�������������������

�� The increase in demand for energy affects ourenvironment adversely as due to this increase,pollutants like CO, CO2, SO2, etc., are released intothe atmosphere which leads to green house effect.

�� It is used as a base to neutralise the ant sting area.

�� No, because copper-T will not prevent contact bodyfluids. Thus, it will not protect her from sex transmit-ted diseases.

OrNo two individuals are absolutely alike in a popula-tion because variation arises due to DNA copying.

�� The refractive index of the material of a prism isdifferent for different colours of light as differentcolours have different speed in the material of aprism.

�� If 1 J of work is required to move a charge of amount1 C from one point to another, then it is said that thepotential difference between the two points is 1 V.

�� First group elements are also known as alkali metals.They possess following properties :

(a) These elements axhibit + 1 valency.

(b) These are very reactive and do not found freelyin nature.

OrAtomic number of X = 2 + 8 + 2 = 12

Atomic number of Y = 2 + 8 + 6 = 16

�� Planaria

� (a) Number of deer increases which will result inless amount of grass leading to soil erosion.

(b) Food available for lions would be less. Amountof grassland will increase.

OrIt is because the amount of energy decreases withsuccessive trophic levels. After five trophic levels,existence of organisms would become impossible withsuch negligible amount of energy.

� This is due to refraction of light. Ray of light travel-ling from air to water, undergoes bending and then

reflection at the lemon's surface. As a result, itappears larger to the observer.

��� Examples :

(i) A fine beam of sunlight entering a smoke-filledroom through a hole.

(ii) Sunlight passing through the trees of forest.

��� The carbon dioxide exhaled by the astronauts in space-ships is neutralised by lithium hydroxide.

OrMetals lying at the top of the activity series are veryreactive and therefore they occur as compounds andnot as free metals.

��� A parallel combination of two resistance (which willbe 1 �) joined in series with the third resistance (2 �).

OrAs 1 � 1/R, the current is reduced to half of its pre-vious value.

��� Transpiration helps in temperature regulation inplants.

��� (b) Both A and R are true but R is not the correctexplanation of assertion.

��� (b) Both A and R are true but R is not the correctexplanation of assertion.

��� (a) A is true but R is false.

Or(b) Both A and R are true but R is not the correct

explanation of A.

��� (i) (a) (ii) (d) (iii) (b) (iv) (d) (v) (a)

�� (i) (b) (ii) (a) (iii) (a) (iv) (c) (v) (d)

�� (i) (c) (ii) (b) (iii) (d) (iv) (d) (v) (c)

��� (i) (d) (ii) (d) (iii) (c) (iv) (c) (v) (a)

��� Equivalent resistance the given network is

1

R =

4 1 2 3

1 1 +

R R + R + R

= 1 1

+ 10 10 + 10 + 10

����� ���� ��� � ������������������ ����������� ����

�1

R=

1 1 +

10 30

= 3 + 1

30

= 4

30

� R = 30

7.54

� �

Current drawn from the battery

I = V 3 30 2

R 7.5 75 5� � �

� I = 0.4 A

��� Four reasons for adopting contraceptive methods are :

(i) To increase the gap between two children.

(ii) To prevent unwanted pregnancy.

(iii) To prevent transmission of STDs.

(iv) To control population growth.

Or

If a woman is using a coppet-T, it will not help inprotecting her from sexually transmitted diseases.Copper-T prevents only implantation in the uterus.

Sexually transmitted disease caused due to bacterialinfection is gonorrhoea and viral infection is AIDS(Acquired Immune Deficiency Syndrome).

��� f = – 15 cm, h0 = 2 cm, u = – 30 cm

Using,1

f = 1 1

�v u

, we get

1

v=

1 1–

f u

= 1 1

––15 – 30

= 2 –1

–30

= 1

– 30� v = – 30 cm

��� Lungs contain millions of alveoli which provide a sur-face for the exchange of gases. An extensive net-work of blood vessels is present in the wall of thealveoli. By lifting our ribs and flatten the diaphragm,the chest cavity becomes spacious. Air is sucked intothe lungs and alveoli. The oxygen from the breath,diffuses into the blood and CO2 from the blood broughtfrom the body, diffuse into the air.

��� (a) Sodium is bigger than magnesium as it has lessernuclear charge so there is less force of attractionbetween nucleus and valence electrons and lesseffective nuclear charge. It is, therefore, biggerin size.

(b) Sodium is the most metallic element is Period 3.

��� (i) Sodium, carbon (diamond).(ii) Mercury is liquid metal and bromine is liquid

non-metal.Or

(a) Gallium.(b) Lead.

��� (a) Food chain is a sequence of who eats whom inan ecosystem.

(b) Grass � grasshopper � frog � snake � hawk

(c) No, lizard is not cruel and ugly. Lizards are apart of many food chains. Without them foodchain will be disrupted.

(d) Lizard is secondary consumer in food chain.

�� (a) Power of lens is the degree of convergence ordivergence of light rays falling on it. Power of alens is the reciprocal of its focal length.

(b) S.I. unit of power of lens is dioptre. 1 dioptre isthe power of a lens whose focal length is 1 metre.

(c) Focal length of convex lens = + 25 cmFocal length of concave lens = – 10 cm

Total power, P = Power of convex lens+ Power of concave lens

= 100

25�+

100

–10� ��

= 4 – 10 = – 6 DPower of combination is – 6 D.

�� (a) 2NaCl(aq) + 2H2O(l) ���� 2NaOH(aq) (Brine solution) + Cl2(g) + H2 (g)

Three products, sodium hydroxide, chlorine gasand hydrogen gas are produced and the processis called chloro-alkali process.

(b) (i) Baking soda (NaHCO3) is added for fastcooking. It is produced using sodium chlorideas one of the raw materials.

NaCl + H2O + CO2 + NH3 � NH4Cl+ NaHCO3 (Baking soda)

(ii) When baking powder, mixture of bakingsoda and a mild edible acid, i.e, tartaric acidis heated or mixed in water, CO2 producedduring the reaction causes bread or cake softand spongy.

NaHCO3 + H+ ��CO2 + H2O + Sodium salt of acid(from any acid)

Sample Paper 5����

(c) Washing soda is used for removing permanenthardness of water.

��� (a) Inert elements are placed in group 18.(b) B2–, C–1, E2– and F–1 ions would be formed by B,

C, E and F respectively.(c) F element would have chemical properties similar

to C.(d) A is Helium (He) element having one shell only K.(e) Both A (Helium) and D (Neon) are inert noble

gases whose octet is complete.(f) B (Oxygen) is the most abundant element in the

earth’s crust.

���

(a) The stomata are minute pores having two kidneyshaped guard cells.

(b) The guard cells, called stomatal aperture andare rich in chloroplasts.

(c) The guard cells regulate the opening and closingof stomatal aperture.

(d) When water flows into the guard cells, they swelland it tends them to open stomatal aperture.

(e) When the guard cells shrink, the stomatal porecloses due to the loss of water.

Functions :(i) Exchange of gases between the plant and

atmosphere.(ii) Transpiration.

Or

(a)

(b) Holozoic nutrition.Amoeba takes food by using temporary fingerlike extensions called pseudopodia which fuseover the food particle forming a food vacuole.Inside the food vacuole, complex substances arebroken down into simpler ones by catabolismwhich then diffuse into cytoplasm. The remainingundigested material is thrown out. Pseudopodiaare also helpful is locomotion.

��� Parents :

F1 generation :

F2 generation :

(a) The colour of all the flowers in F1 generation willbe blue.

(b) Percentage of white flower plants in F2 generationwill be 25.

(c) The ratio of genotype BB and Bb in F2 progenywill be 1 : 2

��� (i) Na, K (ii) Ca, Mg (iii) He, Ne

Or� Carbon compounds are named as homologous

series because they are derived from same generalformula, having same functional group, similarchemical properties and show gradation in physicalproperties. Each member differs from successivemember by —CH2—.

� The two consecutive members of alkane seriesare methane (CH4) and ethane (C2H6).

� These members of a homologous series showgradual change in their physical properties withincrease in molecular masses.

� Their molecular masses and functional groupsdetermine their physical and chemical properties,respectively.

��� (a) Mercury.

(b) Graphite.

(c) Aluminium.

(d) A pure metal is always deposited at thecathode.

(e) Zinc oxide (ZnO) is an amphoteric oxide.

����� ���� ��� � ������������������ ����������� ����

��� Vegetative Propagation : Method by which plantsreproduce by their vegetative parts such as roots,stems and leaves is known as vegetative propagation.Vegetative propagation occurs naturally as well asby artificial means such as plant tissue culture.Natural Vegetative Propagation : Mint, Sugarcanereproduce naturally by roots.� Sugarcane and jasmine reproduce naturally by

stems regeneration.� Bryophyllum reproduce naturally by leaves.

Fig. Vegetative propagation by roots insweet potato

Artificial Vegetative Propagation : There are threemethods of artificial propagation :(i) Cutting : Cutting is a method in which a piece of

stem, root, leaf when placed partly under moistcondition in soil, develops into roots and givesrise to new plants under the influcence of growthfactors and growth regulators.Example : Rose, sugarcane and grape etc.

(ii) Layering : In this method, a part of stem of plantis pulled and buried in soil, while, it is attachedand supported by parent plant. When layeredbranch develops root then it is separated parentplant.

(iii) Grafting : In this method, two parts of differentplants are joined together which unite and growas one plant. The portion of the plant that is graftedon to the other plant is called scion and the plant inwhich grafting takes place is called stock.Example : Rose, mango, citrus etc.

Significance of vegetative propagation :(i) Plants can bear flower and fruits earlier, as

compare to natural.

(ii) Plants which have lost the ability to produceviable seeds can also reproduce by vegetativepropagation.

(iii) Seedless varieties can be obtained like as papaya.(iv) All plants are genetically almost similar to the

parent plant.

Or(a) Reproduction is not essential for survival of

the individual but require for stability of speciesbecause :(i) Reproduction needs a lot of energy.(ii) As a result of reproduction, genetic information

is transferred from one generation to nextthrough genes.

(iii) DNA copying takes place with high constancyand considerable variations i.e., advantagesto the species for stability in the changingenvironment.

(b) The ratio of chromosome number between anegg and its zygote is 1 : 2. Sperm is geneticallydifferent from the egg in the way that it containseither X or Y chromosome whereas, an eggalways contains an X chromosome.

��� Resistivity :(i) It is the measure of a material’s ability to oppose

the flow of current.(ii) It depends on the property of the material. Its value

is constant for a particular range of temperature.(iii) Unit of resistivity is ohm metre.Resistance :(i) It is a measure of the opposition that a circuit (or

on electrical element) offers to the flow ofelectric current.

(ii) Resistance of a conductor is directly proportionalto its length and inversely proportional to its areaof cross section.

(iii) Unit of resistance is ohm.The resistors are generally made of thin wires whilethe wires used in connections are made comparativelythicker and are of copper or aluminium. This isbecause thicker wire has less resistance than thinnerwire.

Or

(a) Sulphur is a non-metal Magnesium is a metal

(i) Poor conductor of heat and electricity. (i) Good conductor heat and electricity.(ii) Neither malleable nor ductile. (ii) Malleable and ductile.(iii) S + O2 � SO2 (iii) 2Mg + O2 � 2MgO

SO2 + H2O � H2SO3 (Sulphurous acid) MgO + H2O � Mg(OH)2 (Magnesium hydroxide)Sulphur dioxide is acidi oxide. Magnesium oxide is basic in nature.

(b) (i) It is because metals are sonorous, i.e., they produce sound when strike with a hard substance.(ii) It is because copper is good conductor of electricity.

�������������������

�� 3 2

H H| |

CH CH Cl or H — C — C — Cl| |H H

�� Sixth period is the longest with 32 elements.

�� X = Fe, Y = Cu, Displacement reaction.Or

X = Calcium oxide (Quick lime), Combination reaction.�� The resistance of a voltmenter is very high and for

an ideal voltmeter, its value is infinity.Or

The electrical resistivity of copper is low.

�� When a bar magnet is withdrawn from inside thecoil, the deflection in the galvanometer is towardsthe left.

�� Induced magnetic field will be in the form of concen-tric circles in the plane of paper.

�� Heart beat is due to the rhythmic contraction andrelaxation of heart muscles. One contraction (sys-tole) and one relaxation (diastole) of heart constituteone heart beat.

� Cellular DNA is the informatin source for makingproteins in cells.

�

Or

��� P = 1

(in metre)f

F = 1

P =

1+

2 = + 0.5 m

��� (a) Plants(b) Tiger

Or

Plants capture only 1% of sunlight. Therefore, theamount of energy captured will be 500 joule (1/100 ×50000 = 500 Joule).

��� It is to carry sperm from testes, which enter penisfor their release.

Or

Because both produce gametes and sex hormones.

��� Such a ray falls normally on the mirror. So, its angleof incidence is 0°.

��� (a) Both A and R are true and R is correct explana-tion of A.

Or

(a) Both A and R are true and R is correct explana-tion of the A.

��� (c) A is false but R is true.

��� (c) A is true but R is false.

��� (i) (a) (ii) (d) (iii) (a) (iv) (c) (v) (b)

�� (i) (b) (ii) (b) (iii) (a) (iv) (c) (v) (b)

�� (i) (a) (ii) (b) (iii) (b) (iv) (b) (v) (a)

��� (i) (c) (ii) (a) (iii) (c) (iv) (d) (v) (d)

��� (a) Rr and Rr.

(b) Red colour of flowers is the dominant trait whilewhite colour is the recessive trait.

Or

(Break down of glucose by various pathways)

��� The series consists of members of same family withsimilar physical and chemical properties, therefore,called homologous series :

����� ���� ��� � ������������������ ����������� �����

(i) CH3OH and (ii) CH3CH2OH are two consecu-tive members of homologous series.

Alkyl group –CH3 and CH3CH2 part determinesphysical properties. Functional group —OH de-termines chemical properties of the compunds.

��� 1. Take a healthy leaf from the potted plant.

2. Remove a part of the peel from the lower surfaceof the leaf. You can do this by folding the leaf overand gently pulling the peel apart using forceps.Keeps the peel in a watch glass containing water.

3. Put a few drops of safranin stain in a watch glass.After 2-3 minute take out the peel and place it onclean glass slide.

4. Put a drop of glycerine over the peel and place aclean covers lip gently over it with the help of aneedle. Remove the excess stain and glycerine withthe help of blotting paper and observe the slideunder magnifications of the compound microscope.

��� Decomposition reactions are those in which a com-pound breaks down to form two or more substances.These reactions require a source of energy to pro-ceed. Thus, they are the exact opposite of combina-tion reactions in which two or more substances com-bine to give a new substance with the release of en-ergy.

���

Or

��� (a) Monocromatic light will not get split and emerge

out at the same angle.

(b) When a narrow beam of white light passes

through a prism, it emerges as a specturm of all

components of white light. White light gets split

into seven colours (VIBGYOR).

��� (a) Object should be placed at < 40 cm (less than

40 cm) in front of the mirror, i.e. between focusand pole as concave mirror forms a virtual, erectand magnified image when object is placedbetween focus and pole.

(b) Image will be bigger than the object.

�� (a) Bacteria and fungi are called decomposers asthey breakdown the organic complex matter intosimple inorganic matter that become recycled andremained in soil.

(b) Two roles of decomposers are :

(i) Decomposers breakdown dead living ofplants and animals thereby act as cleaningagents of nature.

(ii) Decomposers help in maintaining the fertil-ity of soil by adding humus content and nu-trients like N, P, K etc. in soil.

Or

(a) Use of CFCs (Chlorofluorocarbon) in refrigera-tion, fire extinguishers and aerosol sprayers.

(b) The harmful effects of depletion of ozone layerare :

(i) Due to depletion of ozone layer, U.V.radiation reaches the earth and causes skincancer, inflamation to eyes in humans.

(ii) The depletion of ozone layer may lead tovariations in global rainfall, ecological distur-bances and dwindling of global rood supplies.

(ii) During the production of hydroelectricity,dam do not produce green house gases. Theydo not pollute the atmosphere. It is a cleansource of energy.

(iii) Dams also used for water conservation byholding water for long time. As per need alsocan used for generation of electricity.

�� (a) When magnesium ribbon is burnt in air it pro-duces dazzling light and a white coloured mag-nesium oxide.

2Mg + O2 ���2MgO

Metal oxide is basic in nature.

Sample Paper 6����

(b) A is a non-metal because non-metal oxides areacidic or neutral in nature.AO = CO (carbon monooxide)—Neutral oxideAO2 = CO2 (carbon dioxide)—Acidic oxide

��� (i) The following reaction takes place when bakingsoda is heated during making bread and cake.

2NaHCO3 Heat���� Na2CO3 + H2O + CO2

Carbon dioxide produced during the reactioncauses bread or cake to rise, making them softand spongy.

(ii) Soda-acid fire extinguisher releases water andcarbon dioxide which help in extinguishing fire.2NaHCO3(aq) + H2SO4(l) ��� Na2SO4(aq)

+ 2H2O(l) + 2CO2(g)(iii) pH of baking soda solution is more than 7

because its solution contains OH– ions.

��� (a) Sodium (Na) element has electronic configura-tion 2, 8, 1, because it contains 11 electrons.

(b) C = 6, K L

2 4

� �� ��

, Carbon has a total of two shells,

with 4 electrons in the valence shell.

(c) Al = 13 K L M

2 8 3

� �� ��

, Aluminium has a total of three

shells, with 3 electrons in the valence shell.

(d) He = 2, K

2

� �� ��

, Helium has one shell which is com-

pletely filled with electrons.

(e) C = 6, K L

2 4

� �� ��

, Carbon has twice as many elec-

trons in the second shell as in the first shell.

��� The three kinds of cells present in blood are :(i) RBCs, (ii) WBCs and (iii) Platelets.(i) RBCs : They are involved in the exchange of

gases i.e., oxygen from lungs to blood followedby cells and tissues and then carbon dioxide fromcells and tissues to lungs.

(ii) WBCs : They provide defence to our body. Theyphagocytosed to the micro-organisms enteringour body and protect us from their infections,known as immunity.

(iii) Platelets : The platelets help in clotting of bloodafter injury and hence helps to prevent the ex-cessive loss of blood and also maintain the den-sity of blood. For example, platelets count sup-pressed during dengue fever.

��� Water and minerals are transported through xylem

cells from soil to the leaves. The xylem cells of roots,Water and minerals are transported through xylemcells from soil to the leaves. The xylem cells of roots,stem and leaves are interconnected to form aconducting channel. The root cells take ions fromthe soil. This creates a difference between theconcentration of ions of roots and soil. Therefore,there is a steady movement of water into xylem. Anosmotic pressure is formed and water and mineralsare transported from one cell to the other cells due toosmosis. The continuous loss of water takes placedue to transpiration. Thus, there is continuousmovement of water and mineral molecules andtransportation of water and minerals takes place.

��� R = A

l

Resistance of original wire = R1 = 20 �Length = l1,

Area of cross-section = A1

Resistivity =

Then, R1 = 1

1A

l ...(i)

Since length of the wire is increased, its area of cross-section decreases, as volume of the wire remainsconstant.

Then, New resistance = R2

� A1l1 = A2l2Length = l2 = 2l1

� A1l1 = A2(2l1)

Area of cross-section = A2 = 1A

2

12 2 1

AA , 2

2l l

��� � � �� �� �Q

New resistance, R2 = 2

2A

l ...(ii)

Dividing (i) by (ii),

1

2

R

R= 1

1A

l× 2

2

A

l

� 1

2

R

R= 1

1A

l× 1

1

A

2 2l�

� 1

2

R

R=

14

����� ���� ��� � ������������������ ����������� �����

Then,2

20

R=

1

4

� R2 = 80 �

��� (i) Hydrogen

(ii) OxygenC6H12O6 + 6O2 �� 6CO2 + 6H2O + energy

(iii) Carbon (Graphite), it is a conductor, hence it usedin dry cells.

(iv) Nitrogen because it is an inert gas used in pack-ing of chips.

(v) Sulphur, it is added in natural rubber for increas-ing elasticity of rubber.

Or(a) (i) Electron dot structure of CH4

:

(ii) Electron dot structure of N2 :

(b) Alloy is a homogeneous mixture of two metalsor one metal and other is non-metal.(i) Bronze, mixture of copper and tin.(ii) Solder, mixture of tin and lead.

��� (a) Pollination is the transfer of pollen grains fromthe anther of a flower to the stigma of a carpel.Significance of pollination :

(i) It is necessary for seed formation and thus,perpetuation of species.

(ii) It stimulates the development of fruits.(iii) Cross-pollination brings about genetic recom-

bination of traits.(b) After the pollen lands on a suitable stigma, it has

to reach the female germ cells in the ovary forfertilisation.The pollen tube grows out of the pollen grainthrough the style to reach the ovary.After fertilisation, the zygote divides several timesto form an embryo within the ovule.(i) Ovule becomes seed.(ii) Ovary becomes fruit.

Or(a) The formation of sperms takes place in the tes-

tes. It secretes the hormone, called testosterone.For as 'spermatogenesis', regulating the forma-tion of sperms, know seen in boys at the time ofpuberty.

(b) (i) The fertilisation takes place in the fallopiantubes.

(ii) The implantation occurs in the uterus.The uterus prepares itself every month toreceive and nurture the growing embryo. Thelining thickens and is richly supplied with bloodto nourish the growing embryo.The embryo gets nutrition from the mother’sblood with the help of a special tissue calledplacenta. The development of the child insidethe mother’s body takes approximately ninemonths. On completion of nine months, thechild is born due to a rhythmic contractionsof the muscles in the uterus.