3-sci. 9th sol. (6-10)f - cbse strikercbsestriker.com/images/7-sci-9th-sol-(6-10).pdf · when...

Solved

Time : 3 Hours Maximum Marks : 80

1. It is because air is already saturated with water vapour therefore it will not be able to hold more watervarpour easily.

2. Acceleration due to gravity is always directed towards the centre of the planet or celestial body on which itis measured.

3. (i) It is heterogenous.

(ii) It is opaque.

(iii) The particle of chalk can be separated by filtration.

(iv) Chalk particles can be seen by naked eye.

4. (i) Maintenance of proper temperature.

(ii) Clean housing conditions.

(iii) Hygienic conditions.

(iv) Proper and balanced food.

(v) Prevention and control of disease by vaccination.

5. Broilers :

(i) They are maintained for getting meat.

(ii) They are raised upto 6-7 weeks.

(iii) They need less space and in this conditions they grow fast and have low mortality.

(iv) They need food rich in proteins, adequate fat along with vitamin A and K.

Layers :

(i) They are needed for eggs.

(ii) They start laying egg after 20 weeks.

(iii) They need enough space, suitable temperature and high mortality.

(iv) They need restricted food with vitamins, minerals and micro-nutrients.

6. (a) It is because water comes out through pores which gets evaporated and causes cooling.

2 | Striker CBSE Science, Class-9

(b)

Diagram showing sublimation of camphor

(c) Kelvin = °C + 273 = 35 + 273 = 308 K

7. Copper sulphate solution does not show Tyndall effect because particles are very small and do not causescattering of light.

Water and milk form colloidal solution which shows Tyndall effect because particle are larger which causesscattering of light and show Tyndall effect.

8. Characteristic features of tallophyta are :

(i) They do not have well differentiated body design.

(ii) The plants in this group are commonly called algae.

(iii) These plants are predominantly aquatic.

Two thallophytes which are predominantly aquatic are Spirogyra and Cladophora.

9. Kepler derived three law governing the planetary motion :(a) The orbit of a planet is an ellipse with the sun at one of the foci.(b) The line joining the planet and the sun sweeps equal areas in equal intervals of time.(c) The cube of mean distance of a planet from the sun is directly proportional to square of orbital period,

i.e., r3

T2 = constant.

10. Given : Mass, m = 1200 kg; Initial velocity, u = 0; Displacement, s = 40 m; Time, t = 5 s.

By second equation of motion,

s = ut + 12 at2 = 0 +

12 at2

or a =2st2 =

2 × 40(5)2 = 3·2 ms–2

Work done = Force × Displacement

= ma.s = 1200 × 3·2 × 40 = 153600 J

Final K.E. = Work done = 153600 J

11. (a) Work done is equal to the K.E. possessed by the object, i.e., 12 mv2.

(b) Work done is zero as the direction of force of attraction is perpendicular to displacement.

12. When compression of sound waves strikes the ear drum, the pressure on the outside of ear drum increasesand pushes the ear drum inwards, during rarefaction, ear drum moves outward. Thus eardrum vibrates.

Striker CBSE Science, Class-9 | 3

The vibrations are increased by three bones and middle ear transmits three amplified pressure vibrationsreceived by sound waves to inner ear.In the inner ear, the pressure waves are converted to electrical signals by cochlea.These electric signals are sent to brain by auditory nerves and then brain interprets them as sound.Pinna—Ear canal—Ear drum—Hammar—Anvil—Stirrup—Oval window—Cochlea—Auditory nerve—Brain.

13. Vector are organisms which carry germs from a sick person to some other person acting as intermediator.Examples of Vector :(a) Mosquito : Female Anopheles mosquito spread malaria from an infected person to a healthy person.(b) Flies : Flies act as vector in spreading of the disease sleeping sickness.

14.

Carbon Cycle in Nature

(1) In the process of photosynthesis plants take CO2 to prepare food.(2) Herbivores used the plants in form of food hence ‘C’ reached to herbivores which passed to carnivores

in form of food chain.(3) CO2 returns to biosphere in through : (i) Respiration of plants and animals, (ii) By the decomposition

of organic waste and dead bodies, (iii) Through fossil fuels.15. Even though 75% of the Earth’s surface is covered with water, a majority of it is salt water. Only 3% of

water on the Earth is fresh water, and most of it is in frozen state in glaciers. In addition to scarcity tofresh water, many sources of water supply are contaminated with industrial waste or sewage. Beause ofthese reasons, we should conserve water.

16. (a) 1 mole of Na2CO3.10H2O contains 13 × 6·022 × 1023 atoms of oxygen∴ 0·10 moles of Na2CO3.10H2O contains 13 × 6·022 × 1023 atoms of oxygen

(b) 1 mole of sulphur = 32 gAlso 1 mole of sulphur = 6·022 × 1023 atomsNow, 6·022 × 1023 atoms of sulphur weigh = 32 g

∴ 1 atom of sulphur weighs =32

6·022 × 1023 g = 5·31 × 10–23 g

(c) (NH4)2SO4

17. (a) Bohr made a bold new suggestion that particles at atomic level would behave differently frommacroscopic (bigger) objects.


According to Bohr’s theory :(i) Electrons revolve in certain orbits having well defined energy.(ii) Electrons do not emit radiations as long as they remain in the same orbit.(iii) Supply of energy excites the electron to higher energy level.(iv) Emission of energy takes place when it jumps from higher energy level to lower energy level.

(b)

Sodium-2, 8, 1 Lithium-2, 1 Aluminium-2, 8, 3

18.

(1) Mitochondria : It is also known as power house of the cell because glucose oxidise in it to releaseenergy.

C6H12O6 + 6O2 ⎯⎯→ 6CO2 + 6H2O + ATP (Energy)(2) Plasma Membrane : It is also known as selectively permeable membrane because it allow only

selected substances to come in and move out of the cell.

19. Parenchyms Collenchyms Sclerenchyms

1. Living cells and isodiametricin shape.

1. Living cells, with thickcorners.

1. Dead cells, long and narrowwith tapered ends.

2. Cell walls are thin and madeup of cellulose.

2. Cell walls are thickened atcorners wi th extradeposition of cellulose andpectin.

2. Cell walls are thick due toheavy deposition of lignin.

3. Cells have distinct nucleusand a large central vacuole.

3. Cells have distinct nucleusand dense cytoplasm.

3. Cells do not have a nucleusand cytoplasm.

4. It stores food, waste productsand forms packing tissue.

4. It gives mechanical supportand flexibility.

4. It gives rigidity andmechanical strength to theplant.

5. It is present in all soft parts ofplant, i.e. in stems, roots,leaves, flowers and fruits.

5. It is present below theepidermis in stems andleaves.

5. It is present in xylem andphloem, in shells of nuts, inhard seeds, pulp of pear, etc.


20.

(i) Speed = Slope between 12:00 – 12:30

=65 – 30

30 = 1·17 km/min

(ii) Average speed =100 km

2 h = 50 km/h

(iii) No, because it covers unequal distance in equal time intervals.21. The product of mass and velocity of a body is called momentum.

SI unit : kg ms–1

Mass, m = 50 kg, Velocities, u = 4 ms–1 and v = 8 ms–1, Time, t = 8 s.Initial momentum, p1 = mu = 50 × 4 = 200 kg m/sFinal momentum, p2 = mv = 50 × 8 = 400 kg ms–1

Force =Momentum change

Time

=p2 – p1

t = 400 – 200

8 = 2008 = 25 N

22. In experiment to determine the boiling point of water, mention two important precautions to be taken.23. (i) Magnetic method (ii) Chemical method

24. (1) Chloroplast

(2) Vacuole

(3) Mitochondria

(4) Cytoplasm

(5) Nucleolus

(6) Nucleus

(7) Plasma membrane

(8) Cell wall

25. (i) Presence of scale on body (ii) Presence of initiating membrane26. Weight = m × g = 10 × 10 = 100 N27. Both, transverse wave and longitudinal wave.

●

Solved


1. (i) Molecular mass of H2 = 1 × 2 = 2 u

(ii) Molecular mass of O2 = 2 × 16 = 32 u

(iii) Molecular mass of Cl2 = 2 × 35·5 = 71 u

(iv) Molecular mass of CO2 = 12 + 2 × 16 + 32 = 44 u

(v) Molecular mass of CH4 = 12 + 1 × 4 = 16 u

(vi) Molecular mass of C2H6 = 2 × 12 + 6 × 1 = 24 + 6 = 30 u

(vii) Molecular mass of C2H4 = 2 × 12 + 4 × 1 = 24 + 4 = 28 u

(viii) Molecular mass of NH3 = 14 + 3 × 1 = 17 u

(ix) Molecular mass of CH3OH = 12 + 3 × 1 + 16 + 1 = 12 + 3 + 16 + 1 = 32 u

2. Two or more forces acting upon a body are said to be balanced if they cancel each others effect so that thenet force is zero.

3. Al – e = 13 – 3 = 10, p = 13, n = 14, Cl – e = 17 + 1 = 18, p = 17, n = 18

4. Bee-keeping is called apiculture. Honey and bees wax are the products.

5. Mullets, bhetki, pear spots, shell fish such as prawn, mussels, oysters, sea weeds.

6. (a) It is because ice is lighter, i.e., it has lower density than water.

(b) It has very less force of attraction between particles and particles have high kinetic energy.

(c) ‘B’ has more heat of evaporation and will take more heat from the surroundings, therefore, it willcause more cooling.

7.

Fig. Saparation by saparating funnel (Water-oil) immiscible liquids


8. Protoplasm : It refers to the living substance present in the living cells consisting of cytoplasm andnucleoplasm.Cytoplasm : It is a part of protoplasm filled within the space between nuclear membrane and cellmembrane having cell organelles. It is viscous and homogenous containing water, glucose, oxygen, aminoacids, etc.

9. Arthropoda is the largest group of animals.Salient features of this group are :(a) They have segmented body which is divided into head, thorax and abdomen.(b) They have joined legs and a pair of compound eyes.(c) The body is bilaterally symmetrical.(d) They are found everywhere on the earth.(e) Their body is covered with a hard exoskeleton made of chitin.(f) The coelomic cavity is filled with blood.(g) The circulatory system is open.

10. (a) Distance travelled by train = Length of bridge + Length of train

= 1000 m + 100 m = 1100 m

v = 60 km/h = 60 × 518 =

503 ms–1

Time taken, t =1100 m503 ms–1

= 66 s

(b) (i) The object is at rest.

(ii) The object is moving at constant velocity.

(iii) The motion of the object is non-uniform.

11. (a) Uniform motion

(b) Zero

(c)

12. Archimededs’ principle states that if an object is partially or fully immersed in a fluid, it experiences anupthrust which is equal to weight of fluid displaced by it.

Applications :

(i) In ship and submarine designing.

(ii) In making instruments such as lactometer and hydrometer.

13. (a) Reflecting surface should be at a distance such that echo reaches our ears after a time of at least 0·1second.

(b) Bats send ultrasound squeks which are reflected back when they a prey. The bats detect this reflectedwave and catch their prey.


14. RRR of water bodies mean repair, renovation and restoration of water bodies.It is Govt. of India scheme for Repair, Renovation and Restoration (RRR) of water bodies directly linked toAgriculture started in January, 2005. Estimated cost of the project was Rs. 300 crore to be shared byCentre and State in the ratio of 3 : 1. The no objectives of the Scheme were to restore and augment storagecapacities of water bodies and also to recover and extent their lost irrigation potential. The Schema hasbeen approved for 26 district projects in 15 States.

15. Nitrogen fixation is the process of conversion of gaseous nitrogen from the atmosphere into nitrites andnitrates by the action of micro-organisms. It converts nitrogen into usable form for the plants.Differences :

Nitrification Denitrification1. The process of conversion of nitrites of

nitrates.1. The process of converting nitrates into free

nitrogen.2. This is an intermediate step of nitrogen cycle

in which nitrogen is converted into anotherusable form e.g., Nitrobactor (nitrogen fixingbacteria).

2. This is the last step in which nitrogen isreleased back into its source, the atmosphere,e.g., Pseudomonas (denitrification bacteria).

16. (a) Ca++ Cl– Ca++ SO4– – K+ Cl– K+ SO4

– – Fe++ Cl– Fe++ SO4– –

Ca Cl2 Ca SO4 K Cl K2 SO4 Fe Cl2 Fe SO4

(b) 1 mole of nitrogen atoms = 14 g1 mole of nitrogen atoms = 6·022 × 1023 atoms

6·022 × 1023 atoms of nitrogen weigh = 14 g

1 atom of nitrogen weighs =14

6·022 × 1023 = 2·324 × 10–23 g

17. (a) Rutherford’s experiment established the presence of atomic nucleus.Rutherford’s Experiment (Discovery of Nucleus) : Rutherford bombarded on a gold foil with astream of α-particle, which are positively charged helium nuclei. He made the following observations :(i) Most of the α-rays (99%) passed through gold foil undeviated from their path. Conclusion : Most

of the space around atoms is hollow or empty.(ii) Some of the rays were deviated through larger angles showing that centre of the atom is

positively charged.(iii) Very few rays were deflected back from their path which shows that there is positively charged

heavy centre which occupies very small space which is called nucleus. The whole mass of atom isconcentrated at this centre.Some more conclusions were made on the basis of these observations.

Scattering of αααα-particles by gold foil


(iv) The volume of the nucleus is 1

1‚00‚000 of the total volume of the atom, where the electrons revolve

around the nucleus.(v) The density of nucleus is very high.

(b) Electron configuration = 2, 8, 5 and valency = 3 because it can gain 3 electrons to become stable.18. Nervous Tissue : The cells of nervous tissue are highly specialised for being stimulated and then

transmitting thestimulus very rapidly from one place to another within the body. The brain, spinal cordand nerves are all composed of the neervous tissue. The cells of this tissue are caclled nerve cells orneurons.Functions of Nervous Tissue :(i) Nervous tissue controls all the body activities.(ii) It coordinates among various body parts during anybody function.(iii) Dendrons carry nerve impulses towards the cyton whereas axon carries impulses away from the cyton.Each neuron has three parts—the cyton or cell, dendrites and the axon.(i) Cyton : It is the cell body of a nerve cell that has a large central nucleus and cytoplasm, from which

along thin hair-like parts arise.(ii) Dendrite : The short branched fibre of neuron which receives nerve impulses.(iii) Axon : A single long conducting fibre extending from a neuron that transmits impulses away from the

cell body.

Fig. A neuron-a unit of nervous tissue

19. (i) Whenthe carpet is beaten, it moves. But dust particles and to remain at rest due to their inertia ofrest. So, they get detached from the carpet. As a result, they fall down.

(ii) Initial velocity, u = 0

Final velocity, v = 30 ms–1

Time, t = 10 s

Mass of car, m = 15000 kg

Accceleration, a =v – u

t = 30 – 0

10 = 3 ms–2

f = ma = 15000 × 3 = 45000 N

20. (a) The energy possessed by an object by virtue of its motion is called kinetic energy.

Consider a mass m moving with a speed u and a force F applied on it, which changes its velocity to von displacing by s.


Work done, W = ma ⎝⎜⎛

⎠⎟⎞v2 – u2

2a

So, W =12 m (v2 – u2)

If initial velocity, u is zero, then W = 12 mv2

or K.E. =12 mv2

K.E. cannot be negative as it has all positive quantities. It is a scalar quantity, so no direction is takeninto consideration.

(b) Given : m = 1200 kg, s = 40 m, t = 5 s

Using s = ut + 12 at2 and u = 0

We get a =2st2 =

2 × 40(5)2 =

8025 m/s2

∴ Work done = F.s = ma × s

= 1200 × 8025 × 40

= 153600 joule = 153·6 kJ

21. (a) Disease means being uncomfortable and not at ease.

(b) The two groups which cause diseases are infectious causes and non-infectious causes :

Diseases caused by infectious microbes are called infectious diseases. There are some diseases whichare not caused by infectious agents. Causes of such diseases are mostly internal non-infectious causes.

22. The temperature remains constant during the boiling of water even though heat is supplied continuously.This is because, the heat supplied is absorbed by the water particles and this heat increases their kineticenergy.

23. (i) Chemical charge because new substance (ii) FeS is formed.

24. (a) Staining provides colour to the cell, hence making it visible under microscope.

(b) Spreading the cells important as it helps in proper dispersion of cells.

25. Tap root is found in tea plant, while in onion fibrous roots are found.

26. Apparent loss of weight of the solid in water = 68 – 46 = 22 gwt.

Weight of water displaced by the solid body = 79 – 57 = 22 gwt.

Thus, it is clear that the weight of water displaced by the solid body fully immersed in water is equal to theapparent loss of weight of the given solid in water. Thus, Archimedes’ principle is verified.

27. The speed of pulse in a string is

(a) inversely proportional to the square root of mass per unit length of the string, and

(b) proportional to the square root of tension given to the string.●

Solved


1. 1 mole of cabron atoms = 12 g1 mole of carbon contains = 6·022 × 1023 atoms6·022 × 1023 atoms weigh = 12 g

1 atom of carbon weighs =12

6·022 × 1023 = 1·99 × 10–23 g

2. Distance : The length of path covered by a moving object irrespective of the direction in which object ismoving.

Displacement : The shortest distance from initial position of an object to its final position.

3. (a) No. of moles of oxygen atoms =Given massMolar mass =

6416 = 4 moles

(b) No. of moles =No. of atoms6·022 × 1023

=24·088 × 1023

6·022 × 1023 = 4 moles

4. Milk production can be increased by selective breeding or cross breeding between a local breed like RedSindhi or Sahiwal cow with an exotic bull breed which is selected for the characteristics of long lactationperiod and high milk yield.

5. Mixed Cropping : It is a process of growing two or more crops simultaneously on the same piece of land,e.g. wheat + gram, wheat + mustard or groundnut + sunflower. This reduces risk and gives more benefits,if there is failure in any one of the crops, due to weak monsoon, other will survive.

6. Three differences between Metals and Non-metals :

Metals Non Metals

1. Metals are good conductor of heat andelectricity.

1. Non metals are not conductor of heat andelectricity.

2. Metals are ductile, they can be drawn intowires.

2. Non metals are not ductile.

3. Metals are sonorous, they produces ringingsound when they are hit by any solid.

3. Non metals are not sonorous.

7. (a) The ion which contains two or more than two atoms is called polyatomic ion, e.g.. CO2–3 , NH+

4 arepolyatomic ions.

(b) Ammonium sulphate. NH+4 and SO2–

4 ions are present in it.


8. Diffusion Osmosis

1. It is the movement of molecules from higherconcentration area to lower conentration area.

1. It is the movement of water molecules fromhigher concentration area to lowerconcentration area through semipermeablemembrane.

2. Diffusion take place in all three state ofmatter, solid, liquid, gas.

2. Osmosis take place in liquids only.

9. (a) Two important functions of areolar tissue are as follows :(i) They act as a supporting and packing tissue between organs lying in the body cavity.(ii) They also help in repair of tissues.

(b) The skeletal muscles show alternate dark and light bands or stripes or striations, so they are knownas striated or striped muscles.

10. Let masses be m1 and m2, moving with velocities u1 and u2 initially. On application of force, their velocitiesbecome v1 and v2 in time t.Force F1 and – F2 (Newton’s third law)

m1 (v1 – u1)t =

m2 (v2 – u2)t

⇒ m1v1 – m1u1 = – m2v2 + m2u2

m1v1 + m2u2 = m1u1 + m2u2

11. Initial velocity, u = 40 ms–1, g = – 10 ms–2 (upward motion), Final velocity, v = 0During upward motion, g = – 10 ms–2

Height, h =v2 – u2

2g = 0 – (40)2

2 × (– 10) = 80 m

Net displacement on returning back = zeroTotal distance = 80 m + 80 m = 160 m

12. Iron nail or sheet has greater density than that of water, so it sinks in water; on the other hand, thestructure of the ship is so designed that it has larger air space in it. Hence its averge density becomes lessthan that of water and as a result, it floats on water.

13. Ultrasound is the sound of frequency greater than 20000 Hz. In industry, it is used for :

(a) Cleaning parts located in hard to reach places such as coiled tubes, electronic components, odd shapedobjects etc.

(b) Detecting cracks and flaws in metal blocks used in construction of big structures such as bridges,machines, building, etc.

We cannot use longer wavelengths for such uses because they might bend around the corners of defectivelocation and enter the detector.

14. (a) Biodegradable :(i) These can be broken down into simpler substances and easily disposed off.(ii) They are safe for the environment.(iii) Micro-organisms helps in decomposing thereby the substances can be reused and can enter the

food chain cycle again.Non-biodegradable :(i) These cannot be broken down into simpler harmless substances in nature.(ii) They are harmful substances as they are synthetic products.(iii) Micro-organisms do not work on it.


(b) Acid rain which contains sulphuric acid reacts with the marbles of Taj Mahal and makes it yellow incolour.

15. (i) Due to global warming, temperature on earth in increasing, sea level is rising as snow cover in themountain peaks of the earth northern hemisphere is decreasing due to melting of snow into water.

(ii)

(iii) All cellular processes take place in a water medium. All the reactions that take place within our bodyand within the cells occur between substances that are dissolved in water. Substances are alsotransported from one part of the body to the other in a dissolved form. Organisms need to maintainthe level of water within their bodies in order to stay alive. Thus, water is essential for life.

16. Evaporation is a process in which a liquid changes into vapours.(i) Surface area : Greater the surface area, more will be rate of evaporation e.g., tea becomes cold faster

in a surface than a cup.(ii) Temperature : Higher the temperature, more will be the rate of evaporation. Humidity is more in

summer than in winters due to faster rate of evaporation of water during summer.(iii) Wind speed : Higher the wind speed, more will be the rate of evaporation .e.g, clothes dry up faster

on windy day.(iv) Humidity : Greater the humidity, lesser will be the rate of evaporation e.g., clothes dry up slowly on a

rainy day because humidity in air is more.17. (a) Atomic No. 12, Mass No. 26

(A)∴ No. of electrons = No. of protons = Atomic No. = 12

n = A – p= 26 – 12 = 14

Electronic figuration e = 12 = 2, 8, 2

Valency of element is 2, because it has 2 electrons in valence shell it will loose the electrons of valueshell.


(b) This element ‘X’ combines with ‘Y’ with electric configuration 2, 8, 7 (Its valency will be 1).X2

Y1 ⎯→ XY2

X is MgY is Cl hence MgCl2 (Magnesium chloride)

18. (a) Homo sapiens(b) Human belongs to the class mammalia of vertebrates.(c) Five characteristic features of class mammalia are :

(i) They are warm-blooded animals.(ii) They have four-chambered heart.(iii) They have mammary glands for production of milk to nourish their young ones.(iv) The skin of mammals have hair as well as sweat and oil glands.(v) They give birth to young ones.The exceptions to the above characteristics of mammal are platypus and echidna who lay eggs.

19. (a) Velocity at A = 2 m/s

(b) At t = 4 s, p = mv = 50

1000 kg × 2 m/s = 0·1 kg m/s

(c) Acceleration

(d) Distance = Area of ∆ OAP = 12 × 4 × 2 = 4 m

20. (a) (i) The kinetic energy gained is due to loss in P.E., so the conservation of energy holds good. Gain inK.E. = Loss in P.E.

(ii) Work done is zero as force applied by girl has not displaced the pages from its place. Sincedisplacement = 0, so work = 0.

(iii) Because gravitational force is perpendicular to displacement.(iv) Energy consumed by two electric devices

= P1t1 + P2t2

= [100 × 24 + 500 × 24]= [100 + 500] × 24= 600 × 24= 14400 Wh = 14·4 kWh

21. Cause : Diarrhoea is caused by certain bacteria (E.coli. etc.), protozoans (Entamoeba histolytica, etc.) someviruses (Rotavirus, etc.) and nematodes (Ascars).Symptoms : The main symptoms of diarrhoea are :(a) Frequent loose motions and vomiting.(b) Becomes irritable, sunken eyes, sudden weight loss, weak pulse, deep breathing and fever or fits.Prevention :(a) Food and other eatables must be kept covered.(b) Fruits and vegetables should be thoroughly washed before eating.(c) Proper personal hygiene should be maintained. Hands should be washed with soap before eating food.(d) Community hygiene is also important.(e) Stale or exposed food should not be eaten.

22. (i) Reading of thermometer is 0°C.(ii) Temperature will remain 0°C until the whole ice melts.


23. (a)24. Cell, wall, Nucleus.25. (i) Collenchyma cells are thick walled.

(ii) Cellulose and pectin are present at the corner of the cell.26. Apparent loss of weight of solid in water = 68 – 46 = 22 g wt.

Weight of water displaced by the solid body = 79 – 57 = 22 g wt.27. The speed of pulse in a string is :

(a) Inversely proportional to the square root of mass per unit length of the string.(b) The string used in experiment should be long, soft and flexible.

●

Solved


1. Proton is positively charged particle present in nucleus.

It was discovered by Goldstein.

2. (a) Kinetic energy(b) Potential energy(c) Kinetic energy(d) Kinetic energy

3. (a) 1 mole of H2O = 2 × 1 + 16 = 18 g

18 g of H2O contains 6·022 × 1023 molecules

9 g of H2O contains =6·022 × 1023

18 × 9

= 3·011 × 1023 molecules

(b) 1 mole of NH3 = 14 + 3 × 1 = 14 + 3 = 17 g

1 mole of NH3 contains 6·022 × 1023 molecules

17 g of NH3 contains 6·022 × 1023 molecules

4. It is a pattern of growing two or more crops simultaneously on the same field in a definite pattern asshown in the diagram :

● A few rows of one crop alternate with few rows of the second crop, e.g. soyabean + maize or fingermillet (bajra) + cow pea (lobia).

● The crops are selected such that their nutrient requirements are different.

● It prevents pests and diseases from spreading to all the plants belonging to one crop in the field andreduces loss of both crops and give better results.

5. Manure :

(i) They are organic compounds which contain nutrients in small amounts.

(ii) They help in recycling of waste materials prepared in fabric itself.

(iii) They increase the fertility of the soil.

(iv) They are eco-friendly.

(v) Continuous use is not harmful.

(vi) They do not kill the micro-organisms, which increases and maintains the fertility of the soil.

Fertiliser :

(i) They are inorganic compounds which contain large amount of nutrients.


(ii) They are expensive, prepared in industries.(iii) They improve the fertility but only for a short duration.(iv) They create environmental problems when used in excess.(v) Continuous use is harmful.(vi) They kill micro-organisms.

6. (a) (i) It appears to be homogeneous but actually it is heterogeneous.(ii) It is translucent.(iii) Its particle can be seen with powerful microscope.

(b) Dispersed phase and dispersion medium are two components of colloids.(c) Ink, blood, foam are colloidal solution.

7. (a) Molar mass of NaCl = 23 + 35·5 = 58·5 mol–1

(b) Number of moles of NaCl =Mass of NaCl

Molar mass of NaCl

=5·8558·5 = 0·1 mol

(c) Concentration of solution =Mass of soluteMass solution × 100

=5·85

5·85 + 1000 × 100 = 5·85

1005·85 × 100 = 0·58%

8. (a) These tissues connect various body organs. They connect bones to each other, muscles to bones andbind tissues. They are therefore called connective tissues.

(b) Areolar connective tissue are loose are cellular connective tissue. They act as a supporting andpacking tissue between organs lying in the body cavity. They also help in repairing of tissue.

(c) Adipocytes are filled with fat globules. They keep visceral organs in position forming shock absorbingcushions around them. Storage of fat also act as an insulator.

9. The odometer of an automobile measures the distance travelled by it.

(a) Speed of scooter = 300 m/min = 300 m60 s = 5 ms–1

(b) Speed of car = 36 km/h = 36 × 518 ms–1 = 10 ms–1

Thus, car is moving faster.

10. Pressure is defined as thrust per unit area of a surface. Its SI unit is pascal (Pa).

Given : M = 30 kg, g = 10 m/s2, A = 20 cm × 15 cmThrust = Mass × Acceleration due to gravity

= 30 kg × 10 ms–2 = 300 NArea = 20 cm × 15 cm

= 0·2 m × 0·15 m = 0·03 m2

Pressure =ThrustArea =

300 N0·03 = 104 Pa

11. Sound waves need a material medium for their propagation. These waves cannot travel through vacuum.Thus they are called mechanical waves for example, we can receive light coming from sun, but do not hearthe sound of explosions occurring on its surface.

12. The disease AIDS is caused by retrovirus (a RNA virus) known as Human Immunodeficiency Virus (HIV).Two modes of transmission of AIDS :(a) Sexual contact (b) Blood transfusion.


Symptoms : Swollen lymph nodes, regular fever, sweating at night and weight loss. It may cause severedamage to brain leading to loss of memory, ability to speak and clear thinking.

13. (i) Displacement of the car = zero, as it returns back to initial point.(ii) Let distance from A to B = x

Thus total distance from A to B and B to A = 2x

(iii) Time taken from A to B = x

30 h and from B to A = x

50 h

Total time =x

30 + x

50 = 8x

150 h

Average speed =Total distance travelled

Total time taken

=2x8x

150

= 3·5 kmh–1

14. (a) Nitrogen is an essential nutrient for all types of cultivation. The crop consumed most of the nitrogenfrom the soil during last 15 years and hence, yield from the crop has gone down. Rhizobium bacteriapresent in Soyabean roots can fix atmospheric nitrogen. When the plant dies, the nitrogen getsreleased in the soil to increase fertility.

(b) The officer has shown the value of knowledge on the subject and attitude to solve problemsscientifically which inturn helped Mr. Sharma (the farmer).

(c) During lighting, the high temperature and pressure created in the air converts N2 into oxides ofnitrogen. These oxides dissolve in water to give nitrous and nitric acid and falls on land with rain,these are then taken up by plants.

15. Crop Rotation is defined as the practice of growing different crops on a piece of land in a pre-plannedsuccession/pattern.

Depending upon the duration, crop rotation is done for different crop combinations. If crop rotation is doneproperly then two or three crops can be grown in one year with good harvests.

Availability of moisture and irrigation facility should be kept in mind in choosing plants for crop rotation.

16. (a) Buoyant force = Weight of liquid displaced

= (Volume immersed) × (Density of liquid) × (Acceleration due to gravity)

So the density of the liquid and volume immersed affect the buoyant force.

(b) Buoyant force exerted by a liquid does not depend on its volume.

(c) Hydrometer and lactometer are based on Archimedes’ principle. Submarines are also designedaccording to Archimedes’ principle.

17. (a) Percentage of Isotopes 16 8X and

18

8X

Let Percentage of 18 8X be ‘x’, therefore, percentage of

16

8X will be 100 – x

16·2 =18 × x + 16 (100 – x)

100

1620 = 18x + 1600 – 16x

2x = 20; x = 202 = 10%

∴ % of 18 8X will be 10%

% of 16 8X will be 100 – 10 = 90%.


(b) Positively charged particles and negative charged particles are equal, therefore, an atom is neutral onthe basis of Thomson model.

18. Mitochondria is called the ‘power-house of cell’ because energy required by various chemical activitiesneeded for life is released by mitochondria in the form of ATP. Body uses energy stored in ATP for makingnew chemical compounds and for mechanical work.Three similarities between mitochondria and plastid are :(i) Both mitochondria and plastids have their own DNA and ribosomes.(ii) External structure of mitochondria and plastid are same.(iii) Both mitochondria and plastids have more than one membrane layer.One difference between mitochondria and plastids is that mitochondria are present in both plant andanimal cell whereas plastids are present only in plant cell.

19. The characteristic features of Phlum Mollusca :(a) They have soft, unsegmented body and body is divisible into three regions—head, visceral mass andventral foot.(b) Outer surface is covered with a hard calcareous shell.(c) Sexes are separate.(d) Respiration occurs by gills called etenidia.(e) They may be terrestrial or aquatic.Examples are Pila (snail), Unio (fresh water mussel), Octopus.

20. (a) Galileo, for the first name deduced that objects move with a constant speed when no force acts onthem by studying the motion of objects on an inclined plane. He rolled down a marble down aninclined plane which accelerated as it moved down. Galileo claimed that when marble is released fromone inclined plane, it rolls down and climbs the opposite side upto the same height from which it wasreleased.

If the angle of inclination of second plane was decreased gradually, then the marble travelled fartherdistances unit it reached the same height.

Galileo hypothesised that if the second plane was made horizontal then it would continue to movealong the same path forever trying to reach the same height. In such a case, the unbalanced forceacting on the marble is zero. This means, in order to change the motion of marble, some externalunbalanced force must act on it. In this case, effect of friction on the marble is considered to be zero.Galileo hypothesis thus, laid the foundation for formulation of first law of motion.

(b) Speed of an object changes with time if an external unbalanced force acts upon it. This is because anunbalanced force is required to change the state of motion of an object. If no unbalanced force acts onthe object, it remains at rest or continues to move along a straight line path with uniform velocity.

21. (a) Kinetic energy ∝ v2.

∴ For energies KE1 and KE2,KE1

KE2 =

v12

v22 =

v3

(3v)2 = v2

9v2

KE1

KE2 =

19

(b) Power is defined as work done by an object per unit time.

Given : P = 1500 W = 1·5 kW, t = 10 h

E = Pt = 1·5 × 10 = 15 kWh

1 kWh = 3·6 × 106 J

15 kWh = 15 × 3·6 × 106 J = 5·40 × 107 J


22. A pure solid substance has a definite melting point; therefore, the purpose of determining the melting pointis :(a) to determine the characteristics of a substance.(b) to determine the purity of a substance.

23. Ammoniuum chloride deposits on the inner wall of invested funnel.24. Nucleus, cytoplasm25. Cyton, Dendrites and axon are observed.26. If the density of any solid object is less than that of liquid used. Then a sinker, i.e., a weight which is used

for sinking the solid object can be used to perform the experiment.27. Longitudinal wave

Transverse wave●

Solved


1. Smallest particle which participate in chemical reaction.

2. Gravitation pull of the moon.

3. Atomic No. 6, element is carbon (C).

4. (i) Foot-and-mouth disease-viral disease.

(ii) Anthrax-bacterial disease.

5. Indigenous (Indian) Breeds of Cow are :

(i) Red Sindhi

(ii) Sahiwal

Exotic (Foreign) Breeds of cows :

(i) Jersy (Brown Swiss)

(ii) Karan Swiss.

6. When solid changes into liquid inter molecular force of attraction decreases and distance betweenmolecules increases. Kinetic energy of molecules also increases when liquid change into gas, force ofattraction between molecules becomes very less. This increases intermolecular space and kinetic energy.

7. (i) The centre of atom is positively charge and whole mass of atom is concentrated in the centre.

(ii) Most of part of atom is hollow.

(iii) The size of nucleus is 1

100‚000 of the size of atom.

(iv) The density of nucleus is very high.

8. Location and functions :

(i) Apical meristem : They are present at the growth tips of stems and roots. They increases the lengthof stem and root.

(ii) Lateral meristem : They lie on lateral sides of stems and roots. They increases the girth of stem androot.

(iii) Intercalary meristem : They lie at the base of the leaves or internodes on twigs. They increaseslongitudinal growth of plants.

9. Aves :

(i) They lay eggs.

(ii) Body is covered with a feathery exoskeleton.

(iii) The two forelimbs are modified as wings for flight.


Mammalia :

(i) They give birth to young ones.

(ii) The skin of mammal has hair as well as sweat and oil glands.

(iii) They have two pairs of pentadactyl limbs.

10. u = 54 km/hr or 54 × 5

18 = 27018 = 15 m/s, v = 72 km/h or

72 × 518 =

36018 = 20 m/s, t = 10 s.

(i) Acceleration (a) =v – u

t = 20 – 15

10 = 510 = 0·5 m/s2

(ii) Distance (s) =v2 – u2

2a = 202 – 152

2 × 0·5 = 400 – 225

1 = 175 m

11. u = 0, a = 0·1 ms–2, t = 120 s.

(a) v = u + at = 0 + 0·1 × 120 = 12 ms–1

(b) s = v2 – u2

2s = (12)2 – 02 × 0·1 = 720 m

12. Bullet : Mass mb = 10 g = 0·01 kg

Velocity vb = 400 m/s

Momentum pb = mbvb

= 0·1 × 400 = 4 kg ms–1

Ball : Mass mB = 400 g = 0·4 kg

Velocity vB = 90 km/h = 518 × 90 m/s

Momentum pB = mBvB

= 0·4 × 25 = 10 kg ms–1

Thus cricket ball has higher momentum.

13. (a) The number of complete oscillations in one second is called frequency (f). Its SI unit is hertz (Hz).

(b) If absorbent materials are absent, there will be multiple echoes due to which sound cannot be heardclearly.

14. (a) Burning of fossil fuels like coal and petroleum releases oxides of nitrogen and sulphur. Inhalation ofthese gases is dangerous. These gases also dissolve in rain to give rise to acid rain.

(b) The combustion of fossil fuel also increases the amount of suspended particles in air. These suspendedparticles could be unburnt carbon particles of substances called hydrocarbons. The presence of highlevels of all these pollutants, reduce visibility in cold weather where water also condenses out of airforming smog. Smog is an indication of air pollution.


15. Glass being transparent allows sunlight to pass through it, hence heating the interior of the car. Since heatwaves cannot pass out of the glass, so the heat trapped inside raises the temperature of the interior. This isbecause, glass is transparent to infrared radiation coming from the sun that is having shorter wavelengththan that emitted by the interior of the cars longer wavelength to which the glass is opaque heat from thecannot move out.

16. Filter the mixture. Sand will be residue. Mustard oil and water will be filtrate.Take mustard oil and water in separating funnel.Open the stop cock, water will come out first. Collect it in a beaker. Mustard oil will be left in separatingfunnel and get separated.

Air

↓

Compress and cool by increasingpressure and decreasing temperature

↓

Liquid Air

↓

Allow to warm up slowly in fractionaldistillation column

↓

Gases get separated at different heights

↓

Oxygen Argon Nitrogen

Boiling Point (°C) – 183°C – 186°C – 196°C% Air by Volume 20·9 0·9 78·1

17. Number of moles of NH3 =Given massMolar mass =

10014 + 3 =

10017 = 5·88 moles

Number of molecules = Number of moles × 6·022 × 1023

= 5·88 × 6·022 × 1023

= 35·4 × 1023 = 3·54 × 1024 molecules

Number of moles of N2 =Given massMolar mass =

1002 × 14 =

10028 = 3·57 moles

Number of N2 molecules = Number of moles × 6·022 × 1023

= 3·57 × 6·022 × 1023

= 21·5 × 1023 = 2·15 × 1024 moleculesTherefore, the number of molecules in 100 g of NH3 is more.

(b) Number of moles of carbon =Given massMolar mass =

6024 = 5 moles

Number of moles of Mg =Given massMolar mass =

6024 = 2·5 moles

Ratio = 5 : 2·5Ratio = 2 : 1

18. Explanation : Chloroplast is one of the type of plastid. It has green pigment chlorophyll which trap thesunlight. Chloroplast contains a fluid which is called stroma. Thylakoid pile to form granum. Chloroplast is


double membranous outer and inner membrane. Chloroplast has its own genetic material DNA.Chloroplast is known as kitchen of cell because food is prepared in it in the process of photosynthesis.

19. Thrust :

(i) The perpendicular force acting on a surface is thrust.

(ii) The SI unit of thrust is newton.

Pressure :

(i) Thrust per unit area of a surface is pressure.

(ii) The SI unit of pressure is pascal or N/m2.

1 Pascal : Pressure acting on a surface is one pascal, if a thrust of one newton acts on unit area.

1 Pa = 1 N/1 m2 = 1 N/m2

1 Newton : Thrust exerted on a surface is one newton if it accelerates a body of unit mass by 1 m/s2 whileacting perpendicular to it.

If area of contact is double, pressure becomes half as pressure is inversely proportional to area.

20. (a) Loss in kinetic energy =Gain in potential energy

(b) Given : m = 100 kg, h = 20 m, t = 10 s

P =mgh

t

=100 × 10 × 20

10 = 2000 watt = 2 kW

21. Acute disease : Acute disease are diseases which last for only very short period of time, e.g., common cold.

Chronic disease : Chronic diseases are those diseases which last for al ong period of time, even as muchas for life time. E.g., elephantiasis.

Infectious diseases : Disease which are caused by infectious agents like microbes are called infectiousdiseases.

Non infectious diseases : Disease which are not caused by infectious agents are called non fectiousdiseases. E.g. High Blood Pressure.

Communicable diseases : These diseases are caused by pathogens or infectious agents such as bacteria,virus, fungi, protozoan, worm etc. The disease can spread from one diseased person to a healthy person.E.g., Tuberculosis.

Non communicable disease : Diseases which do not spread from one person to another are called noncommunicable diseases.


22. Camphor

23. 100°C24. Cyton

25. Dicut plant

26. The observed value of apparent loss in the weight of solid object gradually increases as the object isgradually immersed in water. When it is completely immersed in water, it is equal to the weight ofdisplaced water.

27. (a) Pulse returns to the left after bouncing off and is known as reflected pulse.

(b) Transverse wave.● ●

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