SECTION -A
1. The change in colour of the moist litmus paper in the given set-up is due to
i. presence of acid
ii. presence of base
iii. presence of H⁺(aq) in the solution
iv. presence of Litmus which acts as an indicator
(a) i and ii
(b) Only ii
(c) Only iii
(d) Only iv.
EXPLANATION: (option c) litmus changes its colour in the presence of acids and bases hence act as an indicator. in the figure shown, HCl is liberated during the reaction of NaCl and conc H2SO4 which turns blue litmus red ( acid of the solution has H+ ions)
2. In the redox reaction
MnO2 + 4HCl → MnCl2 + 2H2O + Cl2
(a) MnO2 is reduced to MnCl2& HCl is oxidized to H2O
(b) MnO2 is reduced to MnCl2& HCl is oxidized to Cl2
(c) MnO2 is oxidized to MnCl2 & HCl is reduced to Cl2
(d) MnO2 is oxidized to MnCl2 & HCl is reduced to H2O
EXPLANATION: (b) it is an example of redox reaction in which a substance which loses oxygen or gain hydrogen is reduced and which gain oxygen and loses hydrogen is oxidised. in the above reaction MnO2 loses oxygen to form MnCl2 hence it get reduced while HCl loses hydrogen to form Cl2 is said to be oxidised.
3.
Which of the following is the correct observation of the reaction shown in the above set
up?
(a) Brown powder of Magnesium oxide is formed.
(b) Colourless gas which turns lime water milky is evolved.
(c) Magnesium ribbon burns with brilliant white light.
(d) Reddish brown gas with a smell of burning Sulphur has evolved.
EXPLANATION: (c) upon burning of Mg ribbon
Mg+ O2-------> MgO
this reaction occurs with the flash of bright white light.
4 with reference to four gases CO2, CO, Cl2 and O2, which one of the options in the
is the table correct?
EXPLANATION: (b) acidic oxides are produced when acid is added to water. carbon dioxide is an acidic oxide that reacts with water to produce carbonic acid. Cl2 is used for the treatment of water, CO2 is a product of respiration, and CO is a product of incomplete combustion.
5.On placing a copper coin in a test tube containing green ferrous sulphate solution, it will
be observed that the ferrous sulphate solution
(a) turns blue, and a grey substance is deposited on the copper coin.
(b) turns colourless and a grey substance is deposited on the copper coin.
(c) turns colourless and a reddish–brown substance is deposited on the copper coin.
(d) remains green with no change in the copper coin.
EXPLANATION: (d) copper is less reactive than iron, when copper is added to the ferrous sulphate solution, no reaction will take place.
6 Anita added a drop of each of acetic acid and hydrochloric acid on pH paper and compared the colours. Which of the following is the correct conclusion?
(a) pH of acetic acid is more than that of hydrochloric acid.
(b) pH of acetic acid is less than that of hydrochloric acid.
(c) Acetic acid dissociates completely in an aqueous solution.
(d) Acetic acid is a strong acid
EXPLANATION: (a) pH paper is a universal indicator that is used to determine the strength of acids or bases as function of pH. acids gives out more H+ ions as compared to bases. stronger acids dissociate into a higher amount of H+ ions than weaker acids. strong acids have lower pH values than weak acids. pH is acetic acid is less than HCl.
7. The formulae of four organic compounds are shown below. Choose the correct option
(a) A and B are unsaturated hydrocarbons
(b) C and D are saturated hydrocarbons
(c) Addition of hydrogen in presence of catalyst changes A to C
(d) Addition of potassium permanganate changes B to D
EXPLANATION: (c) saturated hydrocarbons are those which has only single bond between two carbon atoms. unsaturated hydrocarbon are those which have double or triple bond between two carbon atoms. compound A is ethene. the addition of hydrogen to a compound in presence of catalyst is called hydrogenation.
ethane+ H2-------> ethane (in the presence of catalyst)
8 In the given transverse section of the leaf identify the layer of cells where maximum
photosynthesis occurs.
(a) I, II
(b) II, III
(c) III, IV
(d) I, IV
EXPLANATION: (b) I upper epidermis II. palisade layer III. spongy cell IV. guard cells
the palisade layer contain chlorophyll and is primary site for photosynthesis. the spongy layer allows the exchange of gases which is necessary for photosynthesis.
9 Observe the experimental setup shown below. Name the chemical indicated as ‘X’ that
can absorb the gas which is evolved as a byproduct of respiration
(a) NaOH
(b) KOH
(c) Ca (OH)2
(d) K2CO3
EXPLANATION: (b) this activity shows that carbon dioxide is necessary for photosynthesis. carbon dioxide released as byproduct of respiration in both humans and plants. KOH is kept in a watch glass under a bell jar to absorb all CO2 present in the bell jar.
2KOH+ CO2 -------> K2CO3 + H2O
10 If a tall pea plant is crossed with a pure dwarf pea plant then, what percentage of F1 and
F2 generation respectively will be tall?
(a) 25%, 25%
(b) 50%, 50%
(c) 75%,100%
(d) 100%, 75%
EXPLANATION: (d)
11 Observe the three figures given below. Which of the following depicts tropic movements
appropriately
(a) B and C
(b) A and C
(c) B only
(d) C only
EXPLANATION:(d) tropic movements are plants' responses to a stimulus in the form of growth. this movement can either towards or away from the stimulus. shoot will grow towards sun while roots towards earth.
12 The diagram shown below depicts pollination. Choose the options that will show a
maximum variation in the offspring.
(a) A, B and C
(b) B and D
(c) B, C and D
(d) A and C
EXPLANATION: (b) A and C shows self-pollination (anther to the stigma of the same flower), B and D show cross-pollination (anther of one flower to the stigma of another flower) leading to variation
13 A complete circuit is left on for several minutes, causing the connecting copper wire to
become hot. As the temperature of the wire increases, the electrical resistance of the wire
(a) decreases.
(b) remains the same.
(c) increases.
(d) increases for some time and then decreases.
EXPLANATION: (c) the electrical resistance of a wire is dependent on the temperature of the conductor. in metals, the higher the temperature, the more resistance will increase. as copper is a metal its resistance increases with an increase in temperature
14 A copper wire is held between the poles of a magnet.
The current in the wire can be reversed. The pole of the magnet can also be changed
over. In how many of the four directions shown can the force act on the wire?
(a) 1
(b) 2
(c) 3
(d) 4
EXPLANATION: (b) by using fleming's left hand rule, two conclusions can be drawn:
1. when the direction of current is kept constant, the magnetic field can be varied in 2 directions. the resultant force on the wire can be in 2 directions: upward or downward
2. when the direction of magnetic field is kept constant, the current can be varied in 2 direction. the resultant force on wire can be upward or downward.
15.
Plastic insulation surrounds a wire having diameter d and length l as shown above. A
decrease in the resistance of the wire would be produced by an increase in the
(a) length l of the wire
(b) diameter d of the wire
(c) temperature of the wire
(d) the thickness of the plastic insulation
EXPLANATION: (b)Resistance is directly proportional to the resistivity of the material, and length of wire. it is inversely proportional on the area of the wire. the resistance of the material would only decrease with an increase in area. this can be done by increasing the diameter.
16 Which of the following pattern correctly describes the magnetic field around a long straight wire carrying current?
(a) straight lines perpendicular to the wire.
(b) straight lines parallel to the wire.
(c) radial lines originating from the wire.
(d) concentric circles centred around the wire.
EXPLANATION: (d) The field consists of concentric circles centred around the wire.
17. These consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below:
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true and R is not the correct explanation of A
(c) A is true but R is false
(d) A is False but R is true
17 Assertion: Silver bromide decomposition is used in black and white photography.
Reason: Light provides energy for this exothermic reaction.
EXPLANATION: (c) silver bromide is used in black-and-white photography (photolysis reaction), it is not an exothermic reaction.
18 Assertion: Height in pea plants is controlled by efficiency of enzymes and is thus
genetically controlled.
Reason: Cellular DNA is the information source for making proteins in the cell.
EXPLANATION: (a) Both A and R are true and R is the correct explanation of A
19 Assertion: Amphibians can tolerate mixing of oxygenated and deoxygenated blood.
Reason: Amphibians are animals with two chambered heart
EXPLANATION: (c) amphians have 3 chambered heart.
20 Assertion: On freely suspending a current – carrying solenoid, it comes to rest in
Geographical N-S direction.
Reason : One end of current carrying straight solenoid behaves as a North pole and
the other end as a South pole, just like a bar magnet.
EXPLANATION:(a) Both A and R are true and R is the correct explanation of A
SECTION – B
21 A clear solution of slaked lime is made by dissolving Ca(OH)2in an excess of water.
This solution is left exposed to air. The solution slowly goes milky as a faint white
precipitate forms. Explain why a faint white precipitate forms, support your
response with the help of a chemical equation.
OR
Keerti added dilute Hydrochloric acid to four metals and recorded her observations
as shown in the table given below:
Select the correct observation(s) and give chemical equation(s) of the reaction
involved.
EXPLANATION: Calcium hydroxide reacts with Carbon dioxide present in the atmosphere to form
Calcium carbonate which results in milkiness/white ppt / Formation of Calcium
carbonate
Ca(OH)₂ + CO₂ → CaCO₃ + H₂O (1mark)
OR
Fe + HCl → FeCl₂/ FeCl₃ + H₂
Zn + HCl → ZnCl₂ + H₂
22 How is the mode of action in beating of the heart different from reflex actions?
Give four examples.
EXPLANATION:
23 Patients whose gallbladders are removed are recommended to eat less oily food. Why?
EXPLANATION: The gallbladder stores bile which helps in the emulsification of lipids. In the absence of stored bile, emulsification of fats will be negligible/ affected/ less and thus fat digestion will be slow. Hence there are such diet restrictions
24 Name the substances other than water, that is reabsorbed during urine formation. What are the two parameters that decide the amount of water that is reabsorbed in the kidney?
EXPLANATION: Glucose, amino acids, salts and a major amount of water are selectively re-absorbed as the urine flows along the tube. The amount of water reabsorbed depends on how much excess water there is in the body, and on how much-dissolved waste there is to be excreted.
25.
State the phenomena observed in the above diagram. Explain with reference to the
diagram, which of the two lights mentioned above will have the higher wavelength?
OR
How will you use two identical prisms so that a narrow beam of white light incident
on one prism emerges out of the second prism as white light? Draw the diagram.
EXPLANATION: Dispersion- The splitting of white light into seven colours on passing through a prism. Velocity is directly proportional to wavelength given constant frequency. So yellow will have greater wavelength than blue as the velocity of yellow light is greater than blue.
OR
Angle of deflections of the two prisms need to be equal and opposite. While the first prism splits the light in the seven colours due to different angles of deflection, the second prism combines the spectrum along a single ray and the colours again combine to give white light as the emergent light.
26 A lot of waste is generated in the neighbourhood. However, almost all of it is biodegradable. What impact will it have on the environment or human health?
EXPLANATION: Excess generation of biodegradable wastes can be harmful as: Its decomposition is a slow process leading to the production of foul smells and gases.It can be the breeding ground for germs that create unhygienic conditions.
SECTION - C
27.
EXPLANATION: i) Displacement
● Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)
● Zn(s) + CuSO4(aq)→ ZnSO4(aq) + Cu(s)
● Pb(s) + CuCl2(aq) → PbCl2(aq) + Cu(s)
ii) Double displacement
Na2SO4 (aq) + BaCl2(aq) → BaSO4 (s) + 2NaCl(aq)
28. Identify the types of reaction mentioned above in (i) and (ii). Give one example for
each type in the form of a balanced chemical equation.
(a) Identify the gasses evolved at the anode and cathode in the above
experimental set up.
(b) Name the process that occurs. Why is it called so?
(c) Illustrate the reaction of the process with the help of a chemical equation.
EXPLANATION: (a) Anode: Chlorine; Cathode: Hydrogen
(b) Chlor alkali process as the products obtained are alkali, chlorine gas and
hydrogen gas Electric current
(c) 2NaCl(aq) + 2H2O(l) 2NaOH(aq) + Cl2 (g) + H2 (g)
29 The leaves of a plant were covered with aluminium foil, how would it affect the
physiology of the plant?
OR
How is lymph an important fluid involved in transportation? If lymphatic vessels
get blocked, how would it affect the human body? Elaborate.
EXPLANATION: No photosynthesis will occur so no glucose will be made. Also, no respiration will take place as no Oxygen will be taken in. No transpiration will occur so there would be no upward movement of water or minerals from the soil as there will be no transpirational pull. Temperature regulation of the leaf surface will be affected.
OR
Lymph carries digested and absorbed fat from the intestine and drains excess fluid from extracellular space back into the blood. Blockage of the lymphatic system will lead to water retention and poor fat absorption in the body
30 Rohit wants to have an erect image of an object using a converging mirror of focal
length 40 cm.
(a) Specify the range of distance where the object can be placed in front of the
mirror. Justify.
(b) Draw a ray diagram to show image formation in this case.
(c) State one use of the mirror based on the above kind of image formation.
EXPLANATION: (a) The object has to be placed at a distance between 0 - 40 cm. This is because image is virtual, erect and magnified when the object is placed between F and P.
(c)Used as a shaving mirror or used by dentists to get an enlarged image of teeth
31 (a) A lens of focal length 5 cm is being used by Debashree in the laboratory as a magnifying glass. Her least distance of distinct vision is 25 cm.
(i) What is the magnification obtained by using the glass?
(ii) She keeps a book at a distance 10 cm from her eyes and tries to read. She is unable to read. What is the reason for this?
(b) Ravi kept a book at a distance of 10 cm from the eyes of his friend Hari. Hari is
not able to read anything written in the book. Give reasons for this?
EXPLANATION: (a)
(b) This is because the least distance of distinct vision is 25 cm.
32 A student fixes a white sheet of paper on a drawing board. He places a bar magnet in the centre and sprinkles some iron filings uniformly around the bar magnet. Then he taps gently and observes that iron filings arrange themselves in a certain pattern.
(a) Why do iron filings arrange themselves in a particular pattern?
(b) Which physical quantity is indicated by the pattern of field lines around the bar magnet?
(c) State any two properties of magnetic field lines.
OR
A compass needle is placed near a current carrying wire. State your observations for the following cases and give reasons for the same in each case-
(a) Magnitude of electric current in the wire is increased.
(b) The compass needle is displaced away from the wire.
EXPLANATION: (a) When iron filings are placed in a magnetic field around a bar magnet, they behave like tiny magnets. The magnetic force experienced by these tiny magnets makes them rotate and align themselves along the direction of field lines.
(b)The physical property indicated by this arrangement is the magnetic field produced by the bar magnet.
(c) Magnetic field lines never intersect, magnetic field lines are closed curves.
OR
(a) The deflection in the compass needle increases as the Magnetic field of the current-carrying conductor is directly proportional to the current flowing through it.
(b) The deflection in the needle decreases as the magnetic field is inversely proportional to the perpendicular distance from the wire.
33 Why is damage to the ozone layer a cause for concern? What are its causes and
what steps are being taken to limit this damage?
EXPLANATION: Damage to the ozone layer is a cause for concern because the ozone layer shields the surface of earth from harmful UV radiations from the sun which cause skin cancer in human beings. Synthetic chemicals like chlorofluorocarbons (CFCs) which are used as refrigerants and in the fire - extinguishers are the main reason for the depletion of the ozone layer.Steps taken to limit this damage - Many developing and developed countries have signed and are obeying the directions of UNEP (United Nations Environment Programme) to freeze or limit the production and usage of CFCs at 1986 levels
SECTION - D
34 Shristi heated Ethanol with a compound A in presence of a few drops of concentrated sulphuric acid and observed a sweet smelling compound B is formed. When B is treated with sodium hydroxide it gives back Ethanol and a compound C.
(a) Identify A and C
(b) Give one use each of compounds A and B.
(c) Write the chemical reactions involved and name the reactions.
OR
(a) What is the role of concentrated Sulphuric acid when it is heated with Ethanol at 443 K. Give the reaction involved.
(b) Reshu by mistake forgot to label the two test tubes containing Ethanol and Ethanoic acid. Suggest an experiment to identify the substances correctly? Illustrate the reactions with the help of chemical equations
EXPLANATION: (a) A – Ethanoic acid/ Or any other carboxylic acid, C- Sodium salt of ethanoic
acid/ any other carboxylic acid/ sodium ethanoate
(b) Use of A- dil solution used as vinegar in cooking/ preservative in pickles
Use of B – making perfumes, flavouring agent
Conc H2SO4
(c) CH3COOH + C2H5OH ----------------> CH3COOC2H5 +H2O
CH3COOC2H5 + NaOH----------------> CH3COONa + C2H5OH
OR
(a) Sulphuric acid acts as a dehydrating agent
Conc H2SO4, 443K
C2H5OH —--------------------> C2H4 + H2O
(b) By reaction with sodium carbonate/ bicarbonate 1M with the samples, ethanol will not react whereas ethanoic acid gives brisk effervescence
2CH3COOH + Na2 CO3 → 2CH3COONa + H2O+ CO2
OR
CH3COOH + NaHCO₃ → CH₃COONa + H2O + CO2
35 (a) Why is it not possible to reconstruct the whole organism from a fragment in complex multicellular organisms?
(b) Sexual maturation of reproductive tissues and organs are necessary link for reproduction. Elucidate.
OR
(a) How are variations useful for species if there is a drastic alteration in the niches?
(b) Explain how the uterus and placenta provide necessary conditions for proper growth and development of the embryo after implantation
EXPLANATION: (a) The reason is that many multi-cellular organisms are not simply a random collection of cells. Specialised cells are organised as tissues, and tissues are organised into organs, which then have to be placed at definite positions in the body. Therefore, the cell-by-cell division would be impractical.
(b) Sexual maturation of reproductive tissues is a necessary link for reproduction because of the need for specialised cells called germ-cells to participate in sexual reproduction. The body of the individual organism has to grow to its adult size, the rate of general body growth begins to slow down, reproductive tissues begin to mature.A whole new set of changes in the appearance of the body takes place like change in body proportions, new features appear. This period during adolescence is called puberty.There are also changes taking place that are different between boys and girls. In girls, breast size begins to increase, with darkening of the skin of the nipples at the tips of the breasts. Also, girls begin to menstruate at around this time. Boys begin to have new thick hair growth on the face and their voices begin to crack.
OR
(a) If the niche were drastically altered, the population could be wiped out. However, if some variations were to be present in a few individuals in these populations, there would be some chance for them to survive. Variation is thus useful for the survival of species over time.
(b) 1. The lining of the uterus thickens and is richly supplied with blood to nourish the growing embryo.
2. The embryo gets nutrition from the mother’s blood with the help of the placenta. It is embedded in the uterine wall.
3. It contains villi on the embryo’s side of the tissue. On the mother’s side are blood spaces, which surround the villi.
4. This provides a large surface area for glucose and oxygen to pass from
the mother to the embryo. The developing embryo will also generate
waste substances which can be removed by transferring them into the
mother’s blood through the placenta.
5. The child is born as a result of rhythmic contractions of the muscles in the
uterus.
36.
The diagram above is a schematic diagram of a household circuit. The house shown in the above diagram has 5 usable spaces where electrical connections are made. For this house, the mains have a voltage of 220 V and the net current coming from the mains is 22A.
(a) What is the mode of connection to all the spaces in the house from the mains?
(b) The spaces 5 and 4 have the same resistance and spaces 3 and 2 have respective resistances of 20Ω and 30Ω. Space 1 has a resistance double that of space 5. What is the net resistance for space 5.
(c) What is the current in space 3?
(d) What should be placed between the main connection and the rest of the house’s electrical appliances to save them from accidental high electric current?
EXPLANATION: (a) All spaces are connected in parallel.
(b) Let Resistance of Space 5 and 4 be R ohms respectively
Resistance of Space 1 = 2 R ohms
Resistance of Space 2 = 30 ohms
Resistance of Space 3 = 20 ohms
Current = 22 A
V= 220 V
Total Resistance= V/I
SECTION - E
37 Two students decided to investigate the effect of water and air on iron object under identical experimental conditions. They measured the mass of each object before placing it partially immersed in 10 ml of water. After a few days, the object were removed, dried and their masses were measured. The table shows their results.
(a) What might be the reason for the varied observations of the two students?
(b) In another set up the students coated iron nails with zinc metal and noted that, iron nails coated with zinc prevents rusting. They also observed that zinc initially acts as a physical barrier, but an extra advantage of using zinc is that it continues to prevent rusting even if the layer of zinc is damaged. Name this process of rust prevention and give any two other methods to prevent rusting.
OR
(b) In which of the following applications of Iron, rusting will occur most? Support your answer with valid reason.
EXPLANATION: a) Rusting occurs in both A and B so there is an increase in mass. As the surface area of B is more, extent of rusting is more
(b) Galvanization
Oiling/ greasing/ painting/ alloying/ chromium plating or any other
OR
b) C - Iron hinges on a gate
Iron is in contact with both atmospheric oxygen and moisture/ water vapour.
38.Pooja has green eyes while her parents and brother have black eyes. Pooja’s husband Ravi has black eyes while his mother has green eyes and father has black eyes.
(a) On the basis of the above-given information, is the green eye colour a dominant or recessive trait? Justify your answer.
(b) What is the possible genetic makeup of Pooja’s brother’s eye colour?
(c) What is the probability that the offspring of Pooja and Ravi will have green eyes? Also, show the inheritance of eye colour in the offspring with the help of a suitable cross.
OR
(d) 50% of the offspring of Pooja’s brother are green eyed. With help of cross show how this is possible.
EXPLANATION: a. Yes, green eye colour is recessive as it will express only in
homozygous condition
b. BB, Bb
c. bb*Bb
Genetic cross 50% of the offspring can have green eye colour
OR
c. Brother is heterozygous(Bb) and wife is green(bb)
Wife bb*Bb brother
50% of the offspring can have green eye colour as per the cross shown
39.
The above images are that of a specialized slide projector. Slides are small transparencies mounted in sturdy frames ideally suited to magnification and projection, since they have a very high resolution and a high image quality. There is a tray where the slides are to be put into a particular orientation so that the viewers can see the enlarged erect images of the transparent slides. This means that the
slides will have to be inserted upside down in the projector tray.To show her students the images of insects that she investigated in the lab, Mrs. Iyer brought a slide projector. Her slide projector produced a 500 times enlarged and inverted image of a slide on a screen 10 m away.
(a) Based on the text and data given in the above paragraph, what kind of lens must the slide projector have?
(b) If v is the symbol used for image distance and u for object distance then with one reason state what will be the sign for 𝑣𝑢in the given case?
(c) A slide projector has a convex lens with a focal length of 20 cm. The slide is placed upside down 21 cm from the lens. How far away should the screen be placed from the slide projector’s lens so that the slide is in focus?
OR
(c)When a slide is placed 15 cm behind the lens in the projector, an image is formed 3 m in front of the lens. If the focal length of the lens is 14 cm, draw a ray diagram to show image formation.
EXPLANATION: (a) Convex Lens
(b) Negative as the image is real and inverted.
(c) 1/f= 1/v- 1/u
1/20 = 1/v- 1/-20
1/v = 1/20 - 1/21
= (21 - 20)/420
= 1/420
v= 420 cm
OR
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