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Posted Date: 01 Feb 2009 Posted By: satish Member Level: Gold
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2008 CBSE science Question paper
Section - A
1. Draw a figure to show how the rate of a chemical reaction in general changes as the temperature of reactants is increased step-wise. 1
Answer :
2. Name the classes of organic compounds represented by the following formulae :
9
Answer :
3. Name any two neutral oxides. 1
Answer :
4. What type of force or forces keep the Sun and its planets in their respective places ?
OR
What force makes an apple on a tree to fall to the ground and what force makes a balloon filled with
hydrogen to rise into air ? 1
Answer :
5. How can it be shown that a magnetic field exists around a wire through which a direct electric current is passing ? 1
Answer :
6. What is the chemical name of washing soda ? Name the three chief raw materials used for making washing soda by the Solvay process. 2
Answer :
7. What is meant by ‘fermentation’ ? Write chemical equations for the two steps involved in preparing ethanol by the fermentation of molasses.
OR
Name the main products formed when :
(i) Ethanol is oxidised by an alkaline solution of KMnO4.
(ii) Propanone and hydrogen cyanide form an addition compound.
(iii) Sodium ethanoate is heated with soda lime.
(iv) Methanal is reduced with hydrogen in the presence of finely divided palladium. 2
Answer :
8. To which galaxy does our earth belong ? How is the shape of this galaxy described ?
‘Our universe is expanding’. What does it mean ? 2
Answer :
9. In cases of artificial satellites what are ‘equatorial’ and ‘polar’ orbits ? Which type of these satellite orbitals will be suitable for collecting data for weather prediction and why ? 2
Answer :
10. Which type of nuclear process is currently used in nuclear electricity generators ? Give one example each for the substances used in this context as :
(i) coolants, (ii) moderators, and (iii) nuclear fuel. 2
Answer :
11. When will the reversible reaction,
N2(g) + O2(g)=2NO(g)
be said to be in equilibrium state ? Write the formula co-relating the concentration of involved substances in this equilibrium state. A reversible reaction has a very low value of its equilibrium constant. What does it signify for the rate of progress of the reaction ? 3
Answer :
12. Besides being large molecules what is the other essential similar structural character of all polymers ? Give one example each for the formation of (0 an addition polymer and (if) a condensation polymer.
OR
State the monomers used and one use each for :
(a) Neoprene, (b) Teflon and © Natural rubber. 3
Answer :
13. (a) What are strategic metals ? Give one example also.
(b) State the reason for the following behaviour of zinc metal :
On placing a piece of zinc metal in a solution of mercuric chloride it acquires a shining silvery surface but when it is placed in a solution of magnesium sulphate no change is observed. 3
Answer :
14. Write chemical equations for the reactions taking place when :
(i) A piece of calcium metal is placed in water. (ii) Ammonia gas comes in contact with hydrogen chloride gas. (iii) Sulphur is heated with concentrated H2SO4. 3
Answer :
15. State the formula correlating the electric current flowing in a conductor and the voltage applied across it. Also show this relationship by drawing a diagram. What would be resistance of a conductor if the current flowing through it is 0.35 ampere when the Xpotential difference across it 1.4 volt ? 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
Answer :
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
Answer :
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
Answer :
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
Answer :
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
Answer :
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
Answer :
22. Name the excretory units present in an earthworm. 1
Answer :
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
Answer :
24. Describe how the sex of the offspring is determined in the zygote in human beings. 2
Answer :
25. State any two practices which can help in the protection of our environment. 2
Answer :
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
Answer :
27. List the sequence of events that occur during the formation of a blood clot after an injury. 3
Answer :
28. What is potable water ? State any four of its necessary characteristics. 3
Answer :
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
Answer :
30. With the help of a labelled diagram describe double fertilisation in plants. 5
Answer :
Pages: 1 2
CBSE Science Examination Question Paper -2004
Filed under:
* Class X
* Science
* Class Xth Previous Year Question Papers
16. 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
Answer :
17. 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
Answer :
18. (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
Answer :
19. (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.
Answer :
20. 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
Answer :
Section-B
21. Write the function of hormone ‘thyroxine’ in our bodies. 1
Answer :
22. Name the part of hind brain which takes part in regulation of respiration. 1
Answer :
23. Give an example of a vestigeal organ present in human body. 1
Answer :
24. 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
Answer :
25. Name two natural agents that can cause erosion of soil. Suggest two ways in which erosion of soil can be checked. 2
Answer :
26. (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
Answer :
27. 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
Answer :
28. (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
Answer :
29. 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
Answer :
30. (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
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