Class X Science 
Previous Year Question Papers (Foreign)

Section - A

1. Give an example of a reaction catalysed by an enzyme.


2. Name the groups of compounds with the following functional groups :
(i) -COOH
(ii)- NH2


3. Name two main combustible components of Biogas.


4. Why are some stars red and some blue in colour ?


5. In what situation do we use Fleming’s right-hand rule ?


6. What change is made in the hardness of steel when :
(i) it is quenched, and
(ii) it is annealed ?


7. What is meant by decarboxylation and esterification of acetic acid ?


OR

Name the products obtained and the chemical equations for oxidation of ethanol to different stages.


8. What is the technique employed to obtain information about the internal layer structure of earth Name the layers of earth other than its crust.


9. What characteristics should be possessed by the fuel to be used in space rockets ? Give an example ot such fuels.


10. With the help of a diagram show how the fission reaction of 235U with thermal neutrons develops into a chain reaction.


11. What is meant by the pH of a solution ? What pH values can be expected for 1 M HCI and solutions and a solution made by mixing equal volumes of the two solutions


12. How is vulcanised rubber obtained from natural rubber ? What structural change is involved in this process ? Give an example of synthetic rubbers. To which class of polymers does this rubber belong .


OR

What are detergents chemically ? What is their advantage over soaps for washing clothes ? How does a soap solution wash out dirt from clothes ?


13. State reasons for the following : .
(i) Zinc oxide is called an amphoteric oxide. (ii) Sodium metal is stored in bottles filled with kerosene oil. (iii) Eatables can be preserved in nitrogen gas.


14. Write chemical equations for the reactions taking place when :
(i) a piece of zinc is placed in a solution of copper (II) sulphate. (ii) sulphur dioxide gas is dissolved in an excess of NaOH solution. (iii) a mixture of ammonia and oxygen gases is passed over platinum heated to about 1073 K-


15. (a) Two conductors A and B of resistances 5 ohm and 10 ohm respectively can be arranged in Parailel and later on in series. In each arrangement the total voltage applied across it is 20 volts. I’1 wmcl1 arrangement will the voltage across A and B be the same and in which case will the current flowing through A and B be the same ?
(b) Calculate the total resistance for each arrangement.



Section - A (All India)

1. How is the rate of reaction influenced by
(i) raising the temperature of reactants ?
(ii) adding to the reacting mixture a product of reaction without change in volume ? 1


2. How are the molecules of aldehydes and ketones structurally different ? 1


3. Name one non-metal and one metal which are in liquid state at room temperature. 1


4. Name two other planets of the Solar System which are similar to the Earth in composition and structure.1


5. How is the strength of the magnetic field at a point near a wire related to the strength of the electric current flowing in the wire ? 1


6. How is chloride of lime chemically different from calcium chloride ? Why does chloride of lime gradually lose its chlorine when kept exposed to air ? 2


7. What is formalin ? How does it react with Tollen’s reagent ? State any one of its uses.


OR

Complete the following reaction equations :

8. What is a galaxy ? Name two common shapes of galaxies. Why is our galaxy called Milky War ? 2


9. State one point of difference between a natural satellite and an artificial satellite. Name the type of orbit suitable for a geostationary satellite. 2


10. Give one example of a nuclear fusion reaction. Describe one method for making such reactions possible. 2


11. State Arrhenius’ concept of acids and bases. Giving reason, select a strong acid and a weak base from amongst the following substances :
H2CO3, HNO3, NaOH, NH4OH 3


12. How is it that we can use detergents for washing clothes even when the water is hard, but not soaps ? What change has been made in the composition of detergents to make them biodegradable ?


OR

What is a polymer ? How have been polymers been classified ? Name one polymer for each of the following applications : (i) For insulating electric wires. (ii) For non-stick coatings on kitchen utensils. (iii) For blending with cotton to make shrink-resist cloth. 3


13. Give reasons for the following :
(i) Silicon counts among metalloids.
(ii) Carbon is not used for making aluminium from aluminium oxide.
(iii) For making hydrogen by reaction with hydrochloric acid, granulated zinc is preferred to a block of zinc. 3


14. Write chemical equations for reactions taking place when :
(i) Zinc carbonate is calcined.
(ii) Ammonia gas is passed over heated copper (II) oxide. (iii) SO2 gas and H2S gas are together bubbled through water. 3


15. What are electrolytes ? Define Faraday’s constant for electrolytic reactions. Find chemical equivalents of Cu(II) (at. wt. 63.5) and Ag(I) (at. wt. 108). 3


16. A 5 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 20 cm.
The distance of the object from the lens is 30 cm. Find the (i) position, (ii) nature and (iii) size of the
image formed. 3


17. (i) What is meant by ‘critical angle’ for a ray of light going from one medium into another ?
(ii) What is the consequence of making angle of incidence of light, at an interface, greater than the
critical angle ? (iii) Why does a cut diamond shine more than a glass piece with diamond cut ?


OR

Draw ray diagrams to show the formation of images when the object is placed in front of a concave mirror.
(i) between its pole and focus points.
(ii) between its centre of curvature and focus point. 3


18. Why is it that iron does not occur as a metal in the crust of the earth ? What are the common compound forms in which iron occurs ? Which of these is more often used for extracting iron ? Why are carbon and limestone mixed with the iron ore before feeding it into the blast furnace ? Write the chemical equations for the reduction step and the slag formation step.


OR

Define an alloy and an amalgam. State the main constituents of the following alloys. In what property is each of them different from its main constituent ?
(i) Stainless steel (ii) Bronze 5


19. With the help of a labelled ray diagram show the formation of image of an object by a compound microscope.
A compound microscope has an objective of focal length 0,5 cm and an eye-piece of focal length 2.5 cm. /if its tube length is 25 cm, calculate what will be the magnifying power of the microscope. 5


20. On what principle does a solar water heater operate ? Draw a labelled schematic diagram for a solar / water heater.
The solar constant at a place is 1.4 kW/m2, How much solar energy will be received at this place per second over an area of 5 m2 ?


OR

What is the main basic cause for winds to blow ? Name a part of India where wind energy is commercially harnessed. Compare wind power and power of water flow in respect of generating mechanical and electrical energies. What is the hindrance in developing them ? 5



Section – B

21. State one of the evolutionary forces leading to the origin of a new species according to the synthetic theory of evolution. I


22. Name the excretory units present in an earthworm. 1


23. A farmer Hoods his Held every day thinking that watering in this manner will result in a better yield of his wheat crop. What will be the result of this action of the farmer ? 1


24. Describe how the sex of the offspring is determined in the zygote in human beings. 2


25. State any two practices which can help in the protection of our environment. 2


26. Define ‘nerve impulse’. Which structure in a neuron helps to conduct a nerve impulse (i) towards the cell body ?
(ii) away from the cell body ? 3


27. List the sequence of events that occur during the formation of a blood clot after an injury. 3


28. What is potable water ? State any four of its necessary characteristics. 3


29. What is the function of gizzard in a grasshopper ? Draw a labelled diagram showing the digestive system of a grasshopper.


OR

What is the function of epiglottis in man ? Draw a labelled diagram showing the human respiratory
system. 3


30. With the help of a labelled diagram describe double fertilisation in plants. 5


31. A convex lens has a focal length of 25 cm. Calculate the distance of the object from the lens if the image is to be formed on the opposite side of the lens at a distance of 75 cm from the lens. What will be the nature of the image ? 3


32. Name the three primary colours of light. A flower has magenta colour in white light. What will its colour appear to be when viewed separately under each of the lights of primary colours ?
What are complementary colours of light ?
OR
With the help of ray-diagrams show the phenomenon of total internal reflection of light and the concept of critical angle for a transparent medium. 3


33. (a) Describe briefly the contact process for manufacturing sulphuric acid starting with sulphur. Write the chemical equations for the involved factions.
(b) In this process SO3 is dissolved in cone. H2SO4 and not in water. Why is it so ?
© Name one large industry based on using sulphuric acid.


OR

(a) Draw a flow chart for the manufacture of ammonia gas by Haber’s Process.
(b) How can we show that ammonia is highly soluble in water and gives an alkaline solution.
© Name a major industry using ammonia as basic material. 5


34. (a) State two main causes of a person developing near sightedness. With the help of a ray-diagram suggest how he can be helped to overcome this disability.
(b) The far point of a myopic person is 150 cm in front of the eye. Calculate the focal length and the power of a lens required to enable him to see distant objects clearly.


OR

(a) How is a simple microscope different from a compound microscope in construction and magnifying power ? A magnifying lens of focal length 6.25 cm is used by a jeweller during his work. His least distance of distinct vision is 25 cm. What magnification is the jeweller getting ?
(b) What is ‘astigmatism1 and how is this vision defect counteracted ? 5 w.


35. Name the major fuel component of biogas. What are its other combustible components ?
Draw a simple labelled diagram of a fixed dome type biogas plant. What is the use for the residual slurry and why ? 5



Section - C

36. Write the function of hormone ‘thyroxine’ in our bodies. 1


37. Name the part of hind brain which takes part in regulation of respiration. 1


38. Give an example of a vestigeal organ present in human body. 1


39. Leaves of a healthy ported plant were coated with vaseline to block the stomata. Will this plant remain healthy for long ? State three reasons for your answer. 2


40. Name two natural agents that can cause erosion of soil. Suggest two ways in which erosion of soil can be checked. 2


41. (i) Who put forward the double helical model of DNA ‘?
(ii) What are the three chemically essential parts of nucleotides constituting a DNA ?
(iii) How many types of nucleotides are present in a DNA molecule ? 3


42. What is meant by pollution of air ? Write any two harmful effects of pollution of air. Name any three techniques used for controlling amounts of gaseous pollutants of our atmosphere. 3


43. (i) When does ovulation occur during the menstrual cycle in a normal healthy woman ?
(ii) Draw a labelled diagram to show the reproductive system of a human female. 3


44. Explain the process by which inhalation occurs during breathing in human beings.


OR

With the help of a diagram describe the process by which excretion occurs in amoeba. 3


45. (i) Name the blood vessel that brings oxygenated blood to the human heart.
(ii) Which chamber of human heart receives oxygenated blood ?
(iii) Explain how oxygenated blood from this chamber is sent to all parts of the body. 5