These sample papers have been taken from CBSE
Question 1: Mendel took tall pea plants and short pea plants and produced F1 progeny through cross-fertilisation. What did Mendel observe in the F1 progeny?
Answer: Mendel observed that all the plants in the F1 generation were tall plants.
Question 2: Name two constituents of biogas.
Answer: Methane and Carbon dioxide
Question 3: Carbon has four electrons in its valence shell. Which type of compounds can be formed by carbon atom and why? Give any one example of such compounds.
Answer: Carbon needs to gain or lose 4 electrons in order to make an ionic compound. But doing so requires a huge amount of energy. Hence, carbon makes compounds by sharing its electrons and thus makes covalent compounds. CCl4 (Carbon tetrachloride) is one such example. In this compound, carbon shares its valence electrons one each with one atom of chlorine.
Question 4: Different parts of brain are associated with specific functions. Name the part of human brain which performs the following functions:
Answer: (a) Hypothalamus, (b) Medulla, (c) Cerebrum and cerebellum, (d) Cerebrum and cerebellum
Question 5: An object is kept 40 cm in front of a concave mirror of focal length 20 cm. Find the position and nature of the image. Draw a ray diagram to show the formation of image in this case.
Answer: Given, u = -40 cm, f = -20 cm, v = ?
Image distance can be calculated as follows:
So, image is formed at 40 cm in front of mirror.
Negative sign shows it is an inverted image.
Image distance is same as object distance, hence image is of same size as object.
As it is formed in front of mirror so it is a real image
Question 6: In the reaction:
MnO2 + 4HCl → MnCl2 + 2H2O + Cl2
(a) Name the compound (i) oxidised, (ii) reduced.
Answer: HCl is getting oxidized and MnO2 is getting reduced
(b) Define oxidation and reduction on its basis.
Answer: Removal of hydrogen is called oxidation, while removal of oxygen is called reduction.
Question 7: 1 g of solid sodium chloride is taken in a clean and dry test tube and 2 mL of conc. sulphuric acid is added to it. If the gas evolved is tested first with dry and then with wet blue litmus paper, in which case will the litmus paper change colour? Give reason for your answer. What inference can be drawn about the nature of the evolved gas? Support your answer with chemical equation for the reaction.
Answer: Following reaction takes place when sodium chloride reacts with sulphuric acid:
2NaCl + H2SO4 → Na2SO4 + 2HCl
HCl dissociates into ions only in the presence of water. So, dry litmus paper does not show color change but wet litmus paper (blue) changes to red. This shows that HCl is acidic.
(a) For the preparation of cakes, baking powder is used. If at home your mother uses baking soda instead of baking powder, how will it affect the taste of the cake and why?
Answer: When baking soda is heated, it gives sodium carbonate; as shown by following equation:
Formation of sodium carbonate, results in bitter taste in the cake, which is not desirable for a tasty cake.
(b) How is baking soda be converted into baking powder?
Answer: Baking soda is converted into baking powder by addition of a edible oil (generally tartaric acid).
(c) What makes the cake soft and spongy?
Answer: Production of carbon dioxide results in formation of a large number of bubbles in the cake mixture. This results in cake becoming soft and spongy.
Question 8: What happens when hydrogen is added to a vegetable oil in the presence of nickel? Name the reaction and write one difference between the physical property of the vegetable oil and the product obtained in this reaction. Write the role of nickel in this reaction.
Answer: When hydrogen is added to a vegetable oil in presence of nickel, the vegetable oil becomes saturated. This reaction is called hydrogenation and is generally used to produce margarine from vegetable oil. While the vegetable oil is a viscous liquid, margarine is semi-solid. Nickel is the catalyst in this reaction.
Question 9: What is geotropism? Draw a labelled diagram of a potted plant showing positive geotropism and negative geotropism.
Answer: The growth in a plant part in response to the gravity is called geotropic movement, or geotropism. Following figure shows positive and negative geotropism in a plant. Roots are positive geotropism while stem is showing negative geotropism.
Question 10: What are acquired traits? Why are these traits generally not inherited over generations? Explain.
Answer: Traits; which are acquired due to interaction with the environment; are called acquired traits. Acquired traits are not inheritable because such traits do not change the genotype of an individual.
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