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No part of this book may be reproduced or transmitted in any form or by any means, C.D. ROM/Audio Video Cassettes or electronic, mechanical
including photocopying; recording or by any information storage and retrieval system without permission in writing from the Publisher.
STD. IXScience
andTechnology
Written as per the revised syllabus prescribed by the Maharashtra State Board
of Secondary and Higher Secondary Education, Pune.
TEID : 881
Printed at: Repro India Ltd., Mumbai
Fifth Edition: April 2015
Salient Features
• Written as per the new textbook.
• Exhaustive coverage of entire syllabus in question answer format.
• Covers answers to all textual questions, intext questions and activities.
• Includes Questions based on diagrams / flow-charts.
• Includes Higher Order Thinking Skills (HOTS).
• Ample Solved and Practice Problems.
• Neat and labelled diagrams.
• Attractive layout of the content.
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Preface
In the case of good books, the point is not how many of them you can get through, but rather how many can
get through to you.
Science is the observation, identification, experimental investigation and theoretical explanation of
phenomenon. It is the study of physical, chemical and biological aspects of natural phenomenon. It dealswith inherent properties of space, matter, energy and their interactions.
Technology is the application of scientific knowledge for the benefit of mankind. It includes the use of
materials, tools, techniques and knowledge to make life more pleasant and work more productive. Whereasscience is concerned with how things happen, technology focuses on making things happen.
The study of Science and technology requires a deep and intrinsic understanding of concepts. Hence to ease
this task we bring to you “Std. IX: Science and Technology” a complete and thorough guide extensivelydrafted to boost the students confidence. The topicwise question and answer format of this book helps the
student to understand each and every concept thoroughly. It includes all the important definitions, laws and
formulae. Neat and labelled diagrams are provided wherever necessary. Numerical problems at the end ofrelated topics help the students to understand the technique of solving numerous problems efficiently.
Lastly, I would like to thank all those who have helped me in preparing this book. There is always room forimprovement and hence we welcome all suggestions and regret any errors that may have occurred in the
making of this book.
A book affects eternity; one can never tell where its influence stops.
Best of luck to all the aspirants!
From
Publisher
No. Chapter Name Page No.
1 World of Matter 1
2 Understanding Matter 14
3 Inside the Atom 26
4 Counting Matter 38
5 Cell: The unit of Life 50
6 Life: Simple and Complex 70
7 Life Around You 94
8 Highway to Health 117
9 Quality Food, Quality Life 142
10 Moving Objects 166
11 The Laws of Motion 183
12 The Pull of the Earth 198
13 Why Bodies Float 212
14 Energy : The Driving Force 225
15 The Music of Sound 243
16 Bonding with Ecosystems 260
17Solid Waste – Ecofriendly
Management273
ont nts
Note: Textual Questions are represented by * mark.
Intext Questions are represented by # mark.
Section A : Chapter No. 3, 4, 10, 11, 12, 13, 14, 15, 16
Section B : Chapter No. 1, 2, 5, 6, 7, 8, 9, 17
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Answer the following questions
in one sentence each
17. ______ is a sublimatory substance.
(A) Iodine
(B) Sodium chloride
(C) Potassium permanganate
(D) Calcium oxide
1.6 Absorption of heat
18. The outer side of the container of a solar
cooker is painted ______.
(A) blue (B) black
(C) white (D) red
19. Cricketers playing a test match wear ______
clothes.
(A) blue (B) black
(C) white (D) red
20. Traditionally umbrellas are ______ in colour.
(A) yellow (B) blue
(C) white (D) black
1.1 Properties of matter
1. The ______ of an object gives an indication of
the amount of matter that an object contains.
2. Matter occupies ______.
3. ______ is made up of very tiny particles.
4. Matter has ______ and ______.
1.2 States of matter
*5. We usually find matter in ______, ______ and
______ forms.
6. The particles in a solid are bound to each other
by a ______.
7. Particles of a solid cannot move much. This is
one of the ______ characteristics of solids.
8. Less viscous liquids ______ easily.
9. Liquefied Petroleum Gas (LPG) cylinders are
used at home and ______ cylinders are used invehicles.
10. ______ spread out to fill the container.
11. ______ can be easily compressed.
1.3 Change of state
*12. On heating, solids get converted to ______
and ______ get converted to gases.
13. ______ describes a physical state of matter.
14. The fourth state of matter is ______.
15. Our body temperature is measured in a unit
called ______.
16. The boiling point of water is ______ C.
1.4 Evaporation, cooling by evaporation,
condensation
17. All liquids can evaporate at ______
temperature under normal air pressure.
18. ______ is the process which creates clouds.
1.5 Sublimation
*19. ______ and ______ are sublimatory
substances.
20. Out of sand and iodine, sand is a ______
substance.
1.6 Absorption of heat
21. ______ enters the object and warms it.
Answers
1. mass 2. space
3. Matter 4. volume, mass
5. solid, liquid, gaseous 6. force
7. physical 8. flow
9. Compressed Natural Gas (CNG)
10. Gases
11. Gases 12. liquids, liquids
13. Phase 14. plasma
15. Fahrenheit 16. 100
17. room 18. Condensation
19. Camphor, naphthalene balls
20. non-sublimatory
21. Heat
1.0 Introduction
1. What is matter?Ans: Anything that occupies space, has mass and
can be perceived through our senses is called
matter.
1.1 Properties of matter
2. What is density?
Ans: Density is the ratio of mass to volume.
Density (d) =Mass(m)
Volume(v)
Fill in the Blanks
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1.2 States of matter
2. State the characteristics of solids.
Ans: Characteristics of solids:
i. Solids have a definite shape and volume.
ii. Most of the solids are rigid, while some
are elastic.iii. Solids are almost incompressible, i.e.,
their volume and shape is not changed
by external force.
iv. The particles in a solid are closely
packed.
*3. Why do solids have definite shape?
Ans: Solids have definite shape because:
i. The particles of solids are very close to
each other.
ii. The forces holding these particles are
strong.
4. What is elasticity of solids?
Ans: Elasticity of solids:
i. When an external force is applied to a
solid, it undergoes a change in its
volume and shape.
ii. When this external force is removed, the
solid regains its original shape and
volume.
iii This property of solids is known as
elasticity.
Eg. Rubber band, spring, etc.
5. State the characteristics of liquids.Ans: Characteristics of liquids:
i. Liquids have a definite volume.
ii. Liquids flow and have the property of
viscosity.
iii. Liquids cannot be compressed easily.
iv. Liquids do not have a definite shape.
They take the shape of the container in
which they are kept.
6. State the characteristics of gases.
Ans: Characteristics of gases:
i. Gases flow.ii. Gases are highly compressible.
iii. Gases spread everywhere in the
available space.
iv. Gases do not have definite shape and
volume.
#7. It is easier to walk through air than
through water. Why is it so?
Ans: i. Air is in gaseous state and water is in
liquid state.
ii. In air, the particles are so far apart that
the resistance offered by them is
negligible.
iii. In water, the particles are closer than in
air and the resistance offered by them is
more than that of air.
Hence, it is easier to walk through air thanthrough water.
1.3 Change of state
*8. What is the physical state of water at:
i. 257 °C ii. 100 °C
iii. 0 °C
Ans: i. At 257 °C, water is in gaseous state.
ii. At 100 C, water co-exists in liquid and
gaseous state.
iii. At 0 C, water co-exists in the solid
and liquid state.9. Why do temperature of a substance
remains constant while changing from one
state to another?
Ans: i. When substance changes from one state
to another distance between two
molecules get increased.
ii. While changing state heat provided tosubstance is utilised in increasing
distance between the molecules of
substance.
1.4 Evaporation, cooling by evaporation,condensation
10. Why does a desert cooler cools better on a
hot dry day?
Ans: i. On a hot dry day, the temperature is
higher. Thus, there is more dryness in
the surrounding air (i.e. relative
humidity of the air is low).
ii. At a high temperature, rate of
evaporation is more. Thus, a desert
cooler produces more cooling which
results in large fall in the temperature ofits surrounding air.
Hence, a desert cooler cools better on a hot
dry day.
#11. We find dew drops, especially in the early
morning on the leaves. Why?
Ans: i. The temperature of air during the early
morning is generally low.
ii. As the temperature falls, the capacity of
air to hold water vapour becomes less.
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iii. During cold nights, the temperature of
air may fall to dew point or below the
dew point.
iv. Thus, excess of water vapour in air
condenses to form drops which falls on
the leaves at night.Hence, we find dewdrops, especially in the
early morning on the leaves.
1.6 Absorption of heat
#12. Why do we paint the outer side of the
container of a solar cooker with black
paint?
Ans: i. In a solar cooker, the food is cooked due
to the heat energy obtained from the
sun.
ii. Black surface absorbs about 98% of the
incident heat radiation that falls on it.
iii. Due to this, the temperature of the solar
cooker increases and the food is cooked
properly.
Hence, we paint the outer side of the container
of a solar cooker with black paint.
#13. Why do cricketers playing test match wear
white clothes?
Ans: i. White clothes reflect most of the radiant
heat falling on them.
ii. Therefore, cricketers do not feel hot
even though it is hot outside.
Hence, cricketers playing test match wear
white clothes.
#14. Traditionally umbrellas are black in colour.
Why are they better than coloured ones?
Ans: i. A black body is a perfect absorber of
heat radiation.
ii. So, the black coloured umbrella absorbsthe heat radiations and does not allow
heat radiations to pass through.
Hence, black umbrellas are better than
coloured ones.
#15. When you go for trekking, which coloured
cap do you prefer to use?
Ans: When I go for trekking, I prefer to use white
coloured cap.
#16. In the state of Rajasthan the temperatures
are very high in summer. Which colour for
the roof is preferable in such regions?
Ans: In Rajasthan, where the temperature is very
high in summer, white colour for the roof is
preferable.
1.3 Change of state
1. Describe the change of phase or change of
state of matter when energy is supplied or
taken away from a substance.
Ans: Change of phase:
i. The phase or state of matter can change
when the temperature changes.
ii. When the temperature is increased, solid
gets converted into liquid and liquid gets
converted into gas.
iii. As the temperature rises, matter moves
to a more active state.
iv. Phase describes a physical state of
matter. Things only move from one
phase to another by physical means.
v. If energy is supplied (like increasing
the temperature or decreasing the
pressure) or if energy is taken away
(like freezing something or increasing
the pressure), a physical change is
created.
*2. The smell of hot sizzling food reaches you
several meters away, but to get the smell
from cold food, we have to go close. Why?
Ans: i. Gases from the hot sizzling food mix
with air easily in the form of vapour.
ii. The molecules of vapour have a lot of
energy. So, these molecules spread
around in all the directions.
+E+E
+E
SolidLiquid
GasPlasma
Each addition of
energy creates achange in state
Answer in brief
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iii. But molecules of gases from cold food
cannot mix easily with air as molecules
have low energy due to its lowtemperature.
Hence, we have to go close to get the smell
from cold food.
1.4 Evaporation, cooling by evaporation,condensation
3. How does the condensation and
evaporation process keep the earth’s
climate balanced?
Ans: i. Condensation is the formation of liquid
drops from vapour.
ii. It usually occurs when a parcel of rising
air expands and cools.
iii. If it cools enough, some of the water
vapour molecules clump together at a
faster rate.iv. This process creates clouds which
results in rain and snow, causing the
earth’s climate to become cooler.
v. When cloud form heat removed from
the earth’s surface through evaporation
is released again in atmosphere.
1.5 Sublimation
#4. How would you separate the mixture of
sand and iodine crystals?
Ans: i. In the mixture of sand and iodine
crystals, iodine is a sublimatory and
sand is a non-sublimatory substance.ii. By using sublimation method, we can
separate the constituents of this mixture.
iii. Take this mixture in a china dish.
iv. Put an inverted gas funnel over it. Place
a cotton plug in its stem.
v. Heat the china dish. Iodine sublimates
and its vapours get condensed on the
inner side of the funnel and cotton plug.
Sand remain in the china dish.
1.4 Evaporation, cooling by evaporation,
condensation
1. EvaporationAns: i. Evaporation is the process by which a
liquid gets converted into gaseous form
at any temperature below its boiling
point.
ii. All liquids evaporate at room
temperature and normal air pressure.
iii. In this process, atoms or molecules
escape from the liquid and turn into
vapour.
iv. There are always a few atoms or
molecules with a lot of energy and some
with very low energy.v. The atoms or molecules with lot of
energy are able to build up enough
energy to get converted into gaseous
state.
vi. Once they reach that energy level, they
leave the liquid state. When the atoms or
molecules leave the liquid, we say it has
evaporated.
vii. The rate of evaporation depends upon
the surface area, temperature, humidity,
wind speed, etc.
1.2 States of matter
1. Solids are rigid.
Ans: i. In solids, the particles are closely
packed together and the forces holding
these particles are strong.
ii Solids are almost incompressible.
iii. Their volume is not changed by any
outside force.iv. Their shape remains unchanged even if
an external force is applied.
Hence, solids are rigid.
2. Gases are more compressible than liquids.
Ans: i. In liquids, the distance between the
neighbouring particles is less than those
in the gases.
ii. In gases, the particles spread out to fill
the container.
Inverted funnel
Iodine
China dish
Burner
Cotton plug
Write short notes on
Give scientific reasons
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iii. The forces of attraction between the
particles are extremely weak in gases,
there are no forces to stop them fromgoing apart but not so weak in liquids.
Hence, gases are more compressible thanliquids.
3. Some liquids like honey flow slowly, while
other liquids such as kerosene flow rapidly.
Ans: i. The differences in flow rate is due to the
property of viscosity.
ii. The viscosity of honey is greater than
that of kerosene.
iii. More viscous a liquid, less is its rate of
flow.
Hence, some liquids like honey flow slowly,
while other liquids such as kerosene flow
rapidly.
*4. A gas exerts pressure on the walls of aclosed container.
Ans: i. In the gaseous state, the particles of a
gas move with a very high speed in alldirections.
ii. As the forces of attraction between the particles of a gas are very weak, they
move fast and collide with the walls of
the container, where a pressure is
created.
Hence, a gas exerts pressure on the walls of a
closed container.
*5. In LPG cylinder, the gas filled is in the
liquefied state.
Ans: i. Gases are highly compressible. They
can be compressed into very small
volumes by applying large pressure.
ii. Gases are liquefied by lowering their
temperature and applying high pressure
where they get compressed. This
process converts the gas into a liquid.
iii. As a result, small LPG cylinders can
contain more gas if it is in liquid form.
Such cylinders can be easily
transported from one place to another.Hence, in LPG cylinder, the gas filled is in the
liquefied state.
1.4 Evaporation, cooling by evaporation,
condensation
#6. In summer, we wear cotton clothes.
Ans: i. The temperature of the surroundings
becomes very high in summer due to
which we feel hot.
ii. Cotton clothes absorb sweat.
iii. Heat is taken from the body for
evaporation of sweat.
iv. Thus, due to evaporation of sweat body
temperature remains constant.
Hence, we use cotton and light coloured
clothes in summer.
7. The tea in a saucer gets cooled faster than
in a cup.
Ans: i. When we pour very hot tea in a saucer,
it cools quickly due to the process of
evaporation.
ii. Evaporation takes place only at the
surface of a liquid. The rate ofevaporation is directly proportional to
the surface area of a liquid.
iii. The exposed surface area of saucer is
greater than the exposed surface area ofa cup.
Hence, tea poured in a saucer gets cooled
faster than in a cup.
1.5 Sublimation
8. Naphthalene balls disappear over a period
of time, without leaving behind any solid
particles.
Ans: i. Naphthalene balls sublimate at room
temperature.
ii. All its molecules go into vapour phasewithout changing into liquid.
iii. This process takes place when
naphthalene balls absorb heat energy
from the surrounding, which occurs
slowly but continuously.
Hence, naphthalene balls disappear over a
period of time, without leaving behind any
solid particles.
1. The fifth state of matter.
2. The unit which is used to measure the body
temperature.
3. The scientist who discovered the Fahrenheit
scale.
4. A substance which is used as fuel in vehicles.
5. A substance which is used as ideal domestic
fuel in our home.
Name the following
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Answers
1. Bose-Einstein condensate
2. Fahrenheit
3. Gabriel Daniel Fahrenheit
4. CNG (Compressed Natural Gas)
5. LPG (Liquefied Petroleum Gas)
1. Two objects can occupy the same space at the
same time.
2. When kerosene and water are mixed together,
water will form the upper layer.
3. The particles of a solid cannot move much.
4. Some liquids flow easily as compared to otherliquids.
5. Liquids do not have a definite volume.
6. Gases cannot be compressed easily.
7. It is easier to walk through water than air.
8. Water freezes at 100C.
9. The absorption of energy from the surrounding
reduces the temperature of the surrounding.
10. The rate of evaporation increases with
increase in humidity.
11. Condensation is the process which creates
clouds.
Answers
1. False: Two objects cannot occupy the same
space at the same time.
2. False: When kerosene and water are mixedtogether, kerosene will form the upper layer.
3. True
4. True
5. False: Liquids have a definite volume.
6. False: Gases can be compressed easily.
7. False: It is easier to walk through air than water.
8. False: Water freezes at 0C.
9. True10. False: The rate of evaporation decreases with
increase in humidity.
11. True
1. Water, Kerosene, Sugar, Milk
2. Stone, Common salt, Ice, Oil
3. Sodium, Hydrogen, Oxygen, Nitrogen
4. Sulphur, Phosphorous, Magnesium, Chlorine
5. Camphor, Iodine, Ammonia, Ammonium
chloride
Answers
1. Sugar: Others are liquids.
2. Oil: Others are solids.3. Sodium: Others are gases.
4. Chlorine: Others are solids.
5. Ammonia: Others are sublimatory substances.
1. Solids 2. Rigid solids
3. Elastic solids 4. Liquids
5. Less viscous liquids
6. Higher viscous liquids
7. Gases
8. Sublimatory substances
Answers
1. Blackboard, Ice
2. Stone, Iron
3. Rubber band, Spring
4. Milk, Oil
5. Water, Kerosene
6. Honey, Lubricants
7. Hydrogen, Oxygen
8. Iodine, Camphor
1. Wooden block: Solid :: Milk: …….
2. Stone: Rigid :: Spring: …..
3. Dust: Solid :: Carbon dioxide: ……
4. Solid: Incompressible :: Gas: ..…..
5. Water: Liquid :: Water vapour: ……..
6. The melting point of solid oxygen: 218.4 °C
:: Melting point of glucose: ..…….
7. Boiling point of water: .......... :: Freezing point
of water: 0 °C
8. Ammonium chloride: Sublimatory substance ::Sodium chloride: ……..
Answers
1. Liquid
2. Elastic
3. Gas 4. Compressible
5. Gas 6. 150 °C
7. 100 °C
8. Non-sublimatory substance
State whether the following
statements are true or false,
If false rewrite the correct
statement
T F
Find the odd man out
Give two examples of
Complete the analogy
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1.
No. Column I Column II
i. Solids a. High compressibility
ii. Liquids b. Incompressible
iii. Gases c. Low compressibility
Ans: (i – b), (ii – c), (iii – a)
2.
No. Column I Column II
i. Solid converts into liquid a. Evaporation
ii. Gas converts into liquid b. Freezing
iii. Liquid converts into gas c. Melting
iv. Liquid converts into solid d. Condensation
Ans: (i – c), (ii – d), (iii – a), (iv – b)
*3.
No.State of
matterA B
1. Gas a. Soil i. Milk
2. Solid b. Kerosene ii. Oxygen
3. Liquidc. Carbon
monoxide
iii. Peas
Ans: (1 – c - ii), (2 – a - iii), (3 – b - i)
1. Solids and Liquids
Solids Liquids
i. Solids have definite
shape.
Liquids do not have
definite shape.
ii. Solids are almost
incompressible.
Liquids are less
compressible.
iii Solids do not flow. Liquids flow.
Eg. Sugar, stone Water, milk
2. Liquids and Gases
Liquids Gases
i. Liquids have
definite volume.
Gases do not have
definite volume.
ii. Liquids have very
low compressibility.
Gases have high
compressibility.
iii Liquids flow upto
certain extent.
Gases flow
everywhere in the
available space.
Eg. Water, kerosene Hydrogen, oxygen
3. Solids and Gases
Solids Gases
i. Solids have definite
shape.
Gases do not have
definite shape.
ii. Solids have definite
volume.
Gases do not have
definite volume.
iii. Solids are
incompressible.
Gases are highly
compressible.
Eg. Table, iron Nitrogen, chlorine
4. Evaporation and Boiling
Evaporation Boiling
i. It takes place at all
temperatures.
It takes place only at
the boiling point.
ii. It causes cooling. It does not cause
cooling.
1. Sample structure of a solid
Ans:
2. Effort needed to compress solid, liquid and
gas
Ans:
More Less
Effort Needed to Compress
GasSolid Liquid
Match the following
Distinguish between the
following pairs
Draw neat & labelled
diagrams of the following
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3. Condensation due to the expansion of air
Ans:
4. Condensation due to direct cooling of air
Ans:
1. In the following figure water changes into
ice:
a. Which type of change is observed in
the process?
b. For this change of state, is energy
released or absorbed?
Ans: a. Changing of water into ice is a physical
change.
b. In freezing (i.e., in conversion of water
to ice), energy is taken away from water.
So, water releases energy to get
converted into ice.
2. In the following figure, water changes to
hydrogen peroxide:
a. Which type of change is observed in
the process?
b. Is this change reversible?
Ans: a. In the process, chemical change is observed.
b. Changing of water into hydrogen
peroxide is not reversible change.
#1. Classify the following into solids, liquids
and gases: Air, bench, kerosene, bag, bottle,
chalk, brass, water vapour, blackboard,
dust, table, soil, chair, water, door, pen,milk, eraser, petrol, book, windowpanes,
ice, diesel, carbon dioxide, cupboard,
oxygen, mercury.
Ans:
Solids Liquids Gases
Bench, bag, bottle,
chalk, brass,
blackboard, dust,
table, soil, chair,
door, pen, eraser,
book,
windowpanes, ice,cupboard
Kerosene, water,
milk, petrol,
diesel, mercury
Air,
water
vapour,
carbon
dioxide,
oxygen
#2. Suggest one scientific word for all of the
following changes:
i. Solid wax converts into liquid wax.
ii. Ice changes into water.
iii. A plastic bowl kept near the flame,
changes its shape.
iv. Frozen butter is kept outside the
refrigerator.
Ans: Melting
y Activity … II (Textbook page no. 1)
Ans: i. No, we cannot count the number of
particles present in a piece of chalk.
ii. The cotton cloth becomes wet due to
absorption of water.
iii. Yes, we can break the stream of water
with our fingers.
iv. No, it is not possible to fill any more
liquid in the bottle as it is already filled
up to the brim. It is air in the spacewhich was earlier occupied by water.
Activity … III (Textbook page no. 2)
Ans: i. The pebble will sink in water becausethe density of pebble is greater than the
density of water, which is not the case in
plastic spoon.
ii. Dry wood, ice, leaves, kerosene, oil,
etc. are some substances which float on
water.
Water Ice
H2O H2O2
Ice
Water
Liquid water
droplets
Rising air parcel
Activities
Miscellaneous
Questions Based on
Diagrams
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Activity … IV (Textbook page no. 3 and 4)
Ans: Observation:
i. The liquids come down in the order ofdecreasing speed as follows:
kerosene > water > milk > honey
ii. Among the four liquids, honey is themost viscous and kerosene is the least
viscous liquid.
iii. Kerosene, water and milk take the
shape of the container faster.
iv. Honey forms layers and these layers
take the shape of the container slowly.
Conclusion:
Rate of flow of liquids depends on their
viscosity.
Activity ... V (Textbook page no. 4)
Ans: i. Inflated balloons become heavier than
uninflated balloons because air inside
the inflated balloons also has some
mass.
ii. a. Yes, we get the smell of incense
stick in the other corner. When
an incense stick is ignited, its
material starts burning. The
fragrance present in the incense
stick is gaseous and spreads into
the air in the form of smoke. As
gas molecules move faster thanliquid or solid, they reach from
one corner of a room to the other
corner easily and so a person at
the other corner gets its smell.
iii. Perfume is a volatile substance (easily
escapes into air). Thus, the molecules
of the perfume spread everywhere in
the surrounding air. So, Sabiha can
smell the perfume though she is sitting
in a far off corner.
Activity … VI (Textbook page no. 5)Ans: i. Small droplets of the water are
observed on the inner surface of the lid
because water vapours from the tea get
condensed.
ii. In winter morning, the temperature of
atmosphere is very low. The coconut
oil freezes at this temperature and
becomes solid. In the summer
morning, the temperature of
atmosphere is higher as compared to
winter. Thus, oil does not freeze and
remains in the liquid state.
Activity … VII (Textbook page no. 7)
Ans: i. The wet handkerchief kept in the
open space would dry up faster.
ii. The puddle will reduce in size due to
evaporation of water present in it.
iii. We feel cool at the site where spirit
is applied.
iv. We pour very hot tea in saucer to cool
it rapidly. By doing so, the exposed
surface area increases and the rate of
evaporation also increases which
makes the tea cool faster.
v. a. The water kept in an earthen pot
becomes cool due to the process
of evaporation. b. Large number of pores are
present on the surface of
earthen pot. Water comes out
continuously from these pores
into the outside environment.
c. As a result, evaporation takes
place and the temperature of
water in the pot decreases.
d. Hence, the water kept in an
earthen pot (matka) becomes
cool even in summer.
Activity … VIII (Textbook page no. 8)
Ans: i. Camphor is a sublimatory substance.
It sublimates at room temperature and
changes into gaseous state slowly.
Due to this, camphor becomes smaller
in size and finally disappears.
ii. Naphthalene balls sublimate at room
temperature. They absorb heat energy
from the surrounding and convert into
gaseous form. Naphthalene present in
the gaseous form get mixed with air
due to which bad odour in the toilet
vanishes. So, naphthalene balls are
kept in the toilets.
Activity … IX (Textbook page no. 8)
Ans: Ammonium chloride is a sublimatory
substance. When heated, ammonium
chloride changes into gaseous state without
changing into liquid state. Ammoniumchloride, thus, gets deposited inside the
inverted funnel and on the cotton plug.
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Std. IX: Science and Technology
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1. Two vessels contain different types of
liquids A and B. If density of A is two times
that of B and volume of both the liquid
remains same, then which liquid has lessmass?
Ans: B liquid has less mass.
2. X and Y are two substances. They are given
same quantity of heat. X changes its state
from solid to liquid. Y changes its state
from solid to gas.
a. Can X change its state from liquid to
gas when more heat is given?
b. What kind of substance is Y?
Ans: a. If more heat is given, then X can change
its state from liquid to gas.
b. Y is a sublimatory substance.
3. Complete the following chart:
Ans: 1. Solids
2. Liquids
3. Condense into liquids.
Type I: Problems based on
Density(d) =Mass(m)
Volume(v)
#1. What is the density of a wooden block of
mass 4 g and sides 2 cm 3 cm 1 cm?
Ans: Given: m = 4 g, l = 2 cm,
b = 3 cm, h = 1 cm
To find : d = ?
Formula: i. v = l b h
ii. d =m
v
Solution:
From formula (i)
v = 2 cm 3 cm 1 cm
= 6 cm3 From formula (ii)
d =4
6 = 0.67 g/cm3
The density of wooden block = 0.67 g/cm3
2. The mass of an iron block is 150 g and
density is 25 g/cm3. Calculate the volume of
the block.
Ans: Given: m = 150 g, d = 25 g/cm3
To find : v = ?
Formula: d = mv
Solution:
From formula
v =m
d
=3
150g
25g/cm = 6 cm3
The volume of iron block = 6 cm3
3. The density of an object is 30 g/cm3 and its
volume is 8 cm3. Calculate the mass of theobject.
Ans: Given: v = 8 cm3, d = 30 g/cm3
To find : m = ?
Formula: d =m
v
Solution:
From formula
m = d v
= 30 g/cm3 8 cm3
= 240 g
Mass of the object = 240 g
Type II: Problems based on (F 32) 5
9= C
4. The temperature of an object is 20 °C.
Express this temperature in Fahrenheit.
Ans: Given: Celsius temperature (C) = 20 °C
To find : Fahrenheit temperature (F) = ?
Formula: (F 32)
5
9= C
Melt into
liquids.
Sublimate into
gases.
Matter
Gases
can be converted
into
Evaporate into gases.
Freeze into solids
can be converted
into1 2
3
HOTS
Solved Examples
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Solution :
From formula
5F = 9C +160
5F = 9 20 +160
= 180 +160
= 340
F =340
5 = 68 F
Temperature in Fahrenheit = 68 F
5. The temperature of an object is 95 F.
Express this temperature in Celsius.
Ans: Given: Temperature in Fahrenheit (F) = 95 F
To find : Temperature in Celsius (C) = ?
Formula: (F 32) 5
9 = C
Solution:
From formula
C = (95 32) 5
9
= 63 5
9
= 7 5
= 35 °C
Temperature in Celsius = 35 C
Type I
1. The mass and volume of an object are 50 g
and 25 cm3 respectively. Calculate the density
of that object.
2. The volume and the density of an object is 18
cm3 and 4 g/cm3 respectively. Calculate the
mass of that object.
3. Find the volume of an object having mass 27 g
and density 3 g/cm3.
Type II
4. Express the following temperature in
Fahrenheit.
i. 45 °C ii. 60 °C
iii. 15 °C iv. 70 °C
5. Express the following temperature in Celsius.
i 104 °F ii. 122 °F
iii. 194 °F iv. 50 °F
1. 2 g/cm3
2. 72 g
3. 9 cm3
4. i. 113 °F ii. 140 °Fiii. 59 °F iv. 158 °F
5. i. 40 °C ii. 50 °C
iii. 90 °C iv. 10 °C
Practice Problems
Answers to Practice Problems