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Science 31/4/2 2018-2019 CBSE (English Medium) Class 10 Question Paper Solution

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Science [31/4/2]
Marks: 80 Academic Year: 2018-2019
Date & Time: 14th March 2019, 2:30 pm
Duration: 3h
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(i) The question paper comprises five sectionsABCD and E. You are to attempt all the sections.

(ii) All questions are compulsory.

(iii) Internal choice is given in sections BCD and E.

(iv) Question numbers 1 and 2 in Section A are one mark questions. They are to be answered in one word or in one sentence.

(v) Question numbers 3 to 5 in Section B are two-marks questions. These are to be answered in about 30 words each.

(vi) Question numbers 6 to 15 in Section C are three-marks questions. These are to be answered in about 50 words each.

(vii) Question numbers 16 to 21 in Section D are five-marks questions. These are to be answered in about 70 words each.

(viii) Question numbers 22 to 27 in Section E are based on practical skills. Each question is a two marks question. These are to be answered in brief.


Section A
[1] 1

Define current. Give its S.I. unit.

Concept: Magnetic Field
Chapter: [0.040999999999999995] Magnetic Effects of Current
[1] 2

Name the component of sunlight which facilitates drying of wheat after harvesting.

Concept: Water Management (Conservation of Water) - Fresh Water Management
Chapter: [0.051] Management of Natural Resources
Section B
[2] 3
[2] 3.a

State the laws of refraction of light.

Concept: Refraction Through a Rectangular Glass Slab
Chapter: [0.03] Natural Phenomena
OR
[2] 3.b

List four characteristics of the image formed by a concave mirror of focal length 40 cm when the object is placed in front of it at a distance of 20 cm from its pole.

Concept: Concave Mirror
Chapter: [0.03] Natural Phenomena
[2] 4

Draw magnetic field lines in and around a current-carrying straight solenoid.

Concept: Magnetic Field Due to a Current Carving Cylindrical Coil (or Solenoid)
Chapter: [0.040999999999999995] Magnetic Effects of Current
[2] 5

Write the name and molecular formula of a carbon compound having its name suffixed with "-ol" and having two carbon atoms in its molecule. With the help of a chemical equation indicate what happens when this compound is heated with excess conc. H2SO4.

Concept: Chemical Equation
Chapter: [0.015] Chemical Reactions
Section C
[3] 6

Define the term evolution. "Evolution cannot be equated with progress." Give examples to justify this statement.

Concept: Human Evolution
Chapter: [0.021] Heredity and Evolution
[3] 7
[1.5] 7.a

Plants do not have any nervous system but yet, if we touch a sensitive plant, some observable changes take place in its leaves. Explain how could this plant respond to the external stimuli and how it is communicated.

Concept: Human Nervous System
Chapter: [0.023] Control and Co-ordination in Animals and Plants
[1.5] 7.b

Name the hormone that needs to be administered to

(i) increase the height of a dwarf plant.

(ii) cause rapid cell division in fruits and seeds.

Concept: The Tropic Movements in Plants
Chapter:
[3] 8
[1.5] 8.a

Write the function of the following in the human alimentary canal:

Saliva

Concept: The Digestive System in Human
Chapter: [0.024] Life Processes

Write the function of the following in the human alimentary canal:

HCl in stomach

Concept: The Digestive System in Human
Chapter: [0.024] Life Processes

Write the function of the following in the human alimentary canal:

Bile juice

Concept: The Digestive System in Human
Chapter: [0.024] Life Processes

Write the function of the following in the human alimentary canal:

Villi

Concept: The Digestive System in Human
Chapter: [0.024] Life Processes
[1.5] 8.b

Write one function each of the following enzymes:

Pepsin

Concept: The Digestive System in Human
Chapter: [0.024] Life Processes

Write one function each of the following enzymes:

Lipase

Concept: The Digestive System in Human
Chapter: [0.024] Life Processes
[3] 9

Salt 'P', commonly used in bakery products, on heating gets converted into another salt 'Q' which itself is used for the removal of hardness of water and a gas 'R' is evolved. The gas 'R', when passed through freshly prepared lime water, turns milky. Identify 'P', 'Q' and 'R', giving a chemical equation for the justification of your answer.

Concept: Chemicals from Common Salt (Uses of Salt) - Preparation and Uses of Baking Soda
Chapter: [0.013999999999999999] Acids, Bases and Salts
[3] 10
[1.5] 10.a

Classify the following reaction into different type:

AgNO3(aq) + NaCl(aq) →AgCl(s) + NaNO3(aq)

Concept: Types of Chemical Change or Chemical Reaction - Single Displacement Reactions
Chapter: [0.015] Chemical Reactions

Classify the following reaction into different type:

CaO(s) + H2O(l) → Ca(OH)2(aq)

Concept: Types of Chemical Change or Chemical Reaction - Direct Combination (or Synthesis) Reaction
Chapter: [0.015] Chemical Reactions

Classify the following reaction into different type:

\[\ce{2KClO3(s)->[\Delta] 2KCl(aq) + 3O2(g)}\]

Concept: Types of Chemical Change or Chemical Reaction - Decomposition Reactions
Chapter: [0.015] Chemical Reactions

Classify the following reaction into different type:

Zn + CuSO4 → ZnSO4 + Cu

Concept: Types of Chemical Change or Chemical Reaction - Single Displacement Reactions
Chapter: [0.015] Chemical Reactions
[1.5] 10.b

Translate the following statement into chemical equation and then balance them.

  • Barium chloride reacts with aluminium sulphate to give aluminium chloride and barium sulphate.
Concept: Chemical Equation
Chapter: [0.015] Chemical Reactions
OR
[3] 10.c
[1] 10.c.1

When a potassium iodide solution is added to a solution of lead (II) nitrate in a test tube, a precipitate is formed.

What is the colour of this precipitate? Name the compound precipitated.

Concept: Chemical Equation
Chapter: [0.015] Chemical Reactions
[1] 10.c.2

When a potassium iodide solution is added to a solution of lead (II) nitrate in a test tube, a precipitate is formed.

Write the balanced chemical equation for this reaction.

Concept: Chemical Equation
Chapter: [0.015] Chemical Reactions
[1] 10.c.3

When a potassium iodide solution is added to a solution of lead (II) nitrate in a test tube, a precipitate is formed.

List two types of reactions in which this reaction can be placed.

Concept: Types of Chemical Change or Chemical Reaction - Double Displacement Reaction
Chapter: [0.015] Chemical Reactions
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[3] 11

How is the method of extraction of metals high up in the reactivity series different from that for metals in the middle? Why can the same process not be applied for them? Name the process used for the extraction of these metals.

Concept: Extraction of Metals
Chapter: [0.012] Metals and Non Metals
[3] 12

The following diagram shows two parallel straight conductors carrying the same current. Copy the diagram and draw the pattern of the magnetic field lines around them showing their directions. What is the magnitude of the magnetic field at a point 'X' which is equidistant from the conductors? Give justification for your answer.

Concept: Force on a Current Carrying Conductor in a Magnetic Field
Chapter: [0.040999999999999995] Magnetic Effects of Current
[3] 13
[3] 13.a

What is the cause of the dispersion of white light through a glass prism? Draw a ray diagram to show the path of light when two identical glass prisms are arranged together in an inverted position with respect to each other and a narrow beam of white light is allowed to fall obliquely on one of the faces of the prisms.

Concept: Dispersion of Light Through Prism
Chapter: [0.03] Natural Phenomena
OR
[3] 13.b

What is meant by scattering of light? Use this phenomenon to explain why the clear sky appears blue or the Sun appears reddish at sunrise.

Concept: Applications of Scattering of Light
Chapter: [0.03] Natural Phenomena
[3] 14
[1.5] 14.a

Natural water bodies are not regularly cleaned whereas an aquarium needs regular cleaning. Why?

Concept: Ecosystem
Chapter: [0.052000000000000005] Our Environment
[1.5] 14.b

What are decomposers? What will be the consequence if the decomposers are completely eradicated from an ecosystem? Give justification in support of your answer.

Concept: Food Chain
Chapter: [0.052000000000000005] Our Environment
OR
[3] 14.c

How is ozone formed in the upper atmosphere? State its importance. What is responsible for its depletion? Write one harmful effect of ozone depletion.

Concept: Ozone Layer Depletion
Chapter: [0.052000000000000005] Our Environment
[3] 15

What is the exploitation of resources with short term aims? List its four advantages.

Concept: Conservation and Judicious Use of Resources
Chapter: [0.051] Management of Natural Resources
Section D
[5] 16
[2.5] 16.a

If we pure-bred tall (dominant) pea plant with pure-bred dwarf (recessive) pea plant we will get pea plants of F1 generation. If we now self-cross the pea plant of F1 generation, then we obtain pea plants of F2 generation.

(a) What do the plants of F2 generation look like?

(b) State the ratio of tall plants to dwarf plants in F2 generation.

(c) State the type of plants not found in F1 generation but appeared in F2 generation, mentioning the reason for the same.

Concept: Heredity
Chapter: [0.021] Heredity and Evolution
[2.5] 16.b

Answer the following question:
What are homologous structures? Give an example. Is it necessary that homologous structures always have a common ancestor? Justify your answer.

Concept: Evidence of Evolution
Chapter: [0.021] Heredity and Evolution
[5] 17
[2] 17.a

Define vegetative propagation. List its two methods.

Concept: Asexual Reproduction in Plant
Chapter: [0.022000000000000002] Reproduction
[1] 17.b

Why is this mode practiced for growing some types of plants?

Concept: The Tropic Movements in Plants
Chapter:
[2] 17.c

Draw labelled diagrams to illustrate budding in Hydra.

Concept: Asexual Reproduction in Plant
Chapter: [0.022000000000000002] Reproduction
OR
[5] 17.d

What is contraception? List four different methods. State four reasons for adopting contraceptive methods.

Concept: Reproductive Health
Chapter: [0.022000000000000002] Reproduction
[5] 18
[2.5] 18.a

List two limitations of Newlands' Law of Octaves.

Concept: Newland's Law of Octaves
Chapter: [0.013000000000000001] Periodic Classification of Elements
[2.5] 18.b

Write the electronic configuration of two elements A and B whose atomic numbers are 20 and 17 respectively. Write the molecular formula of the compound formed when element A reacts with element B. State whether this compound is acidic, basic or neutral. Give a reason to justify your answer.

Concept: Periodic Properties
Chapter: [0.013000000000000001] Periodic Classification of Elements
[5] 19
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[5] 19.a
[2.5] 19.a.1

Distinguish between esterification and saponification reactions with the help of chemical equations for each.

Concept: Ethanoic Acid
Chapter: [0.011000000000000001] Carbon Compounds
[2.5] 19.a.2

With a labelled diagram describe in brief an activity to show the formation of ester.

Concept: Ethanoic Acid
Chapter: [0.011000000000000001] Carbon Compounds
OR
[5] 19.b

What is the difference between soaps and detergents? State, in brief, the cleansing action of soaps in removing an oily spot from a fabric. Why are soaps not very effective when a fabric is washed in hard water? How is this problem resolved?

Concept: Soap
Chapter: [0.011000000000000001] Carbon Compounds
[5] 20
[2.5] 20.a

Define electric power. An electrical device of resistance R is connected across a source of voltage V and draws a current I. Derive an expression for power in terms of current and resistance.

Concept: Electric Power
Chapter: [0.042] Effects of Current
[2.5] 20.b

Two electric bulbs rated 100 W; 220 V and 60 W; 220 V are connected in parallel to electric mains of 220 V. Find the current drawn by the bulbs from the mains.

Concept: Electric Current
Chapter: [0.042] Effects of Current
OR
[2.5] 20.c

How will you infer with the help of an experiment that the same current flows through every part of the circuit containing three resistors R1, R2 and R3 in series connected to a battery of V volts?

Concept: Factors Affecting the Resistance of a Conductor
Chapter: [0.042] Effects of Current
[2.5] 20.d

Study the following circuit and find out:
      (i) Current in 12 Ω resistor.
      (ii) The difference in the readings of A1 and A2, if any.

Concept: Electric Current
Chapter: [0.042] Effects of Current
[5] 21

A person is unable to see objects distinctly placed within 50 cm from his eyes.

(a) Name the defect of vision the person is suffering from and list its two possible causes.

(b) Draw a ray diagram to show the defect in the above case.

(c) Mention the type of lens used by him for the correction of the defect and calculate its power. Assume that the near point for the normal eye is 25 cm.

(d) Draw a labeled diagram for the correction of the defect in the above case.

Concept: Eye Defect and Its Correction: Myopia Or Near-sightedness
Chapter: [0.03] Natural Phenomena
Section E
[2] 22

Which one of the following is the correct set-up for studying the dependence of the current on the potential difference across a resistor and why?

Concept: Electric Potential (Electrostatic Potential) and Potential Difference
Chapter: [0.042] Effects of Current
[2] 23
[2] 23.a

Study the following ray diagram and list two mistakes committed by the student while tracing it. Rectify these mistakes by drawing the correct ray diagram to show the real position and size of the image corresponding to the position of the object AB.

Concept: Concave Mirror
Chapter: [0.03] Natural Phenomena
OR
[2] 23.b

A student has to trace the path of a ray of light through a glass prism. List four precautions he should observe for better results.

Concept: Dispersion of Light Through Prism
Chapter: [0.03] Natural Phenomena
[2] 24

List two observations on the basis of which it may be concluded that the given slide shows binary fission in Amoeba.

Concept: Asexual Reproduction in Plant
Chapter: [0.022000000000000002] Reproduction
[2] 25
[2] 25.a

Write four sequential steps of the procedure of the experiment "Preparing a temporary mount of a leaf peel to show stomata".

Concept: The Digestive System in Human
Chapter: [0.024] Life Processes
OR
[2] 25.b

In the experimental set-up to show that "the germinating seeds give out carbon dioxide", answer the following questions:
(i) Why do we keep the conical flask airtight?
(ii) Name the substance kept in the small test tube inside the conical flask. Write its role.
(iii) Why does water rise in the delivery tube?

Concept: Acid or a Base in a Water Solution
Chapter: [0.013999999999999999] Acids, Bases and Salts
[2] 26
[2] 26.a

A student mixes sodium sulphate powder in barium chloride powder. What change would the student observe on mixing the two powders? Justify your answer and explain how he can obtain the desired change.

Concept: Chemical Equation
Chapter: [0.015] Chemical Reactions
OR
[2] 26.b
[1] 26.b.1

Arrange the following metals in the increasing order of their reactivities:

Copper, Zinc, Aluminium, and Iron

Concept: Physical Properties of Metals
Chapter: [0.012] Metals and Non Metals
[1] 26.b.2

List two observations you would record in your notebook 30 minutes after adding iron filings to copper sulphate solution.

Concept: Electrovalent (Or Ionic) Bond
Chapter: [0.012] Metals and Non Metals
[2] 27

A solution 'X' gives orange colour when a drop of it falls on pH paper, while another solution 'Y' gives bluish colour when a drop of it falls on pH paper. What is the nature of both solutions? Determine the pH of solutions 'X' and 'Y'.

Concept: Strength of Acidic Or Basic Solutions
Chapter: [0.013999999999999999] Acids, Bases and Salts
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CBSE previous year question papers Class 10 Science with solutions 2018 - 2019

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