Click here to get Class X Sample Question Paper & Marking Scheme for CBSE Exam 2020-21
Sub- Science (086) Theory Class -X
Time: 3 Hours Maximum Marks: 80
General Instructions:
(i)
The
question paper comprises four sections A, B, C and D. There are 36 questions in
the question paper. All questions are compulsory.
(ii)
Section–A
- question no. 1 to 20 - all questions and parts thereof are of one mark each.
These questions contain multiple choice questions (MCQs), very short answer
questions and assertion - reason type questions. Answers to these should be
given in one word or one sentence.
(iii)
Section–B
- question no. 21 to 26 are short answer type questions, carrying 2 marks each.
Answers to these questions should in the range of 30 to 50 words.
(iv)
Section–C
- question no. 27 to 33 are short answer type questions, carrying 3 marks each.
Answers to these questions should in the range of 50 to 80 words.
(v)
Section–D
– question no. - 34 to 36 are long answer type questions carrying 5 marks each.
Answer to these questions should be in the range of 80 to 120 words.
(vi) There is no overall choice. However, internal choices have been provided in some questions. A student has to attempt only one of the alternatives in such question
(vii) Wherever necessary, neat and properly labeled diagrams should be drawn.
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SECTION
A |
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No. |
Questions |
Marks |
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1 |
List any two observations
when Ferrous Sulphate is heated in a dry test tube? Ans- • Initial
light green colour changes to reddish brown colour • Colourless
gas is evolved • Gas with
choking smell is evolved OR Identify the products formed when 1 mL of dil. Hydrochloric acid is
added to 1g of Sodium metal? Ans- Sodium Chloride and Hydrogen gas |
1 |
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2 |
Write the chemical name and chemical formula of the salt used to remove
permanent hardness of water. Ans- Sodium Carbonate decahydrate, Na2CO3.10H2O |
1 |
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3 |
Which of the following is not observed
in a homologous series? Give reason for your choice. a) Change in
chemical properties b) Difference in
-CH2 and 14u molecular mass c) Gradation in
physical properties d) Same functional group Ans- a. Change in chemical properties It does not occur due to the
presence of the same functional group. |
1 |
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4 |
Why does the Sun appear
white at noon? |
1 |
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5 |
Both a spherical mirror and a thin spherical lens have a focal length
of (-)15 cm. What type of mirror
and lens are these? |
1 |
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6 |
The image formed by a concave mirror is observed to be real, inverted and larger than the object. Where is the object placed? OR Name the part of a lens through which a ray of light passes without
suffering any deviation. |
1 |
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7 |
In the arrangement shown in figure there are two coils wound on a non- conducting cylindrical rod. Initially the key is not inserted in the circuit. Later the key is inserted and then removed shortly after. 
What are the two observations that can be noted from
the galvanometer reading? |
1 |
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8 |
Draw the magnetic field
lines around a straight current carrying conductor. |
1 |
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9 |
Two unequal resistances are connected in parallel. If you are not provided with any other parameters (eg. numerical values of I and R), what can be said about the voltage drop across the two resistors? OR Some work is done to move a charge Q from infinity
to a point A in space. The potential of the point A is given as V. What is
the work done to move this charge from infinity in terms of Q and V? |
1 |
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10 |
Veins are thin walled and
have valves. Justify. |
1 |
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11 |
How is the wall of small intestine adapted for performing the function
of absorption of food? OR Out of a goat and a tiger, which one will have a longer small
intestine? Justify your answer. |
1 |
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12 |
Explain how ozone being a deadly poison can still perform an essential
function for our environment. OR Give reason why a food
chain cannot have more than four trophic levels. |
1 |
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13 |
State the role of pancreas
in digestion of food. |
1 |
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For question numbers 14, 15 and 16, two statements
are given- one labeled Assertion (A) and
the other labeled Reason (R).
Select the correct answer to these questions from the codes (a), (b), (c) and
(d) as given below: a) Both A and R
are true, and R is correct explanation of the assertion. b) Both A and R
are true, but R is not the correct explanation of the assertion. c) A is true, but
R is false. d) A is false, but
R is true. |
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14 |
Assertion: After white washing the walls, a shiny white finish on walls is
obtained after two to three days. Reason: Calcium Oxide reacts with Carbon dioxide to form Calcium Hydrogen
Carbonate which gives shiny white finish. Ans- (a) |
1 |
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15 |
Assertion: Food chain is responsible for the entry of harmful chemicals in our
bodies. Reason:
The
length and complexity of food chains vary greatly. OR Assertion:
Greater
number of individuals are present in lower trophic levels. Reason:
The
flow of energy is unidirectional. |
1 |
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16 |
Assertion: A geneticist crossed a pea plant having violet flowers with a pea plant
with white flowers, he got all violet flowers in first generation. Reason:
White
colour gene is not passed on to next generation. |
1 |
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Answer Q. No 17 - 20 contain five
sub-parts each. You are expected to answer any four sub- parts in
these questions. |
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17 |
Read the
following and answer any four questions
from 17 (i) to 17 (v) 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. |
1x4 |
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(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 |
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(ii) The graph below represents the blood lactic acid concentration of an athlete during a race of 400 m and shows a peak at point D.  (iii) Study the graph below that represents the amount of energy supplied with respect to the time while an athlete is running at full speed  Choose the correct combination of plots and justification provided in the following table.
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(iv) The characteristic
processes observed in anaerobic respiration
are i) presence of oxygen ii) release of
carbon dioxide iii) release of energy iv) release of lactic acid a)
i) ,ii) only b)
i), ii), iii) only c)
ii), iii), iv)
only d)
iv) only |
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(v) Study the table below
and select the row that has the incorrect information.
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18 |
Read the
following and answer any four questions
from 18 (i) to 18 (v). Metallic Character The ability of an atom to donate electrons and form
positive ion (cation) is known as electropositivity or metallic character.
Down the group, metallic character increases due to increase in atomic size
and across the period, from |
1x 4 |
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left to right
electropositivity decreases due to decrease in atomic size. Non-Metallic Character The ability of an atom to accept electrons to form a negative ion (anion) is called non-metallic character or electronegativity. The elements having high electro-negativity have a higher tendency to gain electrons and form anion. Down the group, electronegativity decreases due to increase in atomic size and across the period, from left to right electronegativity increases due to decrease in atomic size.
Ans-
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18 (i) |
Which of the following correctly represents the decreasing order of
metallic character of Alkali metals plotted in the graph? a) Cs>Rb>Li>Na>K b) K>Rb>Li>Na>Cs c) Cs>Rb>K>Na>Li d) Cs>K>Rb>Na>Li Ans- c)
Cs>Rb>K>Na>Li |
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18 (ii) |
Hydrogen is placed along with Alkali metals in the modern periodic
table though it shows non-metallic character a)
as Hydrogen has one electron
& readily loses electron to form negative ion b)
as Hydrogen can easily lose one
electron like alkali metals to form positive
ion c)
as Hydrogen can gain one electron
easily like Halogens to form negative ion d) as Hydrogen
shows the properties of non-metals Ans- b) As Hydrogen can easily lose one electron like alkali metals to
form positive ion |
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18 (iii) |
Which of the following has
highest electronegativity? a) F b) Cl c) Br d) I Ans-(a) F |
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18
(iv) |
Identify the reason for the gradual change in electronegativity in
halogens down the group. a)
Electronegativity increases down
the group due to decrease in atomic size b)
Electronegativity decreases down
the group due to decrease in tendency
to lose electrons c)
Electronegativity decreases down
the group due to increase in atomic radius/ tendency to gain electron decreases d)
Electronegativity increases down
the group due to increase in forces of attractions between nucleus &
valence electrons Ans- c) Electronegativity decreases down the group due to increase in
atomic radius/ tendency to gain electron decreases. |
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18
(v) |
Which of the following reason correctly justifies that “Fluorine (72pm)
has smaller atomic radius than Lithium (152pm)”? a) F and Li are in
the same group. Atomic size increases down the group b)
F
and Li are
in the same period. Atomic size increases across the period
due to increase in number of shells c) F and Li are in
the same group. Atomic size decreases down the group d)
F and Li are in the same period
and across the period atomic size/radius decreases from left to right. Ans-d) F and Li are in the
same period and across the period atomic |
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19 |
Read the
following and answer any four questions
from 19 (i) to 19 (v) Sumati wanted to see the stars of the night sky. She knows that she needs a telescope to see those distant stars. She finds out that the telescopes, which are made of lenses, are called refracting telescopes and the ones which are made of mirrors are called reflecting telescopes.
Heavy lenses are hard to make and difficult to hold in the right place. Also |
1x 4 |
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since the light is passing through the lens, the
surface of the lens has to be extremely smooth. Any flaws in the lens will
change the image. It would be like looking through a dirty window. |
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19 (i) |
Based on the diagram shown, what kind of lenses would Sumati need to
make the telescope? a) Concave lenses b) Convex lenses c) Bifocal lenses d) Flat lenses |
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19 (ii) |
If the powers of the lenses L1 and L2 are in the
ratio of 4:1, what would be the ratio of the focal length of L1
and L2? a) 4:1 b) 1:4 c) 2:1 d) 1:1 |
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19 (iii) |
What is the formula for
magnification obtained with a lens? a) Ratio of height
of image to height of object b) Double the
focal length. c) Inverse of the
radius of curvature. d) Inverse of the
object distance. |
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19 (iv) |
Sumati did some preliminary experiment with the
lenses and found out that the magnification of the eyepiece (L2)
is 3. If in her experiment with L2 she found an image at 24 cm
from the lens, at what distance did she put the object? a) 72 cm b) 12 cm c) 8 cm d) 6 cm |
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19 (v) |
Sumati bought not-so-thick lenses for the telescope and polished them.
What advantages, if any, would she have with her choice of lenses? a)
She will not have any advantage
as even thicker lenses would give clearer
images. b) Thicker lenses
would have made the telescope easier to handle. c)
Not-so-thick lenses would not
make the telescope very heavy and also allow considerable amount of light to pass. d) Not-so-thick lenses will give her more magnification. |
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20 |
Read the
following and answer any 4 questions from 20 (i) to 20 (v). A solenoid is a long helical coil of wire through
which a current is run in order to create a magnetic field. The
magnetic field of the solenoid is the superposition of the fields due to the
current through each coil. It is nearly uniform inside the solenoid and close
to zero outside and is similar to the field of a bar magnet having a north
pole at one end and a south pole at the other depending upon the direction of
current flow. The magnetic field produced in the solenoid is dependent on a
few factors such as, the current in the coil, number of turns per unit length etc. The following graph is obtained by a researcher
while doing an experiment to see the variation of the magnetic field with
respect to the current in the solenoid. The unit of magnetic field as given in the graph attached is
in milli-Tesla (mT) and the current is given in Ampere.
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4 |
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20 (i) |
What type of energy
conversion is observed in a linear solenoid? a. Mechanical to Magnetic b. Electrical to Magnetic c. Electrical to Mechanical d. Magnetic to Mechanical |
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20 (ii) |
What will happen if a soft
iron bar is placed inside the solenoid? a. The bar will be
electrocuted resulting in short-circuit. b. The bar will be
magnetised as long as there is current in the circuit. c. The bar will be
magnetised permanently. d. The bar will
not be affected by any means. |
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20 (iii) |
The magnetic field lines
produced inside the solenoid are similar to that of … a. a bar magnet |
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b. a straight
current carrying conductor c. a circular
current carrying loop d. electromagnet
of any shape |
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20
(iv) |
After analysing the graph
a student writes the following statements. I.
The magnetic field produced by
the solenoid is inversely proportional to the current. II.
The magnetic field produced by
the solenoid is directly proportional to the
current. III.
The magnetic field produced by the
solenoid is directly proportional to square of the current. IV.
The magnetic field produced by
the solenoid is independent of the current. Choose from the following which of the following would be the correct
statement(s). a. Only IV b. I and III and IV c. I and II d. Only II |
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20
(v) |
From the graph deduce
which of the following statements is correct. a. For a current
of 0.8A the magnetic field is 13 mT b. For larger
currents, the magnetic field increases non-linearly. c. For a current
of 0.8A the magnetic field is 1.3 mT d.
There is not enough information to find the magnetic field
corresponding to 0.8A current. |
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SECTION
B |
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21 |
Bile juice does not have any digestive enzyme but still plays a
significant role in the process of digestion. Justify the statement. OR In birds and mammals the left and right side of the heart are
separated. Give reasons. |
2 |
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22 |
State the events occurring during the process of photosynthesis. Is it
essential that these steps take place one after the other immediately? |
2 |
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23 |
Give a test that can be used to confirm the presence of carbon in a
compound. With a valency of 4, how is carbon able to attain noble gas
configuration in its compounds? OR The number of carbon compounds is more than those formed by all other
elements put together. Justify the statement by giving two reasons. |
2 |
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24 |
The following observations were made by a student on treating four metals P, Q, R and S with the given salt solutions:
Based on the above
observations: (a) Arrange the
given samples in the increasing order of reactivity (b)
Write the chemical formulae of
products formed when Q reacts with CuSO4 solution. Ans- i. S>R>P>Q ii. Cu and QSO4 |
2 |
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25 |
 A student observes the above phenomenon in the lab as a
white light passes through a prism. Among many other colours, he observed the
position of the two colours Red and Violet. What is the phenomenon called? What is the reason for the
violet light to bend more than the red light? |
2 |
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26 |
 A student has two resistors- 2 Ω and 3 Ω. She has to put
one of them in place of R2 as shown in the circuit. The current that she
needs in the entire circuit is exactly 9A. Show by calculation which of the
two resistors she should choose.
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30 |
a. Which of the following reactions is/ are an endothermic reaction(s) where decomposition
also
happens? · Respiration · Heating of lead nitrate · Decomposition
of organic matter · Electrolysis of
acidified water
b.
Silver chloride when kept in the
open turns grey. Illustrate this with a balanced chemical equation. Ans- a. Heating of lead nitrate; and electrolysis of acidified water b. Sunlight 2AgCl(s) 2Ag(s) + Cl2 (g) (No deduction for not
mentioning state of reactants and products.) |
3 |
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31 |
The following table shows the position of five elements A, B, C, D and E in the modern periodic table.
element is a metal with valency two? (ii)
Which element is least reactive? (iii)
Out of D and E which element has a smaller atomic radius? Ans- (i) D, As it is on the left side of the table in group 2 (ii) C,
as it is in the group 18/ Noble gas (iii) E, as we move from left to right
across a period, atomic radius decrease
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3 |
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32 |
a.
Explain the formation of Calcium
Chloride with the help of electron dot structure. (At numbers: Ca = 20; Cl = 17) b.
Why do ionic compounds not
conduct electricity in solid state but conduct electricity in molten and
aqueous state? Ans- a. b. Ionic compounds do not conduct electricity in solid state due
to absence of free ions but they conduct electricity in molten and aqueous
state due to presence of free ions |
3 |
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33 |
Refractive index of water with respect to air is 1.33 and that of
diamond is 2.42. (i) In which medium
does the light move faster, water or diamond? (ii)
What is the refractive index of diamond with
respect to water? |
3 |
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Section
D |
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34 |
Match the following pH
values 1, 7, 10, 13 to the
solutions given below: · Milk of magnesia · Gastric juices · Brine · Aqueous Sodium hydroxide. Amit and Rita decided to bake a cake and added baking soda to the cake
batter. Explain with a balanced reaction, the role of the baking soda.
Mention any other use of baking soda.
Ans- • Milk of magnesia 10 • Gastric
juices 1 • Brine 7 • Aqueous Sodium hydroxide 13 Baking soda undergoes thermal decomposition
to form Na2CO3, CO2 and H2O; CO2 makes the cake fluffy & soft Heat NaHCO3
àNa2CO3 + CO2 + H2O Uses Used in fire extinguishers/ antacid to neutralize
excess acid in stomach / to neutralize the effect of acid in insect sting. |
5 |
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Explain with a balanced reaction, the role of the baking soda. Mention
any other use of baking soda.
OR (i) Four samples A,
B, C and D change the colour of pH paper or solution to Green, Reddish-pink,
Blue and Orange. Their pH was recorded as 7, 2, 10.5 & 6 respectively.
Which of the samples has the highest amount of Hydrogen ion concentration?
Arrange the four samples in the decreasing order of their pH.
(ii)
Rahul found that the Plaster of Paris, which he
stored in a container, has become very hard and lost its binding nature. What
is the reason for this? Al- so, write a chemical equation to represent the
reaction taking place.
(iii)
Give any one use of Plaster of
Paris other than for plastering or smoothening of walls.
Ans- (i) a) B
b) C,A,D,B (ii) Due to moisture in the atmosphere it
converted into Gypsum CaSO4+1½ H2O CaSO4.2H2O (iii) Making toys/dolls or statues /fixing
broken limbs/making decorative materials. |
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35 |
Trace the changes that take place in a flower from gamete formation to
fruit formation. |
5 |
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36 |
In the
given circuit, A, B, C and D are four lamps connected with a battery of 60V.
Analyse the circuit to
answer the following questions. (i) What kind of
combination are the lamps arranged in (series or parallel)? (ii)
Explain with reference to your
above answer, what are the advantages (any two) of this combination of lamps? (iii)
Explain with proper calculations which lamp glows
the brightest? (iv) Find out the
total resistance of the circuit.
OR PQ is a current carrying conductor in the plane of the paper as shown in the figure below.  (i) Find the
directions of the magnetic fields produced by it at points R and S? (ii) Given
r1> r2, where will the strength of the magnetic field
be larger? Give reasons. (iii) If
the polarity of the battery connected to the wire is reversed, how would the
direction of the magnetic field be changed? Explain the rule that is used to find the direction of the magnetic field for a straight current carrying conductor. |
5 |
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