{"id":33905,"date":"2019-10-25T13:16:18","date_gmt":"2019-10-25T07:46:18","guid":{"rendered":"https:\/\/www.cbselabs.com\/?p=33905"},"modified":"2021-09-18T15:15:58","modified_gmt":"2021-09-18T09:45:58","slug":"cbse-previous-year-question-papers-class-10-science-sa2-delhi-2015","status":"publish","type":"post","link":"https:\/\/www.cbselabs.com\/cbse-previous-year-question-papers-class-10-science-sa2-delhi-2015\/","title":{"rendered":"CBSE Previous Year Question Papers Class 10 Science SA2 Delhi 2015"},"content":{"rendered":"
Time allowed: 3 hours \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0Maximum marks: 90<\/strong> SECTION A<\/strong><\/span> Question.2. List two functions performed by the testis in human beings.<\/strong> Question.3. What is the function of ozone in the upper atmosphere? <\/strong> Question.4. List four characteristics of the images formed by plane mirrors. <\/strong> Question.5. Why are forests considered “biodiversity hot spots”? List two ways in which an individual can contribute effectively to the management of forests and wildlife. <\/strong> Question.6. What is meant by “sustainable management”? Why is reuse considered better than recycling? <\/strong> Question.7. With the help of an example, explain the process of hydrogenation. Mention the essential conditions for the reaction and state the change in physical property with the formation of the product.<\/strong> Changes observed:<\/strong><\/p>\n Question.8. What is the difference between the molecules of soaps and detergents, chemically? Explain the cleansing action of soaps.<\/strong> Question.9. How many groups and periods are there in the modern periodic table? How do the atomic size and metallic character of elements vary as we move:<\/strong> Question.10. From the following elements:<\/strong> Question.11. What is DNA copying? State its importance.<\/strong> Question.12. Explain budding in. Hydra with the help of labelled diagrams only.<\/strong> Question.13. List any four contraceptions used by humans. How does their use have a direct effect on \u2019 the health and prosperity of a family.’<\/strong> Question.14. “We cannot pass on to our progeny the experiences and qualifications earned during our life time”. Justify the statement giving reason and examples.<\/strong> Question.15. (a) Planaria, insects, octopus arid vertebrates all have eyes. Can we group eyes of these animals together to establish a common evolutionary origin? Justify your answer, (b) “Birds have evolved from reptiles”. State evidence to prove the statement.<\/strong> Question.16. To construct a ray diagram we use two rays of light which are so chosen that it is easy to determine their directions after reflection from the mirror. Choose these two rays and state the path of these rays after reflection from a concave mirror. Use these two rays to find the nature and position of the image of an object placed at a distance of 15 cm from a concave mirror of focal length 10 cm.<\/strong> Question.17. With the help of a labelled diagram, explain why the sun appears reddish at the sunrise and the sunset.<\/strong> Question.18. After the examinations Rakesh with his friends went on a picnic to a nearby park. All friends carried cooked food packed in plastic bags or plastic cans. After eating the food some friends collected the leftover food and plastic bags etc. and planned to dispose them off by burning. Rakesh immediately checked them and suggested to segregate the leftover food and peels of fruits from the plastic materials and respectively dispose them off separately in the green and red dustbins placed in the comer of the park.<\/strong> Question.19. Explain why carbon forms compounds mainly by covalent bond. Explain in brief two main reasons for carbon forming a large number of compounds. Why does carbon form strong bonds with most other elements?<\/strong> Two properties of carbon which lead to huge number of carbon compounds are:<\/strong><\/p>\n The reason for the formation of strong bonds by the carbon atoms is their small atomic size. Due to the small size of carbon atoms their nuclei hold the shared pairs of electrons between atoms strongly, leading to the formation of strong covalent bonds. The carbon atoms also form strong covalent bonds with the atoms of other elements such as hydrogen, oxygen, nitrogen, sulphur, chlorine and other elements.<\/p>\n Question.20. Write the functions of the following in human female reproductive system:<\/strong> After fertilisation, zygote is formed which develops into an embryo. The embryo gets nutrition from the mother’s blood with the help of a special tissue called placenta. This is a disc which is embedded in the uterine wall. It contains finger-like projections called villi on the embryo’s side of the tissue. On the mother’s side are blood spaces, which surround the villi. This provides a large surface area for glucose and oxygen to pass from the mother to the embryo. In this way, the embryo gets its nutrition.<\/p>\n Question.21. How many pairs of chromosomes are present in human beings? Out of these how many are sex chromosomes? How many types of sex chromosomes are found in human beings? “The sex of a newborn child is a matter of chance and none of the parents may be considered responsible for it”. Draw a flow chart showing determination of sex of a newborn to justify this statement.<\/strong> Question.22. (a) State the laws of refraction of light. Explain the term absolute refractive index of a medium and write an expression to relate it with the speed of light in vacuum. (b) The absolute refractive indices of two media ‘A’ and ‘B’ are 2.0 and 1.5 respectively. If the speed of light in medium ‘B’ is 2 x 108<\/sup> m\/s, calculate the speed of light in: (i) vacuum, (ii) medium ‘A’.<\/strong> Question.23. “A convex lens can form a magnified erect as well as magnified inverted image of an object placed in front of it.” Draw ray diagram to justify this statement stating the position of the object with respect to the lens in each case.<\/strong> Question.24. A student is unable to see clearly the words written on the blackboard placed at a distance of approximately 4 m from him.<\/strong> SECTION B<\/strong><\/span> Question.26. A student prepared 20% sodium hydroxide solution in a beaker to study saponification reaction. Some observations related to this are given below:<\/strong> Question.27. Hard water is not available for an experiment. Some salts are: given below:<\/strong> Question.28. A student identified the various parts of an embryo of a gram seed and listed them as given below:<\/strong> Question.29. Four students A, B, C and D reported the following set of organs to be homologous. Who is correct?<\/strong> Question.30. Study the given diagram and select the correct statement about the device ‘X’:<\/strong> Question.31. A student has obtained a point image of a distant object using the given convex lens. To find the focal length of the lens he should measure the distance between the :<\/strong> Question.32. Four students P, Q, R and S traced the path of a ray of light passing through a glass slab for an angle of incidence 40\u00b0 and measured the angle of refraction. The values, as measured by them were 18\u00b0; 22\u00b0; 25\u00b0 arid 30\u00b0 respectively. The student who has performed the experiment methodically is<\/strong> Question.33. After tracing the path of a ray of light through a glass prism a student marked the angle incidence (\u2220i), angle of refraction (\u2220r), angle of emergence (\u2220e) and the angle of deviation (\u2220D) as shown in the diagram. The correctly marked angles are:<\/strong> Question.34. List two observations which you make when you add a pinch of sodium hydrogen carbonate to acetic acid in a test tube. Write the chemical equation for the reaction that occurs.<\/strong> Question.35. Name the type of asexual reproduction in which two individuals are formed from a single parent and the parental identity is lost.<\/strong> Question.36. To find the image-distance for varying object-distances in case of a convex lens, a student obtains on a screen a sharp image of a bright object placed very far from the lens. After that he gradually moves the object towards the lens and each time focuses its image on the screen.<\/strong> Except for the following questions, all the remaining questions have been asked in Set-I.<\/strong>
\nGeneral Instructions:<\/span><\/strong><\/p>\n\n
SET I<\/strong><\/span><\/h3>\n
\nQuestion.1. Write the name and formula of the 2nd member of homologous series having general formula\u00a0Cn<\/sub>H2n<\/sub>.<\/strong>
\nAnswer.<\/strong> Cn<\/sub>H2n<\/sub> = Alkene
\n2nd member = C3<\/sub>H6<\/sub> (Propene)<\/p>\n
\nAnswer.<\/strong> Two functions of testes are:<\/p>\n\n
\nAnswer.<\/strong> Ozone layer is very important for the existence of life on earth. The function of the ozone layer in the upper atmosphere is to absorb most of the harmful ultraviolet radiations coming from the sun and prevent them from reaching the earth’s surface.<\/p>\n
\nAnswer.<\/strong> The characteristics of the images formed by plane mirrors are:<\/p>\n\n
\nAnswer.<\/strong> Due to the presence of a large number of species (of plants and animals) threatened with extinction, forests are said to be ‘biodiversity hotspots’.
\nThe two ways in which an individual can contribute effectively to the management of forests and wildlife are:<\/p>\n\n
\nAnswer.<\/strong> The development and management of resources in such a way which meets the current basic human needs and also preserves the resources for the needs of future generations, is called sustainable management.
\nThe process of ‘reuse’ is considered better than the process of ‘recycling’ because recycling requires the use of a large amount of energy and money whereas no energy is required for reusing materials.<\/p>\n
\nAnswer.<\/strong> Process of hydrogenation:
\n
\nThe addition of hydrogen to an unsaturated hydrocarbon to obtain a saturated hydrocarbon is called hydrogenation.
\nEssential conditions for the reaction are:<\/strong><\/p>\n\n
\n
\n Answer.<\/strong>
\n<\/p>\n
\n (i) down a group and (ii) from left to right in a period?<\/strong>
\n Answer.<\/strong> There are 18 groups and 7 periods in the modem periodic table.
\n(i) Atomic size and metallic character of the elements increases down a group.
\n(ii)<\/p>\n\n
\n <\/strong>
\n (i) Select the element having one electron in the outermost shell.<\/strong>
\n (ii) two elements of the same group.<\/strong>
\n Write the formula of and mention the nature of the compound formed by the union of 19<\/sub>K and element X (2,8,7).<\/strong>
\n Answer.<\/strong>
\n<\/p>\n
\n Answer.<\/strong> A process in which a DNA molecule produces two similar copies of itself in a reproducing cell through chemical reaction is a called DNA copying.<\/p>\n\n
\n Answer.<\/strong> See Q. 20, 2011 (I Outside Delhi).<\/p>\n
\n Answer.<\/strong> See Q. 12,2014 (I Delhi).<\/p>\n
\n Answer.<\/strong> All traits of the parent cannot be transmitted to the offspring because all traits are not inherited traits, some of the characteristics are acquired. The experiences and qualifications earned during our lifetime are examples of acquired traits.
\nA trait of an organism which is ‘not inherited’ but develops in response to the environment is called an acquired trait. The acquired traits of organisms cannot be passed on to their future generations.
\nOnly those traits can be transmitted to future generations in which changes have occurred in the genes present in the reproductive cells of parent organisms.
\nFor example, If we breed some mice, all the progeny of mice will have tails, just like parents. Now, if we cut the tails of these first generation mice surgically and breed them, we will get new mice, all with full tails. Despite the cutting of tails of mice for a number of generations, a tailless mouse is never born.
\nThis is because the cut tail of mice is an acquired trait which is never passed on to their progeny. This is because cutting the tails of mice does not Change the genes of their reproductive cells.<\/p>\n
\n Answer.<\/strong> (a) The eyes seen in planaria, insects, octopus and vertebrates vary greatly in their structure. These Organisms can be used for studying evolution of eyes as the eyes of planaria are simple without lens, insects have compound eyes and vertebrates have highly specialised eyes. However, all of them perform the same function, that is, vision. Thus, a common evolutionary origin can be established.
\n(b) Birds have evolved from reptiles as the connecting link between reptiles and birds is Archaeopteryx (flying dinosaur). Also, there are some similarities in birds and reptiles. Birds have a four-chambered heart\/ which is also a feature of some reptiles. Both birds and reptiles have separate sexes and internal fertilization occurs in both.<\/p>\n
\n Answer.<\/strong> Ray 1. When an incident ray of light is parallel to the principal axis of a concave mirror, its reflected ray must pass through the principal focus of the concave mirror.
\nRay 2. A ray passing through the principal focus of a concave mirror after reflection will emerge parallel to the principal axis.
\n\u2022 Focal length = 10 cm; Then centre of curvature, C = 20 cm
\n. Object, is placed at 15 cm, i.e., between F & C
\nwhen the object is between F and C (centre of curvature):
\nThe image formed is real, inverted and magnified.It is formed beyond C.
\n<\/p>\n
\n Answer.<\/strong> At the time of sunrise and sunset when the sun is near the horizon, the sunlight has to travel the greatest distance through the atmosphere to reach us. During the long journey of sunlight, most of the shorter wavelength blue-colour present in it is scattered out and away from our line of sight so, the light reaching us directly from the rising sun or setting sun consists mainly of longer wavelength red colour due to which the sun appears red. Due to the same reason, the sky surrounding the rising sun and setting sun also appears red. Thus, at sunrise and sunrise, the sun itself as well as the surrounding sky appear red.
\n<\/p>\n
\n (a) In your opinion, is burning plastic an eco-friendly method of waste disposal? Why? State the advantage of the method suggested by Rakesh.<\/strong>
\n (b) How can we contribute in maintaining the parks and roads neat and clean?<\/strong>
\n Answer.<\/strong> (i) Burning of plastic is not an eco-friendly method of waste disposal because it
\nproduces toxic gases which cause too much air pollution. It has an adverse effect on the health of all types of living organisms including human beings. –
\nThe method of waste disposal Used by Rakesh is advantageous as the leftover food and peels of fruits are biodegradable and can be used as manure.
\nThe plastic bags and cans should be disposed off in red dustbins from where they can be sent for recycling, thereby keeping the environment clean.
\n(ii) \u2022 We should not litter on roads and parks.
\n\u2022 We should not spit on roads and parks.
\n\u2022 We should make it a point to throw the garbage in dustbins and learn to segregate garbage into biodegradable and non-biodegradable.<\/p>\n
\n Answer.<\/strong> The atomic number of carbon is 6 which means that a neutral atom of carbon retains 6
\nelectrons. So, the electronic configuration of carbon is K, L.\u00a0Since, carbon has 4 electrons in its outermost shell so, it should either lose or gain 4 electrons to achieve the inert gas configuration and become stable.<\/p>\n\n
\nThus, it forms compounds mainly by covalent bonds.<\/li>\n<\/ol>\n\n
\n Ovary, oviduct, uterus<\/strong>
\n How does the embryo get nourishment inside the mother’s body? Explain in brief.<\/strong>
\n Answer.<\/strong> Functions of:<\/p>\n\n
\n Answer.<\/strong><\/p>\n\n
\nAnswer.<\/strong> (a) Laws of Refraction:
\n(i) The first law of refraction of light states that the incident ray, the refracted ray and the normal at the point of incidence, all lie in the same plane.
\n(ii) The second law of refraction of light is the Snell’s Law of Refraction. It states that the ratio of sine of the angle of incidence to the sine of angle of refraction is a constant for a given pair of medium.
\n<\/p>\n
\n An object of height 4 cm is placed at a distance of 20 cm from a concave lens of focal length 10 cm. Use lens formula to determine the position of the image formed.<\/strong>
\n Answer<\/strong>. \u2022 A convex lens can form a magnified erect image when the object is placed between the optical centre and principal focus of the convex lens (i.e., between O and F).
\n
\n\u2022 A convex lens can form a magnified inverted image when the object is placed between focus and the centre of curvature (i.e., between F’ and 2F’).
\n<\/p>\n
\n Name the defect of vision the boy is suffering from. Explain the method of correcting this defect. Draw ray diagram for the:<\/strong>
\n (i) defect of vision and also (ii) for its correction.<\/strong>
\n Answer.<\/strong><\/p>\n\n
\nRay diagrams for the defect and for its corrections. See Q. 10, 2012 (1 Delhi).<\/li>\n<\/ul>\n
\nQuestion.25. A student adds 2 mL of acetic acid to a test tube containing 2 mL of distilled water. He then shakes the test tube well and leaves it to settle for some time. After about 5 minutes he observes that in the test tube there is:<\/strong>
\n (A) A clear transparent colourless solution<\/strong>
\n (B) A clear transparent pink solution<\/strong>
\n (C) A precipitate settling at the bottom of the test tube<\/strong>
\n (D) A layer of water over the layer of acetic acid<\/strong>
\n Answer.<\/strong> (A)<\/p>\n
\n (I) Sodium hydroxide solution turns red litmus blue<\/strong>
\n (II) Sodium hydroxide readily dissolves in water ,<\/strong>
\n (III) The beaker containing solution appears cold when touched from .outside<\/strong>
\n (IV) The blue litmus paper turns red when dipped, into the solution<\/strong>
\n The correct observations are:<\/strong>
\n (A) I, II and IV (B) I, II and III<\/strong>
\n (C) only-III and IV (D) only I and II<\/strong>
\n Answer.<\/strong> (D)<\/p>\n
\n (I) Sodium chloride (II) Sodium sulphate<\/strong>
\n (III) Calcium chloride (IV) Calcium sulphate<\/strong>
\n (V) Potassium chloride (VI) Magnesium sulphate<\/strong>
\n Select from the following a group of these salts, each member of which may be dissolved in water to make it hard.<\/strong>
\n (A) I, 11 and V (B) I, III, V<\/strong>
\n (C) III, IV, VI . (D) II, IV, VI<\/strong>
\n Answer.<\/strong> (C)<\/p>\n
\n (I) Testa (II) Plumule<\/strong>
\n (III) Radicle (IV) Cotyledon<\/strong>
\n (V) Tegmen<\/strong>
\n Out of these the actual parts of the embryo are:<\/strong>
\n (A) I, II, III (B) II, III, IV<\/strong>
\n (C) Ill, IV, V (D) II, IV, V<\/strong>
\n Answer.<\/strong> (B)<\/p>\n
\n (A) Wings of a bat and a butterfly<\/strong>
\n (B) Wings of a pigeon and a bat<\/strong>
\n (C) Wings of a pigeon and a butterfly<\/strong>
\n (D) Forelimbs of cow, a duck and a lizard<\/strong>
\n Answer.<\/strong> (D)<\/p>\n
\n <\/strong>
\n (A) Device ‘X’ is a concave mirror of radius of curvature 12 cm<\/strong>
\n (B) Device ‘X’ is a concave mirror of focal length 6. cm<\/strong>
\n (C) Device ‘X’ is a concave mirror of radius of focal length 12 cm<\/strong>
\n (D) Device ‘X’ is a convex mirror of focal length 12 cm<\/strong>
\n Answer.<\/strong> (C)<\/p>\n
\n (A) lens and the object only<\/strong>
\n (B) lens,and the screen only<\/strong>
\n (C) object and the image only<\/strong>
\n (D) lens and the object and also between the object and the image<\/strong>
\n Answer.<\/strong> (B)<\/p>\n
\n (A) P (B) Q (C) R (D) S<\/strong>
\n Answer.<\/strong> (C)<\/p>\n
\n <\/strong>
\n (A) \u2220i and \u2220r (B) \u2220i and \u2220e<\/strong>
\n (C) \u2220i, \u2220e and \u2220D (D) \u2220i, \u2220r and \u2220e<\/strong>
\n Answer.<\/strong> (B)<\/p>\n
\n Answer.<\/strong> When a pinch of sodium hydrogen carbonate is added to acetic acid in a test tube, there are two observations:
\n(i) Brisk effervescence .
\n(ii) Evolution of a colourless and odourless gas which is C02<\/sub>.
\n<\/p>\n
\n Draw the initial and the final stages of this type of reproduction. State the event with which this reproduction starts.<\/strong>
\n Answer.<\/strong><\/p>\n\n
\n (a) In which direction-towards or away from the lens, does he move the screen to focus the object?<\/strong>
\n (b) What happens to the size of image-does it increase or decrease?<\/strong>
\n (c) What happen when he moves the object very close to the lens?<\/strong>
\n Answer.<\/strong> (a) He moves the screen away from lens to focus the object.
\n(b) The size of the image increases.
\n(c) When the object is placed very close to the lens, then no image will be formed on the screen.<\/p>\nSET II<\/strong><\/span><\/h3>\n
\n SECTION A<\/strong><\/span>
\nQuestion.1. Write the name and formula of the 2nd member of homologous series having general formula Cn<\/sub>H2n+2<\/sub>.<\/strong>
\n Answer.<\/strong> Cn<\/sub>H2n+2<\/sub>: Alkane series Name: Ethane (2nd member) Formula: C