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# Board Paper of Class 10 2016 Science (SET 1) - Solutions

(i) The questions paper comprises two section, A and B. You are to attempt both the sections.
(ii) All questions are compulsory.
(iii) There is no choice in any of the questions.
(iv) All questions of Section A and all questions of Section B are to be attempted separately.
(v) Question numbers 1 to 3 in Section A are one mark questions. These are to be answered in one word or one sentence.
(vi) Question numbers 4 to 6 Section A are two marks questions. These are to be answered in about 30 words each.
(vii) Question numbers 7 to 18 in Section A are three marks questions. There are to be answered in about 50 words each.
(viii) Question numbers 19 to 24 in Section A are five marks questions. These are to be answered in about 70 words each.
(ix) Question number 25 to 33 in Section B are multiple choice questions based on practical skills. Each question is a one mark question. You are to select one most appropriate response out of the four provided to you.
(x) Question numbers 34 to 36 in Section B are two marks questions based on practical skills. These are to be answered in brief.

• Question 1
Which element exhibits the property of catenation to maximum extent and why? VIEW SOLUTION

• Question 2
Name the method by which hydra reproduces. Is this method sexual or asexual? VIEW SOLUTION

• Question 3
We often use the word environment. What does it mean? VIEW SOLUTION

• Question 4
AB and CD, two spherical mirrors, from parts of a hollow spherical ball with its centre at O as shown in the diagram. If arc AB = $\frac{1}{2}$ arc CD, what is the ratio of their focal lengths? State which of the two mirrors will always form virtual image of an object placed in front of it and why.

VIEW SOLUTION

• Question 5
What is sustainable development? State its two main objectives. VIEW SOLUTION

• Question 6
List four causes of damage to forests. VIEW SOLUTION

• Question 7
Write the name and molecular formula of an organic compound having its name suffixed with 'ol' and having two carbon atoms in its molecule. Write balanced chemical equation to indicate what happens when this compound is heated with excess conc. H2SO4 and the name of main product formed. Also state the role of conc. H2SO4 in the reaction. VIEW SOLUTION

• Question 8
An organic compound 'P' is a constituent of wine. 'P' on reacting with acidified K2Cr2O7 forms another compound 'Q'. When a piece of sodium is added to 'Q' a gas 'R' evolves which burns with a pop sound. Identify P, Q and R and write the chemical equations of the reactions involved. VIEW SOLUTION

• Question 9
State the main aim of classifying elements. Which is the most fundamental property of elements that is used in the development of Modern Periodic Table? Name and state the law based on this fundamental property. On which side of the periodic table one can find metals, non-metals and metalloids? VIEW SOLUTION

• Question 10
An element 'X' (Atomic number – 20) burns in the presence of oxygen to form a basic oxide.
(a) Identify the element and write its electronic configuration.
(b) State its group number and period number in the Modern Periodic Table.
(c) Write a balanced chemical equation for the reaction when this oxide is dissolved in water. VIEW SOLUTION

• Question 11
What is pollination? List its two types and write a distinguishing feature between the two. VIEW SOLUTION

• Question 12
What happens when
(a) Planaria gets cut into two pieces?
(b) A mature spirogyra filament attains considerable length?
(c) On maturation sporangia burst? VIEW SOLUTION

• Question 13
What is sexual reproduction? List its four significances. VIEW SOLUTION

• Question 14
List two differences in tabular form between dominant trait and recessive traits. What percentage/proportion of the plants in the F2 generation/progeny were round, in Mendel's cross between round and wrinkled pea plants? VIEW SOLUTION

• Question 15
List three factors that provide evidences in favour of evolution in organisms and state the role of each in brief. VIEW SOLUTION

• Question 16
If the image formed by a lens for all positions of the object placed in front of it is always virtual, erect and diminished, state the type of the lens. Draw a ray diagram in support of your answer. If the numerical value of focal length of such a lens is 20 cm, find its power in new cartesian sign conventions. VIEW SOLUTION

• Question 17
Explain in brief the reason for each of the following :
(b) Delayed sunset
(c) Twinkling of stars VIEW SOLUTION

• Question 18
While discussing about coal and petroleum a teacher told his students about PCRA's (Petroleum Conservation Research Association) guidelines to save the fossil fuels while driving vehicles. Deepa was going to her school with her mother who was driving car. At the traffic signal, when the light was red, Deepa suggested her mother to switch of the engine.

(a) Fossil fuels are natural resources, then why do we need to conserve them?
(b) List any two ways of saving the fossil fuels.
(c) State two values exhibited to Deepa. VIEW SOLUTION

• Question 19
(a) You have three unlabelled test tubes containing ethanol, ethanoic acid and soap solution. Explain the method you would use to identify the compounds in different test tubes by chemical tests using litmus paper and sodium metal.

(b) Give the reason of formation of scum when soaps are used with hard water. VIEW SOLUTION

• Question 20
What is vegetative propagation? List with brief explanation three advantages of practising this process for growing some types of plants. Select two plants from the following which are grown by this process:

Banana, Wheat, Mustard, Jasmine, Gram. VIEW SOLUTION

• Question 21
(a) Why did Mendel choose garden pea for his experiments? Write two reasons.
(b) List two contrasting visible characters of garden pea Mendel used for his experiment.
(c) Explain in brief how Mendel interpreted his results to show that the traits may be dominant or recessive. VIEW SOLUTION

• Question 22
Suppose you have three concave mirrors A, B and C of focal lengths 10 cm, 15 cm and 20 cm. For each concave mirror you perform the experiment of image formation for three values of object distance of 10 cm, 20 cm and 30 cm. Giving reason answer the following:

(a) For the three object distances, identify the mirror/mirrors which will form an image of magnification – 1.
(b) Out of the three mirrors identify the mirror which would be preferred to be used for shaving purposes/makeup.
(c) For the mirror B draw ray diagram for image formation for object distances 10 cm and 20 cm. VIEW SOLUTION

• Question 23
At what distance from a concave lens of focal length 20 cm a 6 cm tall object be placed so as to obtain its image at 15 cm from the lens? Also calculate the size of the image formed.

Draw a ray diagram to justify your answer  for the above situation and label it. VIEW SOLUTION

• Question 24
(a) What is dispersion of white light? State its cause.

(b) "Rainbow is an example of dispersion of sunlight." Justify this statement by explaining, with the help of a labelled diagram, the formation of a rainbow in the sky. List two essential conditions for observing a rainbow. VIEW SOLUTION

• Question 25
Consider the following oils :

(I) Mobil oil

(II) Castor oil

(III) Turpentine oil

(IV) Kerosene

(V) Mustard oil

(VI) Coconut oil

Which of these can be used for prepartion of soap?

(a) I, II, III, VI

(b) II, V, VI

(c) II, III, V, VI

(d) II, III, VI VIEW SOLUTION

• Question 26
The chemical mostly used in the preparation of most of the soaps we use is

(a) Sodium chloride

(b) Potassium hydroxide

(c) Sodium hydroxide

(a) Potassium chloride VIEW SOLUTION

• Question 27
A student is testing water to know which is best for cleansing purposes with soaps. He would find that the cleansing action of soaps is best when he uses water obtained from

(a) rain

(b) tap

(c) hand pump

(d) pond VIEW SOLUTION

• Question 28
A student determines the focal length of a device 'X' by focusing the image of a distant object on a screen placed 20 cm from the device on the same side as the object. The device 'X' is

(a) Concave lens of focal length 10 cm

(b) Convex lens of focal length 20 cm

(c) Concave mirror of focal length 10 cm

(d) Concave mirror of focal length 20 cm VIEW SOLUTION

• Question 29
A teacher sets up the stand carrying a convex lens of focal length 15 cm at 42.7 cm mark on the optical bench. He asks four students A, B, C and D to suggest the position of screen on the optical bench so that a distinct image of a distant tree is obtained almost immediately on it. The positions suggested by the students were as

A. 12.7 cm

B. 29.7 cm

C. 57.7 cm

D. 72.7 cm

The correct position of the screen was suggested by

(a) A

(b) B

(c) C

(d) D VIEW SOLUTION

• Question 30
A student has traced the path of a ray of light through a glass slab as follows. If you are asked to label 1, 2, 3 and 4, the correct sequencing of labeling  ∠i, ∠e, ∠r and lateral displacement respectively is

(a) 2, 1, 3, 4

(b) 1, 2, 3, 4

(c) 1, 3, 2, 4

(d) 1, 3, 4, 2 VIEW SOLUTION

• Question 31
In an experiment to trace the path of a ray of light through a triangular glass prism, a student would observe that the emergent ray

(a) is parallel to the incident ray.

(b) is along the same direction of incident ray.

(c) gets deviated and bends towards the thinner part of the prism.

(d) gets deviated and bends towards the thicker part (base) of the prism. VIEW SOLUTION

• Question 32
The students of a class were asked by the teacher to study the different parts of an embryo of an angiosperm. Given below are the essential steps for the experiment :

A. Soak the seeds in plain water and keep them overnight.

B. Cut open the soaked seed and observe its different parts.

C. Take some healthy seeds in a petri-dish.

D. Drain the excess water, cover the seeds with a wet cotton cloth and leave them as it is for a day.

The correct sequence of these steps is

(a) C, A, D, B

(b) C, D, A, B

(c) A, C, D, B

(d) A, C, B, D VIEW SOLUTION

• Question 33
A basket of vegetables contains Carrot, Potato, Sweet potato, Radish, Tomato and Brinjal. Which of them represent the homologous structures?

(a) Carrot, sweet potato and potato

(c) Carrot, potato and tomato

(d) Brinjal and radish VIEW SOLUTION

• Question 34
A student is studying the properties of acetic acid in his school laboratory. List two physical and two chemical properties which he must observe and note in his record book. VIEW SOLUTION

• Question 35
In which asexual reproduction two individuals are formed from a single parent and the parental identity is lost? Draw the initial and the final stages of this type of reproduction to justify your answer. Write the event which this process starts. VIEW SOLUTION

• Question 36
To find the image distance for varying object distances in case of a convex lens of focal length 15 cm, a student obtains on a screen a sharp image of a bright object by placing it at 20 cm distance from the lens. After that he gradually moves the object away from the lens and each time focuses the image on the screen.

(a) In which direction-towards or away from the lens does he move the screen to focus the object?

(b) How does the size of image change?

(c) Approximately at what distance does he obtain the image of magnification –1?

(d) How does the intensity of image change as the object moves farther and farther away from the lens? VIEW SOLUTION
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