MAHESH TUTORIALSSubject : Science And Technology

Chapter : 1, 2, 3, 4, 7, 8, 9, 12, 13, 14Model Answer Paper

Test - Date: Marks : 100 Time: 3 Hrs.

GSEB Batch : 10th Std. Eng. Medium

SET - B

PART - ASelect a proper option (a), (b), (c) or (d) from those given below each questions : 50

1. (b) Nanotechnology2. (d) 90 nm3. (a) Bucky ball4. (c) It consists of multiple concentric nanotubes of varying diameters.5. (a) 6422 kg6. (b) Irregular7. (b) virtual8. (b) Convex mirror9. (c) 1 m

10. (c) maximum, least11. (c) Green12. (b) Subtractive13. (c) retina14. (d) Red15. (b) Violet, Green, Blue16. (c) red, blue, green17. (b) Bitter18. (a) H30

+

19. (b) Salt + Water20. (a) Oxidizing agent21. (d) 8.522. (b) 323. (c) Magnetic separation24. (b) CO25. (b) Electrolysis26. (a) Oxidation27. (c) Slag28. (b) Zn > Al > Fe > Cu29. (c) Sulphur30. (c) Hydrogen31. (d) Dihydrogen gas with dioxygen gas32. (a) Henry Cavendish33. (b) Oxy hydrogen34. (a) Platinum Gauge35. (d) H2S2O736. (a) Bacterias37. (c) Mouth38. (b) Alveoli39. (c) oxygen40. (c) Bronchioles41. (d) Phloem42. (b) Translocation43. (d) Both (a) and (c)44. (b) Pure45. (c) lungs46. (c) lymph47. (c) excretion

48. (b) Phototropism49. (c) Photonastic50. (b) Pituitary

PART - BSECTION - A

Answer the following questions : [2 marks] 101. Nanoscience is the study of the fundamental principles of molecules and other

systems whose at least one of the dimensions lie between 1nm to 100 nm range. Nanotechnology is defined as building atom -by- atom or molecule by molecule

structures that will be helpful in manufacturing devices and systems.OR

1.

Bucky ball/ Fullerenes is a special form of carbon molecule. Bucky ball is alsoknown as Buckminsterfullerene.

Bucky ball comprises of 60 carbon atoms in the architectural configuration of asoccer ball (sphere).

Here, each carbon atom is bonded to three adjacent carbon atoms forming a sphere,which is around 1.0 nm in diameter.

The bonds between 60 carbon atoms form a pattern of joined hexagons and pentagonsthat is similar to the panels on a soccer ball.

2. Concave mirror should be used for shaving. When the object is kept between the principal focus and pole of a concave mirror,

the image is formed behind the mirror which is virtual, erect and magnified. Hence, the face should be kept near the principal focus while shaving.

3. Molecular mass of KOH = 1 (Atomic mass of k) + 1 (Atomic mass of O) +1 (Atomic mass of H)

= 39 + 16 + 1= 56 gm/mole

To prepare 1000ml 1M KOH solution 56gm KOH will be required.

To prepare 125ml 0·03M KOH =125 0 03 56

1000

= 0·21 gm

= 210mg 210mg KOH will be required.

OR3. Give definations.(i) Bronsted-Lowry Acid: The substance which donates a proton (H+) to other

substance is called Bronsted-Lowry Acid.(ii) Bronsted-Lowry Base: The substance which accepts a proton from other

substance is called Bronsted Lowry base.

4. Given : Image distance u = –10 cmRadius of curvature R = 30 cmObject height h = 6 cm

Focal Length f =R2

=302

= + 15 cm

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Formula : Mirror formula,1u

+1v

=1f

1v

110

=1

15

1v =

115

-110

=1

15 +

110

1v

=2 330

v =305

= 6 cm

Here image distance is positive hence image is formed behind mirror and image isvirtual.

Magnification m =vu

=6

10= 0.6

But m =h'h

Height of image, h= mh = 0.6 × 6 = 3.6 cm

5. Slag is lighter in weight than iron, so it floats in molten iron. This prevents conversion of iron to its oxide by oxygen. Slag is cooled to form solid and used for construction of roads.

SECTION - BAnswer the following questions : [2 marks] 10

6. Dilute sulphuric acid can be prepared by adding concentrated sulphuric acid slowlyto water.

As heat is produced during this, pieces of ice are placed around the vessel. Dilute sulphuric acid cannot be prepared by adding water to concentrated sulphuric

acid. It can be prepared but the difficulty is that when concentrated acid is added to

water, heat is produced in large proportion and so there is possibility of drops of acidto fall on our body.

Hence acid is added to water as the heat liberated will be absorbed by the water andwater is not added to acid as it may be harmful.

7.Sr.No Aerobic respiration Anerobic respiration

1 It takes place in presence of oxygen It takes place in absence of oxygen2 End products are CO2 and water End products are Ethanol or lactic

acid.3 It takes place in cytoplasm and

mitochondriaIt takes place only in cytoplasm

4 Aerobic repiration produces aconsiderable amount of energy

Much less energy is produced

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8.

No. Arteries Veins1 They carry blood from heart to organs. They carry blood from organs to heart.2 Arteries are under pressure. Veins are not under pressure.3 Walls of arteries are thick and elastic. Walls of veins are thin.4 Arteries carry pure blood except

pulmonary arteries.Veins carry impure blood exceptpulmonary vein.

9. Thigmonasty - is the nastic movement of a plant part in response to touch.Eg - Mimosa plant.

Photonasty - is the movement of plant part in response to light.Eg - Lotus & Sunflower open in morning.

Thermonasty - is the movement of plant parts in response to temperature.Eg - Flower of Tulip plant

OR9. We immediately withdraw our hand when we touch a very hot or cold object. Such

immediate response towards any kind of stimulus is called reflex action. A reflex action is defined as an unconscious and involuntary response of effector

organs to stimulus. In reflex action a message from the receptors is relayed by the sensory nerves to

the spinal cord that sends information to generate a response through motor nervesto the effector organ. This entire pathway is called the reflex arc.

The reflex action is performed by the spinal cord when the brain is busy or at rest.Later on the activities are conveyed to the brain.

Reflex ActionThe Autonomous Nervous System

10. A rainbow is a natural spectrum visible in the sky after rainshower. It is caused bythe dispersion of sunlight by tiny water droplets present in the atmosphere.

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Internalreflectionof light

RedRefraction of light

Violet

Ranindrop

Formation of rainbow

A rainbow is always formed in the direction opposite to that of sun. The water dropletsact like small prisms. They disperse the incident light first, then reflect it internallyand finally refract it again while it comes out of the rain drops as shown in thefigure.

The different colours of light enter into our eye due to the dispersion and internalreflection of light.

Looking from lower to higher order, colours from violet towards red is known asprimary rainbow.

Sometime a second rainbow is seen in the sky.The order of colours in this upperrainbow is reverse to the primary rainbow. This second rainbow is called secondaryrainbow.

Rainbow is also seen on a sunny day at a water fall when sun is behind the observer.

SECTION - CAnswer the following questions : [3 marks] 15

11. We know that stomach plays an important role in digestion of food. As food entersthe stomach, hydrochloric acid is secreted in the stomach.

The pH of this acid changes between 1 and 3. At this low value of pH the enzymenamed pepsin becomes active.

Pepsin is helpful in digestion of protein in the food. Proportion of protein is much more in food like fish, eggs, meat, etc. Hydrochloric

acid is secreted more for the digestion of such food. Because of this, there is pain or, irritation in the stomach.

In commom language, we call it acidity. Basic substances are taken for the remedy of acidity. They are know as antacids. Mostly sodium hydrogen carbonate (NaHCO3) and magnesium hydroxide [Mg(OH)2]

are used as antacids. Calcium carbonate and aluminium hydroxide are also known antacid substances.

Such liquid mixtures and tablets are available in market.

12. When a ray of light travels from optically denser medium to optically rarer medium,it bends away from the normal at the surface separating two media.

B B1 B2B3 B4

> CC

Optically rarermedium

Optically densermedium

As the angle of incidence increases, the angle of refraction also increases and theray of light moves farther away from the normal after refraction.

The angle of incidence at which the angle of refraction is 900 is called critical angle(C).

For the angle of incidence greater than critical angle,the light is completely reflectedback in the denser medium.

The surface separating these two media acts like a 'mirror'.This phenomenon isknown as total internal reflection of light.

Sparkling of diamond and optical fibres used in signal communication work on theprinciple of total internal reflection.

OR

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13. The method that is used for direct extraction of sulphur from the core of the earthis called Frasch method.

This method is based on the low melting point of sulphur. In this method, as shownin Figure three concentric pipes are passed below in the soil so that they touch thelayer of the sulphur.

Superheated water vapour is passed at 443 K temperature in the soil through theouter most cylinder. Sulphur melts because of its low melting point.

Afterwards, air at high pressure is passed through the innermost cylinder so thatsulphur and water in the central cylinder come out on the outer surface and getscooled.

Sulphur is insoluble in water and so it can be easily separated.

Vapour of water

Hot water meltssulphur

Molten sulphurand air

Hot compressed air

Three concentricpipes

Molten sulphur goes towardsupper surface because of highpressure of compressed air

Frasch method for production of sulphur Sulphur is also obtained from pretoleum and natural gas. Firstly, sulphur compounds are converted into hydrogen sulphide (H2S). Sulphur dioxide is obtained by its combustion. Sulphur obtained in free state when sulphur dioxide is heated with H2S in presence

of Fe2O3 catalyst.

2H2S(g) + 3O2(g) 2SO2(g) + 2H2O(g)

SO2(g) + 2H2S 2 3

573K[Fe O ] 3S(s) + 2H2O(g)

14. Plants donot have any excretory system. In plants O2 is considered as waste product which is generated during

photosynthesis. So this O2 is released back to the atmosphere. Transpiration helps to remove excess water. Many plant waste products are stored in cellular vacuoles. Other waste products are stored as resins and gums.

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Far-sightedness1. The eye lens does not vary its thickness

as per the requirement but remainsthin.

2. The light rays from objects nearby theeyes are focused behind the retina. Asa result the nearby objects are not seenclearly.

3. The light rays from distant objects arefocused on the retina and a clear imageis formed. Hence distant objects areseen clearly.

4. This defect can be removed by usingconvex lens of appropriate focal length.

Near-sightedness

1. The eye lens does not vary its thicknessas per the requirement but remainsthick.

2. The light rays from objects at fardistances are focused before the retina.As a result the distant objects cannot beseen clearly.

3. The light rays from objects nearby theeyes are focused on retina. As a resultthe nearby objects are seen clearly.

4. This defect can be removed by usingconcave lens of appropriate focal length.

OR14. There are three types of blood vessels, (1) Arteries, (2) Veins and (3) Capillaries.(i) Arteries :

The blood vessels which carry blood from the heart to different organs are calledarteries.

Their walls are thick and elastic. They enter into the organs and branch into small vessels called arterioles.

(ii) Veins : The blood vessels which carry blood from the different organs to the heart are

called veins. Their walls are thin and non-elastic. They contain valves. Different veins join to form the vena cava.

(iii) Blood Capillaries : Around the tissue, the arterioles break up into fine vessels, called capillaries. The capillaries are thin-walled and narrow. Capillaries unite to form very small blood vessels called venules. Venules unite

to form veins.

15. The nerve cell is the structural and functional unit of nervous system. The nerve cell has 3 components -

(a) Cell body(b) Dendrites(c) Axons

The cell body has cytoplasm and nucleus. Nerve fibres i.e short & long fibres stretch out from cell body. Dendrites - are the short fibres on the cell body. Axon - are the long fibres on the cell body. Insulating myelin sheath made up of fat & protein protects axons. Messages acquired at the dendrite sets off a chemical reaction creating an electric

impulse called nerve impulse. Dendrite pick up message from the receptors pass it to cell body then to axon. Axon pass the message to another nerve cell through synapse. Synapse - is a very small gap present between the two nerve cells.

Nerve Cell

SECTION - DAnswer the following questions : [5 marks] 15

16. (i) Intake of air into lungs is called as inhalation.(ii) When the diaphragm and the muscles attached to the ribs contract, the volume

inside the thoracic cavity increases.(iii)This decreases air pressure in the lungs and so oxygen rich air from the

atmosphere rushes into the lungs, through the nostrils.(iv) The oxygen rich air enters the alveolar sacs of the lungs where gaseous exchange

takes place.

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(v) When diaphragm relaxes, the volume decreases and the pressure in the lungsincreases.

(vi) As a result the carbon dioxide containing air is pushed out of the lungs.(vii)The air containing the carbon dioxide is pushed out which is termed as

exhalation.

17. The far distance objects such as planets, stars and moon etc. appear very small andclose to each other. They can be observed by astronomical telescope.

The ray diagram for astronomical telescope is shown by figure. Construction :- Astronomical telescope has co-axial arrangement of two convex lenses. Lens towards

the object is called objective lens and the convex lens near the eye is called the eyepiece.

- The focal length of objective lens (f0) is large as compared to the eye-piece.

f0

Objective lens

EEye

Piece

A’

B’B’’ B

A’’

image

Ray Coming from

far distance

fe

O

Working :- When telescope is focused on a distant object, parallel rays coming from the object

from real, inverted and diminished image A’B’.- This image acts as an object for eye piece arranged in such a way that its virtual,

magnified and erect image A”B” will be formed. Thus final image of object is virtual, inverted and diminished.

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17. The formula which gives relation between object distances (u), image distance (v)and focal length (f) of mirror is known as mirror formula.

F

A’

C

fA

BP

Pole

M

M’V

R

u

B’

B

A

CB

A’

F

We shall derive this formula for concave mirror of small aperture. As shown in figure when the object AB of height (h) is kept in front of the concave

mirror beyond the centre of curvature (C) the image formed is real, inverted anddiminished (of height h').

According to Cartesian Sign Convention.Object distance = PB = -uFocal length PF = -fImage distance PB' = -vRadius of curvature PC = -R

From figure it is clear that right angled triangles ABP and A'B'P are similartriangles.

A'B'AB

=PB'PB

-v v= =

-u u........... (1)

Similarly right angled triangles ABC and A'B'C are similar triangles

A'B'AB

=CB'CB

........... (2)

But, CB' = PC - PB'= -R - (-v)= -R + v

CB = PB - PC= - u - (- R)= - u + R

A'B'AB

=-R+v-u+R ........... (3)

Comparing equation (1) and (3),

vu

=-R+v-u+R

-uv + Rv = -Ru + vu Rv + Ru = 2uv R(v + u) = 2uv ........... (4)

Dividing equation (4) by Ruv on both sides,

v u 2uv R

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1 1 2u v R ........... (5)

When the object is at infinite distance, the image is formed at the focus F.Therefore, substituting object distance u = and image distance

v = f in equation (5) we have,1 1 2

+ =f R

1 2f R

1 0

Rf =

2............ (6)

This shows that the principal focus (f) is a midpoint between pole (P) and centre ofcurvature(c) along principal axis.

Substituting the value of R = 2f from equation (6) in equation (5), we have

1 1 1+ =u v f ............ (7)

Equation (7) is known as Mirror formula which is also valid for convex mirror.

18. The method to obtain aluminium from alumina by electrochemical method wasinvented by American chemist Charles Martin Hall and French scientist Paul Heroultin 1886.

Hence, this method is also known as Hall-Heroult method. Electric current cannot pass through solid form of alumina. Also, melting point of alumina is very high 2348 K. Electrolysis at such a high temperature is very expensive. Hence, cryolite (Na3AlF6) is added so that electrolysis can be carried out easily. This mixture works as better electric conductor than melted alumina. The melting point can be brought still lower by addition of feldspar (CaF2). As shown in Figure, the mixture of alumina, cryolite and feldspar is electrolysed in

a vessel of iron having inner surface layered with carbon. In this cell, the rods of carbon are joined by copper clamp as anode and carbon

layered graphite is taken as cathode. On passing the electric current molten aluminium is deposited on cathode and

dioxygen gas is produced at the anode.

Electrolysis cell for the extraction of aluminium

Molten AlMolten Al outlet

Graphite with carbonlayer (cathode)

Iron vessel

MoltenAl O +Na AlF

2 3

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Carbon anode Copperclamps

The molten aluminium collected at the bottom of the cell is taken out.Cathod : 2Al3+

(l) + 6e- 2Al(l)

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Anode : 6O-2(l) 3O2(g) + 12e-

The dioxygen gas produced at the anode reacts with rod of carbon and forms carbondioxide.

As a result anode is corroded. Hence, then are frequently replaced.C(s) + O2(g) CO2(g)

OR18.

im puritiesclay, sand

ore + water + turpentine

Froth carryingsulphide ore

tube

airFrothcontaining

m ineral

Froth floatation m ethod

The Froth floatation process is commonly used to concentrate the sulphideores (like copper, zinc and lead sulphide ore).Process :

Powder of ore is mixed with water & pine oil in a big vessel. Sulphide particles of ore stick to the turpentine by wetting while particles of day

and clay do not get wetted with turpentine. Air is blown with pressure in this liquid mixture through a tube. Froth is formed near sulphide particles and it comes up at surface. Heavy particles of clay, sand etc get wetted with water and settle down. Foam containing sulphide particles is taken to another container and washed with

water.

**** Best of Luck****

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