CBSE Board Science Sample Papers for Class 10

Time: 3 Hours
Max Marks: 75
General Instructions:
1. The question paper comprises of two sections, A and B. You are to attempt both the sections.
2. The candidates are advised to attempt all the questions of Section A separately and questions of Section B separately.
3. All questions are compulsory.
4. There is no overall choice. However, internal choice has been provided in some questions.
You are to attempt only one option in such questions.
5. Marks allocated to every question are indicated against it.
6. Question numbers 1-5 in Section A and 21-23 in Section B are very short answer questions. These are to be answered in one word or one sentence.
7. Question numbers 6-10 in Section A and 24, 25 in Section B are short answer questions.
These are to be answered in 30-40 words each.
8. Questions numbers 11-17 in Section A and 26-29 in Section B are also short answer questions. These are to be answered in 40-50 words each.
9. Question numbers 18-20 in Section A and 30 in Section B are long answer questions.
These are to be answered in 70 words each.

Q1. What is the effect of an increase in temperature on the rate of a chemical reaction?     1

Q2. Name any two isotopes which readily undergo nuclear fission.     1

Q3. Name the functional groups present in:      1
(a) CH3 COOH
(b) CH3 CO CH3

Q4. Why does it take longer to burn wet wood?      1

Q5. Why are Zirconium, Titanium and Chromium classified as strategic metals?       1

Q6. Define the terms
(a) Astronomical Unit
(b) Light year
Give approximate value of each in SI units.       2

Q7. Explain giving reasons:
(i) Tartaric acid is a component of baking powder used in making cakes.
(ii) Gypsum, CaSO4 2H2O is used in the manufacture of cement.       2

Q8. Calculate the energy released (in MeV) when1 kg mass is completely converted into energy. (Take 1 MeV = 1.6 x 10—13 J, c = 3.0 x 108ms—1)         2
When Uranium undergoes fission, 0.1% of the total mass is converted into energy.
Calculate the total amount of energy released in joules during an explosion of an atom bomb which contains 5kg of Uranium.

Q9. When a copper wire is left in silver nitrate solution, it is observed that the solution turns bluish green.
(a) Explain this observation.
(b) Write the balanced chemical equation to represent the change taking place.        2

Q10. State Right Hand Thumb rule to find the direction of the magnetic field around a current carrying straight conductor. How will this magnetic field be affected on-
(a) increasing the current through the conductor?
(b) changing the direction of flow of current in the conductor?        2

Q11. (a) Name the product formed when methanol undergoes controlled oxidation.
(b) Describe with necessary chemical equations the test you would perform to identify the above product.
(c) Name the compound formed when ethanoic acid reacts with ethanol in the presence of concentrated sulphuric acid.        3


(a) Propanone can be manufactured from Cumene. Write the corresponding chemical equation.
(b) Name the compound formed when propanone is reduced. Which reducing agent is generally used in the process?
(c) How is propanone converted to ethanoic acid?

Q12. Two identical resistors, each of resistance 10 ohms, are connected (i) in series (ii) in parallel, in turn, to a battery of 6 volts. Calculate the ratio of power consumed in the combination of resistors in two cases.        3

Q13. An aqueous solution has hydrogen ion concentration,
[H+] = 1.0 x 10—10 mol L—1
(a) Determine the pH of this solution.
(b) Is the solution acidic, basic or neutral?
(c) Will the pH of the above solution increase or decrease on adding a drop of 1M HC1 to it? Justify your answer.           3

Q14. Draw a labelled diagram of a dry cell. Write the chemical equations involved
i) at the anode
ii) at the cathode while the cell is working.       3

Q15. Distinguish between polar and equitorial orbits of artificial satellites. Which of the above two orbits is suitable for a
i) geostationary satellite
ii) satellite used for weather forecasting?         3


How do we locate the position of the pole star in the sky? Why is the pole star so special?

Q16. (a) Draw a flow diagram illustrating the principle used in the manufacture of ammonia by Haber process.
(b) Describe an activity to show that ammonia is basic and is highly soluble in water.         3

Q17. Explain giving reasons:
i) Detergent made up of molecules in which branching is minimum are preferred these days.
ii) In the manufacture of condensation polymers, each monomer should have at least two reactive sites. Why? Cite an example to support your answer.           3

Q18. Biogas technologies are gaining acceptance by both rural and urban population. Why?
What is biogas? How is it obtained from cow dung? Draw a labelled diagram of a fixed dome type biogas plant.         5


What is meant by the term 'refining of petroleum'? Draw a labelled diagram of petroleum distillation tower. Why CNG is considered an environment friendly fuel?

Q19. Name the lightest element. Why is its presence in the Free State in the earth's atmosphere negligible? With a labelled diagram, describe how this element can be prepared in the laboratory. How is this element used in?
a) Space programmes
b) Oil industry?               5


a) Name the chief ore of iron. How is it concentrated?
b) Describe the extraction of iron from the concentrated ore with the help of
i) a labelled diagram of the furnace used.
ii) necessary chemical equations representing the chemical changes occurring during the process.

c) How is the conversion of iron into iron oxide prevented during the extraction of iron?

Q20. Explain Myopia with the help of suitable ray diagrams. How can this defect of vision be corrected?
A boy uses spectacles of focal length —50 cm. Name the defect of vision he is suffering from. Compute the power of this lens.      5

Q21. What is the name given to a set of unpaired chromosomes of an organism?         1

Q22. What clue does the fossil Archeapteryx provide in regard to organic evolution?     1

Q23. What is meant by 'homologous organs'?     1

Q24. Differentiate between biodegradable and non-biodegradable pollutants. Classify the following under the above two categories         2
DDT, Paper, Cotton cloth, plastics

Q25. Name any two organs that are homologous to human hand. To which category of organs would you place wings of birds and wings of insects?    3

Q26. a) Draw a labelled diagram of a neuron.
b) Which part of the human brain is responsible for
i) intelligence and memory
ii) adjustment of movement of posture ?             3

Q27. Name the types of sex chromosomes present in
i) Human male and
ii) Human female
What will be the sex of the child produced if a sperm carrying 'Y' chromosome fertilizes the egg ? Name an insect in which similar type of sex determination takes place.         3

Q28. Draw a labelled diagram of the longitudinal section of pistil of a flower. What will happen to the pollen of mango flower if it falls in the stigma of guava flower?         3

Q29. Write the sequence of steps and processes in the primary and secondary treatments of the sewage before it is passed into the final (tertiary) step.                 3

Q30. How do (i) temperature (ii) water and (iii) carbon dioxide affect the rate of photosynthesis? During which state of photosynthesis do the following occur:
a) Synthesis of ATP and DPH
b) Synthesis of Carbohydrates?             5