Class 10 Science Previous Year Question Paper 2023

          SCIENCE (Set - 1)

★ Please check that this question paper contains 27 printed pages. ★ Q.P. Code given on the right hand side of the question paper should be written on the title page of the answer-book by the candidate. ★Please check that this question paper contains 39 questions. ★Please write down the serial number of the question in the answer-book before attempting it. ★15 minute time has been allotted to read this question paper. The question paper will be distributed at 10.15 a.m. From 10.15 a.m. to 10.30 a.m., the students will read the question paper only and will not write any answer on the answer-book during this period.

Time allowed : 3 hours           Maximum Marks : 80

General Instructions :

Read the following instructions very carefully and strictly follow them :

(i) This question paper comprises 39 questions. All questions are compulsory.

(ii) This question paper is divided into five sections A, B, C, D and E.

(iii) Section A Questions No. 1 to 20 are multiple choice questions. Each question carries 1 mark.

(iv) Section B Questions No. 21 to 26 are very short answer type questions. Each question carries 2 marks. Answer to these questions should be in the range of 30 to 50 words.

(v) Section C Questions No. 27 to 33 are short answer type questions. Each question carries 3 marks. Answer to these questions should in the range of 50 to 80 words.

(vi) Section D Questions No. 34 to 36 are long answer type questions. Each question carries 5 marks. Answer to these questions should be in the range of 80 to 120 words.

(vii) Section E Questions No. 37 to 39 are of 3 source-based/case-based units of assessment carrying 4 marks each with sub-parts.

(viii) There is no overall choice. However, an internal choice has been provided in some sections. Only one of the alternatives has to be attempted in such questions.

      Section – A

This section has 20 multiple choice questions (Q.No. 1 – 20). All questions are compulsory. 20 ×1 = 20

1. Which of the following is an example of endothermic process ?

(a) Formation of slaked lime

(b) Decomposition of vegetable matter into compost

(c) Dissolution of ammonium chloride in water

(d) Digestion of food in our body

2. In the given experimental set-up, if the experiment is carried out separately with each of the following solutions the cases in which the bulb will glow is/are :

Photo

(i) Dilute hydrochloric acid

(ii) Dilute sulphuric acid

(iii) Glucose solution

(iv) Alcohol

(a) (i) only

(b) (ii) only

(c) (i) and (ii)

(d) (ii), (iii) and (iv)

3. In order to balance the following chemical equation, the values of the coefficients x and y respectively are :

 

(a) 2, 4        (b) 2, 2         (c) 2, 3       (d) 4, 2

4. When zinc reacts with sodium hydroxide, the product formed is :

(a) Sodium oxide            (b) Sodium zincate

(c) Zinc hydroxide          (d) Zinc oxide

5. Among the following, the metal with lowest density is :

(a) Lithium      (b) Lead     (c) Magnesium      (d) Aluminium

6. The number of electrons in the outermost shell of the atom of a non-metal can be :

(a) 1, 2 or 3      (b) 3, 4 or 5     (c) 5, 6 or 7     (d) 5, 6 or 8

7. The total number of electrons shared in the formation of an ethyne molecule is :

(a) 6      (b) 3       (c) 10       (d) 4

8. Sphincter muscles are present at the exit of :

(a) Stomach and small intestine

(b) Stomach and anus

(c) Small intestine and large intestine

(d) Oesophagus and stomach

9. In the following diagram, identify the cells through which massive amounts of gaseous exchange takes place for photosynthesis :

Photo

(a) I   (b) IV  (c) III    (d) II

10. During vigorous exercise, the occurrence of cramps in the outer muscles of an athlete is due to the conversion of pyruvate to :

(a) Glucose     (b) Ethanol      (c) Lactic acid     (d) Lactose

11. Plants which bear unisexual flowers are :

(a) Mustard and Papaya

(b) Hibiscus and Watermelon

(c) Mustard and Hibiscus

(d) Watermelon and Papaya

12.When an ‘X’ bearing sperm fertilise the egg , the resulting zygote has the following combination of chromosomes :

(a) 44 + XX       (b) 44 + XY          (c) 22 + XX          (d) 22 + XY

13. An object is placed in front of a convex mirror at infinity. According to the New Cartesian Sign Convention, the sign of the focal length and the sign of the image distance in this case are respectively :

(a) + ,  –   (b) –  , +     (c) – ,  –  (d) + , +

14. For verifying Ohm’s law, we design an electric circuit diagram in which we show the arrangement of different circuit components. We find that with respect to the resistor, the :

(a) ammeter is connected in parallel and the voltmeter in series.

(b) ammeter is connected in series and the voltmeter in parallel.

(c) ammeter and voltmeter are both connected in series.

(d) ammeter and voltmeter are both connected in parallel.

15. In a resistive circuit if the current is increased to two times, the percentage change in the amount of heat dissipated in the circuit would be :

(a) 400%          (b) 300%         (c) 200%           (d) 100%

16. A positron enters a uniform magnetic field at right angles to it as shown.The direction of force experienced by the positron will be :

Photo

(a) to the right

(b) to the left

(c) into the page

(d) out of the page

For Questions number 17 to 20, two statements are given one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.

(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).

(c) Assertion (A) is true, but Reason (R) is false.

(d) Assertion (A) is false, but Reason (R) is true.

17. Assertion (A) : Sodium oxide is an amphoteric oxide.

Reason (R) : Metal oxides which react with both acids as well as bases are known as amphoteric oxides.

18. Assertion (A) : When a bacterium divides into two, and the resultant two bacteria divide again, the four bacteria produced would be almost similar.

Reason (R) : DNA copying involves small inaccuracies in the reproduction process.

19. Assertion (A) : A person suffering from myopia cannot see the distant objects clearly.

Reason (R) : A converging lens is used for the correction of myopic eye as it can form real as well as virtual images of the objects placed in front of it.

20. Assertion (A) : Magnetic field lines do not intersect each other.

Reason (R) : Magnetic field lines are imaginary lines, the tangent to which at any point gives the direction of the field at that point.

      SECTION = B (2M)

21. (a) What is observed when aqueous solutions of potassium iodide and lead nitrate are mixed together ? Name the type of reaction and write the chemical equation for the reaction that occurs. 2

OR

(b) When copper powder is heated in a watch glass, a black substance is formed.

(i) Why is this black substance formed ? Name it.

(ii) How can this black substance be reversed to its original form ? 2

22. (a) Why is it important to prevent oxygenated and deoxygenated blood from mixing in birds and mammals ?

(b) Which animals can tolerate some mixing of the oxygenated and deoxygenated blood streams ? On what factor does the body temperature of these animals depend ?

23. Mendel crossed a pure tall pea plant (TT) with a pure short pea plant (tt) and obtained all tall plants in F1 generation.

(a) What is the gene combination present in the plants of F1 generation ?

(b) Give reason why only tall plants are observed in F1 progeny.

(c) What will be the ratio of the plants obtained in the F2 generation when F1 plants are self-pollinated ? 2

24. (a) When and where does a rainbow appear in the sky ? Draw a labelled ray diagram to show its formation. 2

OR

(b) What is scattering of light ? Why does the clear sky appear blue ? 2

25. V – I graph for two conducting wires A and B are as shown. If both wires are of the same length and same diameter, which of the two is made of a material of high resistivity ? Give reasons to justify your answer.

Photo

26. We do not clean ponds or lakes but an aquarium needs to be cleaned regularly. Why ?

SECTION = C

27. Silver chloride kept in a china dish turns grey in sunlight.

(a) Write the colour of silver chloride when it was kept in the china dish.

(b) Name the type of chemical reaction taking place and write the chemical equation for the reaction.

(c) State one use of the reaction. Name one more chemical which can be used for the same purpose. 3

28. With the help of suitable chemical equations, list the two main differences between roasting and calcination. How is metal reduced from the product obtained after roasting/calcination of the ore ? Write the chemical equation for the reaction involved.

29. (a) (i) What is the first step in the breakdown of glucose during aerobic and anaerobic respiration ? Where does it take place ?

(ii) ATP is called the energy currency of the cell. Why ?

(iii) What is meant by residual volume of air in a breathing cycle ? 3

OR

(b) Write in sequence the steps for experimental verification of the fact that sunlight is essential for photosynthesis . 3

30. Name the hormone released and the gland which secretes it in human beings during scary situations. How does the body respond to enable it to deal with the situation ?

31. (a) A student has focussed the image of an object of height 3 cm on a white screen using a concave mirror of focal length 12 cm. If the distance of the object from the mirror is 18 cm, find the values of the following :

(i) Distance of the image from the mirror

(ii) Height of the image [3M]

OR

(b) Define power of a lens. The focal length of a lens is 10 cm. Write the nature of the lens and find its power. If an object is placed at a distance of 20 cm from the optical centre of this lens, according to the New Cartesian Sign Convention, what will be the sign of magnification in this case ? 3

32. Explain the meaning of overloading of an electrical circuit. List two possible causes due to which overloading may occur in household circuits. Write one preventive measure that should be taken to avoid overloading of domestic circuits.

33. Explain how some harmful chemicals enter our bodies through the food chain. Why is the concentration of these harmful chemicals found to be maximum in human beings ? 3

     SECTION = D

34. (a) An acid ‘X’ and alcohol ‘Y’ react with each other in the presence of an acid catalyst to form a sweet smelling substance ‘Z’ . Identify ‘X’ , ‘Y’ and ‘Z’ . Write the chemical equation for the reaction involved and name it . The substance ‘Z’ on treatment with sodium hydroxide produces back the alcohol ‘Y’  and sodium ethanoate.  Write the chemical equation for the reaction involved and name it, giving justification for the name. [5M]

OR

(b) (i) Name the simplest saturated hydrocarbon. Draw its electron dot structure. Which type of bonds exist in this compound ?

(ii) Name any two mixtures of the carbon compound used as a fuel in daily life, of which the above mentioned compound is an important component.

(iii) In which homologous series of carbon compounds can this compound be placed ? Write the general formula of the series.

(iv) Which type of flame is produced on burning it ?  [5M]

35. (a) (i) List three points of difference between nervous and hormonal mechanisms for control and coordination in animals.

(ii) How are auxins related with the bending of plant shoot towards unidirectional light ? Explain. 5

OR

35. (b) (i) Name the disorder which a person is likely to suffer from due to the following :

(I) Over-secretion of growth hormone

(II) Deficiency of oestrogen in females

(III) Less secretion of thyroxine

Also name the gland that secretes each of the hormones mentioned above.

(ii) How is the timing and amount of hormone released regulated ? Explain with the help of an example. [5M]

36. (a) An object is placed in front of a convex lens of focal length f. If the distance of the object from the lens is 2f, draw a ray diagram to show the formation of the image. Write the value of magnification in this case.

(b) A student has focussed the image of a candle flame on a white screen using a convex lens. The situation is as given below :

Length of the flame = 2 cm

Focal length of the lens = 12 cm

Distance of the flame from the lens = 16 cm

If the flame is perpendicular to the principal axis of the lens, calculate the values of the following :

(i) Distance of the image from the lens

(ii) Length of the image formed  [5M]

SECTION = E

The following questions are source-based/case-based questions. Read the case carefully and answer the questions that follow.

37. The teacher while conducting practicals in the laboratory divided the students into three groups and gave them various solutions to find out their pH and classify them into acidic, basic and neutral solutions.

Group A – Lemon juice, vinegar, colourless aerated drink

Group B – Tomato juice, coffee, ginger juice

Group C – Sodium hydroxide, sodium chloride, lime water

(a) For the solutions provided, which group is/are likely to have pH value (i) less than 7, and (ii) greater than 7 ? 1

(b) List two ways of determining pH of a solution .

(c) Explain, why the sour substances such as lemon juice are effective in cleaning the tarnished copper vessels. 2

OR

(d)  pH has great importance in our daily life”. Justify this statement by giving two examples.

38. All the reproductive methods of living organisms are broadly categorized into two types : 1. Asexual reproduction, and 2. Sexual reproduction.

Asexual reproduction involves the participation of a single parent without the formation of gametes, fertilisation and transfer of genetic material. This method is a common means of rapidly increasing offsprings under favourable conditions.

(a) Name the type of fission that occurs in Leishmania and Plasmodium. 1

(b) Write one advantage of sexual mode of reproduction over asexual reproduction. 1

(c) Give reasons why :

(i) Colonies of yeast fail to multiply in water but multiply in sugar solution.

(ii) Rhizopus individuals do not grow on a dry slice of bread. 2

OR

(c) Name the filamentous structures a student could identify when he collected water from a pond that appeared dark green. How do these organisms multiply ? Explain.

39. Consider the following electrical circuit diagram in which nine identical resistors of 3Ω each are connected as shown. If the reading of the ammeter  is 1 ampere, answer the following questions :

Photo

(a) What is the relationship between the readings of and ? Give reasons for your answer. 1

(b) What is the relationship between the readings of and ? 1

(c) Determine the reading of the voltmeter  . 2

OR

(c) Find the total resistance of the circuit. 2

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Class 10 Science Previous Year Question Paper 2023

(FOR VISUALLY IMPAIRED CANDIDATES ONLY)

★ Please check that this question paper contains 27 printed pages. ★ Q.P. Code given on the right hand side of the question paper should be written on the title page of the answer-book by the candidate. ★ Please check that this question paper contains 39 questions. ★ Please write down the serial number of the question in the answer-book before attempting it. ★ 15 minute time has been allotted to read this question paper. The question paper will be distributed at 10.15 a.m. From 10.15 a.m. to 10.30 a.m., the students will read the question paper only and will not write any answer on the answer-book during this period.

                               SCIENCE , 2023

Time allowed : 3 hours       Maximum Marks : 80

 General Instructions :

Read the following instructions very carefully and strictly follow them :

(i) This question paper comprises 39 questions. All questions are compulsory.

(ii) This question paper is divided into five sections A, B, C, D and E.

(iii) Section A Questions No. 1 to 20 are multiple choice questions. Each question carries 1 mark.

(iv) Section B Questions No. 21 to 26 are very short answer type questions. Each question carries 2 marks. Answer to these questions should be in the range of 30 to 50 words.

(v) Section C Questions No. 27 to 33 are short answer type questions. Each question carries 3 marks. Answer to these questions should in the range of 50 to 80 words.

(vi) Section D Questions No. 34 to 36 are long answer type questions. Each question carries 5 marks. Answer to these questions should be in the range of 80 to 120 words.

(vii) Section E Questions No. 37 to 39 are of 3 source-based/case- based units of assessment carrying 4 marks each with sub-parts.

(viii) There is no overall choice. However, an internal choice has been provided in some sections. Only one of the alternatives has to be attempted in such questions.

SECTION = A

This section has 20 multiple choice questions (Q.No. 1 - 20). All questions are compulsory. 20 × 1 = 20

1. After burning a magnesium ribbon a student collected the ash so formed in a watch glass. He then dissolved this ash in water and tested the nature (acidic or basic) of the solution using pH paper and litmus solution. His correct observation would be :

(a) Its pH is 10 and it turns blue litmus to red.

(b) Its pH is 4 and it turns blue litmus to red.

(c) Its pH is 4 and it turns red litmus to blue.

(d) Its pH is 10 and it turns red litmus to blue.

2. Consider the following reaction :

   

This reaction is an example of which one of the following two reactions ?

(a) Displacement reaction as well as redox reaction

(b) Double displacement reaction as well as redox reaction

(c) Displacement reaction as well as combination reaction

(d) Combination reaction as well as double displacement reaction

3. Select the correct statement from the following :

(a)  is a product of respiration whereas CO is a product of photosynthesis.

(b)  is a product of respiration whereas is a product of chlor-alkali process.

(c)  is a product of photosynthesis whereas  is a product of chlor-alkali process.

(d)  is a product of incomplete combustion whereas CO is a product of respiration.

4. On placing a silver coin in a test tube containing blue solution of  , a student would observe after some time, say 20 minutes, that the  solution

(a) turns green and a grey substance is deposited on the coin.

(b) turns colourless and a grey substance is deposited on the coin.

(c) remains blue with no change in the silver coin.

(d) turns colourless and reddish brown substance is deposited on the coin.

5. A compound X is used in the paper, soap and glass industries.

(a) anhydrous sodium carbonate ( )

(b) sodium carbonate decahydrate ( )

(c) sodium hydrogen carbonate ( )

(d) sodium sulphate hemihydrate ( )

6. Select from the following, a salt whose aqueous solution will have pH less than seven.

(a) Sodium chloride            (b) Potassium sulphate

(c) Sodium carbonate        (d) Ammonium chloride

7. The hydrocarbon which will decolourize bromine water is :

(a)       (b)         (c)         (d) 

8. The organ that secretes insulin is :

(a) gall bladder           (b) small intestine        (c) pancreas           (d) stomach

9. During deficiency of oxygen in the tissues of human beings, pyruvate is converted into lactic acid in :

(a) cytoplasm        (b) golgi body         (c) mitochondria       (d) chloroplast

10. When a pure tall pea plant is crossed with a pure dwarf pea plant, the percentage of tall pea plant in F1 and F2 generation pea plants respectively will be :

(a) 100%; 25%            (b) 100%; 50%       (c) 100%; 75%       (d) 100%; 100%

11. The voluntary actions such as reading and writing are controlled by :

(a) cerebellum (b) cerebrum      (c) medulla        (d) pons

12. When an organism breaks into a number of parts and each part develops into a complete organism, it is known as :

(a) budding         (b) regeneration         (c) vegetative propagation       (d) spore formation

13. SI unit of electrical resitivity is :

(a) ohm metre (b) ohm per metre  (c) ohm / metre² (d) ohm / metre³

14. You have a thin resistance wire having a thick plastic insulation. A decrease in the resistance of this wire would be produced if somehow we increase the :

(a) thickness of the plastic insulation

(b) temperature of the wire

(c) length of the wire

(d) diameter of the wire

15. An electron projected towards east is deflected towards south by a uniform magnetic field. The direction of the magnetic field is :

(a) upwards      (b) downwards      (c) towards north     (d) towards west

16. A student has a long straight thick copper wire. If he passes a current in this wire he would get a magnetic field whose pattern must be :

(a) radial lines originating from the wire.

(b) concentric circles centred around the wire.

(c) straight lines parallel to the wire.

(d) straight lines perpendicular to the wire.

For Questions number 17 to 20, two statements are given one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.

(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).

(c) Assertion (A) is true, but Reason (R) is false.

(d) Assertion (A) is false, but Reason (R) is true.

17. Assertion (A) : It is possible to store copper sulphate solution in a container made of iron sheet.

Reason (R) : Iron is a more reactive metal than copper.

18. Assertion (A) : Human beings have one pair of sex chromosomes.

Reason (R) : All children, whether boys or girls, inherit an X-chromosome from their father.

19. Assertion (A) : The rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms.

Reason (R) : The amount of oxygen dissolved in water is fairly low as compared to the amount of oxygen in air.

20. Assertion (A) : Magnetic fields interact with moving charges and not with charges at rest.

Reason (R) : Charges produce magnetic field only when they move.

SECTION = B

21. (a) What is a balanced chemical equation ? Why do we balance chemical equations ? 2

OR

(b) Why does the colour of iron sulphate solution fade when a piece of zinc is dipped in it ? Give chemical equation for the reaction involved. 2

22. List four life-processes that are essential for maintaining life. 2

23. (a) How is oxygen transported in human beings ? 2

OR

(b) What is saliva ? State its role in the digestion of food. 2

24. Name the process by which the amount of urine produced in human beings is regulated. Where and how is this process carried out ? 2

25. (a) (i) What is the (I) least distance of distinct vision, and

(II) far point of a normal human eye ?

(ii) A student is unable to see distinctly a chart hanging on the wall of his classroom. Name the defect of vision he is suffering from and the type of corrective lens he must use in his spectacles. 2

OR

(b) Write the main function of each of the following in the human eye :

(i) Cornea

(ii) Iris

(iii) Retina

(iv) Ciliary muscles 2

26. Construct a food chain comprising the following organisms :

Hawk, Frogs, Snakes, Plants

Which of these will have the highest concentration of the harmful chemicals such as pesticides ? Name the phenomenon. 2

   SECTION = C

27. A student is heating ferrous sulphate crystals in a boiling tube.

(a) State the change in colour he is likely to observe during the process of heating.

(b) Name the gases produced during heating.

(c) Write chemical equation for the reaction. 3

28. (a) (i) Name one antacid. State how it helps to relieve indigestion in the stomach.

(ii) A student wants to dilute a strong acid such as sulphuric acid. For this purpose, why should the acid be added to water and not water to the acid ? 3

OR

(b) A student dropped a few pieces of white marble in dilute hydrochloric acid contained in a test tube. The gas evolved was then passed through freshly prepared lime water.

(i) Name the gas evolved.

(ii) State the change the student would observe in lime water.

(iii) What change would be observed if excess of this gas is passed through lime water ? Give reason for your answer in (ii) and (iii) given above. 3

29. (a) Define geotropism and explain the term positive geotropism and negative geotropism giving one example for each. 3

OR

(b) Name the plant hormone that helps in the bending of the plant stem towards light. Explain its function. Also name this phenomenon. 3

30. A student wants to draw a ray diagram to show the formation of image due to a concave mirror when an object is placed in between its focus and centre of curvature.

(a) Write the minimum number of incident rays required.

(b) State the paths of the incident rays.

(c) State the paths of the reflected rays.

(d) Write the sign of magnification according to the New Cartesian Sign Convention. 3

31. (a) A candle flame and a screen are placed 1 m apart. When a lens is placed exactly in the middle of the two, a distinct image of the candle flame is observed on the screen.

(i) Name the type of the lens used.

(ii) How is focal length of the lens determined in this case ? State the method and determine its value.

(iii) Write the power of the lens used. 3

OR

(b) (i) Define absolute refractive index.

(ii) The absolute refractive indices of water and glass areandrespectively. If the speed of light in glass is  m/s, find :

(I) Speed of light in vacuum

(II) Speed of light in water 3

32. What is a solenoid ? How does a current carrying solenoid behave when suspended freely and why ? Give its one main use. 3

33. Define the term ecosystem. List its two main components. We do not clean natural ponds or lakes, but an aquarium needs to be cleaned regularly. Why ? 3

SECTION = D

34. (a) Write the names of the following compounds :

(i) 

(ii)

(b) What is a homologous series of carbon compounds ? Construct a homologous series of alcohols.

(c) What happens when ethanol reacts with ethanoic acid in the presence of an acid ? Name the reaction and write its chemical equation. 5

35. (a) (i) Define vegetative propagation. List its any two advantages.

(ii) Write in tabular form two differences between binary fission and multiple fission giving one example for each. 5

OR

(b) (i) State in brief the functions of the following organs in the human female reproductive system :

(I) Ovary

(II) Fallopian tube

(III) Uterus

(ii) What is menstruation ? Why does it occur ? 5

36. (a) Derive an expression for the amount of heat produced when a current flows through a resistor for a given time.

(b) 200 joules of heat energy is produced each second in a resistor of 8 . Find :

(i) The current flowing through the resistor, and

(ii) The potential difference across the ends of the resistor. 5

SECTION = E

Q.No. 37 to 39 are source-based/case-based questions with 3 sub-parts. Internal choice is provided in one of these sub-parts.

37. Decomposition is a type of reaction in which a single compound splits into two or more simple compounds. Decomposition reactions are generally classified into three types, depending upon the type of energy required for the reaction. The three types are thermal decomposition, photolytic decomposition and electrolytic decomposition.

(a) Why are decomposition reactions known as endothermic reactions ? 1

(b) Give an example of photolytic decomposition. 1

(c) Name the gas liberated at the (i) cathode, and (ii) anode when water is electrolysed. Write the molar ratio of hydrogen and oxygen (Hydrogen : Oxygen) liberated during electrolysis. 2

OR

(c) What happens when lead nitrate powder is heated in a boiling tube ? Write chemical equation for the reaction. 2

38. Hormones are chemical informational molecules that are required in minute amounts and are directly poured into the blood stream. The animal hormones are secreted in the desired amounts by the endocrine glands. Each hormone is responsible for carrying out specific actions in the body. The deficiency or excess of hormones has a harmful effect on our body. Hence, the timing and the amount of hormones secreted by glands are controlled by the feedback mechanism.

(a) Name the hormones secreted by ovary and testes. 1

(b) Write the function of adrenaline. 1

(c) Write the name and function of a hormone secreted by

(i) Pituitary gland and (ii) Thyroid gland. 2

OR

(c) What is the meaning of feedback mechanism ? 2

39. A simple magnifier or microscope is a convex lens of small focal length. In order to use such a lens as a microscope, the lens is held near the object to get an erect, magnified and virtual image of the object. However, this microscope has a maximum limiting magnification. For much larger magnification we use a compound microscope in which two convex lenses are used, one compounding the effect of the other. The lens nearest the object, called the objective, forms a real, inverted and magnified image of the object. This image serves as the object for the second lens, the eyepiece which functions essentially like a simple microscope or magnifier and produces the final image.

(a) You have a compound microscope in which a convex lens of focal length f is used as objective. What should be the distance of the object from the objective in terms of f ? 1

(b) List two properties of the final image obtained from a compound microscope. 1

(c) An object is placed in front of a convex lens at a distance of two times the focal length of the lens. List two properties of the image formed and write the value of magnification produced by the lens using the New Cartesian Sign Convention. 2

OR

(c) An object is placed in front of a convex lens at a distance more than two times the focal length of the lens. List two properties of the image formed and write the value of magnification produced by the lens using the New Cartesian Sign Convention. 2

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Class 10 Science Compartment Previous Year Question and Answer 2023

                                                    Science , 2023 (Set - 1)

★Please check that this question paper contains 27 printed pages. ★Q.P. Code given on the right hand side of the question paper should be written on the title page of the answer-book by the candidate. ★Please check that this question paper contains 39 questions. ★Please write down the serial number of the question in the answer-book before attempting it. ★15 minute time has been allotted to read this question paper. The question paper will be distributed at 10.15 a.m. From 10.15 a.m. to 10.30 a.m., the students will read the question paper only and will not write any answer on the answer-book during this period.

Time allowed : 3 hours                                    Maximum Marks : 80

General Instructions :

Read the following instructions very carefully and strictly follow them :

(i) This question paper comprises 39 questions. All questions are compulsory.

(ii) This question paper is divided into five sections A, B, C, D and E.

(iii) Section A Questions No. 1 to 20 are multiple choice questions. Each question carries 1 mark.

(iv) Section B Questions No. 21 to 26 are very short answer type questions. Each question carries 2 marks. Answer to these questions should be in the range of 30 to 50 words.

(v) Section C Questions No. 27 to 33 are short answer type questions. Each question carries 3 marks. Answer to these questions should in the range of 50 to 80 words.

(vi) Section D Questions No. 34 to 36 are long answer type questions. Each question carries 5 marks. Answer to these questions should be in the range of 80 to 120 words.

(vii) Section E Questions No. 37 to 39 are of 3 source-based/case-based units of assessment carrying 4 marks each with sub-parts.

(viii) There is no overall choice. However, an internal choice has been provided in some sections. Only one of the alternatives has to be attempted in such questions.

                 SECTION = A

This section has 20 multiple choice questions (Q.No. 1 20). All questions are compulsory. 20 × 1 = 20

1. In the electrolysis of water, if the mass of the gas collected at the anode is  and the mass of the gas collected at the cathode is , the value of () is :

(a) 8      (b) 16      (c) 1/16       (d) 1/8

2. Consider the following substances :

(i) Acidified       (ii) Alkaline       (iii) Oxygen       (iv) Hydrogen

Out of these, the commonly used oxidising agents are :

(a) (i) and (ii) only

(b) (ii) and (iii) only

(c) (i), (ii) and (iii)

(d) (i), (ii) and (iv)

3. Select from the following compounds which is not a base :

(a) Sodium hydroxide       (b) Calcium hydroxide          (c) Sodium sulphate         (d) Zinc oxide

4. 2 g of yellow sulphur powder is burnt in a china dish and the fumes are collected in a test tube. Water is added in the test tube and the solution is tested separately with blue and red litmus paper. The correct option is :

(a) Blue litmus remains blue and red litmus turns blue.

(b) Blue litmus turns red and red litmus remains red.

(c) Blue litmus turns red and red litmus turns blue.

(d) Blue litmus remains blue and red litmus remains red.

5. Which one of the following metals is malleable and a poor conductor of electricity ?

(a) Copper        (b) Zinc       (c) Lead     (d) Silver

6. You want to test for hardness of water but hard water is not available in the laboratory. Which of the following compounds may be dissolved in pure water to make it hard ?

(i) Hydrogen Carbonate of Sodium

(ii) Sulphate of Magnesium

(iii) Chloride of Calcium

(iv) Carbonate of Sodium

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (iii) and (iv)

(d) (i) and (iv)

7. Which one of the following properties of Carbon is not responsible for its formation of large number of compounds ?

(a) Tetravalency           (b) Isomerism         (c) Allotropy             (d) Catenation

8. Which one of the following molecules is produced initially when glucose breaks down in the cytoplasm of a cell in aerobic as well as anaerobic respiration ?

(a) Lactic acid     (b) Ethanol      (c) Carbon dioxide      (d) Pyruvate

9. As compared to daytime, the amount of carbon dioxide released by the plants during night is more because :

(a) It is not produced during daytime.

(b) It is stored in the leaves of plants during daytime.

(c) Major amount of carbon dioxide produced is used up for photosynthesis during daytime.

(d) Plants do not respire during daytime.

10. The organism in which an outgrowth on the parent body develops into a new individual is :

(a) Amoeba     (b) Paramecium      (c) Rhizopus       (d) Yeast

11. In a cross between pure tall pea plants (TT) and pure dwarf pea plants (tt) the offsprings of F1 generation were all tall. When F1 generation was self-crossed, the gene combinations of the offsprings of F2 generation will be :

(a) TT : Tt : tt       (b) TT : tt        (c) Tt : tt       (d) TT : Tt

12. When an object is placed beyond 2F of a convex lens, the nature of the image formed is :

(a) Real, inverted and diminished

(b) Real, erect and magnified

(c) Virtual, erect and magnified

(d) Real, inverted and magnified

13. When a narrow beam of white light passes through a glass prism it splits into its component colours ? This phenomenon is called :

(a) Diffusion of light

(b) Total reflection of light

(c) Scattering of light

(d) Dispersion of light

14. A material used for making heating elements of electrical heating devices should have :

(a) High resistivity and high melting point.

(b) High resistivity and low melting point.

(c) Low resistivity and high melting point.

(d) Low resistivity and low melting point.

15. The resistance of a wire does not depend on its :

(a) Length

(b) Area of cross-section

(c) Shape

(d) Material

16. The shape of magnetic field lines produced

(i) inside a solenoid

(ii) around a straight conductor, both carrying current of the same magnitude are, respectively :

(a) (i) straight, (ii) circular

(b) (i) circular, (ii) circular

(c) (i) straight, (ii) straight

(d) (i) circular, (ii) straight

For Questions number 17 to 20, two statements are given one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.

(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).

(c) Assertion (A) is true, but Reason (R) is false.

(d) Assertion (A) is false, but Reason (R) is true.

17. Assertion (A) : In the reaction,  sodium chloride is precipitated.

Reason (R) : When an aqueous solution is added to another aqueous solution, an insoluble substance is formed, which is called precipitate.

18. Assertion (A) : A hormone called abscisic acid inhibits growth in plants.

Reason (R) : The role of auxins is opposite to that of abscisic acid in plants.

19. Assertion (A) : Each human trait is influenced by both paternal and maternal DNA.

Reason (R) : As compared to the father, the mother contributes more amount of genetic material to the child.

20. Assertion (A) : A rainbow is an artificial spectrum of white light appearing in the sky after a rain shower.

Reason (R) : The water droplets act like small prisms.

SECTION = B

21. (a) A metal ‘A’ reacts violently with cold water and the gas evolved catches fire. Another metal ‘B’ when dipped in water starts floating . The metal ‘C’ does not react either with cold or hot water, but reacts with steam . The metal ‘D’ does not react with water at all . Identity the metals ‘A’ , ‘B’ , ‘C’ and ‘D’ .

OR

(b) When two compounds namely sodium chloride and calcium chloride are heated directly, one by one on the flame of a burner, they impart different colours to the flame.

(i) Name the colour imparted by (1) sodium chloride and (2) calcium chloride.

(ii) Are these compounds soluble in organic solvents such as kerosene or petrol ? Justify your answer. 2

22. Name the glands which add their secretions to the sperms. List two function of these secretions. 2

23. “In human beings, the sex of a newborn child depends on the father and not the mother”. Justify this statement with the help of a flow diagram . 2

24. (a) Find the magnification of the image formed by a spherical mirror from the following data : u = – 20 cm, f = – 15 cm.  2

OR

(b) Draw a labelled ray diagram for the image formation by a concave mirror when an object is placed between its centre of curvature and focus. 2

25. What will happen if an electric oven of rating 3 kW; 220 V is operated in a domestic electric circuit (220 V) that has a current rating of 10 A ? Give reason to justify your answer.

26. (a) State any one advantage of using cloth bags over plastic bags.

(b) List any two methods by which the solid wastes generated in urban areas can be safely disposed off. 2

SECTION = C

27. What is photosynthesis ? Name the organelle and the organs in which photosynthesis takes place. Where does the oxygen liberated come from during this process ? What happens to the carbohydrates which are not immediately used by the plant ? 3

28. (a) An organic compound X when reacts with sodium liberates hydrogen. The same compound X when heated at 443 K in the presence of concentrated sulphuric acid gives an unsaturated hydrocarbon.

(i) Identify X

(ii) Write the chemical equations for the above mentioned reactions and state the role of concentrated sulphuric acid in the second reaction. 3

OR

(b) (i) Why are carbon compounds exceptionally stable ?

(ii) Differentiate between saturated and unsaturated compounds. Give structures of both the types of compounds having three carbon atoms in their molecules. 3

29. (a) Give the structure and function of alveoli in human respiratory system.

(b) What is meant by residual volume of air in the lungs ? 3

30. Write any two ways by which plants obtain carbon dioxide. What causes the opening and closing of the stomata ? 3

31. What is Tyndall effect ? Give two examples where this phenomenon is observed. Give reason to explain this phenomenon. 3

32. (a) (i) Differentiate between a solenoid and a circular coil.

(ii) Explain how a solenoid can be made in a school laboratory.

(iii) Write one use of the strong magnetic field produced inside a current carrying solenoid. 3

OR

(b) With the help of a labelled circuit diagram, illustrate the pattern of the magnetic field lines of the magnetic field produced around a straight current carrying conductor. Explain how, with the help of right-hand thumb rule, we can determine and mark the direction of magnetic field lines due to a current. 3

33. Define trophic levels. At which trophic level do we find (i) secondary and (ii) tertiary consumers in a food chain ? What will happen if all the organisms of a trophic level die ? Give reasons to justify your answer. 3

SECTION = D

34. (a) (i) An aqueous solution turns blue litmus red. Which of the following solutions when added in excess would reverse the change ?

(1) Lemon juice

(2) Magnesium hydroxide

(3) Vinegar

(4) Calcium sulphate

(ii) Out of the following, which compound/compounds will turn the phenolphthalein solution pink ?

(1) 

(2)  

(3) HCl

(4) NaOH

(iii) Name a gas whose aqueous solution is basic. Write the formula/name of this solution.

(iv) A basic substance is used to treat a honey-bee sting. Why ?

(v) Name the acid which is present in (1) Tomato and

(2) Tamarind. 5

OR

(b) (i) Define water of crystallisation.

(ii) Write the chemical name and formula of a compound having water of crystallisation in its molecule and appears blue.

(iii) Write the chemical formula of bleaching powder. Write a balanced chemical equation of the reaction involved in its preparation. List its three uses. 5

35. (a) (i) Name the parts in the human female reproductive system where the following functions take place :

(1) Maturation of eggs

(2) Fusion of the egg and the sperm

(3) Implantation of the zygote

(ii) What happens to the egg

(1) when it is fertilised ?

(2) when it is not fertilised ? 3+2=5

OR

(b) (i) Explain by giving one example each :

(1) Unisexual flowers

(2) Bisexual flowers

(ii) Name the labelled parts A, B, C and D in the diagram given below.

Photo

(iii) “Pollination may occur without fertilization but fertilization will not take place without pollination”. Give reason to justify this statement. 5

36. (a) The commercial unit of electric energy is commonly known as ‘unit’ . Write its actual name and establish the relationship between this unit and the SI unit of energy.

(b) The current rating of a circuit is 1·0 A. How many LED lamps of power rating 8 W; 220 V can safely be used simultaneously in this circuit ?

SECTION = E

The following questions are source-based/case-based questions. Read the case carefully and answer the questions that follow.

37. The iron pillar in Qutab Minar complex in Delhi was built 1600 years ago. It is still standing intact and shows no signs of rusting even today. This shows that the ancient metallurgists of India in those times had fully developed metallurgical processes as well as the techniques of protection of different metals. The protection of metals, was done by several processes like coating of a thin film of another metal, alloying etc.

(a) Where is iron placed in the reactivity series of metals ? Write the form/forms in which its ores are found in nature. 1

(b) Differentiate between roasting and calcination. 1

(c) Explain any two methods that are employed to prevent rusting/corrosion of metals. 2

OR

(c) Why is aluminium used to join railway tracks or the cracked machine parts of iron ? Write a balanced chemical equation for the reaction which occurs. 2

38. In animals the control and coordination is provided by nervous and muscular tissues. Nervous tissue is made of an organized network of nerve cells or neurons. In human beings, thinking is a complex activity which involves more complex mechanisms and neural connections. These are concentrated in the brain which is the main coordinating centre of the human body. The brain and spinal cord constitute the Central Nervous System which receives information from all parts of the body and integrates it.

(a) How is the brain protected from shocks and injuries ? 1

(b) Write the main functions of (i) sensory neuron and (ii) motor neuron in a reflex arc. 1

(c) Which part of the brain is involved in activities like (i) picking a pencil and (ii) vomiting ? State whether these actions are voluntary or involuntary. 2

OR

(c) How does the central nervous system communicate with other parts of the body to carry out various activities ? Name two components of this system. 2

39. When a ray of light moving in a medium enters obliquely into another medium, it bends from its path. This phenomenon is called refraction of light. The ability of a medium to refract light is also expressed in terms of optical density. It is not the same as mass density. We use the terms ‘rarer medium’ and ‘denser medium’ respectively . When we say that a medium ‘B’. The speed of light is lighter in a rarer medium than a denser medium . Thus a ray of light travelling from a rarer medium to a denser medium  Thus a ray of light travelling from a rarer medium to a denser medium slows down and bends towards the normal .

(a) Define the term absolute refractive index of a medium. 1

(b) Absolute refractive indices of water and glass are 4/3 and 3/2 respectively.

(i) In which one of the two media is the speed of light more ?

(ii) If a ray of light enters obliquely from glass to water, will it bend towards the normal or away from the normal ? 1

(c) The absolute refractive indices of water and glass are 4/3 and 3/2 respectively. If the speed of light in glass is  m/s, find the speed of light in (i) water and (ii) vacuum. 2

OR

(c) “A ray of light incident on a rectangular glass slab immersed in any medium emerges parallel to itself”. Draw a labeled ray diagram to justify this statement . 2  

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Class 10 Science Previous Year Question and Answer 2023

                 (FOR VISUALLY IMPAIRED CANDIDATES ONLY)

                                         Science (Set - 5)

Time allowed : 3 hours             Maximum Marks : 80

★Please check that this question paper contains 27 printed pages. ★Q.P. Code given on the right hand side of the question paper should be written on the title page of the answer-book by the candidate. ★Please check that this question paper contains 39 questions. ★Please write down the serial number of the question in the answer-book before attempting it. ★15 minute time has been allotted to read this question paper. The question paper will be distributed at 10.15 a.m. From 10.15 a.m. to 10.30 a.m., the students will read the question paper only and will not write any answer on the answer-book during this period.

General Instructions :

Read the following instructions very carefully and strictly follow them :

(i) This question paper comprises 39 questions. All questions are compulsory.

(ii) This question paper is divided into five sections A, B, C, D and E.

(iii) Section A Questions No. 1 to 20 are Multiple Choice Questions. Each question carries 1 mark.

(iv) Section B Questions No. 21 to 26 are Very Short Answer type questions. Each question carries 2 marks. Answer to these questions should be in the range of 30 to 50 words.

(v) Section C Questions No. 27 to 33 are Short Answer type questions. Each question carries 3 marks. Answer to these questions should in the range of 50 to 80 words.

(vi) Section D Questions No. 34 to 36 are Long Answer type questions. Each question carries 5 marks. Answer to these questions should be in the range of 80 to 120 words.

(vii) Section E Questions No. 37 to 39 are of 3 Source-based/Case- based units of assessment carrying 4 marks each with sub-parts.

(viii) There is no overall choice. However, an internal choice has been provided in some sections. Only one of the alternatives has to be attempted in such questions.

SECTION = A

This section has 20 Multiple Choice Questions (Q.No. 1 20). All questions are compulsory. 20 × 1=20

1. In order to balance the following chemical equation, the values of x and y respectively are :

 

(a) 2, 2      (b) 4, 2       (c) 2, 4        (d) 4, 4

2. The aqueous solution of which one of the following salts will have pH more than seven ?

(a)     (b) NaCl       (c)    (d)

3. Triple covalent bond is found in :

(a)        (b)       (c)      (d)  

4. Which of the following oxide(s) is/are soluble in water to form alkali/alkalies ?

(i)        (ii)         (iii)        (iv) 

(a) (ii) and (iv) (b) Only (iii)

(c) (i), (ii) and (iv) (d) Only (iv)

5. Carbon dioxide gas is not produced when hydrochloric acid reacts with :

(a) Limestone  (b) Lime water    (c) Baking Soda    (d) Marble

6. In the process of galvanisation of iron, the metal used for the coating over iron is :

(a) Aluminium    (b) Gallium       (c) Zinc    (d) Lead

                                                  O

                                                  ||

7. The carbon compound having  – C – H functional group is :

(a) Propanal    (b) Propanone      (c) Propyne     (d) Propanol

8. The inner lining of stomach is protected from hydrochloric acid by :

(a) Bile      (b) Mucus     (c) Pepsin      (d) Saliva

9. Select the correct statement from the following :

(a) Trypsin digests proteins, whereas lipase digests carbohydrates.

(b) Trypsin digests carbohydrates, whereas lipase digests proteins.

(c) Trypsin digests emulsified fats, whereas lipase digests proteins.

(d) Trypsin digests proteins, whereas lipase digests emulsified fats.

10. Spinal cord originates from :

(a) Cerebellum       (b) Pons      (c) Hypothalamus       (d) Medulla

11. Select the mismatched pair :

(a) Adrenal gland Adrenaline

(b) Thyroid gland Thyroxin

(c) Pituitary gland Insulin

(d) Ovary Estrogen

12. Select from the following, a disease which is not transmitted sexually :

(a) Gonorrhoea      (b) Tuberculosis     (c) HIV-AIDS      (d) Syphilis

13. Potential difference can also be represented as :

(a) 

(b) Work done × Charge

(c) Work done × Charge × Time

(d) 

14. Two LED bulbs of 12 W and 6 W are connected in series. If the current flowing through 6 W bulbs is 0 005 A, the current that flows through 12 W bulb is :

(a) 0 005 A           (b) 0 01 A            (c) 0 0025 A          (d) 0 02 A

15. According to the International colour coding, wires used in electrical appliances which require earthing are :

(a) Live is brown; Neutral is blue and Earth is black

(b) Live is brown; Neutral is blue and Earth is green

(c) Live is red; Neutral is green and Earth is blue

(d) Live is red; Neutral is green and Earth is black

16. From a power station, the power is transmitted to distant places in the form of AC at a very high voltage because :

(a) electricity is less dangerous at high voltages.

(b) electricity is generated at high voltage.

(c) transmission is faster at high voltage.

(d) at high voltage, the loss of energy during transmission is less.

For Questions number 17 to 20, two statements are given one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.

(a) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of the Assertion (A).

(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).

(c) Assertion (A) is true, but Reason (R) is false.

(d) Assertion (A) is false, but Reason (R) is true.

17. Assertion (A) : Ethyne is widely used for cutting and welding iron and steel.

Reason (R) : Ethyne is an unsaturated hydrocarbon involving carbon-to-carbon triple bond.

18. Assertion (A) : ATP is the energy currency for most of the cellular processes.

Reason (R) : Endothermic processes in the cell use ATP to carry out reactions.

19. Assertion (A) : Pancreas produces a hormone called insulin.

Reason (R) : Insulin increases the blood sugar level in the human body

20. Assertion (A) : A current carrying straight solenoid, when suspended freely rests in geographical north-south direction.

Reason (R) : Earth behaves as a huge magnet which has the north pole towards the geographical south, whereas the current carrying solenoid behaves like a bar magnet.

SECTION = B

21. Give one example each of the reaction in which :

(a) (i) a more reactive metal displaces a less reactive metal from its aqueous salt solution and the colour of the solution changes.

(ii) an insoluble precipitate is formed. 2

OR

(b) When a zinc plate is dipped in ferrous sulphate solution for some time, it is observed that the pale green colour of the solution disappears.

(i) Explain the observation.

(ii) Write the chemical equation for the reaction taking place. 2

22. Name the site of complete digestion in the human body and write the name of the end products formed of (i) carbohydrates, (ii) fats, and (iii) proteins. 2

23. Give an example of a plant hormone that promotes growth. Explain how this hormone promotes the growth of tendril around a support. 2

24. Pancreas has dual nature. Justify this statement with an example. 2

25. (a) A student cannot see distinctly the charts hanging in the science laboratory. Name the defect of vision he/she is suffering from. List two causes of this defect. Suggest the type of lenses for the modification of this defect. 2

OR

(b) A person cannot see distinctly the objects placed at the least distance of distinct vision for a normal eye. However, he can easily read a newspaper by placing it at a distance of 40 cm from his eyes. Name the defect of vision in this case. List its two causes. Suggest the type of lenses for his spectacles. 2

26. Name two non-biodegradable substances. In the following food chain, maximum concentration of harmful non-biodegradable chemicals was found in the bodies of hawks. Why ?

Grass → Rabbits → Snakes → Hawks  2

SECTION = C

27. Consider the types of reaction mentioned below in (i) and (ii) :

(i) AB + C2B A(BC)2

(ii) ABO3 AO + BO2

Photo

(a) Identify the types of reactions mentioned in the chemical equations (i) and (ii).

(b) Give one example for each type of reaction in the form of word equation or chemical equation. 3

28. You have three test tubes containing three colourless liquids, say conc. sulphuric acid, conc. solution of sodium hydroxide and conc. solution of sodium sulphate. You also have strips of pH paper.

(a) How would identify these three liquids using pH paper strips ?

(b) Which two liquids, when mixed together in proper quantities can form a neutral salt solution ?

(c) Write the chemical equation for the reaction that will occur between the two liquids mixed in (b). 3

29. (a) List three events that occur during the process of photosynthesis in plants. 3

OR

(b) What is lymph ? How is lymph different from blood plasma in composition ? List two functions of lymph. 3

30. A candle flame is placed at a distance of 18 cm from the optical centre of a convex lens. If its image is formed on a screen placed at a distance of 36 cm from the lens, answer the following questions :

(a) What is the magnification of the image formed ?

(b) What is the focal length of the lens ? Use the Lens Formula to determine it. 3

31. (a) Define the following terms in the context of spherical mirrors :

(i) Pole            (ii) Centre of curvature         (iii) Principal axis       (iv) Principal focus

(b) An object is placed at a distance of 60 cm from the pole of a concave mirror. If its real and inverted image is formed on a screen placed at a distance of 60 cm in front of the mirror, what is the focal length of the mirror ? Give justification for your answer. 3

32. (a) State Ohm s law. List two factors on which the resistance of a cylindrical conductor at a given temperature depends. A wire was drawn into a wire of double its length by melting it. If the resistance of the old wire was R, what is the resistance of the new wire ? 3

OR

(b) (i) Write the formula for finding the value of the equivalent resistance of three resistors of resistance and , when the resistors are connected in (i) series, and (ii) parallel.

(ii) List two advantages of connecting electrical devices in parallel with the source of electricity instead of connecting them in series. 3

33. Define ecosystem. List two artificial (man-made) ecosystems . Natural ecosystems like forests and lakes do not require regular cleaning, whereas the artificial ecosystems start giving foul smell if not cleaned regularly. Why ? 3

SECTION = D

34. (a) Write the molecular formula of methane and ethane, stating the general formula of the homologous series to which these compounds belong. What is the difference in the molecular mass in between the two successive members of a homologous series ?

(b) Write the name and molecular formula of an alcohol having two carbon atoms in its molecule. Write balanced chemical equation to indicate what happens when this compound is heated at 443 K with excess conc.. Name the main product formed in the reaction stating the function of conc. in the reaction. 5

OR

(a) How do the following conversions take place ? Write chemical equation for each :

(i) Ethanol to Ethanoic acid

(ii) Ethene to Ethane

(b) Give one example each with chemical equation for the following reactions :

(i) Combustion reaction

(ii) Substitution reaction

(iii) Saponification reaction 5

35. (a) What is regeneration ? Which types of cells are used by such multicellular organisms to regenerate ? Name the organism which exhibits this process.

(b) State one function of each of the following parts of the human male reproductive system :

(i) Vas deferens

(ii) Testes

(iii) Prostate glands 5

OR

(a) What is meant by pollination ? Name and differentiate between the two types of pollination.

(b) What happens to the pollen which falls on a suitable stigma ?

(c) Mention the post-fertilisation changes that occur in

(i) Ovary and (ii) Ovule in the flower. 5

36. (a) What is a solenoid ? When a current is passed through a long, hollow and straight solenoid, a magnetic field is produced. Where is the strength of the magnetic field produced maximum and what is the pattern of the magnetic field at this place ?

(b) State Fleming s Left Hand Rule. Apply this rule to solve the following problem :

A straight conductor is placed in east-west direction in a uniform magnetic field. If on passing current from east to west, the conductor moves towards north, what is the direction of magnetic field ? 5

        SECTION = E

Q.No. 37 to 39 are Source-based/Case-based questions with 3 sub-parts. Internal choice is provided in one of these sub-parts.

37. When a ray of light moving in a medium enters obliquely in another medium, it bends from its path. This phenomenon is called refraction of light. The ability of a medium to refract light is expressed in terms of optical density. The term optical density is not the same as mass density. If we compare two optical media, the one with the larger absolute refractive index is an optically denser medium than the other. Also, the speed of light through a given medium is inversely proportional to its optical density.

(a) Define the term absolute refractive index of a medium. 1

(b) Refractive indices of glass, water and carbon disulphide are 1.50, 1.33 and 1.62 respectively. In which one of these media is the speed of light (i) highest, and (ii) lowest ? 1

(c) (i) The absolute refractive indices of glass and water are 3/2 and 4/3 respectively. If the speed of light in water is  m/s, find the speed of light in (I) vacuum, and (II) glass. 2

OR

(ii) The absolute refractive indices of glass and water are 3/2 and 4/3 respectively. Find the refractive index of water with respect to glass.

38. The melting points and the boiling points of ionic compounds are comparatively much higher than that of the covalent compounds. The ionic compounds are so called because they are formed by the transfer of electrons from a metal to a non-metal. In the ionic compounds, the transfer of electrons from one element to the other is controlled by their electronic configurations. It is because every element tends to attain a completely filled valence shell of its nearest noble gas or a stable octet.

(a) The atomic number of sodium is 11. Write its electronic configuration and state the number of electrons it can lose to have a stable octet. 1

(b) The atomic number of chlorine is 17. Write its electronic configuration. Name the nearest noble gas whose octet chlorine will attain after gaining one electron. 1

(c) (i) Show the formation of MgO by the transfer of electrons. The atomic numbers of magnesium and oxygen are 12 and 8 respectively. 2

OR

(ii) Write the symbols and names of the anion and the cation present in the aqueous solution of the following compounds :

(I) Sodium chloride

(II) Potassium nitrate 2

39. Besides heart, the human circulatory system consists of a network of closed branching blood vessels and the blood that circulates continuously in all parts of the human body. The human heart is a muscular organ which is as big as our fist. It has four chambers two upper chambers called atria and two lower chambers called ventricles. The right side of the human heart is separated from the left side by a dividing wall, which is known as septum.

(a) Name the smallest blood vessel and state its role in the circulation of blood. 1

(b) Write the importance of platelets in the human blood. 1

(c) (i) Write in tabular form, two differences between an artery and a vein. 2

OR

(ii) Why is blood circulation in the human heart called double circulation ? Explain. 2