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CLASS 7 SCIENCE

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rd

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PREFACE In order to maintain a Uniform Education System across the country, many State Boards are implementing a Single Curriculum System via National Council of Educational Research & Training (NCERT). In the best interest of Secondary and Senior Secondary students, the Department of Education in Science & Mathematics (DESM) and NCERT have together developed Exemplar Problems in Science & Mathematics. These include practice questions of various typologies and difficulty levels which aid in in depth learning of concepts. They also contain conceptual problems which are a part of the CBSE Board Syllabus as well as the Syllabus of various Competitive Exams like IIT JEE, NEET, AIIMS, etc. Considering the diversity and the varied difficulty level of questions in these two subjects, we, at Oswaal Books have launched OSWAAL NCERT PROBLEMS-SOLUTIONS. They are a compilation of all the Questions of the Latest Editions of NCERT Textbook & NCERT Exemplar in a Chapter-wise & Topic-wise format along with their complete solutions. These also include Previous Years' Examination Questions fully solved with their respective sources. We believe that OSWAAL NCERT PROBLEMS-SOLUTIONS will help the students in school and after school in practicing and preparing extensively for both, Final Examinations as well as Competitive Examinations with utmost confidence! Some Special Features of Oswaal NCERT Problems-Solutions are: z Chapter-wise & Topic-wise presentation z Chapter Objectives : A sneak peek into the chapter z Mind Map : A single page snapshot of the entire chapter z Quick Review : Concept-based study material z Tips & Tricks : Useful guidelines for attempting each question perfectly z Oswaal QR Codes : For Quick Revision on your Mobile Phones & Tablets We hope that OSWAAL NCERT PROBLEMS-SOLUTIONS will help you at every step as you move closer to your educational goals. We wish you all great success ahead!! All the Best! TEAM OSWAAL

(5)

CONTENTS z

Mind Maps

7 - 24

1. Nutrition in Plants

1- 7

2. Nutrition in Animals

8 - 17

3. Fibre to Fabric

18 - 24

4. Heat

25 - 31

5. Acids, Bases and Salts

32 - 40

6. Physical and Chemical Changes

41 - 47

7. Weather, Climate and Adaptations of Animals to Climate

48 - 53

8. Winds, Storms and Cyclones

54 - 59

9. Soil

60 - 66

10. Respiration in Organisms

67 - 74

11. Transportation in Animals and Plants

75 - 80

12. Reproduction in Plants

81 - 86

13. Motion and Time

87 - 93

14. Electric Current and Its Effects

94 - 100

15. Light

101 - 107

16. Water : A Precious Resource

108 - 113

17. Forests : Our Lifeline

114 - 120

18. Waste-Water Story

121 - 127

‰‰

(6)

M ll

rane

Minerals

ins Vitam

Protein s

S

In this mode of nutrition, organisms obtain nutrition from dead and decaying matters.

Plants which use saprotrophic mode of nutrition.

Nucleus is surrounded by a jelly-like substance called cytopasm.

Rhizobium bacteria which lives in the roots nodules of leguminous plants and fixes atmospheric nitrogen into nitrites and nitrates in the soil.

Cells have distinct centrally located spherical structure called nucleus.

It is a thin flexible layer around the cells of all living things.

Ce

Fat s

M

of ode

? lants

Nutrition

op h otr t Au

In this mode of nutrition Organisms depend on others for their food.

It is a type of pore ope on leave of plan ning ts. Leaves of Plan ts have green p lan t. from wh ich anisms Org sites take their food para .

Meaning It is the process by which green plants and some other organisms Sto use sunlight to synthesize foods m at from carbon dioxide and water.

ic

In this mode of nutrition, Organisms make their food themselves from simple substances.

It is the mode of taking food by an organism and its utilisation by the body.

isms that liv es Organ or on a host. n i h t i w t eating plants. Insec

H os t

is Photosynthes

np ni

tio tri

Nutrition in Plants

Wh

b em

N u cle us

nu at is

The bodies of living organisms are made of tiny units

C y top lasm

CHAPTER : 1 nutrition in plants

ap r otr oph N ic riti on

(7) ut

a

f so e od m s er ts Oth lan p n in nutrit io

(8) Passes chewed food from mouth to stomach

Digestion of food takes place

an

ing

sio

n

I

Partial digestion takes place

nte sti n

e

of

Rumen is a part of stomach in grass eating animals where they store swallowed food.Here food is partially digested.

trients

ma ls

Nu

ydrates to boh cose r a C Glu Prot Amin ei ns t oa o ci d s

Undigested food is completely remove out through anus. Process called Egestion.

Grass Eating Ani

Complete digestion takes place

nt es tin e

Large I

D

n in stio e g i

It includes nutrients requirement mode of intake of food and its utilisation in the body

Nutrition in Animals

ag us

Oe sop h

Amoeba capture the food by false foot pseudopedia and digest in food vacoule.

M e ach Stom

C o nv er

CHAPTER : 2 nutrition in animals

a ll Sm

als w Mohair is obtainedOther anim l o yield wo from Augora goats. The fur of Camels, Llama and Apaca in S. America

Wool is obtained from the fleece of sheep or yak

h hic

Cle

Small fluffy burrs are picked out from the hair.

Fibres are coloured in various dyes

im

r es Fib al

Fibre to Fabric

An The fibres are straightened combed and rolled into yarn.

The hairy skin is sent to a factory where hair of different textures are separated.

f Burrs

The sheared skin with hair is thoroughly washed.

rt in g

arin go

Dyeing

ling Rol

St e p sf or o p f r o fib ces res sin g i n t ow o ol .

So

The fleece of the sheep along with a thin layer of skin removed from its body.

S h ea ri n g

obt ai n ed

e

f ro

m

re ltu u ric

a

Scouring

S

O

ren

ce

(b) Mulberry tree (d) Cocoons

Leaf of mulberry

The female silkmoth lays eggs which hatch into larvas called catterpillar. The next stage pupa, its weaves a net to hold itself called Cocoon. The silk is obtained from Cocoon.

Rearing Silkworms

(c) Larva (Caterpillar/Silkworm) feeding on mulberry leaves

(a) Female silwarm moth with eggs

comes from t he fibres Silk the silkmoth. f o s n o coco

f Silkmoth.

Diag ram

ur cc

go arin Re

Mind map : learning made simple

MIND MAP

ls ma i n

|9

Co ns

fT so d in La bo rat or

yT h

e om rm e h

ter

e

et e om rm

r

K

uct i

It should be kept upright, bulb on should be surrounded from all sides.

ent

u tr

ct i

on

ss

Heat flows from hotter object to colder object.

sf

.

of the heat that falls on them.

c Pro

n tio

When fluid is heated, it carries Convection thermal energy along with it and moves away from the source. This transfer in Convection. Co nd uc tio n Transfer of Heat from one particles to the adjacent particle. In solids, heat is transferred by Conduction.

ia Rad

It is generated by the emission of elecromagnetic waves. It takes place through vaccum or transparent medium.

Dark coloured clothes which absorbs heat and wool is a poor conductors of heat.

mers Light coloured clothes um which reflect most S In

ject of an ob

e is measu red peratur Tem o m m r e e h t T e r. by

emperature for t s e th t or cold) C lo (ho

Tra n

ture

re m su a e

eat

It measures the temperature of objects. The range is -10°C to 110°C.

Constr

ra pe

Heat

Te m

Mind map : learning made simple

e

fH ro

It consists of a long, It measures body narrow, uniform, glass temperature. The tube. It has a bulb at one range is 35°C to end. The bulb contains 42°C. mercury. It also has a kink.

Clinical The

rm o me ter

M

10 | OSWAAL NCERT Solutions Textbook+Exemplar, SCIENCE, CLASS-VII

e

ea kb ases

f so e p Ty

s

In

us extracted Litm he from lic ns Ch i Ros e P na eta l

c di

rs ato

The substances used to test whether a substance is acidic or basic.

Sy n di t c

eu t

ral isat ion

s Acid

N

t An

t bi

Us e s i n ev er y

y

ids

da

c of A

ition fin De

s pe Ty

O

St

s ng s ro cid A k Wea

Excessive use of chemical fertilisers makes the soil acidic. It is treated with baseslike Quick lime or slaked lime.

The reaction between an acid and a base is known as neutralisation. Salt and Water are produced in this process with the evolution of heat.

They have a sour taste and corrosive in nature. A concentratred acid cuts through clothes. Good conductor of electricity.

Mineral Acid s

lif

When an antbite it inject acidic (formic acid). It can be neutralise by rubbing baking soda.

Undigested food causes acidity in stomach. To relieve milk of magnesia is takento neutralise acid.

Acids, Bases and Salts

The Solution which do not change the colour of either red or blue litmus.

phthalein Pheno

s rtie They are soapy to touch. They have Prope bitter taste.They react with acids to neutralises.

n

Natu ral I

I

nd i ca tor s

t he

e

Aci ds

rg an ic

W Ac id

Mind map : learning made simple

MIND MAP

e

ic

s or at

| 11

De fin itio

acteristics Char

r

a lis tal s y

It is the process by which a solid forms, where the atoms and molecules are highly organised into a structure known as Crystals.

C

tion

Curdling of milk Rusting of Iron Burning of wax wick

Changes are permanent and irreversible. They cause release or absorption of energy. New substances with new properties are formed.

An irrevessible chemical reaction involving the rearrangement of the atoms of one or more substances and a change in their chemical properties

n

Physical and Chemical Change

n lva Ga

is

es

Shape size and state can change temporary. No new substance is formed only the arrangement of molecules altered. No energy change takes place.

Melting of Ice involves a change from a solid to a liquid. Boiling of water, Dissolving sugar in water

cteristics

Any change that occurs without altering the chemical composition of a substance is a physical change

Deposition of layer of a metal like chromium or zinc on Iron called galvanisation.

pl

Chara

on

am Ex

n atio

The red or orange coating that forms on the surface of iron when exposed to air and moisture, consisting ferric hydroxide and ferric oxide

Ex am p

les

Mind map : learning made simple

ting Ru s

ni ti

De fi

12 | OSWAAL NCERT Solutions Textbook+Exemplar, SCIENCE, CLASS-VII

p as gr r Long tails fo tree of branches

in

g

d sharp d an e v r n ice. lk o cu a , w g on s t o w cla

st

ak be h e Long and larg nc bra n reach fruits o

s

Polar Bea r

ream lin ed

o

es .

ird

nB

Body is st

Tou

t es

Weather, Climate and Adaptions of Animals to Climate

i

De fin it eg io n

la r Po

R

Sun is the primary source of energy

These regions are covered with snow and it is very cold. For 6 months, the sunsets and the next 6 months, the sunrise.

un

The average weather pattern taken over a longtime, 25 years is called the climate

It is measured by an instrument called rain guage.

The day to day condition of the atmosphere at a place

Clim ate

on

S

Climate is hot and humid because it is located around the equator.

Ad als apt ions in Anim

R

T r o pic al

ca

Birds remain warm to survive, so they migrate to warmer regions, during winters.

fo r

ins gu n Pe

Cli

ai n

L

Mind map : learning made simple

MIND MAP

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e m at

ex er ts p

On heating, air expands and occupies space. The warm air is lighter than cold air, so it rises.

r High speed winds Air pressu re are accompained by regulates w reduced air pressure. inds pe e d

Ai r

Pro p erties of A

ir

by

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A storm of heaving rain accompanied by lightning, thunder, wind and sometimes hail. It occurs when moist air near the ground becomes heated and rises forming cloud that produce precipitation.

Cyclones

Wind, Storms and Cyclones

De

es tru

Moving air is called Wind.

d

It is a violently rotating column of air, in contact with the ground and often visible as a funnel cloud.

re

Thunder storm

Due to this pressure, the leaves of trees, banners flutter when the wind is blowing.

Air moves from the region where direction of the air pressure is high to the region where the pressure is low.

It can damage houses, telephones and other communication systems, trees etc. causing tremendous loss of life and property.

Cyclone is a system of winds rotating inwards to an area of low barometric pressure with an anticlockwise or clockwise circulation.

Bet ween land and w ater

In summers, the land warms up faster and the air over the land gets heated rises, The winds flow from water to land.

The air in equator region becomes warm. The warm air rises and the cooler air from the poles moves in. These winds blow from the north, to south towards the equator.

Mind map : learning made simple

Disasters

su es

To rn a do es

fin itio n

14 | OSWAAL NCERT Solutions Textbook+Exemplar, SCIENCE, CLASS-VII

Moisture

n

r

in s oil

Pe rco lat io

e at

w of

r a te

oil in s Pro p il erties of So

V

cla

d

ixt ur e y w of s ith an hu

M

Soil Eros ion

Anchorage the plants and supplies water and nutrients.

Soil l

oi

Types of S

y lit

i ta

Upper Layer of earth consisting a mixture of organic remains, clay rock particles.

yer

ve n ti on

Third La

tation Planting Vege ation Afforest

s rock Ma de up of small

It has lesser amount of humus but more of minerals layer is harder.

A vertical section through different layers of the soil. Humus and minerals rich in top soil.

Mind map : learning made simple

MIND MAP

Pre

d an us m

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