CBSE Set Qa1 Science Class X 1999 Sample Test Papers For Class 10th for students online
Science
Class X (CBSE)
You are on Answers 1 - 20
General
Instructions :
(i) All questions are compulsary.
(ii) Question number 1 to 10 are very short answer question,carrying 1 mark
each.They are to be answered in one or two sentences.
(iii) Question number 11 to 20 are short answer questions,each carrying 2 marks.
Answer to them should not exceed 40 words each.
(iv) Question numbers 21 to 30 are also short answer questions,each
carrying 3 marks. Answer to them should not exceed 60 words each.
(v) Question numbers 31 to 33 are long answer questions,each carrying 5 marks.
Answer to them should not normally exceed 100 words each.
Q.1 Name
the orbit of the satellites that help in satellite communication.
Ans1. Geostationary satellite
Q.2 A torch cell converts one form of energy into another
form. Name these two forms.
Ans2. Chemical energy 
Electrical
energy
Q.3 Name the process that forms the basis of hydrogen bomb.
Ans3. Nuclear fusion
Q.4 How does the conductivity of a semi conductor change when
certain impurities are added to it ?
Ans4. Impurities increase the conductivity of the semi-conductors.
Q.5 Name any two constituents of petroleum which are not used
as fuel.
Ans5. Asphalt and lubricating oil
Q.6 Why does common salt become moist in rainy season?
Ans6. Common salt contains impurities of magnesium chloride, which make it
deliquescent and it absorbs water from humid air and becomes moist.
Q.7 Which property of diamond makes it a suitable material
for high precision thermometers ?
Ans7. Diamond has a very high melting point which makes it a good substance
to be used in high temperature thermometres.
Q.8 Name the Vitamin which gets oxidised when cut fruits are
left exposed to air for a long time.
Ans8. Vitamin C
Q.9 In a food chain comprising lion, grass and deer, which
will (i) transfer the maximum amount of energy (ii) receive minimum amout of
energy.
Ans9. (i) Grass will transfer the maximum amount of energy.
(ii) The lion will recieve the minimum amount of energy.
Q.10 Which of the following is a true solution ?
Ans10. Vinegar in water is a true solution.
Q.11 The lungs perform 2.4J of work during each exapnsion.
How many times per minute do they expand if their power is 2 watts?
Ans11. Work done by lungs in a expansion = 2.4 J
Power of lungs = 2 W
Work
Power 
Time
Work
Time
Power
2.4
J
Time taken by lungs in an expansion
= 1.2 S
2
W
Number of expansion in 1 min = 60 S
60 s
1.2 s
= 50 expansions
Ans = 2 watts will be able to do 50 expansions.
Q.12 Cadmium rods play an important role in a nuclear
reactor. What happens (i) when they are completely inserted into nuclear fuel,
and (ii) when they are slowly withdrawn from nuclear fuel.
Ans12. (i) When cadmium rods are completely inserted into fuel, all neutrons
are absorbed and the chain reaction of the nuclear fission stops.
(ii) When these rods are slowly withdrawn the fission reaction starts and goes
on increasing as the rods get withdrawn. They are withdrawn till they absorb the
correct number of neutrons leaving behind just the right number of neutrons to
sustain the reaction and yield energy at a constant rate.
Q.13 Mention any two differences between a planet and a star.
Ans13.
|
|
Star |
Planet |
|
1 |
Star has its own light to illuminate |
Planets depend on the light from stars to shine |
|
2 |
Stars have a planet system of their own |
Planets have satellites of their own |
Q.14 A compound which is prepared from gypsum has the
property of hardening when mixed with proper quantity of water. Identify the
compound. Write the chemical equation of its
preparation. Mention one important use of the compound.
Ans14. The compound is Plaster of Paris.
It is prepared by dry-heating gypsum (CaSO4.2H2O).
2 (CaSO4.2H2O) 
(CaSO4)2.H2O + 3 H2O
It is used in surgery to maintain joints in a fixed position.
Q.15 Which catagory of compounds is formed when one hydrogen
atom of an alkane moleule is replaced by a hydroxyl group? Name the functional
groups in the following compounds.
|
Compound
|
|
| (i) |
 |
| (ii) |
|
Ans15. The compound formed is an Alcohol (R-OH).
|
Compound |
the functional group |
|
| (i) | |
Carboxyl group |
| (ii) | |
Ester group |
Q.16 How is
the polar nature of water responsible for dissolving (i) Sodium Chloride (ii)
sugar ?
Ans16. Being polar, water molecules interact with the negative Cl-
and positive Na+ ions of the ionic compound NaCl. It makes a coat
around the two ions and does not let the dissociated ions to get reassociated.
Sugar is a nonpolar molecule and water molecules form loose Hydrogen-bonds with
the hydroxyl groups of the sugar molecule.Thus the sugar molecule get dissolved.
Q.17 Give an example of a food chain consisting of four
organisms at different trophic levels. Give the scientific term used to indicate
the first and third trophic level.
Ans17. An example of the food-chain is:
Phytoplanktons Small animals
Fish Big Fish
I
II
III
IV
First Trophic level is called "Producers"
Third Trophic level is called "Primary Carnivores"
Q.18 What is biological fixation? How is it different from
nitrification ? Give an example of organism involved in each of these ?
Ans18. "Biological Fixation" refers to converting atmospheric
nitrogen into biologically usable nitrates by bacteria and algae. Nitrification
is one part of the nitrogen-cycle in which process nitrites are converted to
nitrites and
then to nitrates.
Biological fixation: Rhizobium
Nitrification: Nitrosomonas (NH3NO2-),
Nitrobacter (NO2-)
Q.19 Differentiate between arithmatic progression and
geometric progression in tems of food and population.
Ans19. Food Production grows in arithematic progression. In
arithematic progression the subsequent factors are a product of the sum of
earlier factors:
2 4
6 10
16
Population grows in geometric progression. In geometric progression the
subsequent factors are a multiplication product of the earlier factors:
1 2
4 8
16
Since population grows in geometric progression, it has a much faster growth
than the rate of growth of the food production.
Q.20 What is immunity ? Name the diseases against which DPT
vaccine acts as a preventive measure.
Ans20. Immunity is the natural defence of the body to fight infections.
DPT vaccine acts as a preventive measure for the following three diseases:
D : Diphtheria
P : Pertussis (Whooping Cough)
T : Tetanus
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