Science Past Year Paper SA-2 Solution(Set -1 Outside Delhi) - 2015, Class 10, CBSE Class 10 Notes | EduRev

Past Year Papers For Class 10

Created by: Manju Sen

Class 10 : Science Past Year Paper SA-2 Solution(Set -1 Outside Delhi) - 2015, Class 10, CBSE Class 10 Notes | EduRev

 Page 1


Outside Delhi – 31/1 Page 1 
 
Strictly Confidential- (For Internal and Restricted Use Only) Secondary School Examination 
SUMMATIVE ASSESSMENT - II 
March 2015 
 
Marking Scheme – Science (Outside Delhi) 31/1 
 
 
1. The Marking Scheme provides general guidelines to reduce subjectivity in the marking. It carries 
only suggested value points for the answer. These are only guidelines and do not constitute the 
complete answer. Any other individual response with suitable justification should also be 
accepted even if there is no reference to the text. 
 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should not be 
done according to one's own interpretation or any other consideration. Marking Scheme should 
be strictly adhered to and religiously followed. 
 
3. If a question has parts, please award marks in the right hand side for each part. Marks awarded 
for different parts of the question should then be totalled up and written in the left hand margin. 
 
4. If a question does not have any parts, marks be awarded in the left hand side margin. 
 
5. If a candidate has attempted an extra question, marks obtained in the question attempted first 
should be retained and the other answer should be scored out. 
 
6. Wherever only two/three of a 'given' number of examples/factors/points are expected only the 
first two/three or expected number should be read. The rest are irrelevant and should not be 
examined. 
 
7. There should be no effort at 'moderation' of the marks by the evaluating teachers. The actual 
total marks obtained by the candidate may be of no concern of the evaluators. 
 
8. All the Head Examiners / Examiners are instructed that while evaluating the answer scripts, if the 
answer is found to be totally incorrect, the (X) should be marked on the incorrect answer and 
awarded ‘0’ marks. 
  
9. ½ mark may be deducted if a candidate either does not write units or writes wrong units in the 
final answer of a numerical problem. 
 
10. A full scale of mark 0 to 100 has to be used. Please do not hesitate to award full marks if the 
answer deserves it. 
 
11. As per orders of the Hon’ble Supreme Court the candidates would now be permitted to obtain 
photocopy of the Answer Book on request on payment of the prescribed fee. All Examiners/Head 
Examiners are once again reminded that they must ensure that evaluation is carried out strictly 
as per value points given in the marking scheme. 
 
 
 
 
Page 2


Outside Delhi – 31/1 Page 1 
 
Strictly Confidential- (For Internal and Restricted Use Only) Secondary School Examination 
SUMMATIVE ASSESSMENT - II 
March 2015 
 
Marking Scheme – Science (Outside Delhi) 31/1 
 
 
1. The Marking Scheme provides general guidelines to reduce subjectivity in the marking. It carries 
only suggested value points for the answer. These are only guidelines and do not constitute the 
complete answer. Any other individual response with suitable justification should also be 
accepted even if there is no reference to the text. 
 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should not be 
done according to one's own interpretation or any other consideration. Marking Scheme should 
be strictly adhered to and religiously followed. 
 
3. If a question has parts, please award marks in the right hand side for each part. Marks awarded 
for different parts of the question should then be totalled up and written in the left hand margin. 
 
4. If a question does not have any parts, marks be awarded in the left hand side margin. 
 
5. If a candidate has attempted an extra question, marks obtained in the question attempted first 
should be retained and the other answer should be scored out. 
 
6. Wherever only two/three of a 'given' number of examples/factors/points are expected only the 
first two/three or expected number should be read. The rest are irrelevant and should not be 
examined. 
 
7. There should be no effort at 'moderation' of the marks by the evaluating teachers. The actual 
total marks obtained by the candidate may be of no concern of the evaluators. 
 
8. All the Head Examiners / Examiners are instructed that while evaluating the answer scripts, if the 
answer is found to be totally incorrect, the (X) should be marked on the incorrect answer and 
awarded ‘0’ marks. 
  
9. ½ mark may be deducted if a candidate either does not write units or writes wrong units in the 
final answer of a numerical problem. 
 
10. A full scale of mark 0 to 100 has to be used. Please do not hesitate to award full marks if the 
answer deserves it. 
 
11. As per orders of the Hon’ble Supreme Court the candidates would now be permitted to obtain 
photocopy of the Answer Book on request on payment of the prescribed fee. All Examiners/Head 
Examiners are once again reminded that they must ensure that evaluation is carried out strictly 
as per value points given in the marking scheme. 
 
 
 
 
Outside Delhi – 31/1 Page 2 
 
MARKING SCHEME 
CLASS X – OUTSIDE DELHI 
Code No. 31/1 
 
 Expected Answer/ Value point Marks Total 
 SECTION – A   
    
Q1. Seven 1 1 
    
Q2. Reproduction 1 1 
    
Q3. 1000 J 1 1 
    
Q4. 
i) 
3
4
?
g
n ; 
2
3
?
w
n ; m/s 10 2
8
? ?
g
? 
  
  
g
g
c
n
?
? 
½ 
 
  
? m/s 10 2
3
4
8
? ? ? ?
g g
n c ? = 
8
10 67 . 2 ? m/s  
½ 
 
 ii) 
w
w
c
n
?
? 
 
 
  
? m/s 10 78 . 1
3
10 2 67 . 2
8
8
? ?
? ?
? ?
w
w
n
c
? 
1 2 
 Note: Full marks to be awarded for those who attempt with the correct 
values of refractive indices. 
  
    
Q5. Causes: Disposal of industrial effluents   
               Human activities like bathing, washing, immersion of ashes, etc.   
               Disposal of untreated sewage ½, ½   
                (any two)   
 Harmful effects on health – Spreads water borne diseases, 
- Consumptions of contaminated fishes 
        (or any other relevant affect) ½, ½  2 
    
Q6. Biodiversity  - number and range of variety of species of life forms in an 
area 1  
 Effect – loss of diversity may lead to a loss of ecological stability 1 2 
    
Q7. ? Test 1 (Litmus Test) ½  
 Take two strips of blue litmus paper. Place a drop each of the alcohol and 
carboxylic acid on these strips separately. The blue litmus paper turns red in the 
case of carboxylic acid and remains unaffected in the case of alcohol. 1 
 
 ? Test 2 (Sodium hydrogen carbonate test / sodium carbonate test) ½  
 A pinch of sodium hydrogen carbonate or sodium carbonate is added, to both 
separately. If brisk effervescence with the evolution of a colorless gas is 
1 
 
Page 3


Outside Delhi – 31/1 Page 1 
 
Strictly Confidential- (For Internal and Restricted Use Only) Secondary School Examination 
SUMMATIVE ASSESSMENT - II 
March 2015 
 
Marking Scheme – Science (Outside Delhi) 31/1 
 
 
1. The Marking Scheme provides general guidelines to reduce subjectivity in the marking. It carries 
only suggested value points for the answer. These are only guidelines and do not constitute the 
complete answer. Any other individual response with suitable justification should also be 
accepted even if there is no reference to the text. 
 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should not be 
done according to one's own interpretation or any other consideration. Marking Scheme should 
be strictly adhered to and religiously followed. 
 
3. If a question has parts, please award marks in the right hand side for each part. Marks awarded 
for different parts of the question should then be totalled up and written in the left hand margin. 
 
4. If a question does not have any parts, marks be awarded in the left hand side margin. 
 
5. If a candidate has attempted an extra question, marks obtained in the question attempted first 
should be retained and the other answer should be scored out. 
 
6. Wherever only two/three of a 'given' number of examples/factors/points are expected only the 
first two/three or expected number should be read. The rest are irrelevant and should not be 
examined. 
 
7. There should be no effort at 'moderation' of the marks by the evaluating teachers. The actual 
total marks obtained by the candidate may be of no concern of the evaluators. 
 
8. All the Head Examiners / Examiners are instructed that while evaluating the answer scripts, if the 
answer is found to be totally incorrect, the (X) should be marked on the incorrect answer and 
awarded ‘0’ marks. 
  
9. ½ mark may be deducted if a candidate either does not write units or writes wrong units in the 
final answer of a numerical problem. 
 
10. A full scale of mark 0 to 100 has to be used. Please do not hesitate to award full marks if the 
answer deserves it. 
 
11. As per orders of the Hon’ble Supreme Court the candidates would now be permitted to obtain 
photocopy of the Answer Book on request on payment of the prescribed fee. All Examiners/Head 
Examiners are once again reminded that they must ensure that evaluation is carried out strictly 
as per value points given in the marking scheme. 
 
 
 
 
Outside Delhi – 31/1 Page 2 
 
MARKING SCHEME 
CLASS X – OUTSIDE DELHI 
Code No. 31/1 
 
 Expected Answer/ Value point Marks Total 
 SECTION – A   
    
Q1. Seven 1 1 
    
Q2. Reproduction 1 1 
    
Q3. 1000 J 1 1 
    
Q4. 
i) 
3
4
?
g
n ; 
2
3
?
w
n ; m/s 10 2
8
? ?
g
? 
  
  
g
g
c
n
?
? 
½ 
 
  
? m/s 10 2
3
4
8
? ? ? ?
g g
n c ? = 
8
10 67 . 2 ? m/s  
½ 
 
 ii) 
w
w
c
n
?
? 
 
 
  
? m/s 10 78 . 1
3
10 2 67 . 2
8
8
? ?
? ?
? ?
w
w
n
c
? 
1 2 
 Note: Full marks to be awarded for those who attempt with the correct 
values of refractive indices. 
  
    
Q5. Causes: Disposal of industrial effluents   
               Human activities like bathing, washing, immersion of ashes, etc.   
               Disposal of untreated sewage ½, ½   
                (any two)   
 Harmful effects on health – Spreads water borne diseases, 
- Consumptions of contaminated fishes 
        (or any other relevant affect) ½, ½  2 
    
Q6. Biodiversity  - number and range of variety of species of life forms in an 
area 1  
 Effect – loss of diversity may lead to a loss of ecological stability 1 2 
    
Q7. ? Test 1 (Litmus Test) ½  
 Take two strips of blue litmus paper. Place a drop each of the alcohol and 
carboxylic acid on these strips separately. The blue litmus paper turns red in the 
case of carboxylic acid and remains unaffected in the case of alcohol. 1 
 
 ? Test 2 (Sodium hydrogen carbonate test / sodium carbonate test) ½  
 A pinch of sodium hydrogen carbonate or sodium carbonate is added, to both 
separately. If brisk effervescence with the evolution of a colorless gas is 
1 
 
Outside Delhi – 31/1 Page 3 
 
observed, it indicates the presence of carboxylic acid. 
If no change is observed then it confirms the presence of the alcohol. 
 ? Test 3 – Ester test  or any other suitable test                   (any two)  3 
    
Q8.  
 
1 
 
 In pure oxygen, ethyne undergoes complete combustion and high temperature 
suitable for welding is attained. 1  
 Whereas air contains less percentage /amount of oxygen which results in 
incomplete combustion of ethyne and the temperature required for welding is not 
attained. 1 3 
    
Q9. Property             P                Q   
(a) No. of electrons in the 
atom 
3 
11 
19 
4 
12 
20 
  
   (any one pair) ½  
(b) Size of the atom Bigger Smaller ½  
(c) Metallic character More metallic Less metallic ½  
(d) Tendency to lose electrons More Less ½  
(e) Formula of oxides P
2
O QO ½  
(f) Formula of chlorides PCl QCl
2
 ½ 3 
 Note: For parts (e) and (f) examples using symbols of elements may also be 
accepted. 
  
    
Q10. Electronic configuration of element with atomic no. 16 is 2,8,6. 1  
 Since it has 3 shells, the period no. will be 3. ½  
 Since the no. of valence electrons is 6, the group no. will be 10 + 6 = 16. ½  
 Valency of the element will be 8- valence electrons  ie  8 – 6 = 2. 1 3 
    
Q11. Characteristics: 
Two parents are involved, 
Two dissimilar gametes are formed, gamete formation involves meiosis, 
Variations are produced, 
Occurs in all the higher and some of the lower organisms, 
Fertilization / fusion of gametes leading to zygote formation  
Slow.   
  ½ x 6 3 
Page 4


Outside Delhi – 31/1 Page 1 
 
Strictly Confidential- (For Internal and Restricted Use Only) Secondary School Examination 
SUMMATIVE ASSESSMENT - II 
March 2015 
 
Marking Scheme – Science (Outside Delhi) 31/1 
 
 
1. The Marking Scheme provides general guidelines to reduce subjectivity in the marking. It carries 
only suggested value points for the answer. These are only guidelines and do not constitute the 
complete answer. Any other individual response with suitable justification should also be 
accepted even if there is no reference to the text. 
 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should not be 
done according to one's own interpretation or any other consideration. Marking Scheme should 
be strictly adhered to and religiously followed. 
 
3. If a question has parts, please award marks in the right hand side for each part. Marks awarded 
for different parts of the question should then be totalled up and written in the left hand margin. 
 
4. If a question does not have any parts, marks be awarded in the left hand side margin. 
 
5. If a candidate has attempted an extra question, marks obtained in the question attempted first 
should be retained and the other answer should be scored out. 
 
6. Wherever only two/three of a 'given' number of examples/factors/points are expected only the 
first two/three or expected number should be read. The rest are irrelevant and should not be 
examined. 
 
7. There should be no effort at 'moderation' of the marks by the evaluating teachers. The actual 
total marks obtained by the candidate may be of no concern of the evaluators. 
 
8. All the Head Examiners / Examiners are instructed that while evaluating the answer scripts, if the 
answer is found to be totally incorrect, the (X) should be marked on the incorrect answer and 
awarded ‘0’ marks. 
  
9. ½ mark may be deducted if a candidate either does not write units or writes wrong units in the 
final answer of a numerical problem. 
 
10. A full scale of mark 0 to 100 has to be used. Please do not hesitate to award full marks if the 
answer deserves it. 
 
11. As per orders of the Hon’ble Supreme Court the candidates would now be permitted to obtain 
photocopy of the Answer Book on request on payment of the prescribed fee. All Examiners/Head 
Examiners are once again reminded that they must ensure that evaluation is carried out strictly 
as per value points given in the marking scheme. 
 
 
 
 
Outside Delhi – 31/1 Page 2 
 
MARKING SCHEME 
CLASS X – OUTSIDE DELHI 
Code No. 31/1 
 
 Expected Answer/ Value point Marks Total 
 SECTION – A   
    
Q1. Seven 1 1 
    
Q2. Reproduction 1 1 
    
Q3. 1000 J 1 1 
    
Q4. 
i) 
3
4
?
g
n ; 
2
3
?
w
n ; m/s 10 2
8
? ?
g
? 
  
  
g
g
c
n
?
? 
½ 
 
  
? m/s 10 2
3
4
8
? ? ? ?
g g
n c ? = 
8
10 67 . 2 ? m/s  
½ 
 
 ii) 
w
w
c
n
?
? 
 
 
  
? m/s 10 78 . 1
3
10 2 67 . 2
8
8
? ?
? ?
? ?
w
w
n
c
? 
1 2 
 Note: Full marks to be awarded for those who attempt with the correct 
values of refractive indices. 
  
    
Q5. Causes: Disposal of industrial effluents   
               Human activities like bathing, washing, immersion of ashes, etc.   
               Disposal of untreated sewage ½, ½   
                (any two)   
 Harmful effects on health – Spreads water borne diseases, 
- Consumptions of contaminated fishes 
        (or any other relevant affect) ½, ½  2 
    
Q6. Biodiversity  - number and range of variety of species of life forms in an 
area 1  
 Effect – loss of diversity may lead to a loss of ecological stability 1 2 
    
Q7. ? Test 1 (Litmus Test) ½  
 Take two strips of blue litmus paper. Place a drop each of the alcohol and 
carboxylic acid on these strips separately. The blue litmus paper turns red in the 
case of carboxylic acid and remains unaffected in the case of alcohol. 1 
 
 ? Test 2 (Sodium hydrogen carbonate test / sodium carbonate test) ½  
 A pinch of sodium hydrogen carbonate or sodium carbonate is added, to both 
separately. If brisk effervescence with the evolution of a colorless gas is 
1 
 
Outside Delhi – 31/1 Page 3 
 
observed, it indicates the presence of carboxylic acid. 
If no change is observed then it confirms the presence of the alcohol. 
 ? Test 3 – Ester test  or any other suitable test                   (any two)  3 
    
Q8.  
 
1 
 
 In pure oxygen, ethyne undergoes complete combustion and high temperature 
suitable for welding is attained. 1  
 Whereas air contains less percentage /amount of oxygen which results in 
incomplete combustion of ethyne and the temperature required for welding is not 
attained. 1 3 
    
Q9. Property             P                Q   
(a) No. of electrons in the 
atom 
3 
11 
19 
4 
12 
20 
  
   (any one pair) ½  
(b) Size of the atom Bigger Smaller ½  
(c) Metallic character More metallic Less metallic ½  
(d) Tendency to lose electrons More Less ½  
(e) Formula of oxides P
2
O QO ½  
(f) Formula of chlorides PCl QCl
2
 ½ 3 
 Note: For parts (e) and (f) examples using symbols of elements may also be 
accepted. 
  
    
Q10. Electronic configuration of element with atomic no. 16 is 2,8,6. 1  
 Since it has 3 shells, the period no. will be 3. ½  
 Since the no. of valence electrons is 6, the group no. will be 10 + 6 = 16. ½  
 Valency of the element will be 8- valence electrons  ie  8 – 6 = 2. 1 3 
    
Q11. Characteristics: 
Two parents are involved, 
Two dissimilar gametes are formed, gamete formation involves meiosis, 
Variations are produced, 
Occurs in all the higher and some of the lower organisms, 
Fertilization / fusion of gametes leading to zygote formation  
Slow.   
  ½ x 6 3 
Outside Delhi – 31/1 Page 4 
 
    
Q12. Chromosomes – thread like structures made up of DNA found in the 
nucleus. 1  
 The original number of chromosomes becomes half during gamete 
formation.  
Hence, when the gametes combine, the original number of chromosomes 
gets restored in the progeny. (or same thing explained in the form of  a 
flow chart). 1,1 3 
    
Q13. Significance – prevent STDs, 
Advantage of small family, 
Less mortality among new borns, 
Reduces the cases of maternal mortality. ½ x 4  
    
 Areas which have improved – Family Planning, 
- Decrease in STD  cases 
                                     (any other) ½ x 2 3 
    
Q14. Homologous organs – study of homologous organs suggests that the 
organs having same structure but performing different functions have 
evolved from a common ancestor. 
Ex. - forelimbs of a frog, lizard, bird and man. 
½ 
 
 
½   
    
 Analogous organs – show adoption of organs for common use. 
Ex. – wings of butterfly and wings of bat. 
½ 
½   
    
 Fossils – provide the missing links between two species. 
Ex. – Archeopteryx / fossils of some dinosaurs with feathers. 
½ 
½  3 
    
Q15. ? Speciation – evolution of a new species from pre-existing species 
? Occurring due to accumulation of variations 
? By processes like genetic drift / geographical barriers like mountains, 
rivers etc., leading to incapability to reproduce amongst themselves in 
the population. ½ × 3  
    
 Natural selection – 
? Change in frequency of some genes in a population 
? Which give survival advantage to a species from elimination. 
? Ex. – in a population of beetles, a new variation (green colour) get 
survival benefit / advantage to green beetles whereas other (red) 
perishes. ½ × 3 3 
    
    
    
    
    
    
    
    
Page 5


Outside Delhi – 31/1 Page 1 
 
Strictly Confidential- (For Internal and Restricted Use Only) Secondary School Examination 
SUMMATIVE ASSESSMENT - II 
March 2015 
 
Marking Scheme – Science (Outside Delhi) 31/1 
 
 
1. The Marking Scheme provides general guidelines to reduce subjectivity in the marking. It carries 
only suggested value points for the answer. These are only guidelines and do not constitute the 
complete answer. Any other individual response with suitable justification should also be 
accepted even if there is no reference to the text. 
 
2. Evaluation is to be done as per instructions provided in the Marking Scheme. It should not be 
done according to one's own interpretation or any other consideration. Marking Scheme should 
be strictly adhered to and religiously followed. 
 
3. If a question has parts, please award marks in the right hand side for each part. Marks awarded 
for different parts of the question should then be totalled up and written in the left hand margin. 
 
4. If a question does not have any parts, marks be awarded in the left hand side margin. 
 
5. If a candidate has attempted an extra question, marks obtained in the question attempted first 
should be retained and the other answer should be scored out. 
 
6. Wherever only two/three of a 'given' number of examples/factors/points are expected only the 
first two/three or expected number should be read. The rest are irrelevant and should not be 
examined. 
 
7. There should be no effort at 'moderation' of the marks by the evaluating teachers. The actual 
total marks obtained by the candidate may be of no concern of the evaluators. 
 
8. All the Head Examiners / Examiners are instructed that while evaluating the answer scripts, if the 
answer is found to be totally incorrect, the (X) should be marked on the incorrect answer and 
awarded ‘0’ marks. 
  
9. ½ mark may be deducted if a candidate either does not write units or writes wrong units in the 
final answer of a numerical problem. 
 
10. A full scale of mark 0 to 100 has to be used. Please do not hesitate to award full marks if the 
answer deserves it. 
 
11. As per orders of the Hon’ble Supreme Court the candidates would now be permitted to obtain 
photocopy of the Answer Book on request on payment of the prescribed fee. All Examiners/Head 
Examiners are once again reminded that they must ensure that evaluation is carried out strictly 
as per value points given in the marking scheme. 
 
 
 
 
Outside Delhi – 31/1 Page 2 
 
MARKING SCHEME 
CLASS X – OUTSIDE DELHI 
Code No. 31/1 
 
 Expected Answer/ Value point Marks Total 
 SECTION – A   
    
Q1. Seven 1 1 
    
Q2. Reproduction 1 1 
    
Q3. 1000 J 1 1 
    
Q4. 
i) 
3
4
?
g
n ; 
2
3
?
w
n ; m/s 10 2
8
? ?
g
? 
  
  
g
g
c
n
?
? 
½ 
 
  
? m/s 10 2
3
4
8
? ? ? ?
g g
n c ? = 
8
10 67 . 2 ? m/s  
½ 
 
 ii) 
w
w
c
n
?
? 
 
 
  
? m/s 10 78 . 1
3
10 2 67 . 2
8
8
? ?
? ?
? ?
w
w
n
c
? 
1 2 
 Note: Full marks to be awarded for those who attempt with the correct 
values of refractive indices. 
  
    
Q5. Causes: Disposal of industrial effluents   
               Human activities like bathing, washing, immersion of ashes, etc.   
               Disposal of untreated sewage ½, ½   
                (any two)   
 Harmful effects on health – Spreads water borne diseases, 
- Consumptions of contaminated fishes 
        (or any other relevant affect) ½, ½  2 
    
Q6. Biodiversity  - number and range of variety of species of life forms in an 
area 1  
 Effect – loss of diversity may lead to a loss of ecological stability 1 2 
    
Q7. ? Test 1 (Litmus Test) ½  
 Take two strips of blue litmus paper. Place a drop each of the alcohol and 
carboxylic acid on these strips separately. The blue litmus paper turns red in the 
case of carboxylic acid and remains unaffected in the case of alcohol. 1 
 
 ? Test 2 (Sodium hydrogen carbonate test / sodium carbonate test) ½  
 A pinch of sodium hydrogen carbonate or sodium carbonate is added, to both 
separately. If brisk effervescence with the evolution of a colorless gas is 
1 
 
Outside Delhi – 31/1 Page 3 
 
observed, it indicates the presence of carboxylic acid. 
If no change is observed then it confirms the presence of the alcohol. 
 ? Test 3 – Ester test  or any other suitable test                   (any two)  3 
    
Q8.  
 
1 
 
 In pure oxygen, ethyne undergoes complete combustion and high temperature 
suitable for welding is attained. 1  
 Whereas air contains less percentage /amount of oxygen which results in 
incomplete combustion of ethyne and the temperature required for welding is not 
attained. 1 3 
    
Q9. Property             P                Q   
(a) No. of electrons in the 
atom 
3 
11 
19 
4 
12 
20 
  
   (any one pair) ½  
(b) Size of the atom Bigger Smaller ½  
(c) Metallic character More metallic Less metallic ½  
(d) Tendency to lose electrons More Less ½  
(e) Formula of oxides P
2
O QO ½  
(f) Formula of chlorides PCl QCl
2
 ½ 3 
 Note: For parts (e) and (f) examples using symbols of elements may also be 
accepted. 
  
    
Q10. Electronic configuration of element with atomic no. 16 is 2,8,6. 1  
 Since it has 3 shells, the period no. will be 3. ½  
 Since the no. of valence electrons is 6, the group no. will be 10 + 6 = 16. ½  
 Valency of the element will be 8- valence electrons  ie  8 – 6 = 2. 1 3 
    
Q11. Characteristics: 
Two parents are involved, 
Two dissimilar gametes are formed, gamete formation involves meiosis, 
Variations are produced, 
Occurs in all the higher and some of the lower organisms, 
Fertilization / fusion of gametes leading to zygote formation  
Slow.   
  ½ x 6 3 
Outside Delhi – 31/1 Page 4 
 
    
Q12. Chromosomes – thread like structures made up of DNA found in the 
nucleus. 1  
 The original number of chromosomes becomes half during gamete 
formation.  
Hence, when the gametes combine, the original number of chromosomes 
gets restored in the progeny. (or same thing explained in the form of  a 
flow chart). 1,1 3 
    
Q13. Significance – prevent STDs, 
Advantage of small family, 
Less mortality among new borns, 
Reduces the cases of maternal mortality. ½ x 4  
    
 Areas which have improved – Family Planning, 
- Decrease in STD  cases 
                                     (any other) ½ x 2 3 
    
Q14. Homologous organs – study of homologous organs suggests that the 
organs having same structure but performing different functions have 
evolved from a common ancestor. 
Ex. - forelimbs of a frog, lizard, bird and man. 
½ 
 
 
½   
    
 Analogous organs – show adoption of organs for common use. 
Ex. – wings of butterfly and wings of bat. 
½ 
½   
    
 Fossils – provide the missing links between two species. 
Ex. – Archeopteryx / fossils of some dinosaurs with feathers. 
½ 
½  3 
    
Q15. ? Speciation – evolution of a new species from pre-existing species 
? Occurring due to accumulation of variations 
? By processes like genetic drift / geographical barriers like mountains, 
rivers etc., leading to incapability to reproduce amongst themselves in 
the population. ½ × 3  
    
 Natural selection – 
? Change in frequency of some genes in a population 
? Which give survival advantage to a species from elimination. 
? Ex. – in a population of beetles, a new variation (green colour) get 
survival benefit / advantage to green beetles whereas other (red) 
perishes. ½ × 3 3 
    
    
    
    
    
    
    
    
Outside Delhi – 31/1 Page 5 
 
Q16. Convex mirror ½  
 
 
1  
 Use: As rear view mirror in vehicles/ Also in Malls, Hotels, 
Airports for security reasons. ½  
 Why: ? Forms erect image, ½  
  ? Wider field of view. ½ 3 
    
Q17. (i) Scattering – Phenomenon of spreading of light (diffused reflected 
light) caused by minute particles (dust, smoke etc.) in the 
atmosphere. 1  
 (ii) Sky appears blue because blue color of sunlight scatters more 
strongly (due to shorter wavelength) than the red color by the fine 
particles in the air.   
 OR   
 At sunrise the blue color of sunlight get scattered due to smaller 
wave length while passing through the thicker layers of the 
atmosphere. The red component (due to longer wavelength) reaches 
us, giving red appearance, of the Sun. 2 3 
 Note: If explained by following diagram (fully labeled) give full credit.   
 
 
  
    
Q18. Biodegradable substances – can be broken down into simpler substances 
by nature / decomposers/ bacteria/ saprophytes/ saprobionts. 
Ex. – Human Excreta/ Vegetable peels, etc. (any one) 
½ 
 
½   
 Non-biodegradable substances – can’t be broken down into simpler 
substances by nature / decomposers. 
Ex. – Plastic/ glass (or any other)                                        (any one) 
½ 
 
½   
 Habits: 
- Use of separate dustbins for biodegradable and non 
biodegradable waste, 
- Reuse of things such as poly-bags, etc., 
- Recycle of waste 
- Use of cotton /jute bags for carrying vegetables etc. 
                                                                                                 (any two) ½ x 2 3 
Read More
Offer running on EduRev: Apply code STAYHOME200 to get INR 200 off on our premium plan EduRev Infinity!

Complete Syllabus of Class 10

Dynamic Test

Content Category

Related Searches

video lectures

,

Free

,

CBSE Class 10 Notes | EduRev

,

study material

,

Objective type Questions

,

shortcuts and tricks

,

Extra Questions

,

Semester Notes

,

Exam

,

MCQs

,

Previous Year Questions with Solutions

,

practice quizzes

,

CBSE Class 10 Notes | EduRev

,

CBSE Class 10 Notes | EduRev

,

past year papers

,

Science Past Year Paper SA-2 Solution(Set -1 Outside Delhi) - 2015

,

Sample Paper

,

Class 10

,

mock tests for examination

,

Important questions

,

ppt

,

Viva Questions

,

Science Past Year Paper SA-2 Solution(Set -1 Outside Delhi) - 2015

,

Science Past Year Paper SA-2 Solution(Set -1 Outside Delhi) - 2015

,

Summary

,

Class 10

,

pdf

,

Class 10

;