has 46 chromosomes in all.

(b) Snail. This indicates that sex is not determined genetically in such animals.

NCERT Solutions for CBSE Class 10 Science: All Chapters

14. List any four characteristics of a good fuel.


Characteristics of a good fuel:

(i) It should possess low ignition temperature.

(ii) It should not leave residue after burning, i.e., it should burn completely.

(iii) It should be easily available and accessible

(iv) It should be easy to store and transport.

15. Name the two sets of nerves that constitute the peripheral nervous system.


Sympathetic nervous system and Parasympathetic nervous system.

16. What is hyperacidity? How antacid works to cure it?


Hyperacidity is caused by excess of hydrochloric acid in stomach.

Antacid is basic in nature. It neutralizes excess of acid and gives relief from pain caused by hyperacidity.               

17. State difference between the wire used in the element of an electric heater and in a fuse wire.


The wire used in the element of electric heater has a high resistivity and have a high melting point, so that even at a high temperature element do not burn while fuse wire have a low melting point and high resistivity so that it will melt if a current of large magnitude passes through the wire.     

18. An object is placed at a distance of 12 cm in front of a concave mirror of radius of curvature 30 cm. List four characteristics of the image formed by the mirror.  (2) 


Here, radius of curvature of concave mirror, R = 30 cm.
Therefore, focal length of the mirror, f = R/2 = 30/2 = 15 cm 
Also, object distance, u = 12 cm

Hence, knowing the focal length of mirror and the object distance, it is clear that the object is placed between the focus and pole of the mirror. 
So, in case of a concave mirror for an object placed between focus and pole of the mirror, the image formed will be:  
(i)  Erect 
(ii) Larger in size than that of the object 
(iii) Virtual and
(iv) Behind the mirror.   

CBSE Class 10 Science Exam Pattern 2020

19. Name the stimulus involved in each of the following phenomenon:

(i) Phototropism               (ii) Geotropism.


(i) Light (ii) Gravity.

20. For what position of a current carrying conductor placed in a magnetic field, the maximum force acts on it?


To obtain the maximum force acting on the current carrying conductor placed in a magnetic field, the conductor should be placed perpendicular to the magnetic field, i.e. the direction of current should be at right angle to the direction of the magnetic field.

21. How will you test for the gas which is liberated when hydrochloric acid reacts with an active metal?


Bring a burning matchstick near the gas. It burns with ‘pop’ sound showing that it is hydrogen gas.

22. Explain what is galvanisation. What purpose is served by it?


The process of coating the iron objects by zinc metal is called galvanisation.

Galvanisation is used to prevent rusting of iron.       

23. A compound ‘X’ on heating with excess conc. sulphuric acid at 443 K gives an unsaturated compound ‘Y’. ‘X’ also reacts with sodium metal to evolve a colourless gas ‘Z’. Identify ‘X’, ‘Y’ and ‘Z’. Write the equation of the chemical reaction of formation of ‘Y’ and also write the role of sulphuric acid in the reaction.


  • X-Ethanol/ (C2H5OH)/Ethyl Alcohol
  • Y- Ethene / (C2H4)
  • Z- Hydrogen/ (H2)
  • Role of sulphuric acid - dehydrating agent

24. Write a and b in the given flow chart of neuron through which information travels as an electrical impulse.

Dendrite → a →b → End point of Neuron


a. Axon

b. Cell body

CBSE Class 10 Science Exam 2019: Important questions with solutions

25. A Mendelian experiment consisted of breeding pea plants bearing violet flowers with pea plants bearing white flowers. What will be the result in F1 progeny ?


Violet flowers

26. In the following food chain, 100 J of energy is available to the lion. How much energy was available to the producer?
                                                            Plants → Deer → Lion 


Here we will use the 10% law of transfer of energy.

As, it is given that 100 J of energy is available to lion. 
Let the amount of enrgy available to deer be x Joules.
According to 10% law, 
Energy available to lion = 10% of energy of deer
            100 J = 10/100 × x 

⟹             x = 1000 J
Now, let the amount of enrgy available to plants be y Joules.
Again applying 10% law, we have:

Energy available to deer = 10% of energy of plant

            1000 J = 10/100 × y 

⟹                y = 10000 J
So, the energy available to plants, i.e., producer is 10,000J.

27. Write the energy conversion that takes place in a hydro power plant.


Potential /Kinetic/ Mechanical Energy into Electrical energy

28. Explain two main advantages associated with water harvesting at the community level.


Two advantages associated with water harvesting at community level are:
1. It helps to raise the water level by the process of recharging.

2. It can resolve the problem of water crisis in areas affected by drought or having inadequate water resources.

We have also prepared a set of questions based on practical skills. A few questions in CBSE Class 10 Science Paper may be asked to test your practical knowledge. So, go through the important practical based questions provided below to recall some important practical concepts and write appropriate answers in the exam.

CBSE Class 10 Science Important Practical Based Questions for Board Exam 2020

Students must practice these important questions to acquaint with the important topics of Class 10 Science and track their preparedness for the upcoming Board Exam 2020. Moreover, the solutions provided here will give students an idea about how to frame proper solution to each question in the board exam so as to secure maximum marks.

To get more of such useful articles for CBSE Class 10 Board Exam preparations, click on the following links:


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