CBSE Previous Year Question Papers Class 10 Science 2019 Outside Delhi Set I<\/h3>\n
Section – A<\/strong><\/p>\n Question 1. Question 2. Section – B<\/strong><\/p>\n Question 3. Question 4. Question 5. Section – C<\/strong><\/p>\n Question 6. Question 7. Question 8. Question 9. Question 10. Question 11. Question 12. 1. Stigma is the top part of carpel and is sticky. So, it receives the pollen from the anther of stamen. Question 13. Question 14. Question 15. Section – D<\/strong><\/p>\n Question 16. (b) (i) On moving from left to right in a , period, the metallic character of elements decreases because electropositive character decreases. Question 17. (b) Two neurons are not joined to one another completely. There is a small gap between a pair of neuron. This gap is called synapse. The nerve impulse are carried out to this gap by the help of neurotransmitter (chemical substance). The conduction of nerve impulse through the synapse takes place in the form of electrical nerve impulse. When a stimulus acts on the receptor, an electrical impulse is produced with the help of chemical reaction. This electrical impulse passes through the synapse and then to the other neuron. Thus, in this way nerve impulses travel in the body. In trough A, the root of seedling gets water from both sides (because the soil is watered uniformly) in trough B, the roots gets water oozing out from the clay pot which is kept on the right side. So, the root of seedling in trough B grows and bends towards the source of water to the right side. The experiment shows that the root of a plant grows towards water. In other words, the root of a plant is positively hydrotropic.<\/p>\n Question 18. Question 19. Question 20. Question 21. Section – E<\/strong><\/p>\n Question 22. Question 23. Question 24. Question 25. Question 26. Question 27. Note: Except for the following questions, all the remaining questions have been asked in previous set.<\/p>\n Section – A<\/strong><\/p>\n Question 1. Question 2. Section – B<\/strong><\/p>\n Question 3. Question 4. Question 5. Section – C<\/strong><\/p>\n Question 6. Question 7. Question 10. Steps to minimise the pollution caused by various energy sources are:<\/p>\n Question 14. Section – D<\/strong><\/p>\n Question 16. (b) In Mendel’s experiment, when pure tall pea plants were crossed with pure dwarf pea plants, only tall pea plants were obtained in F1<\/sub> generation. On selfing, the pea plants of F1<\/sub> generation both tall and dwarf pea plants were obtained in F2<\/sub> generation. The reappearance of the dwarf pea plants in F2<\/sub> generation proves that the dwarf trait was inherited but not expressed in F1<\/sub> generation. The recessive trait does not express itself in the presence of the dominant trait. So, it is possible that one trait may be inherited but may not be expressed in an organism.<\/p>\n Question 20. (b) The reddish appearance of the sun at sunrise ‘ and sunset is due to the scattering of blue colour present in the sunlight away from our line of sight and leaves behind the mainly red colour of the direct sunlight which reaches the human eye. Note: Except for the following questions, all the remaining questions have been asked in previous sets.<\/p>\n Section – A<\/strong><\/p>\n Question 1. Question 2. Section – B<\/strong><\/p>\n Question 3. Question 4. Question 5. Section – C<\/strong><\/p>\n Question 6. Question 7. Question 9. Question 10. Question 15. Section – D<\/strong><\/p>\n Question 16. Question 20. The variations in the characters of the obtained offsprings from sexual reproduction enable them to adapt according to the environment and struggle for their existence. Over a period of time, the characters accumulate within the species and the formed species give rise to new species and this process goes on.<\/p>\n CBSE Previous Year Question Papers Class 10 Science 2019 Outside Delhi Time allowed: 3 hours Maximum marks: 80 General Instructions: The question paper comprises five sections, A, B, C, D and E. You are to attempt all the sections. All questions are compulsory. Internal choice is given in Sections B, C, D and E. Questions …<\/p>\n","protected":false},"author":27,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spay_email":""},"categories":[2],"tags":[],"yoast_head":"\n
\nName two industries based on forest produce. [1]
\nAnswer:
\nTimber industries and paper manufacturing industries are based on forest produce.<\/p>\n
\nWhy are the heating elements of electric toasters and electric irons made of an alloy rather than a pure metal? [1]
\nAnswer:
\nThe resistivity of an alloy is generally higher than that of its constituent metals. Alloys do not oxidise (bum) readily at higher temperatures. Therefore, conductors of electric heating devices, such as toasters and electric irons, are made up of an alloy rather than pure metal.<\/p>\n
\nWrite the molecular formula of ethene and draw its electron dot structure. [2]
\nAnswer:
\nThe molecular formula of ethene is C2<\/sub>H4<\/sub>
\nElectron dot structure of ethene.
\n![\"CBSE](\"https:\/\/i2.wp.com\/live.staticflickr.com\/65535\/48372116816_c0167ae89a_o.png?resize=309%2C122&ssl=1\")
<\/p>\n
\nGiven reasons:
\n(a) Platinum, gold and silver are used to make jewellery.
\n(b) Metals like sodium and potassium are stored under oil.
\nOR
\nSilver articles become black when kept in open for some time, whereas copper vessels lose their shiny brown surfaces and gain a green coat when kept in open. Name the substances present in air with which these metals react and write the name of the products formed. [2]
\nAnswer:
\n(a) Platinum, gold and silver are used to make jewellery because of its bright and shiny surface. This property is called metallic lustre.
\n(b) Metals like sodium and potassium are stored under oil because they are very reactive in nature, they react with oxygen present in air. Thus to prevent their oxidation they are kept in the oil.
\nOR
\nSilver articles become black when kept in open for some time, whereas copper vessel lose their shiny brown surfaces and gain a green coat when kept in open because silver articles reacts with sulphur compounds such as hydrogen sulphide present in the air to form silver sulphide (Ag2<\/sub>S) whereas copper reacts slowly with CO2<\/sub> and water present in the air to form green coating of mixture of copper carbonate and copper hydroxide.<\/p>\n
\nThe absolute refractive index of Ruby is 1.7. Find the speed of light in Ruby. The speed of light in a vacuum is 3 \u00d7 108<\/sup> m\/s. [2]
\nAnswer:
\nWe know that,
\nRefractive index of ruby
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372246882_f6e5850bb2_o.png?resize=289%2C60&ssl=1\")
\n![\"CBSE](\"https:\/\/i2.wp.com\/live.staticflickr.com\/65535\/48372116976_ca0101308d_o.png?resize=358%2C192&ssl=1\")
<\/p>\n
\nOn heating blue coloured powder of copper (II) nitrate in a boiling tube, black copper oxide, O2<\/sub> and a brown gas X is formed. [3]
\n(a) Identify the type of reaction and gas X.
\n(b) Write the balanced chemical equation of the reaction.
\n(c) Write the pH range of aqueous solution of the gas X.
\nAnswer:
\n(a) Decomposition reaction
\nThe gas X is Nitrogen dioxide (NO2<\/sub>)
\n![\"CBSE](\"https:\/\/i2.wp.com\/live.staticflickr.com\/65535\/48372247047_a3a967731c_o.png?resize=370%2C136&ssl=1\")
\n(c) Oxides of non-metals are acidic. Therefore the aqueous solution of this gas would be acidic.
\nThe pH would be less than 7<\/p>\n
\n(a) While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?
\n(b) Dry hydrogen chloride gas does not change the colour of dry litmus paper why?
\nOR
\nHow is sodium hydroxide manufactured in industries? Name the process. In this process, a gas X is formed as a byproduct. This gas reacts with lime water to give a compound Y, which is used as a bleaching agent in the chemical industry. Identify X and Y and write the chemical equation of the reaction involved. [3]
\nAnswer:
\n(a) The process of mixing concentrated acid with water is highly exothermic.
\nSo, when a concentrated acid is added to water then heat is easily absorbed by a large amount of water. Thus it is recommended to add acid to water and not water to the acid.
\n(b) Dry hydrogen chloride does not contain any hydrogen ions in it, so it does not show acidic behaviour and thus does not change the colour of dry litmus paper.
\nOR
\nSodium hydroxide is manufactured by the electrolysis of a concentrated aqueous solution of sodium chloride.
\n![\"CBSE](\"https:\/\/i1.wp.com\/live.staticflickr.com\/65535\/48372117076_3053a7b6aa_o.png?resize=372%2C170&ssl=1\")
\nThe process of manufacture of sodium hydroxide by electrolysis process is called the chloralkali process.
\nGas X is chlorine gas and compound Y is calcium oxychloride (Bleaching powder)
\n![\"CBSE](\"https:\/\/i2.wp.com\/live.staticflickr.com\/65535\/48372247177_a11a54952a_o.png?resize=369%2C93&ssl=1\")
<\/p>\n
\nWhat are amphoteric oxides? Give an example. Write balanced chemical equations to justify your answer. [3]
\nAnswer:
\nThose oxides which behave both acidic and basic oxides are called amphoteric oxides.
\nExample: Al2<\/sub>O3<\/sub> (Alumina)
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372247207_a7e15ef67e_o.png?resize=351%2C118&ssl=1\")
<\/p>\n
\nWhat is a homologous series of carbon compounds ? Give an example and list its three characteristics. [3]
\nAnswer:
\nA homologous series is a group of organic compounds having similar structures and similar chemical properties in which the successive compounds differ by CH2<\/sub> group.
\nExample: Alkanes with general formula Cn<\/sub>H2n+2<\/sub>
\nCharacteristics:<\/p>\n\n
\nList in tabular form three distinguishing features between autotrophic nutrition and heterotrophic nutrition. [3]
\nAnswer:<\/p>\n\n\n
\n S.No.<\/strong><\/td>\n Autotrophic nutrition<\/strong><\/td>\n Heterotrophic nutrition<\/strong><\/td>\n<\/tr>\n \n 1.<\/td>\n In this mode of nutrition, organisms make their own food.<\/td>\n In this mode of nutrition, the organisms do not make their own food.<\/td>\n<\/tr>\n \n 2.<\/td>\n CO2 and H2O are required for the preparation of food as raw materials.<\/td>\n They depend on autotrophs for their food either directly or indirectly.<\/td>\n<\/tr>\n \n 3.<\/td>\n Chlorophyll and sunlight are essentially needed.<\/td>\n Chlorophyll and sunlight are not needed.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\nWhat is transpiration? List its two functions.
\nOR
\n(a) What is translocation? Why is it essential for plants?
\n(b) Where do the substances in plants reach as a result of translocation? [3]
\nAnswer:
\nThe evaporation of water from the leaves of a plant is called transpiration.
\nFunctions of transpiration
\n1. It helps in the upward movement of water and minerals from the root to the leaves through the stem.
\n2. Helps in cooling the plant surface.
\nOR
\n(a) The transport of food from leaves to other parts of the plant is called translocation. Translocation is essential for plants because without it food prepared by the leaves cannot reach other parts of the plant for their growth and development.
\n(b) The substances in plants reach other tissues in plants from the leaves as a result of translocation.<\/p>\n
\nWhat is carpel? Write the function of its various parts. [3]
\nAnswer:
\nThe flask-shaped organ in the centre of a flower is called carpel. It is also called a female reproductive organ of the plant.
\nIt is made up of three parts:<\/p>\n\n
\n2. Style connects stigma to ovary.
\n3. Ovary contains female gametes of the plant and helps in reproduction.<\/p>\n
\nA student holding a mirror in his hand directed the reflecting surface of the mirror towards the Sun. He then directed the reflected light on to a sheet of paper held close to the mirror.
\n(a) What should he do to bum the paper?
\n(b) Which type of mirror does he have?
\n(c) Will he be able to determine the approximate value of the focal length of this mirror from this activity ? Give reason and draw ray diagram to justify your answer in this case.
\nOR
\nA 10 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 12 cm. The distance of the object from the lens is 18 cm. Find the nature, position and size of the image formed. [3]
\nAnswer:
\n(a) He should place the sheet of paper at the focus of the mirror to burn the paper.
\n(b) He has a concave mirror.
\n(c) Yes, the sheet of paper will start burning at the focus of the mirror which will give an approximate value of focal length, i.e., the distance between the mirror and the point where the sheet of paper starts burning.
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372117311_5ded3a2199_o.png?resize=335%2C233&ssl=1\")
\nA concave mirror forms a real image of the sun.
\nOR
\nGiven: Height of object, h1<\/sub>\u00a0= +10 cm.
\nFocal length, f = +12 cm.
\nObject distance, u = -18 cm.
\nFrom the lens formula,
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372247317_808f87a27c_o.png?resize=271%2C401&ssl=1\")
\nThe position of image formed is at distance of 36 cm from convex lens.
\nSince the value of the magnification is more than 1 (it is 2), the image formed is larger than object.
\nThe minus sign of magnification shows that image is formed below the principal axis. Hence, the image formed is real and inverted.<\/p>\n
\nWhat are solar cells? Explain the structure of solar panel. List two principal advantages associated with solar cells. [3]
\nAnswer:
\nSolar cells are the devices which convert solar energy into electricity.
\nA simple solar cell is made up of a sandwich of a silicon-boron layer and a silicon-arsenic layer. Boron and arsenic are present in a very small amount. A piece of wire is soldered into the top of the upper layer of cell and another piece of wire is soldered at the bottom of the lower layer to pass on the current. The solar cell is covered with a glass cover for protection.
\nAdvantages:<\/p>\n\n
\nWrite the essential function performed by ozone at the higher levels of the Earth’s atmosphere ? How is it produced ? Name the synthetic chemicals mainly responsible for the drop of amount of ozone in the atmosphere. How can the use of these chemicals be reduced? [3]
\nAnswer:
\nOzone layer absorbs most of the harmful ultraviolet radiations from the sun to the earth. It is formed high up in the atmosphere by the action of ultraviolet radiation on oxygen gas. Chlorofluorocarbons are the synthetic chemicals responsible for the drop of amount of ozone in the atmosphere.
\nThe use of these chemicals can be reduced by:<\/p>\n\n
\n(a) List any three observations which posed a challenge to Mendeleev’s Periodic law.
\n(b) How does the metallic character of elements vary on moving from
\n(i) left to right in a period,
\n(ii) from top to bottom in a group of the Modem Periodic Table?
\nGive a reason for your answer.
\nOR
\nThe electrons in the atoms of four elements A, B, C and D are distributed in three shells having 1, 3, 5 and 7, electrons respectively in their outermost shells. Write the group numbers in which these elements are placed in the Modem Periodic Table. Write the electronic configuration of the atoms of B and D, and the molecular formula of the compound formed when B and D combine. [5]
\nAnswer:
\n(a) Three observations which posed a challenge to Mendeleev’s Periodic law are:<\/p>\n\n
\n(ii) Ongoing down in a group of the periodic table, the metallic character of elements increases because of electropostive character of elements increases.
\nOR
\nA – 1st group.
\nB – 13th group.
\nC – 15th group.
\nD – 17th group.
\nElectronic configuration
\nB \u2192 Atomic number = 13.
\nK L M
\n2 8 3
\nD \u2192 Atomic number = 17
\nK L M
\n2 8 7
\nThe molecular formula of the compound when B and D combine is BD3<\/sub>.<\/p>\n
\n(a) Why is the use of iodised salt advisable? Name the disease caused due to deficiency of iodine in our diet and state its one symptom.
\n(b) How do nerve impulses travel in the body? Explain.
\nOR
\nWhat is hydrotropism? Design an experiment to demonstrate this phenomenon. [5]
\nAnswer:
\n(a) Iodised salt is advisable because iodine is necessary for the formation of thyroxine hormone by the thyroid gland. Goitre is the disease caused due to its deficiency.
\nSymptom: The neck of the person appears to be swollen due to the enlargement of thyroid gland.<\/p>\n
\nOR
\nThe movement of root of plants towards water is called hydrotropism.
\nTake two glass troughs A and B fill each one of them two-thirds with soil. In trough A plant a tiny seedling figure (a). In trough B plant a similar seedling and also place a small ‘clay pot’ inside the soil figure (b). Water the soil in trough A daily and uniformly. Do not water the soil in trough B but put some water in the clay pot buried in the soil. Leave both the troughs for a few days.
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372117421_6e7fe8a7f7_o.png?resize=357%2C356&ssl=1\")
\nNow, dig up the seedlings carefully from both the trough without damaging their roots. We will find that the root of seedling in trough A is straight. On the other hand, the root of seedling in trough B is found to be bent to the right side (towards the clay pot containing water) figure (b). This can be explained as follows.<\/p>\n
\n(a) What are homologous structures ? Give an example.
\n(b) “The sex of a newborn child is a matter of chance and none of the parents may be considered responsible for it.” justify this statement with the help of a flow chart showing sex-determination in human beings. [5]
\nAnswer:
\n(a) The structures which have the same basic design but different functions are called homologous structures or homologous organs.
\nExample: Forelimbs of a man, a lizard, a frog they have same basic design of bones but perform different functions.
\n(b) The sex of a newborn depends on what happens at the time of fertilization.
\n1. If a sperm carrying X chromosome fertilizes the ovum carrying X chromosome, then the girl child will be born and the child will have XX combination of sex chromosomes.
\n2. If a sperm carrying Y chromosome fertilizes the ovum carrying X chromosome, then the child born will be a boy and the child will have XY combination of sex chromosome.
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372117401_ef428e69aa_o.png?resize=265%2C184&ssl=1\")
\nThe above presentation clearly shows that it is matter of chance whether the newborn will be boy or girl and none of the parents may be considered responsible for it.<\/p>\n
\nWhen do we consider a person to be myopic or hypermetropic ? List two causes of – hypermetropia. Explain using ray diagrams how the defect associated with hypermetropic eye can be corrected. [5]
\nAnswer:
\nMyopia is the defect in vision in which a person cannot see the distant objects clearly whereas in hypermetropia is the defect in which a person cannot see nearby objects clearly. Hypermetropia is caused due to:
\n1. Decrease in converging power of eye-lens.
\n2. Too short eye ball.
\nIn a hypermetropic eye, the image of near by object lying at normal near point N (at 25 cm) is formed behind the retina.
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372247417_295b7ff734_o.png?resize=413%2C344&ssl=1\")
\nHypermetropic eye can be corrected using convex lenses. When a convex lens of suitable power is placed in front of hypermetropic eye, then the diverging rays of light from the object are converged first by the convex lens used. This form a virtual image of the object at another near point N’.
\nNow, the rays can be easily focused by the eye lens to form an image on retina.<\/p>\n
\n(a) How will you infer with the help of an experiment that the same current flows through every part of a circuit containing three resistors in series connected to a battery?
\n(b) Consider the given circuit and find the current flowing in the circuit and potential difference across the 15 \u2126 resistor when the circuit is closed. [5]
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372117491_95eeda8c29_o.png?resize=245%2C124&ssl=1\")
\nOR
\n(a) Three resistors R1<\/sub>, R2<\/sub> and R3<\/sub> are connected in parallel and the combination is connected to a battery, ammeter, voltmeter and key. Draw suitable circuit diagram and obtain an expression for the equivalent resistance of the combination of the resistors.
\n(b) Calculate the equivalent resistance of the following network:
\n![\"CBSE](\"https:\/\/i2.wp.com\/live.staticflickr.com\/65535\/48372117516_fd26bb55c3_o.png?resize=244%2C97&ssl=1\")
\nAnswer:
\n(a) Let three resistors R1<\/sub>, R2<\/sub> and R3<\/sub> are connected in series which are also connected with a battery, an ammeter and a key as shown in figure.
\n![\"CBSE](\"https:\/\/i1.wp.com\/live.staticflickr.com\/65535\/48372117556_d1651a2246_o.png?resize=251%2C131&ssl=1\")
\nWhen key is closed, the current starts flowing through the circuit. Take the reading of ammeter. Now change the position of ammeter to anywhere in between the resistors and take its reading. We will observe that in both the cases reading of ammeter will be same showing same current flows through every part of the circuit above.
\n(b) Given,
\nR1<\/sub> = 5 \u2126, R2<\/sub> = 10 \u2126, R3<\/sub> = 15 \u2126, V = 30 V
\nTotal resistance, R = R1<\/sub> + R2<\/sub> + R3<\/sub> [\u2235 5 \u2126, 10 \u2126 and 15 \u2126 are connected in series]
\n= 5 + 10 + 15
\n= 30 \u2126
\nPotential difference, V = 30 V
\nCurrent in the circuit, I = ?
\nFrom Ohm’s law.
\nI = \\(\\frac { V }{ R }\\) = \\(\\frac { 30 }{ 30 }\\) = 1 A
\nCurrent flowing in the circut = 1 A
\nPotential difference across 15 \u2126 resistors = IR3 = 1 \u00d7 15 = 15 V
\nOR
\n(a) Let R1, R2 and R3 are three resistance connected in parallel to one another and R is the equivalent resistance of the circuit. A battery of V volts has been applied across the ends of this combination. When the switch of the key is closed, current I flows in the circuit such that,
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372247497_e1830c811e_o.png?resize=334%2C489&ssl=1\")
\n![\"CBSE](\"https:\/\/i2.wp.com\/live.staticflickr.com\/65535\/48372247522_b089fda6d2_o.png?resize=369%2C496&ssl=1\")
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372247542_e47b450cb9_o.png?resize=274%2C163&ssl=1\")
\n10 \u2126 and 10 \u2126 are connected in series.
\nEquivalent resistance of the circuit = 10 \u2126 + 10 \u2126 = 20 \u2126<\/p>\n
\nDraw the pattern of magnetic field lines produced around a current-carrying straight conductor passing perpendicularly through horizontal cardboard. State and apply the right-hand thumb rule to mark the direction of the field lines. How will the strength of the magnetic field change when the point where magnetic field is to be determined is moved away from the straight conductor ? Give reason to justify your answer. [5]
\nAnswer:
\nMaxwell’s Right Hand Thumb rule states that if the current-carrying wire is imagined to be held in the right hand so that thumb points in the direction of current, then the direction in which fingers encircle the wire will give the direction of magnetic field lines around the wire. If we hold the current-carrying straight wire so that thumbs Magnetic field pattern due to a straight current-carrying wire in upward direction points the direction of current, the direction of magnetic field lines will be anticlockwise. The strength of the magnetic field is inversely proportional to the distance of the point of observation from the wire. So, as we move away from the wire the strength of magnetic decreases.
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372247567_9a16469ffc_o.png?resize=333%2C365&ssl=1\")
<\/p>\n
\nA teacher provided acetic acid, water, lemon juice, aqueous solution of sodium hydrogen carbonate and sodium hydroxide to students in the school laboratory to determine the pH values of these substances using pH papers. One of the students reported the pH values of the given substances as 3, 12, 4, 8 and 14 respectively. Which one of these values is not correct? Write its correct value stating the reason.
\nOR
\nWhat would a student report nearly after 30 minutes of placing duly cleaned strips of aluminium, copper, iron and zinc in freshly prepared iron sulphate solution taken in four beakers? [2]
\nAnswer:
\nThe value of pH for water is not correct. The correct value of pH of water is 7 because it has almost equal concentration of H+<\/sup> and OH–<\/sup> due to which it is neutral.
\nOR
\nAluminium displaces the iron from iron sulphate and the colour of two solution changes from green to brown.
\nNo change takes place when copper strip is dipped in iron sulphate solution.
\nNo cfiange will be observed when iron strips are dipped in iron sulphate solution.
\nThe colour of the solution changes from green to colourless when zinc is added to iron sulphate solution.<\/p>\n
\nWhat is observed when a pinch of sodium hydrogen carbonate is added to 2 mL of acetic acid taken in a test tube? Write chemical equation for the reaction involved in this case. [2]
\nAnswer:
\nCO2<\/sub> gas is evolved with brisk effervescence when sodium hydrogen carbonate is added to acetic acid.
\n![\"CBSE](\"https:\/\/i1.wp.com\/live.staticflickr.com\/65535\/48372247602_d0107daf63_o.png?resize=368%2C144&ssl=1\")
<\/p>\n
\nList in proper sequence four steps of obtaining germinating dicot seeds.
\nOR
\nAfter examining a prepared slide under the high power of a compound microscope, a student concludes that the given slide shows the various stages of binary fission in a unicellular organism. Write two observations on the basis of which such a conclusion may be drawn. [2]
\nAnswer:
\n1. The root is formed when radicle of seed grows.
\n2. The root grows downward into the soil and absorbs water and minerals from the soil.
\n3. The shoot is formed from the upward growth of plumule.
\n4. The green leaves are developed when the shoot comes above the ground.
\nOR
\n1. A single parent divides to form two daughter cells.
\n2. The nucleus of mature cell seems elongated and a grove is formed in cell which divides the nucleus.<\/p>\n
\nList four precautions which a student should observe while preparing a temporary mount of a leaf peel to show stomata in his school laboratory. [2]
\nAnswer:<\/p>\n\n
\nDraw the path of a ray of light when it enters one of the faces of a glass slab at an angle of nearly 45\u00b0. Label on it
\n(i) angle of refraction
\n(ii) angle of emergence and
\n(iii) lateral displacement.
\nOR
\nA student traces the path of a ray of light through a glass prism as shown in the diagram, but leaves it incomplete and unlabelled. Redraw and complete the diagram. Also label on it \u2220i, \u2220e, \u2220r, and \u2220D. [2]
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372247632_eb54aeae3b_o.png?resize=202%2C133&ssl=1\")
\nAnswer:
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372117706_e5be44829d_o.png?resize=296%2C428&ssl=1\")
<\/p>\n
\nThe current flowing through a resistor connected in a circuit and the potential difference developed across its ends are as shown in the diagram by milliammeter and voltmeter readings respectively: [2]
\n(a) What are the least counts of these meters?
\n(b) What is the resistance of the resistor?
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372117731_1db3ac1b2a_o.png?resize=346%2C151&ssl=1\")
\nAnswer:
\n(a) 10 mA and 0.1 V
\n(b) V = 2.4 volt, I = 250 mA = 0.25 A
\nFrom Ohm’s law.
\nR = \\(\\frac { V }{ I }\\) = \\(\\frac { 2.4 }{ 0.25 }\\) = 9.6 \u2126<\/p>\nCBSE Previous Year Question Papers Class 10 Science 2019 Outside Delhi Set II<\/h3>\n
\nWrite two advantages associated with water harvesting at the community level. [1]
\nAnswer:<\/p>\n\n
\nShould the resistance of a voltmeter be low or high? Give reason. [1]
\nAnswer:
\nThe resistance of a voltmeter should be high because voltmeter is connected parallel to the component of a circuit and it also takes negligible current from the circuit in order to measure the potential difference accurately.<\/p>\n
\nDraw electron dot structure of carbon dioxide and write the nature of bonding between carbon and oxygen in its molecule.
\nOR
\nList two properties of carbon which lead to the huge number of carbon compounds we see around us, giving the reason for each. [2]
\nAnswer:
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372166576_96341330ba_o.png?resize=210%2C36&ssl=1\")
\nCovalent bond (double bond) is present in between C and O.
\nOR
\nTwo properties of carbon which lead to the huge number of carbon compounds are :<\/p>\n\n
\nGive reason:
\n(a) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
\n(b) Aluminium is a highly reactive metal; still, it is widely used in making cooking utensils. [2]
\nAnswer:
\n(a) Carbonate and sulphide ores are usually converted into oxides during the process of extraction because obtaining a metal from its metal oxide is much easier than from metal carbonates and sulphides.
\n(b) Aluminium is highly reactive metal still it is widely used in making cooking utensils because it reacts with 02 present in air to from aluminium oxide that forms a protective layer and protects the metal from corrosion.<\/p>\n
\nThe power of a lens in +5 diopters. What is the nature and focal length of this lens ? At what distance from this lens should an object be placed so as to get its inverted image of the same size? [2]
\nAnswer:
\nGiven, P = + 5D
\nWe have,
\nPower, P = \\(\\frac { 1 }{ f(in meter) }\\)
\n+5 = \\(\\frac { 1 }{ f }\\)
\nf = \\(\\frac { 1 }{ 5 }\\) m = \\(\\frac { 100 }{ 5 }\\) = 20 cm
\nFocal length, f = 20 cm (or +20 cm).
\nSince the focal length of the lens is positive. Therefore, the nature of the lens is convex.
\nSame size and inverted image is formed when
\nMagnification, m = -1
\nAlso, m = \\(\\frac { v }{ u }\\)
\nv = -u
\nFrom the lens formula,
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372247732_0f838558bd_o.png?resize=282%2C253&ssl=1\")
<\/p>\n
\nList two types of transport system in human beings and write the functions of any one of these. [3]
\nAnswer:
\nLymphatic system and blood circulatory system are two types of transport system in human beings.
\nFunctions of blood circulatory system:<\/p>\n\n
\nDistinguish between pollination and fertilisation. Mention the site and the product of fertilisation in a flower. [3]
\nAnswer:<\/p>\n\n
\nSite of fertilisation in flower is ovary. Product of fertilisation in flower is zygote.<\/li>\n<\/ol>\n
\nList three environmental consequences of using fossil fuels. Suggest three steps to minimise the pollution caused, by various energy sources. [3]
\nAnswer:
\nThe combustion of fossil fuels releases different harmful products. Three environmental consequences of using fossil fuels are:<\/p>\n\n
\n
\nWhich compounds are called (i) alkanes, (ii) alkenes and (iii) alkynes? C4<\/sub>H10<\/sub> belongs to which of these? Draw two structural isomers of this compound. [3]
\nAnswer:
\n(i) The hydrocarbons in which carbon atoms are connected by only single covalent bonds are called alkanes.
\n(ii) The hydrocarbons in which carbon atoms are connected by the double bond are called alkene.
\n(iii) The hydrocarbons in which carbon atoms are connected by the triple bond are called alkynes.
\nC4<\/sub>H10<\/sub> belongs to alkane
\n![\"CBSE](\"https:\/\/i1.wp.com\/live.staticflickr.com\/65535\/48372247757_397784d842_o.png?resize=353%2C129&ssl=1\")
<\/p>\n
\n(a) What are the dominant and recessive traits?
\n(b) “Is it possible that a trait is inherited but may not be expressed in the next generation ?” Give a suitable example to justify this statement. [5]
\nAnswer:
\n(a) The trait which can express its effect over contrasting trait is called dominant trait whereas the trait which cannot express its effect over contrasting trait or which gets suppressed by the contrasting trait is called recessive trait. The inherited trait which is not expressed will be a recessive trait.<\/p>\n
\n(a) What is the scattering of light? Explain how the colour of the scattered light depends on the size of the scattering particles.
\n(b) Explain the reddish appearance of the Sun at sunrise or sunset. Why does it not appear red at noon? [5]
\nAnswer:
\n(a) Scattering of light is the phenomenon in which a part of the incident light is dispersed in different directions.
\nDependence of colour and scattered light on the size of particles:<\/p>\n\n
\nThe reason for Sun not appearing red at the noon is that the light has to travel a relatively shorter distance through the atmosphere to reach us and therefore, only a litte of blue colour of the white light is scattered.<\/p>\nCBSE Previous Year Question Papers Class 10 Science 2019 Outside Delhi Set III<\/h3>\n
\nWhy does the cord of an electric oven not glow while it’s heating element does? [1]
\nAnswer:
\nThe resistance of the heating element of an electric oven is very high. As the current flows through the heating element it becomes too hot and glows red. On the other hand the cord of an electric oven low resistance hence it does not become red during the flow of current.<\/p>\n
\nAlthough coal and petroleum are produced by the degradation of biomass, yet we need to conserve these resources. Why? [1]
\nAnswer:
\nWe need to conserve coal and petroleum because they are formed in millions of years and are non-renewable also and their rate of consumption is very high. So these are limited and cannot last for longer time.<\/p>\n
\nWhat is atmospheric refraction? List two phenomena which can be explained on the basis of atmospheric refraction. [2]
\nAnswer:
\nIn atmosphere, there are layers of different densities and refractive indices, when the light ray is passed through these layers refraction of light takes place which is called atmospheric refraction.
\nTwo phenomenon that can be explained on the basis of atmospheric refraction are:<\/p>\n\n
\nName a metal of medium reactivity and write three main steps in the extraction of this metal from its sulphide ore. [2]
\nAnswer:
\nZinc
\nThe steps involved in the extraction of zinc from zinc sulphide are:
\n1. Roasting of sulphide ore in the presence of air to convert it into metal oxide.
\n![\"CBSE](\"https:\/\/i1.wp.com\/live.staticflickr.com\/65535\/48372247767_2ee7396c6b_o.png?resize=346%2C141&ssl=1\")
\n2. Reduction of metal oxide with carbon to get free metal.
\n![\"CBSE](\"https:\/\/i2.wp.com\/live.staticflickr.com\/65535\/48372117861_daa83800c5_o.png?resize=354%2C71&ssl=1\")
\n3. Refining of impure metal to get pure metal.<\/p>\n
\nList two chemical properties on the basis of which ethanol and ethanoic acid may be differentiated and explain how.
\nOR
\nUnsaturated hydrocarbons contain multiple bonds between two carbon atoms and these compounds show addition reactions. Out of saturated and unsaturated carbon compounds, which compounds are more reactive? Write a test to distinguish ethane from ethene. [2]
\nAnswer:
\n1. Ethanol does not react with sodium bicarbonate but ethanoic acid reacts with sodium bicarbonate releasing CO2 gas.
\n2. Ethanol does not change the colour of blue litmus paper but ethanoic acid changes the colour of blue litmus to red due to presence of carboxylic acid group.
\nOR
\nUnsaturated carbon compounds are more reactive than saturated carbon compounds. Bromine water is decolourized by ethene but there is no change of colour of bromine water with ethane.
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372311067_050042a29c_o.png?resize=339%2C114&ssl=1\")
<\/p>\n
\nWhat happens to a beam of white light when it gets refracted through a glass prism? Which colour deviates the most and the least after refraction through a prism? What is likely to happen if a second identical prism is placed in an inverted position with respect to the first prism. Justify your answer.
\nOR
\nA student needs spectacles of power -0.5 D for the correction of his vision. [3]
\n(i) Name the defect in vision the student is suffering from.
\n(ii) Find the nature and focal length of the corrective lens.
\n(iii) List two causes of this defect.
\nAnswer:
\nWhen white light is refracted through a glass prism, it gets split into its constituting colours at different angles. This phenomenon is called Dispersion of Light.
\nForming a rainbow,
\n![\"CBSE](\"https:\/\/i1.wp.com\/live.staticflickr.com\/65535\/48372117886_f0ac209548_o.png?resize=318%2C151&ssl=1\")
\nLeast deviated colour is red whereas most deviated colour is violet.
\nWhen second identical prism is placed in an inverted position with respect to first prism, recombination of the spectrum will take place and white light will be obtained.
\nOR
\n(i) Myopia.
\n(ii) Concave lens with the focal length of 200 cm
\nGiven, P = -0.5 D
\nWe have,
\nP = \\(\\frac { 1 }{ f }\\) m
\nf = \\(\\frac { 1 }{ P }\\) = \\(\\frac { 1 }{ (-0.5) }\\)
\nf = -2 m = -200 cm
\n(iii) Two causes of Myopia are:<\/p>\n\n
\nDefine a food chain. Design a terrestrial food chain of four trophic levels. If a pollutant enters at the producer level, the organisms of which trophic level will have the maximum concentration of the pollutant in their bodies? What is this phenomenon called? [3]
\nAnswer:
\nIt is the sequence of arrangement of a living organism in a community in which one organism consumes another organism to transfer food energy.
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372117931_d4440523ea_o.png?resize=191%2C229&ssl=1\")
\nGrass \u2192 Insect \u2192 Frog \u2192 Bird
\nThe organism at a higher tropic level will have a maximum concentration of pollutants. This phenomenon is called biological magnification.<\/p>\n
\nDuring the reaction of some metals with dilute hydrochloric acid, the following observations were made by a student:
\n(a) Silver does not show any change.
\n(b) Some bubbles of gas are seen when a lead is reacted with the acid.
\n(c) The reaction of sodium is found to be highly explosive.
\n(d) The temperature of the reaction mixture rises when aluminium is added to the acid.
\nExplain these observations giving an appropriate reason. [3]
\nAnswer:
\n(a) Silver is covered with a thin layer of silver chloride, so it does not react with dilute hydrochloric acid.
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372247882_de5d649cf0_o.png?resize=345%2C79&ssl=1\")
\n(b) Bubbles of hydrogen gas are evolved when lead is reacted with the acid.
\n![\"CBSE](\"https:\/\/i1.wp.com\/live.staticflickr.com\/65535\/48372118016_4f054979d4_o.png?resize=331%2C102&ssl=1\")
\n(c) The reaction of sodium is found to be highly explosive because sodium is very reactive in nature.
\n![\"CBSE](\"https:\/\/i1.wp.com\/live.staticflickr.com\/65535\/48372118076_f2a0b1b2e1_o.png?resize=350%2C163&ssl=1\")
\n(d) The temperature of the reaction mixture rises when aluminium is added to the acid because the reaction is highly exothermic in nature.
\n![\"CBSE](\"https:\/\/i1.wp.com\/live.staticflickr.com\/65535\/48372118096_25a42fc79f_o.png?resize=343%2C147&ssl=1\")
<\/p>\n
\nGiven below are the steps for the extraction of copper from its ore. Write the chemical equation of the reactions involved in each case. [3]
\n(i) Roasting of copper (I) sulphide.
\n(ii) Reduction of copper (I) oxide from copper (I) sulphide
\n(iii) Electrolytic refining.
\nAnswer:
\n![\"CBSE](\"https:\/\/i2.wp.com\/live.staticflickr.com\/65535\/48372246797_d87ba4868c_o.png?resize=328%2C372&ssl=1\")
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372118136_a679042e43_o.png?resize=350%2C241&ssl=1\")
<\/p>\n
\n(a) Budding, fragmentation and regeneration, all are considered as an asexual mode of reproduction. Why?
\n(b) With the help of neat diagrams, explain the process of regeneration in Planaria. [3]
\nAnswer:
\n(a) Budding, fragmentation and regeneration are considered as an asexual mode of reproduction because only one parent is involved no sex cells are involved.
\n(b) Regeneration in planaria.
\n![\"CBSE](\"https:\/\/i2.wp.com\/live.staticflickr.com\/65535\/48372246722_8a2e0b66e9_o.png?resize=399%2C232&ssl=1\")
\nThe process of getting back a full organism from its body parts is called regeneration. Planaria reproduces by this method in which if the body of Planaria somehow gets cut into a number of pieces, then each body piece can regenerate into a complete Planaria by growing all the missing parts.<\/p>\n
\nA 6 cm tall object is placed perpendicular to the principal axis of a concave mirror of focal length 30 cm. The distance of the object from the mirror is 45 cm. Use mirror formula to determine the position, nature and size of the image formed. Also, draw labelled ray diagram to show the image formation in this case.
\nOR
\nAn object 6 cm in size is placed at 50 cm in front of a convex lens of focal length 30 cm. At what distance from the lens should a screen be placed in order to obtain a sharp image of the object? Find the nature and size of the image. Also, draw a labelled ray diagram to show the image formation in this case. [5]
\nAnswer:
\nGiven, Height of the object = 6 cm
\nFocal length, f = -30 cm
\nObject distance, u = -45 cm
\nImage distance, v = ?
\nHeight of image, hi<\/sub> = ?
\nWe have,
\n\\(\\frac { 1 }{ f }\\) = \\(\\frac { 1 }{ v }\\) + \\(\\frac { 1 }{ u }\\)
\n![\"CBSE](\"https:\/\/i0.wp.com\/live.staticflickr.com\/65535\/48372246432_afb2357045_o.png?resize=262%2C456&ssl=1\")
\n![\"CBSE](\"https:\/\/i1.wp.com\/live.staticflickr.com\/65535\/48372246657_243a378a89_o.png?resize=404%2C566&ssl=1\")
\n![\"CBSE](\"https:\/\/i2.wp.com\/live.staticflickr.com\/65535\/48372246552_7a41b3585c_o.png?resize=403%2C163&ssl=1\")
\n![\"CBSE](\"https:\/\/i2.wp.com\/live.staticflickr.com\/65535\/48372246517_370dc3d962_o.png?resize=258%2C456&ssl=1\")
\nHence, the image formed is virtual, erect and magnified.<\/p>\n
\nWhat is sexual reproduction? Explain how this mode of reproduction gives rise to more viable variations than asexual reproduction. How does this affect evolution? [5]
\nAnswer:
\nThe production of new organisms from two parents by making use of their sex cells is called sexual reproduction.
\nIn sexual reproduction, more viable variations are observed than asexual reproduction as two parents is involved. In the case of asexual reproduction single parent organism gives rise to offsprings which are genetically identical to their parents. This limits the scope of variation in characters of offsprings. Due to sexual reproduction, the extent of variation is much large and therefore choices of evolution is also high.<\/p>\nCBSE Previous Year Question Papers<\/a><\/h4>\n","protected":false},"excerpt":{"rendered":"