CBSE 10th Science Exam 2021 : Important Practical Questions & Solutions

In this article, you will get important practical based questions for CBSE class 10 Science Board Exam 2021. All the questions are thoroughly solved.

Given below are some very important practical based questions to prepare for CBSE Class 10 Science exam:

1. A student adds a spoon full of powdered sodium hydrogen carbonate to a flask containing ethanoic acid. List two main observations that he/she must note in his/her notebook about the reaction that takes place. Also, write the chemical equation for the reaction


Two main observations during the reaction are:

(i) Brisk effervescence

(ii) Sodium acetate is formed

The chemical equation for the reaction is:

2CH3COOH + Na2CO3 → 2CH3COONa + CO2 + H2O

2. Mention the essential material (chemicals) to prepare soap in the laboratory. Describe in brief the test of determining the nature (acidic/alkaline) of the reaction mixture of saponification reaction.


Raw Materials Required For the preparation of soap in the laboratory are :

  • Vegetable oil
  • Sodium Hydroxide
  • Common salt

Test to determine the nature of reaction mixture: When a red litmus paper is dipped in the reaction mixture, the paper changes its colour to blue. Hence, the reaction mixture of the saponification reaction is basic in nature.

3. Write two precautions to be taken while identifying different parts of an embryo of a dicot seed.


(i) The slide should be properly focused.

(ii) Slide should be observed first under low-power magnification and then under high-power magnification of the compound microscope.

4. A student is to conduct an experiment to show CO2 is released during respiration. List two precautions that he/she must take for obtaining correct observation.


Two precautions to be taken are:

(i) Germinating seeds (living) should be used.

(ii) The experiment set up must be air-tight.

5. A student focuses the image of a candle flame, placed at about 2 m from a convex lens of focal length 10 cm, on a screen. After that, he moves gradually the flame towards the lens and each time focuses its image on the screen.

(a) In which direction does he move the lens to focus the flame on the screen?

(b) What happens to the size of the image of the flame formed on the screen?

(c) What difference is seen in the intensity (brightness) of the image of the flame on the screen?

(d) What is seen on the screen when the flame is very close (at about 5 cm) to the lens?


(a) The student moves the lens away from the screen to focus the image because on moving the candle towards the lens, the image distance increases.
(b)The size of the image increases when the object is moved towards the lens.
(c) Intensity of the image decreases.
(d) When the candle is moved very close to the lens, no image is formed on the screen. A virtual image is formed behind the candle on the same side of the screen.

6. A student dropped a few pieces of marble in dilute hydrochloric acid contained in a test tube. The evolved gas was then passed through lime water. What change would be observed in lime water? Write balanced chemical equation for both the change observed?


When dilute HCl is added to marble which is calcium carbonate, it forms calcium chloride, water and carbon dioxide. The chemical equation for the reaction is as follows:

CaCO3 + 2HCl → CaCl2 + H2O + CO2

Carbon dioxide gas turns lime water milky due to the formation of calcium carbonate.

The chemical equation showing the reaction between lime water and carbon dioxide is as follows:

Ca(OH)2 + CO2 → CaCO3 + H2O

7. An incomplete ray diagram is shown below where the image A'B' for an object AB (placed somewhere in front of the lens) is formed after refraction through the convex lens.

Observe the above and use the given information to fill in the following blanks :

(i) The object AB would have been placed _________ .

(ii) Size of the object would have been_________than the size of image.


(i) The object AB would have been placed beyond 2F

(ii) Size of the object would have been greater than the size of an image.

8. What happens when ethanol is heated with acidified potassium dichromate solution? Write the chemical equation.


Ethanol is oxidised to ethanoic acid with the help of acidified K2Cr2O7.


9. Students were asked to observe the permanent slides showing different stages of budding in yeast under high power of a microscope.

(a) Which adjustment screw (coarse/fine) were you asked to move to focus the slides?

(b) Draw three diagrams in a correct sequence showing budding in yeast. 


(a) A fine screw is used to focus the slides of budding in yeast under high power of a microscope. (b) Sequence showing budding in yeast: 

10. 5% alkaline potassium permanganate solution is added drop by drop in a test tube containing warm ethanol. Write your observation and chemical equation of the reaction taking place.


On adding 5% alkaline potassium permanganate (KMnO4) solution to warm ethanol, the purple colour of KMnOdisappears with the appearance of brown colour and a smell of vinegar which indicates the formation of acetic acid.

11. The values of current I flowing in a given resistor for the corresponding values of potential difference V across the resistor are given below:

Plot a graph between V and I and calculate the resistance of the resistor.


The plot for V vs. I for the given data is shown below: 

The voltage is plotted on x-axis and current is plotted on the y-axis. 


12. Draw a path of a light ray passing through a prism. Label angle of incidence and angle of deviation in the ray diagram.


Diagram showing the path of a light ray passing through a prism is given below:

Here, i = angle of incidence

= angle of deviation

13. What do you observe when you drop a few drops of acetic acid to a test tube containing: 

(a) Phenolphthalein 

(b) Distilled water 

(c) Universal indicator 

(d) Sodium hydrogen carbonate 


Acetic acid is a weak acid. On adding to the given solutions, it will show the following observations:

(a) Acetic acid will remain colourless in phenolphthalein which is a base indicator.

(b) Acetic acid will dissolve in distilled water forming a clear solution.

(c) Acetic acid turns the colour of the universal indicator to pale orange. 

(d) When added to sodium hydrogen carbonate powder, acetic acid will give brisk effervescence due to the formation of CO2 gas. 

14. Mention the four events that occur during binary fission in amoeba.


Four events that occur during binary fission in amoeba are:

(i) The cell elongates.

(ii) The amount of cytoplasm and nucleus gets doubled.

(iii) A furrow forms.

(iv) The cell divides into two daughter cells.

15. A student added a few pieces of aluminium metal to two test tubes A and B containing aqueous solutions of iron sulphate and copper sulphate. In the second part of her experiment, she added iron metal to another test tubes C and D containing aqueous solutions of aluminium sulphate and copper sulphate. In which test tube or test tubes will she observe the colour change? On the basis of this experiment, state which one is the most reactive metal and why?


In the test tube A, B, D she will observe colour change (No splitting of marks) Aluminum is the most reactive metal, because it displaces Iron, Zinc and Copper from their aqueous salt solutions.

16. What is observed when a solution of sodium sulphate is added to a solution of barium chloride taken in a test tube? Write equation for the chemical reaction involved and name the type of reaction in this case.


When a solution of sodium sulphate is added to a solution of barium chloride taken in a test tube formation of a white precipitate is observed.

Chemical equation for reaction is:

 Na2SO4 (aq) + BaCl2 (aq) → BaSO4 (s) + 2NaCl (aq)

(white ppt.)

This is a type of double displacement reaction.

17. List the steps of preparation of temporary mount of a leaf peel to observe stomata.


The steps are:

i. Removal of peel from leaf.

ii. Stain with safranin.

iii. Put the stained peel on a clean slide.

iv. Mount it with glycerine and coverslip.

18. Name the process by which an amoeba reproduces. Draw the various stages of its reproduction in a proper sequence.


Amoeba reproduces by the method of binary fission.

Diagram to show the various stages of reproduction in amoeba is given below:

The practice is the key to sure success. So, students must solve more and more practice questions to assess their preparation for the board exams and keep a track of their performance.


13 February, 2021, 1:24 pm

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CBSE CLASS 10th 2021 : Case Study Questions For Maths & Science

This article will guide you through:

  • What are case study questions?
  • Class 10 Case Study question examples
  • How to get case-based questions for free?
  • How to attempt the case-based questions?

What are case study questions?

Questions based on case studies are some real-life examples. The questions are asked based on a given paragraph i.e. Case Study. Usually, 4-5 questions are asked on the basis of the given passage. In most cases, these are either MCQs or assertion & reason type questions. Let’s take an example to understand. There is one paragraph on how nitrogen is generated in the atmosphere. On the basis of this paragraph, the board asks a few objective type questions. In other words, it is very similar to the unseen passages given in language papers. But the real cause may be different. So, read this article till the end to understand it thoroughly.

Class 10 Science Case Study Question Examples:

Case-based Question -1

Read the following and answer any four questions:
Salt of a strong acid and strong base is neutral with a pH value of 7. NaCl common salt is formed by a combination of hydrochloride and sodium hydroxide solution. This is the salt that is used in food. Some salt is called rock salts bed of rack salt was formed when seas of bygone ages dried up. The common salt thus obtained is an important raw material for various materials of daily use, such as sodium hydroxide, baking soda, washing soda, bleaching powder.

    1. Which of the following does not form an acidic salt?
      1. Phosphoric acid
      2. Carbonic acid
      3. Hydrochloric acid
      4. Sulphuric acid
    2. Which of the following salts has no water of crystallization?
      1. Blue vitriol
      2. Washing soda
      3. Baking soda
      4. Gypsum
    3. The formula of baking soda is
      1. K2CO
      2. KHCO3
      3. NaHCO3
      4. Na2CO3
    4. Which of the following is treated with chlorine to obtain bleaching powder
      1. CaSO4
      2. Ca(OH)2
      3. Mg(OH)2
      4. KOH
    5. Which of the following salt is used for removing the permanent hardness of water?
      1. Washing soda
      2. Baking soda
      3. Bleaching powder
      4. NaOH

Case-based Question -2

Read the following and answer any four questions:
In resistance for a system of the resistor, there are two methods of joining the resistors together as shown below

It showed an electric current in which 3 resistors having resistor R1, R2 and R3 respectively are join end to end i.e series. While the combination of the resistor in which 3 resistors connected together which points X and Y are said to be parallel.

    1. The total potential difference across a combination of a resistor in series is equal to
      1. V1 + V2 + V3
      2. V– V+V2
      3. V+ V2
      4. None of these
    2. In a series combination of resistor, the current is
      1. same at every point of the circuit
      2. different at every point of the circuit
      3. zero
      4. can not be determined
    3. The electrical energy disputed in the resistor is given by
      1. W = VIT
      2. W = VIR
      3. W = RIT
      4. W = RT
    4. If 5 resistor, each of value 0.2 ohm are connected in series what will be the resultant resistance
      1. 1 ohm
      2. 10 ohm
      3. 6 ohm
      4. 8 ohm

Case-based Question -3

Read the following and answer any four questions:
In the electrolytic refining of copper. The electrolyte is a solution of acidified copper sulfate. There are an anode and cathode. Refining is carried out by passing an electric current.

    1. The anode is ________.
      1. pure strips
      2. impure copper
      3. refined copper
      4. none of these
    2. Anode mud consists of:
      1. insoluble impurities
      2. soluble impurities
      3. pure metal
      4. impure metal
    3. Which of the following are refined electrolytically: (A) Au, (B) Cu, (C) Zn, (D) K
      1. A and B
      2. B and C
      3. A, B, and C
      4. B, C, and D
    4. On passing, electric current Cu is deposited on:
      1. cathode
      2. anode
      3. bottom of cathode
      4. bottom of anode
    5. Which one of the following four metals would be displaced from the solution of its salt by the other three metals?
      1. Zn
      2. Mg
      3. Cu
      4. Ag

How to Attempt the Case-Based Questions in Science?

Before answering this question, let’s read the text given:

All living cells require energy for various activities. This energy is available by the breakdown of simple carbohydrates either using oxygen or without using oxygen.

See, there are only two sentences and CBSE is asking you 5 questions based on these two sentences. Now let’s check the first questions given there.

(i) Energy in the case of higher plants and animals is obtained by
a) Breathing
b) Tissue respiration
c) Organ respiration
d) Digestion of food

Now let us know if you can relate the question with the paragraph directly. The two sentences are about energy and how it is obtained. But neither the question nor the options have any similar text in the paragraph.

So the conclusion is, in most cases, you will not get direct answers from the passage. You will get only an idea about the concept. If you know it, you can answer it but reading the paragraph even 100 times is not going to help you.

Case Study based Questions Class 10 Mathematics:

Here is an example of a case study based question for class 10 Mathematics.

Suresh is having a garden near Delhi. In the garden, there are different types of trees and flower plants. One day due to heavy rain and storm one of the trees got broken as shown in the figure. The height of the unbroken part is 15 m and the broken part of the tree has fallen at 20 m away from the base of the tree.
Using the Pythagoras answer the following questions:

  1. What is the length of the broken part?
    1. 15 m
    2. 20 m
    3. 25 m
    4. 30 m
  2. What was the height of the full tree?
    1. 40 m
    2. 50 m
    3. 35 m
    4. 30 m
  3. In the formed right-angle triangle what is the length of the hypotenuse?
    1. 15 m
    2. 20 m
    3. 25 m
    4. 30m
  4. What is the area of the formed right angle triangle?
    1. 100 m2
    2. 200 m2
    3. 60 m2
    4. 150 m2
  5. What is the perimeter of the formed triangle?
    1. 60 m
    2. 50 m
    3. 45 m
    4. 100 m

Is it Easy or Difficult?

As discussed, all the questions are objective only and most of them are very straightforward questions so, these questions are going to be very easy to solve. Students can score good marks if they practice such questions before the board exams.


9 February, 2021, 10:54 am

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CBSE BOARD EXAM 2021 : Covid-19 Guidelines By CBSE And Mandatory Protocols

The Class 12 exams will begin on May 4, 2021, and will be held in two sessions, the first from 10:30 am to 1:30 pm and the second between 2:30 pm to 5:30 pm. The Class 10 exams will begin on May 6, 2021, and will be held in a single shift.

An additional 15 minutes time will be provided to the students to read the question papers. This time, apart from the regular exam-day guidelines, the CBSE has also released the COVID-19 guidelines such as all the board exams students will have to wear face masks. The Union Education Minister Ramesh Pokhriyal ‘Nishank’ also said that the exam centres will be allocated in a way to avoid overcrowding at one place. This time, apart from the regular exam-day guidelines, the CBSE has also released the COVID-19 guidelines such as all the board exams students will have to wear face masks. The Union Education Minister Ramesh Pokhriyal ‘Nishank’ also said that the exam centres will be allocated in a way to avoid overcrowding at one place.

CBSE Class 12 Exams: important points:

  • Class 12 board papers will be held in two shifts to reduce the number of days of the conduct of examinations. In the second shift, those exams will be conducted which are not held abroad.

  • The exams will be conducted in the second shift only on four days.

  • Class 12 exams will be conducted for a total of 114 subjects

  • The CBSE Class 12 exams will start on May 4 with the English Elective / Core paper. The Class 12 CBSE Exams will end on June 11 with Entrepreneurship/ Biotechnology / Library and Information Science / Beauty and Wellness / Agriculture.

CBSE Class 10 Exams: important points:

  • On days when the Class board exams will be held in the evening shift, Class 10 board exams will be held in the morning shift at more exam centres to maintain social distancing in and around the exam halls.

  • Class 10 exams will be conducted for a total of 75 subjects

  • The exams will begin on May 4 with language papers -- Odia, Kannada and Lepcha and will end on June 7 with the Computer Applications paper.

  • Most of the exams will be held for a duration of three hours but subjects including Painting, Carnatic Music and Hindustani Music will be conducted for two-hours’ duration between 10:30 am and 12:30 pm.

In addition to this, the government has also tried to reduce the stress on the board exams students and follow COVID-19 protocols

  • Sufficient time has been given between two board exams to allow the students to prepare for each paper without much stress

  • No school staff which has worked in the morning shift will also be given the evening shift to reduce the burden on them.

  • This year, the board exams will spread over fewer days. Board exams 2021 will be held over 39 days, 6 days lesser than the previous year when the board exams were held over 45 days.

  • Date sheet has been prepared in a manner that the total number of students at examination centres would not be more complying to the COVID-19 norms.

  • CBSE Answer booklets will be distributed to the students from 10 am to 10:15 am and for the afternoon session at 2 pm

  • Students will be provided with the CBSE Question papers 15 minutes before the start of the exam to allow the students to read the question paper.


3 February, 2021, 4:02 pm

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CBSE 10th,12th Board Exam 2021 : Board Exam Time Table Released

The Central Board of Secondary Education (CBSE) has released the Class 10 and Class 12 board exams date sheets on its official website Alternatively, the CBSE board exam date sheets can also be checked and downloaded on mobile phones.

Class 10th Time Table 2021

Class 12th Time Table 2021

CBSE Class 12 date sheet:

May 4 - English

May 8 - Physical Education

May 13- Physics

May 18- Chemistry

May 19 - Political Science

May 24- Biology

May 25- Economics

May 28- Sociology

May 29- Information Technology

June 1 - Maths

June 2 - Geography

Class 10 date sheet

May 6- English

May 10- Hindi

May 15- Science

May 21: Maths

May 27: Social Science

The CBSE board exams date sheets have the dates on which the papers will be conducted, and the name of each paper along with their codes. During the examination, the board exam students will have to enter the paper code and paper name as well in the answer sheet which will also be mentioned on the CBSE board exam admit cards.

Steps to download CBSE Class 10, Class 12 date sheets

  • Step 1: Go to the official website –

  • Step 2: Click on the new website

  • Step 3: Click on the date sheet link under the latest updates section

  • Step 4: Select the class

  • Step 5: Download the PDF date sheet

The CBSE board exams will be conducted in pen-and-paper mode at the designated examination centers. CBSE admit cards will also be released soon which will bear details including the name, address and board exams center, and the exams’ dates.


2 February, 2021, 5:32 pm

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CBSE 10th Board Exams 2021 : Tips to Cover Whole Syllabus In End Months

Check the CBSE Class 10 study plan to cover and revise the whole syllabus before the exam. Know how to utilize the last three months before the exam judiciously.

CBSE Class 10 Board Exam Dates 2020-2021 have been announced by the board. CBSE 10th & 12th Board Exams 2021 will commence from 4th May 2021 and conclude on 10th June 2021. Now these last three months before the exam are crucial for students. They can use these months to prepare well for their upcoming exams and pave the way for good scores. We are going to discuss here the CBSE Class 10 Study Plan for the upcoming CBSE Class 10 Board Exam 2021. This study plan will give the class 10 students a clear target for the last three months before the CBSE Board Exam. Know the three months plan here to prepare for the exams in an easy and organized manner.

Learn the untouched topics in February:

In February month, students should concentrate on finishing the remaining chapters and topics. They should go through the revised CBSE Class 10 Syllabus 2020-2021 to know the topics prescribed for the Board Exam 2021. In the revised syllabus, many topics have been removed. Therefore, students should be aware of the deleted portion of the syllabus that will not be tested in the board exam. Prepare all the units mentioned in the syllabus as they all are important from the exam point of view. Solve at least 2-3 problems related to each topic you read in the book. Do not miss the examples given in the NCERT book.

Revise the whole syllabus in March:

Revision is extremely important to do well in your exam. It not only helps you to remember the facts, definitions, topics, and methodologies that you had learned some time ago but also works the best in boosting up your confidence level. Go through all fifteen chapters. Solve all the exercise questions given in the Class 10 NCERT Book. Also, try to solve the NCERT Exemplar Problems. Be attentive while solving any question and take care of the steps involved in a solution. Solving different types of questions will give you a key insight into areas that you are good at, and others that require more attention. During revision, it’s better to focus more on the weaker topics to get good scores in your exam.

Practice more and more in April:

This is the month of strengthening your knowledge. Do not start with any new topic in this last month before the exam. The best thing will be to solve more and more previous years' question papers of CBSE Class 10 Class. Remember, the material in the board exam paper will seem to be more advanced than what you have practiced in the textbook. Solving the old question papers is the best way to get familiarised with such advanced questions. Also, solve the latest CBSE Class 10 Sample Paper to acquaint yourself with the format and number of questions for the upcoming CBSE Class 10 Maths Board Exam 2021. All you have to do in the April months is to solve previous years' question papers and sample papers to assess your preparedness and increase your confidence for the exam.

In last, we suggest all the candidates prepare smartly for their exams. They should use these three months very judiciously to prepare their entire syllabus well.


28 January, 2021, 1:13 pm

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