Time allowed: 3 hours<\/strong> General Instructions<\/strong><\/p>\n SECTION-A<\/strong><\/p>\n Question 1<\/strong>. Question 2<\/strong>. Question 3<\/strong>. Question 4<\/strong>. Question 5<\/strong>. Question 6<\/strong>. OR<\/strong><\/p>\n Define magnification produced by spherical mirrors and how does it help us in finding out if an image is real or virtual ?<\/p>\n Question 7<\/strong>. Question 8<\/strong>. Question 9<\/strong>. Question 10<\/strong>. OR<\/strong><\/p>\n How can you as an individual contribute or make a difference to the management of:<\/p>\n Question 11<\/strong>. Question 12<\/strong>. Question 13.<\/strong> OR<\/strong><\/p>\n Elements have been arranged in the following sequence on the basis of their increasing atomic masses.<\/p>\n F, Na, Mg, Al, Si, P, S, Cl, Ar, K.<\/p>\n (a) Pick two sets of elements which have similar properties. Question 14.<\/strong> Question 15<\/strong>. Question 16<\/strong>. Question 17<\/strong>. OR<\/strong><\/p>\n (a) Methane is burned in sufficient air. Question 18<\/strong>. Question 19<\/strong>.. Question 20<\/strong>. Question 21<\/strong>. OR<\/strong><\/p>\n Why is the process of menstruation necessary ?<\/p>\n SECTION-B<\/strong><\/p>\n Question 22<\/strong>. Question 23.<\/strong> Question 24<\/strong>. Question 25<\/strong>. Question 26<\/strong>. OR<\/strong><\/p>\n Draw a ray diagram to show the principal focus of a concave mirror.<\/p>\n Question 27<\/strong>. ANSWERS<\/strong><\/span> Answer 1.<\/strong> Answer 2.<\/strong> Answer 3.<\/strong> Answer 4.<\/strong> Answer 5.<\/strong> Answer 6.<\/strong> OR<\/strong><\/p>\n Magnification produced by a spherical mirror gives the relative extent to which the image of the object is magnified with respect to the object size. It is expressed as the ratio of the size of the image to the size of the object and is represented by the letter m.<\/p>\n If h is the height of the object and h’ is the height of the image, then magnification m produced by the spherical mirror is given by If the magnification has a plus sign, then the image is virtual and erect and if the magnification has a minus sign, then the image is real and inverted.<\/p>\n Answer 7.<\/strong> Answer 8.<\/strong> HCl + H2<\/sub>O \u2192 H3<\/sub>0+\u00a0<\/sup>+ Cl-<\/p>\n The separation of H+ ions from the HCl molecule cannot occur in the absence of water. The process of dissolving acid in water is highly exothermic. The acid must be slowly added to the water with constant stirring, water must not be added to the acid.<\/p>\n Answer 9.<\/strong> Answer 10.<\/strong> OR<\/strong><\/p>\n (a)<\/strong> Forests and wild life:<\/p>\n (b)<\/strong> Water resources:<\/p>\n (c)<\/strong> Coal and petroleum:<\/p>\n Answer 11.<\/strong> Answer 12.<\/strong> Answer 13.<\/strong> OR<\/strong><\/p>\n (a)<\/strong> (i) F and Cl Answer 14.<\/strong> Answer 15.<\/strong><\/p>\n Answer 16.<\/strong> Answer 17.<\/strong> CH3<\/sub>COOH + C2<\/sub>H5<\/sub>OH \u2192 CH3<\/sub>COOC2<\/sub>H5<\/sub><\/p>\n They are sweet substances used in making perfumes and as flavouring agents. Esters react in the presence of an acid or a base to give back the alcohol and carboxylic acid. This reaction is called saponification reaction. It is used in the preparation of soap.<\/p>\n OR<\/strong><\/p>\n Answer 18.<\/strong> These chemicals then enter the food chain. As they are not degraded they are gradually accumulated in each trophic level. Finally all of them reach the human bodies. Food grains like rice, wheat, vegetables, fruits, and meat contain varying amounts of pesticide residues. It is difficult to completely remove them by washing. Hence any organism at the top of the food chain is likely to get a fairly large amount of the harmful substances that enter the food chain at every level. So the effect of the various pollutants is maximised in human beings.<\/p>\n
\nMaximum marks : 80<\/strong><\/p>\n\n
\nWhere are guard cells found and what is their function ?\u00a0\u00a0[1]<\/strong><\/p>\n
\nWhat are the large number of filtering units found in the kidney known as ?\u00a0\u00a0[1]<\/strong><\/p>\n
\nWhat is an alloy ? Give two examples.\u00a0\u00a0[2]<\/strong><\/p>\n
\nWhen you look at a lemon kept inside water in a glass dish it appears bigger than its actual size. Can you explain why ?\u00a0\u00a0[2]<\/strong><\/p>\n
\nWhat kind of movement is seen in the roots of plants ?\u00a0\u00a0[2]<\/strong><\/p>\n
\nShow by ray diagram the nature, position and size of the image formed by a convex mirror when the object lies between infinity and pole of the mirror.\u00a0\u00a0[3]<\/strong><\/p>\n
\nOn what factors does the strength of an electromagnet depend ?\u00a0\u00a0[3]<\/strong><\/p>\n
\nWhy acids do not show acidic behaviour in the absence of water ?\u00a0\u00a0[3]<\/strong><\/p>\n
\nWhy is carbon able to form a large number of molecules ?\u00a0\u00a0[3]<\/strong><\/p>\n
\nWhy are forests called biodiversity hotspots ? Who are the stakeholders in the conservation of forests ?\u00a0\u00a0[3]<\/strong><\/p>\n\n
\nHow is self-pollination different from cross-pollination ? Give examples where we find them.\u00a0\u00a0[3]<\/strong><\/p>\n
\nCompute the heat generated while transferring 96000 coulombs of charge in one hour through a potential difference of 50 V.\u00a0\u00a0[3]<\/strong><\/p>\n
\nHow does the electronic configuration of an atom relate to its position in the Modem Periodic Table ?\u00a0\u00a0[3]<\/strong><\/p>\n
\n(b) The given sequence represents which law of classification of elements ?<\/p>\n
\nWhat are plant hormones ? Give some examples.\u00a0\u00a0[3]<\/strong><\/p>\n
\nState the changes that take place in the uterus when:\u00a0\u00a0[3]<\/strong>
\n(a) Implantation of embryo has occurred.
\n(b) Female gamete or egg is not fertilised.<\/p>\n
\nAn electric lamp, whose resistance is 20 \u2126 and a conductor of 4 \u2126 resistance are connected to a 6 V battery. Calculate:\u00a0\u00a0[5]<\/strong><\/p>\n\n
\nWhat are the properties of ethanoic acid ?\u00a0\u00a0[5]<\/strong><\/p>\n
\n(b) Ethanoic acid is reacted with sodium hydroxide
\n(c) Ethanoic acid is treated with sodium carbonate.
\n(d) Ethanol is treated with sodium.
\n(e) Ethanol is mixed with ethanoic acid in the presence of an acid.<\/p>\n
\nHuman beings are on top of any food-chain. Is this harmful to humans in the long run ? Does the term biological magnification apply here ?\u00a0\u00a0[5]<\/strong><\/p>\n
\nSometimes after a shower of rain we can see a colourful rainbow. Explain its formation on the basis of reflection, refraction or dispersion.\u00a0\u00a0[5]<\/strong><\/p>\n
\nWhat is thermal decomposition ? Are decomosition reactions opposite of combination reactions ? Show with examples.\u00a0\u00a0[5]<\/strong><\/p>\n
\nWhat are the different methods of contraception ?\u00a0\u00a0[5]<\/strong><\/p>\n
\nWhat is an alloy ? Name some things made up of alloys that we use daily.\u00a0\u00a0[2]<\/strong><\/p>\n
\nAn element has an atomic number of 6 and a mass number of 12. Find out which group and period it belongs to.\u00a0[2]<\/strong><\/p>\n
\nHow is sex determined in human beings ? Show with the help of chromosomes.\u00a0\u00a0[2]<\/strong><\/p>\n
\nWhen we chew bread it tastes sweet. Why ? What is the role of saliva in digestion of food ?\u00a0\u00a0[2]<\/strong><\/p>\n
\nShow the path of light through a triangular glass prism with a neat labelled diagram.\u00a0\u00a0[2]<\/strong><\/p>\n
\nWhich uses more energy: a 250 W T.V. set in one hour or a 1200 W toaster in 10 minutes ?\u00a0\u00a0[2]<\/strong><\/p>\n
\nSECTION-A<\/strong><\/p>\n
\nGuard cells are found on either side of the stomata on the surface of leaves. Stomata are small pores through which gaseous exchange and evaporation of water takes place. The bean shaped guard cells swell when water flows into them causing the stomata to open. Similarly when the guard cells shrink the pore closes.<\/p>\n
\nThe large number of filtering units in the kidney are known as nephrons. Each nephron has two parts, renal corpuscle and renal tubule. The renal corpuscle consists of a bunch of capillaries called glomerulus present in a cup shaped structure called Bowman’s capsule.<\/p>\n
\nAn alloy is a homogeneous mixture of two or more metals or a metal and a non-metal. It is prepared by first melting the primary metal and then dissolving the other elements in it in definite proportions. It is then cooled to room temperature. Alloying helps to get the good qualities of all the constituents. Some well-known alloys are brass, bronze, solder and amalgam.<\/p>\n
\nYes, when we look at a lemon kept inside water in a glass dish it appears bigger than its actual size. This is because of the process of refraction. Light rays, as they pass from air to the water below tend to bend towards the normal at the point of interface.<\/p>\n
\nThe roots of plants show trophic movements. Roots tend to move towards gravity and water so they are said to be positively geotropic and hydrotropic. Roots move away from sunlight and hence are said to be negatively phototropic.<\/p>\n
\n![\"CBSE](\"https:\/\/i1.wp.com\/www.ncert-solutions.com\/wp-content\/uploads\/2018\/10\/CBSE-Sample-Papers-for-Class-10-Science-Set-5-1.png?resize=394%2C201&ssl=1\")
\nWhen the object lies between infinity and the pole of the convex mirror the image is virtual and erect, between P and F behind the mirror and diminished in size.<\/p>\n
\nm = Height of the image (h’)\/Height of the object (h)
\nMagnification m is also related to the object distance (u) and image distance (\u03c5)
\nMagnification(m) = h’\/h = -\u03c5\/u<\/p>\n
\nThe strength of an electromagnet depends on the following factors:<\/p>\n\n
\nAcids do not show acidic behaviour in the absence of water. This is because the H+ions are produced only in the presence of water. The H+ ions cannot exist alone but they exist only after combining with water molecules.
\nIf water is added to HCl the reaction occurs as follows:<\/p>\n
\nCarbon has the unique ability to form bonds with other atoms of carbon giving rise to large molecules. This property is called catenation. We can find compounds with long chains of carbon or even carbon atoms arranged in a ring. In addition carbon atoms can be linked by single, double or triple bonds. As carbon is tetravalent it forms covalent bonds with four other atoms of carbon or atoms of some other monovalent element. These bonds are very strong and so the elements are very stable. Compounds of carbon which are linked by only single bonds between carbon atoms are called saturated compounds. Compounds of carbon having double or triple bonds between their carbon atoms are called unsaturated compounds. No other element exhibits the kind of catenation seen in carbon. This is why we see such a large number of compounds with many carbon atoms linked to each other.<\/p>\n
\nForests are called biodiversity hotspots because they support a huge variety of life forms. The range of different life forms like bacteria, fungi, ferns, flowering plants, nematodes, insects, birds, reptiles make up the forest biodiversity. The stakeholders in the conservation of forests are:<\/p>\n\n
\n
\n
\n
\nSelf-pollination is the process by which pollen-grains are transferred from the anther to the stigma of the same flower. This is generally found in bisexual flowers like hibiscus, mustard etc. Whereas cross-pollination is the process by which pollen-grains are transferred from the anther of one flower to the stigma of another flower either in the same plant or another plant. This is found in unisexual flowers or unisexual plants. Some examples are papaya, watermelon, pumpkin etc.<\/p>\n
\nGiven: V = 50 V, Q = 96000 C, t = 1 hour = 60 x 60 = 3600 sec
\nWe know that,
\nElectric current (I) = \\(\\frac { Q }{ t } =\\frac { 96000 }{ 3600 } A\\)
\nNow,
\nHeat (H) =VIt
\n= \\(50\\times \\frac { 96000 }{ 3600 } \\times 3600\\)
\n= 50 x 96000 J = 4800000 J = 4.8 x 106<\/sup> J<\/p>\n
\nThe electronic configuration of an atom gives us the atomic number of an element as the number of electrons is equal to the number of protons in the atom. The atomic number of an element is a more fundamental property than its atomic mass. The Modern Periodic Table has 18 vertical columns known as groups and 7 horizontal rows known as periods. The elements present in a group have the same number of valence electrons. In other words groups in the Modern Periodic Table signify an identical outer shell electronic configuration. Similarly in a period, the atomic number increases by one unit as we move from left to right. The position of an element in the table tells us about its chemical reactivity.<\/p>\n
\n(ii) Na and K.
\n(b)<\/strong> Newland’s law of octaves.<\/p>\n
\nPlant hormones are chemicals that help to coordinate growth, development and responses to the environment. They are synthesised at places far away from where they act and simply diffuse to the area of action. Some of the plant hormones are auxins, gibberellins, cytokinins and abscisic acid.<\/p>\n\n
\n
\nGiven: Resistance of the electric lamp, R1<\/sub> = 20 \u2126
\nResistance of the conductor, R2<\/sub> = 4 \u2126
\n(a)<\/strong> Total resistance in the circuit = R1<\/sub> + R2<\/sub> = 20 \u2126 + 4 \u2126 = 24 \u2126
\n(b)<\/strong> Total potential difference = 6 V
\nBy Ohm’s law, the current (I) flowing through the circuit will be = V\/R
\n\\(\\frac { 6 }{ 24 } \\) \u2126
\n= 0.25 A
\n(c)<\/strong> On applying Ohm’s law to the lamp and conductor separately, we get
\nPotential difference across the electric lamp =I x R1<\/sub> = 0.25 x 20 = 5 V
\nPotential difference across the conductor = I x R2<\/sub> = 0.25 x 4 = 1 V<\/p>\n
\nEthanoic acid is commonly called acetic acid and belongs to the group called carboxylic acids. The melting point of pure ethanoic acid is 290 K and hence it often freezes during winter in cold climates. So it is also known as glacial acetic acid. 5-8% solution of acetic acid in water is called vinegar which is used as a preservative in pickles. Carboxylic acids are weak acids.
\nEthanoic acid reacts with ethyl alcohol in the presence of an acid catalyst to produce esters.<\/p>\n\n
\nHuman beings are on top of any food chain. This means the maximum concentration of several harmful chemicals get accumulated in the human bodies. This is also called biological magnification. We have seen how water is polluted by different substances. Pesticides and some chemicals are used to protect crops from pests. These enter the soil and the water that flows on this soil. When this water is absorbed by the roots of plants it enters the plants. Similarly when aquatic animals drink water some chemicals enter their bodies too.<\/p>\n