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Science 31/1/3 2018-2019 CBSE (English Medium) Class 10 Question Paper Solution

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Science [31/1/3]
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 sections. A. B. C. D and E. You have to attempt all the sections.

II.  All questions are compulsory.

III.  Internal choice is given in sections B, C, D 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

If you could use any source of energy for heating your food which one would you prefer? State one reason for your choice. 

Concept: Source of Energy
Chapter: [0.14] Sources of Energy
[1] 2

Write the function of the voltmeter in an electric circuit.

Concept: Household Electrical Circuits
Chapter: [0.13] Magnetic Effects of Electric Current
Section - B
[2] 3

What happens to the image distance in the normal human eye when we decrease the distance of an object, say 10 m to 1 m? Justify your answer. 

Concept: Human Eye: Structure of the Eye
Chapter: [0.11] The Human Eye and the Colourful World
[2] 4

List two different functions performed by the pancreas in our body.

Concept: Human Digestive System
Chapter: [0.06] Life Processes
[2] 5

Answer the following question.
How it can be proved that the basic structure of the Modern Periodic Table is based on the electronic configuration of atoms of different elements?

Concept: The Modern Periodic Table
Chapter: [0.05] Periodic Classification of Elements
OR
[1] 5.1

The electronic configuration of an element is 2, 8, 4. State it: 
group and period in the Modern Periodic Table.

Concept: Periodic Properties
Chapter: [0.05] Periodic Classification of Elements
[1] 5.2

The electronic configuration of an element is 2, 8, 4. State it: 
name and write its one physical property.

Concept: Periodic Properties
Chapter: [0.05] Periodic Classification of Elements
Section - C
[3] 6
[3] 6.1

Answer the following question.
How can we help in reducing the problem of waste disposal? Suggest any three methods.

Concept: Wastes Generated in Our Environment
Chapter: [0.15] Our Environment
OR
[3] 6.2

Answer the following question.
Define an ecosystem. Draw a block diagram to show the flow of energy in an ecosystem.

Concept: Ecosystem
Chapter: [0.15] Our Environment
[3] 7
[1.5] 7.1

List three advantages of:

Exploiting resources with short term aims.

Concept: Conservation and Judicious Use of Resources
Chapter: [0.16] Sustainable Management of Natural Resources
OR
[1.5] 7.2

List three advantages of: 

Using a long term perspective in managing our natural resources. 

Concept: Sustainability of Natural Resources
Chapter: [0.16] Sustainable Management of Natural Resources
[3] 8

Answer the following question:
What is a rainbow? Draw a labelled diagram to show the formation of a rainbow.

Concept: Applications of Scattering of Light
Chapter: [0.11] The Human Eye and the Colourful World
[3] 9

Nervous and hormonal systems together perform the function of control and coordination in human beings. Justify this statement with the help of an example.

Concept: Human Nervous System
Chapter: [0.07] Control and Co-ordination
[3] 10

Answer the following question.
Trace the sequence of events Whichoccur when a bright light is focused on your eyes.

Concept: Human Eye: Structure of the Eye
Chapter: [0.11] The Human Eye and the Colourful World
[3] 11

What is photosynthesis?

Concept: Mode of Nutrition in Plant - Autotrophic Nutrition
Chapter: [0.06] Life Processes
[3] 12
[3] 12.1

Answer the following question.
Name the plant Mendel used for his experiment. What type of progeny was obtained by Mendel in F1 and F2 generations when he crossed the tall and short plants? Write the ratio he obtained in F2 generation plants.

Concept: Heredity
Chapter: [0.09] Heredity and Evolution
OR
[3] 12.2

List three distinguishing features, in tabular form, between acquired traits and the inherited traits.

Concept: Evolution
Chapter: [0.09] Heredity and Evolution
[3] 13
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[3] 13.1

Answer the following question.
2 g of silver chloride is taken in a china dish and the china dish is placed in sunlight for some time. What will be your observation in this case? Write the chemical reaction involved in the form of a balanced chemical equation. Identify the type of chemical reaction.

Concept: Types of Chemical Change or Chemical Reaction - Decomposition Reactions
Chapter: [0.01] Chemical Reactions and Equations
OR
[3] 13.2
[1.5] 13.2.1

Identify the type of reaction taking place of the following case and write the balanced chemical equation of the reaction:
Zinc reacts with silver nitrate to produce zinc nitrate and silver.

Concept: Chemical Equation
Chapter: [0.01] Chemical Reactions and Equations
[1.5] 13.2.2

Identify the type of reaction taking place of the following case and write the balanced chemical equation of the reaction:
Potassium iodide reacts with lead nitrate to produce potassium nitrate and lead iodide.

Concept: Chemical Equation
Chapter: [0.01] Chemical Reactions and Equations
[3] 14
[1] 14.1

Based on the group valency of element write the molecular formula of the following compound giving justification:
Oxide of first group elements.

Concept: Periodic Properties
Chapter: [0.05] Periodic Classification of Elements
[1] 14.2

Based on the group valency of element write the molecular formula of the following compound giving justification:

Halide of the elements of group thirteen

Concept: Periodic Properties
Chapter: [0.05] Periodic Classification of Elements
[1] 14.3

Based on the group valency of element write the molecular formula of the following compound giving justification:

Compound formed when an element A of group 2 combines with an element B of group seventeen.

Concept: Periodic Properties
Chapter: [0.05] Periodic Classification of Elements
[3] 15
[1] 15.1

Explain the following: 

Sodium chloride is an ionic compound which does not conduct electricity in solid state whereas it does conduct electricity in the molten state as well as in an aqueous solution.

Concept: Electrovalent (or Ionic) Bond
Chapter: [0.03] Metals and Non Metals
[1] 15.2

Explain the following: 

Reactivity of aluminium decrease if it is dipped in nitric acid.

Concept: Physical Properties of Metals
Chapter: [0.03] Metals and Non Metals
[1] 15.3

Explain the following:

Metals like calcium and magnesium are never found in their free state in nature.

Concept: Types of Elements: Non-metal
Chapter: [0.03] Metals and Non Metals
Section - D
[5] 16
[5] 16.1
[2.5] 16.1.1

Answer the following question.
With the help of a suitable circuit diagram prove that the reciprocal of the equivalent resistance of a group of resistances joined in parallel is equal to the sum of the reciprocals of the individual resistances. 

Concept: Electric Circuit
Chapter: [0.12] Electricity
[2.5] 16.1.2

Solve the following question:
In an electric circuit, two resistors of 12 0 each are joined in parallel to a 6 V battery. Find the current drawn from the battery.

Concept: System of Resistors - Resistances in Parallel
Chapter: [0.12] Electricity
OR
[5] 16.2

Answer the following question.
An electric lamp of resistance 20 Ω and a conductor of resistance 4 0 are connected to a 6 V battery as shown in the circuit. Calculate: 

(a) the total resistance of the circuit,  

(b) the current through the circuit, 

(c) the potential difference across the  (i) electric lamp and (ii) conductor, and

(d) power of the lamp.

Concept: Electric Current
Chapter: [0.12] Electricity
[5] 17
[2.5] 17.1

Draw magnetic field lines produced around a current-carrying straight conductor passing through cardboard. Name, state and apply the rule to mark the direction of these field lines.

Concept: Magnetic Field Lines
Chapter: [0.13] Magnetic Effects of Electric Current
[2.5] 17.2

How will the strength of the magnetic field change when the point where the magnetic field is to be determined is moved away from the straight wire carrying constant current? Justify your answer.

Concept: Effects of Electric Current - Magnetic Effect of Electric Current
Chapter: [0.13] Magnetic Effects of Electric Current
[5] 18

An object is placed at a distance of 60 cm from a concave lens of focal length 30 cm.
(i) Use the lens formula to find the distance of the image from the lens.
(ii) List four characteristics of the image (nature, position, size, erect/inverted) formed by the lens in this case.
(iii) Draw a ray diagram to justify your answer of the part (ii).

Concept: Concave Lens
Chapter: [0.1] Light - Reflection and Refraction
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[5] 19
[5] 19.1

Answer the following question.
How does suitable pollination lead to fertilization?

Concept: Sexual Reproduction in Flowering Plants
Chapter: [0.08] How do Organisms Reproduce?
OR
[5] 19.2
[2.5] 19.2.1

Identify the given diagram.
Name the parts 1 to 5. 

Concept: Human Reproductive System
Chapter: [0.08] How do Organisms Reproduce?
[2.5] 19.2.2

Answer the following question.
What is contraception? List three advantages of adopting contraceptive measures.

Concept: Human Reproductive System
Chapter: [0.08] How do Organisms Reproduce?
[5] 20
[5] 20.1

Answer the following question.
Write the chemical formula and name of the compound which is the active ingredient of all alcoholic drinks. List its two uses.

Write the chemical equation and name of the product formed when this compound reacts with -
(i) Sodium metal  
(ii) hot concentrated sulphuric acid

Concept: Ethanol
Chapter: [0.04] Carbon and its Compounds
OR
[5] 20.2

Answer the following question.
What is methane? Draw its electron dot structure. Name the type of bonds formed in this compound. Why are such compounds:
(i) poor conductors of electricity? and  
(ii) have low melting and boiling points? What happens when this compound burns in oxygen?

Concept: The Covalent Bond
Chapter: [0.03] Metals and Non Metals [0.04] Carbon and its Compounds
[5] 21

Write the main difference between an acid and a base. 

Concept: Acid or a Base in a Water Solution
Chapter: [0.02] Acids, Bases and Salts

With the help of suitable examples explain the term neutralization and the formation of – 
(i) acidic,  
(ii) basic and  
(iii) neutral salts

Concept: Types of Double Displacement: Neutralization Reaction
Chapter:
Section - E
[2] 22

Answer the following question.
In the experimental set up to show that "CO2 is given out during respiration", name the substance taken in the small test tube kept in the conical flask. State its function and the consequence of its use.

Concept: Respiration
Chapter: [0.06] Life Processes
[2] 23
[1] 23.1

A student is observing the temporary mount of a leaf peel under a microscope. Draw a labelled diagram of the structure of stomata as seen under the microscope

Concept: Sexual Reproduction in Flowering Plants
Chapter: [0.08] How do Organisms Reproduce?
OR
[1] 23.2

Draw labelled diagrams to illustrate budding in Hydra.

Concept: Asexual Reproduction - Asexual Reproduction in Plant
Chapter: [0.08] How do Organisms Reproduce?
[2] 24

Answer the following question.
List four precautions which a student should observe while determining the focal length of a given convex lens by obtaining an image of a distant object on a screen. 

Concept: Convex Lens
Chapter: [0.1] Light - Reflection and Refraction
[2] 25
[2] 25.1

Answer the following question.
While studying the dependence of potential difference ( V) across a resistor on the current (I) passing through it, in order to determine the resistance of the resistor, a student took 5 readings for different values of current and plotted a graph between V and t. He got a straight line graph passing through the origin. What does the straight-line signify? Write the method of determining the resistance of the resister using this graph. 

Concept: System of Resistors - Resistors in Series
Chapter: [0.12] Electricity
OR
[2] 25.2

What would you suggest to a student if while performing an experiment he finds that the pointer/needle of the ammeter and voltmeter do not coincide with the zero marks on the scales when the circuit is open? No extra ammeter/voltmeter is available in the laboratory.

Concept: Electric Potential (Electrostatic Potential) and Potential Difference
Chapter: [0.12] Electricity
[2] 26

Answer the following question.
In three test tubes A, B, and C, three different liquids namely, distilled water, underground water and distilled water in which a pinch of calcium sulphate is dissolved, respectively are taken. Equal amount of soap Answer is added to each test tube and the contents are shaken. In which test tube will the length of the foam (lather) be longest? Justify your answer.

Concept: Soap
Chapter: [0.04] Carbon and its Compounds
[2] 27
[2] 27.1

Blue litmus is added to two test tubes A and B containing dilute HCl and NaOH. Answer respectively. In which test tube a colour change will be observed? State the colour change and give its reason.

Concept: Applications of Scattering of Light
Chapter: [0.11] The Human Eye and the Colourful World
OR
[2] 27.2

Answer the following question.
What is observed when 2 mL of dilute hydrochloric acid is added to 1 g of sodium carbonate taken in a clean and dry test tube? Write a chemical equation for the reaction involved.

Concept: Chemical Equation
Chapter: [0.01] Chemical Reactions and Equations

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