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## Science Class 9

Created by: Dr Manju Sen

## Class 9 : Notes | EduRev

``` Page 1

CBSE IX | SCIENCE
Sample Paper – 8 Solution

CBSE
Class IX Science
Sample Paper – 8 Solution

Section A
1. The main objective of mixed cropping is to reduce the risk of crop failure due to adverse
weather.

2. Processes which play an important role in the oxygen cycle:
(a) Photosynthesis
(b) Respiration

Section B

3. The ozone layer absorbs harmful ultraviolet radiations emitted by the Sun and prevents
them from reaching the surface of the Earth, as these radiations cause harmful effects to
human beings, plants and animals.

4. A car is moving with a velocity of 20 m/s.
2
22
2
u 20 m/s
The body comes to rest after applying the brakes
v = 0
acceleration = -1m/s
Distance covered (s)= ?
by using the 3 kinematical equation we get,
v u 2as
0 20 2 ( 1)
0 400 2
24
??
?
??
? ? ? ? ? ?
? ? ?
??
rd
s
s
s 00
400
s = 200 metres.
2
??

OR
u = 0.6 m/s
a= - 0.05 m/s
2
(deceleration)
t = ?
v = u + at
0 = 0.6 + (-0.05) x t
Thus, t = -0.6/(0.05) = 12 s
Thus, it takes the body 12 s to come to rest.

Page 2

CBSE IX | SCIENCE
Sample Paper – 8 Solution

CBSE
Class IX Science
Sample Paper – 8 Solution

Section A
1. The main objective of mixed cropping is to reduce the risk of crop failure due to adverse
weather.

2. Processes which play an important role in the oxygen cycle:
(a) Photosynthesis
(b) Respiration

Section B

3. The ozone layer absorbs harmful ultraviolet radiations emitted by the Sun and prevents
them from reaching the surface of the Earth, as these radiations cause harmful effects to
human beings, plants and animals.

4. A car is moving with a velocity of 20 m/s.
2
22
2
u 20 m/s
The body comes to rest after applying the brakes
v = 0
acceleration = -1m/s
Distance covered (s)= ?
by using the 3 kinematical equation we get,
v u 2as
0 20 2 ( 1)
0 400 2
24
??
?
??
? ? ? ? ? ?
? ? ?
??
rd
s
s
s 00
400
s = 200 metres.
2
??

OR
u = 0.6 m/s
a= - 0.05 m/s
2
(deceleration)
t = ?
v = u + at
0 = 0.6 + (-0.05) x t
Thus, t = -0.6/(0.05) = 12 s
Thus, it takes the body 12 s to come to rest.

CBSE IX | SCIENCE
Sample Paper – 8 Solution

5. An ion is a charged particle which can be negatively or positively charged.
In NaCl:
Cation Anion
Name Sodium Chloride
Symbol Na
+
Cl
-

Section C

6. Limitations of Thomson's atomic model:
? Although Thomson's atomic model explained why an atom is electrically neutral, it
could not explain the distribution of electrons in the atom.
? If we accept that electrons are embedded in the positive charge, then the opposite
electric charges should cancel each other out and the charged sphere would become
chargeless.
? Thomson's model could not explain why different elements have different chemical
properties.
(a) Fresh water supplies hydrogen and oxygen to plants.
(b) It provides enough moisture to the soil for the germination of seeds.
(c) Irrigated soil is soft and new roots can penetrate and grow very well.
(d) It causes an increase in the number of tillers in crop plants, as they cannot grow in
dry soil.
(e) It helps in the absorption of minerals and salts by roots which are necessary for the
growth and development of plants.

8.
(a) Naphthalene easily undergoes sublimation, i.e. change of state of naphthalene from
solid to gas without the intervening liquid state. Thus, naphthalene balls form
naphthalene vapour which disappears into the air with time without leaving any
solid residue.
(b) Gaseous particles possess high speed and move very rapidly in all directions.
When perfume is sprayed, its particles diffuse into the particles of air at a very fast
rate and reach our nostrils. This enables us to smell the perfume from a distance.
(c) After a hot sunny day, people sprinkle water on the roof or open ground because the
large latent heat of vaporisation of water helps to cool the hot surface.
9. The body experiences uniform velocity if it travels in a specified direction in a straight
line and moves over equal distances in equal intervals of time.
Two ways to change the velocity of a body:
i) Change the speed of the body
ii) Keep the speed constant and change the direction
Page 3

CBSE IX | SCIENCE
Sample Paper – 8 Solution

CBSE
Class IX Science
Sample Paper – 8 Solution

Section A
1. The main objective of mixed cropping is to reduce the risk of crop failure due to adverse
weather.

2. Processes which play an important role in the oxygen cycle:
(a) Photosynthesis
(b) Respiration

Section B

3. The ozone layer absorbs harmful ultraviolet radiations emitted by the Sun and prevents
them from reaching the surface of the Earth, as these radiations cause harmful effects to
human beings, plants and animals.

4. A car is moving with a velocity of 20 m/s.
2
22
2
u 20 m/s
The body comes to rest after applying the brakes
v = 0
acceleration = -1m/s
Distance covered (s)= ?
by using the 3 kinematical equation we get,
v u 2as
0 20 2 ( 1)
0 400 2
24
??
?
??
? ? ? ? ? ?
? ? ?
??
rd
s
s
s 00
400
s = 200 metres.
2
??

OR
u = 0.6 m/s
a= - 0.05 m/s
2
(deceleration)
t = ?
v = u + at
0 = 0.6 + (-0.05) x t
Thus, t = -0.6/(0.05) = 12 s
Thus, it takes the body 12 s to come to rest.

CBSE IX | SCIENCE
Sample Paper – 8 Solution

5. An ion is a charged particle which can be negatively or positively charged.
In NaCl:
Cation Anion
Name Sodium Chloride
Symbol Na
+
Cl
-

Section C

6. Limitations of Thomson's atomic model:
? Although Thomson's atomic model explained why an atom is electrically neutral, it
could not explain the distribution of electrons in the atom.
? If we accept that electrons are embedded in the positive charge, then the opposite
electric charges should cancel each other out and the charged sphere would become
chargeless.
? Thomson's model could not explain why different elements have different chemical
properties.
(a) Fresh water supplies hydrogen and oxygen to plants.
(b) It provides enough moisture to the soil for the germination of seeds.
(c) Irrigated soil is soft and new roots can penetrate and grow very well.
(d) It causes an increase in the number of tillers in crop plants, as they cannot grow in
dry soil.
(e) It helps in the absorption of minerals and salts by roots which are necessary for the
growth and development of plants.

8.
(a) Naphthalene easily undergoes sublimation, i.e. change of state of naphthalene from
solid to gas without the intervening liquid state. Thus, naphthalene balls form
naphthalene vapour which disappears into the air with time without leaving any
solid residue.
(b) Gaseous particles possess high speed and move very rapidly in all directions.
When perfume is sprayed, its particles diffuse into the particles of air at a very fast
rate and reach our nostrils. This enables us to smell the perfume from a distance.
(c) After a hot sunny day, people sprinkle water on the roof or open ground because the
large latent heat of vaporisation of water helps to cool the hot surface.
9. The body experiences uniform velocity if it travels in a specified direction in a straight
line and moves over equal distances in equal intervals of time.
Two ways to change the velocity of a body:
i) Change the speed of the body
ii) Keep the speed constant and change the direction

CBSE IX | SCIENCE
Sample Paper – 8 Solution

10. Balanced force is a force where the resultant of all the forces acting on a body is zero.
Unbalanced force is a force where the resultant of all the forces acting on a body is not
zero.
A child applies a force of 20 N and the force applied by the object on the ground is 20 N;
thus, the net force applied on the body will be zero.
As the total net force on the object is zero. The force applied on it was a balanced force.

11. Pressure is the ratio of force (F) exerted by a body to the area (A) upon which the body
is exerting the force. Also, weight (W) is the force exerted by a body due to the Earth’s
gravitational pull, i.e. F = W.

?
?
? ? ? ?
2
W mg
Acceleration due to gravity (g) 10 m / s
W 5 10 50 N
?
? ? ?
? ? ? ?
? ? ?
22
Force (F)
Pressure (P) =
Area (A)
i) for the surface of 50 25 cm to be in contact with the floor.
Area of the surface that is in contact with the floor (A)= b 50 25
A 50 25 1250 cm 0.125 m
50
P 40
0.125
0 Pa

Pressure exerted by the block on the floor is 400 Pascal.

?
? ? ?
? ? ? ?
? ? ?
22
ii) for the surface of 75 50 cm to be in contact with the floor.
Area of the surface that is in contact with the floor (A)= b 75 50
A 75 50 3750 cm 0.375 m
50
P 133.3 Pa
0.375

Pressure exerted by the block on the floor is 133.3 Pascal.
Page 4

CBSE IX | SCIENCE
Sample Paper – 8 Solution

CBSE
Class IX Science
Sample Paper – 8 Solution

Section A
1. The main objective of mixed cropping is to reduce the risk of crop failure due to adverse
weather.

2. Processes which play an important role in the oxygen cycle:
(a) Photosynthesis
(b) Respiration

Section B

3. The ozone layer absorbs harmful ultraviolet radiations emitted by the Sun and prevents
them from reaching the surface of the Earth, as these radiations cause harmful effects to
human beings, plants and animals.

4. A car is moving with a velocity of 20 m/s.
2
22
2
u 20 m/s
The body comes to rest after applying the brakes
v = 0
acceleration = -1m/s
Distance covered (s)= ?
by using the 3 kinematical equation we get,
v u 2as
0 20 2 ( 1)
0 400 2
24
??
?
??
? ? ? ? ? ?
? ? ?
??
rd
s
s
s 00
400
s = 200 metres.
2
??

OR
u = 0.6 m/s
a= - 0.05 m/s
2
(deceleration)
t = ?
v = u + at
0 = 0.6 + (-0.05) x t
Thus, t = -0.6/(0.05) = 12 s
Thus, it takes the body 12 s to come to rest.

CBSE IX | SCIENCE
Sample Paper – 8 Solution

5. An ion is a charged particle which can be negatively or positively charged.
In NaCl:
Cation Anion
Name Sodium Chloride
Symbol Na
+
Cl
-

Section C

6. Limitations of Thomson's atomic model:
? Although Thomson's atomic model explained why an atom is electrically neutral, it
could not explain the distribution of electrons in the atom.
? If we accept that electrons are embedded in the positive charge, then the opposite
electric charges should cancel each other out and the charged sphere would become
chargeless.
? Thomson's model could not explain why different elements have different chemical
properties.
(a) Fresh water supplies hydrogen and oxygen to plants.
(b) It provides enough moisture to the soil for the germination of seeds.
(c) Irrigated soil is soft and new roots can penetrate and grow very well.
(d) It causes an increase in the number of tillers in crop plants, as they cannot grow in
dry soil.
(e) It helps in the absorption of minerals and salts by roots which are necessary for the
growth and development of plants.

8.
(a) Naphthalene easily undergoes sublimation, i.e. change of state of naphthalene from
solid to gas without the intervening liquid state. Thus, naphthalene balls form
naphthalene vapour which disappears into the air with time without leaving any
solid residue.
(b) Gaseous particles possess high speed and move very rapidly in all directions.
When perfume is sprayed, its particles diffuse into the particles of air at a very fast
rate and reach our nostrils. This enables us to smell the perfume from a distance.
(c) After a hot sunny day, people sprinkle water on the roof or open ground because the
large latent heat of vaporisation of water helps to cool the hot surface.
9. The body experiences uniform velocity if it travels in a specified direction in a straight
line and moves over equal distances in equal intervals of time.
Two ways to change the velocity of a body:
i) Change the speed of the body
ii) Keep the speed constant and change the direction

CBSE IX | SCIENCE
Sample Paper – 8 Solution

10. Balanced force is a force where the resultant of all the forces acting on a body is zero.
Unbalanced force is a force where the resultant of all the forces acting on a body is not
zero.
A child applies a force of 20 N and the force applied by the object on the ground is 20 N;
thus, the net force applied on the body will be zero.
As the total net force on the object is zero. The force applied on it was a balanced force.

11. Pressure is the ratio of force (F) exerted by a body to the area (A) upon which the body
is exerting the force. Also, weight (W) is the force exerted by a body due to the Earth’s
gravitational pull, i.e. F = W.

?
?
? ? ? ?
2
W mg
Acceleration due to gravity (g) 10 m / s
W 5 10 50 N
?
? ? ?
? ? ? ?
? ? ?
22
Force (F)
Pressure (P) =
Area (A)
i) for the surface of 50 25 cm to be in contact with the floor.
Area of the surface that is in contact with the floor (A)= b 50 25
A 50 25 1250 cm 0.125 m
50
P 40
0.125
0 Pa

Pressure exerted by the block on the floor is 400 Pascal.

?
? ? ?
? ? ? ?
? ? ?
22
ii) for the surface of 75 50 cm to be in contact with the floor.
Area of the surface that is in contact with the floor (A)= b 75 50
A 75 50 3750 cm 0.375 m
50
P 133.3 Pa
0.375

Pressure exerted by the block on the floor is 133.3 Pascal.

CBSE IX | SCIENCE
Sample Paper – 8 Solution

OR
?
??
?
?
11
1
22
1
2
2
2
Gravitation constant G  6.7 10 Nm / kg
Mass of 1st box
The for
(m ) 15 kg
ce of gravitation is ca
Mass of 2nd
lculated by
box(m ) = 25 kg
the box
using the eq
es are lying
ua
o
tion
mm
F = G
n the
r
floor
? ?
?
?
??
?
??
? ? ?
11
2
11
at the distance of 20cm
from one another.
r 20 cm
Substituting all the relevant values in the above equation
15 25
F = 6.7 10
20
F 6.28 10 N

12.

OR
Atomicity: Number of atoms in a single molecule of an element is called atomicity.
Name of element Atomicity
Neon Monoatomic
Nitrogen Diatomic
Phosphorus Tetra-atomic
Sulphur Poly-atomic

Page 5

CBSE IX | SCIENCE
Sample Paper – 8 Solution

CBSE
Class IX Science
Sample Paper – 8 Solution

Section A
1. The main objective of mixed cropping is to reduce the risk of crop failure due to adverse
weather.

2. Processes which play an important role in the oxygen cycle:
(a) Photosynthesis
(b) Respiration

Section B

3. The ozone layer absorbs harmful ultraviolet radiations emitted by the Sun and prevents
them from reaching the surface of the Earth, as these radiations cause harmful effects to
human beings, plants and animals.

4. A car is moving with a velocity of 20 m/s.
2
22
2
u 20 m/s
The body comes to rest after applying the brakes
v = 0
acceleration = -1m/s
Distance covered (s)= ?
by using the 3 kinematical equation we get,
v u 2as
0 20 2 ( 1)
0 400 2
24
??
?
??
? ? ? ? ? ?
? ? ?
??
rd
s
s
s 00
400
s = 200 metres.
2
??

OR
u = 0.6 m/s
a= - 0.05 m/s
2
(deceleration)
t = ?
v = u + at
0 = 0.6 + (-0.05) x t
Thus, t = -0.6/(0.05) = 12 s
Thus, it takes the body 12 s to come to rest.

CBSE IX | SCIENCE
Sample Paper – 8 Solution

5. An ion is a charged particle which can be negatively or positively charged.
In NaCl:
Cation Anion
Name Sodium Chloride
Symbol Na
+
Cl
-

Section C

6. Limitations of Thomson's atomic model:
? Although Thomson's atomic model explained why an atom is electrically neutral, it
could not explain the distribution of electrons in the atom.
? If we accept that electrons are embedded in the positive charge, then the opposite
electric charges should cancel each other out and the charged sphere would become
chargeless.
? Thomson's model could not explain why different elements have different chemical
properties.
(a) Fresh water supplies hydrogen and oxygen to plants.
(b) It provides enough moisture to the soil for the germination of seeds.
(c) Irrigated soil is soft and new roots can penetrate and grow very well.
(d) It causes an increase in the number of tillers in crop plants, as they cannot grow in
dry soil.
(e) It helps in the absorption of minerals and salts by roots which are necessary for the
growth and development of plants.

8.
(a) Naphthalene easily undergoes sublimation, i.e. change of state of naphthalene from
solid to gas without the intervening liquid state. Thus, naphthalene balls form
naphthalene vapour which disappears into the air with time without leaving any
solid residue.
(b) Gaseous particles possess high speed and move very rapidly in all directions.
When perfume is sprayed, its particles diffuse into the particles of air at a very fast
rate and reach our nostrils. This enables us to smell the perfume from a distance.
(c) After a hot sunny day, people sprinkle water on the roof or open ground because the
large latent heat of vaporisation of water helps to cool the hot surface.
9. The body experiences uniform velocity if it travels in a specified direction in a straight
line and moves over equal distances in equal intervals of time.
Two ways to change the velocity of a body:
i) Change the speed of the body
ii) Keep the speed constant and change the direction

CBSE IX | SCIENCE
Sample Paper – 8 Solution

10. Balanced force is a force where the resultant of all the forces acting on a body is zero.
Unbalanced force is a force where the resultant of all the forces acting on a body is not
zero.
A child applies a force of 20 N and the force applied by the object on the ground is 20 N;
thus, the net force applied on the body will be zero.
As the total net force on the object is zero. The force applied on it was a balanced force.

11. Pressure is the ratio of force (F) exerted by a body to the area (A) upon which the body
is exerting the force. Also, weight (W) is the force exerted by a body due to the Earth’s
gravitational pull, i.e. F = W.

?
?
? ? ? ?
2
W mg
Acceleration due to gravity (g) 10 m / s
W 5 10 50 N
?
? ? ?
? ? ? ?
? ? ?
22
Force (F)
Pressure (P) =
Area (A)
i) for the surface of 50 25 cm to be in contact with the floor.
Area of the surface that is in contact with the floor (A)= b 50 25
A 50 25 1250 cm 0.125 m
50
P 40
0.125
0 Pa

Pressure exerted by the block on the floor is 400 Pascal.

?
? ? ?
? ? ? ?
? ? ?
22
ii) for the surface of 75 50 cm to be in contact with the floor.
Area of the surface that is in contact with the floor (A)= b 75 50
A 75 50 3750 cm 0.375 m
50
P 133.3 Pa
0.375

Pressure exerted by the block on the floor is 133.3 Pascal.

CBSE IX | SCIENCE
Sample Paper – 8 Solution

OR
?
??
?
?
11
1
22
1
2
2
2
Gravitation constant G  6.7 10 Nm / kg
Mass of 1st box
The for
(m ) 15 kg
ce of gravitation is ca
Mass of 2nd
lculated by
box(m ) = 25 kg
the box
using the eq
es are lying
ua
o
tion
mm
F = G
n the
r
floor
? ?
?
?
??
?
??
? ? ?
11
2
11
at the distance of 20cm
from one another.
r 20 cm
Substituting all the relevant values in the above equation
15 25
F = 6.7 10
20
F 6.28 10 N

12.

OR
Atomicity: Number of atoms in a single molecule of an element is called atomicity.
Name of element Atomicity
Neon Monoatomic
Nitrogen Diatomic
Phosphorus Tetra-atomic
Sulphur Poly-atomic

CBSE IX | SCIENCE
Sample Paper – 8 Solution

13.
(a) Measures for the prevention of diseases caused by mosquitoes:
? Avoid water logging
? Ensure proper and regular disinfection
? Promote the use of mosquito nets and repellents
(b) Values displayed by Seema in taking the initiative: (any two)
? Community service
? Social responsibility
? Environmental protection
? Awareness about healthy living conditions
(c) School activities to promote values in school students:
? Organising campaigns for creating awareness among the masses
? Organising debates
? Arranging similar community services
? Group discussion

14.
(a) When surrounded by a hypotonic solution, the cell takes up water by osmosis.
(b) The cell swells, building up pressure against the cell wall.
(c) The cell wall exerts an equal pressure against the swollen cell.
(d) Because of the cell wall, such cells can withstand hypotonic solutions to a great
extent.
OR
Different cells of our body assume different sizes and shapes to perform certain
specific functions. Our complex body carries out a wide range of functions. If all the
cells of our body were of the same size, shape and volume, then they would all
perform the same function and the other important functions would not be carried
out, making human life impossible.

15.
(a) During the day, the air above the land gets heated up faster and starts rising.
(b) As this air rises, a region of low pressure is created and the air above the sea moves
into this area of low pressure. The direction of the wind would be from the sea to
the land.
(c) During the night, both land and sea begin to cool. Since water cools down slower
than the land, the air above the sea would be warmer than the air above the land. As
a result, the wind current is from the land to the sea.

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