10 Science Solved Sample Paper 1

Question: 11. What is meant by isomerism? Why do first three members of the alkane series not show isomerism? Write the structure of two isomers of the fourth member of this series. [3]

Answer: Isomerism is the existence of two or more compounds having same molecular formula but different structures.
It is not possible for them to have different structures/ only one structure is possible for each of them.
Structures: CH₃ — CH₂ — CH₂ — CH₃ ;

CH₃ — CH — CH₃ 
।
 CH₃

Question: 12. The atomic number of three elements A, B and C are given below: [3]
Element:                           A          B           C
Atomic Number:            5          7            10
Answer the following:
(1). Write the group number of the three elements in the Modern Periodic Table.
(2). Mention the period of these elements in the Modern Periodic Table.
(3). Out of these three elements which one has smallest atomic radius and why?

Answer:

1. Element:              A          B           C
   Group No.:         13         15          10
2. All the three elements belong to the second period.
3. ‘C’ is smallest, as the atomic size decreases from left to right in a period.

Question: 13. The reproductive parts of angiosperms are located in the flower. State the change that take place in the flower after the germinated pollen reach the ovules.  [3]
Or
Why is DNA copying an essential part of the process of reproduction? State one main advantage of sexual reproduction over asexual reproduction? [3]

Question: 14. A spherical mirror produces an image of magnification – 1, when an object is placed on the principal axis of the mirror at a distance of 40 cm from its pole. [3]
(1). Identify the nature of image.
(2). Identify the nature of spherical mirror.
(3). Find the distance between the object and its image.
(4). How will the nature of the image change, if the object is shifted 10 cm. towards the mirror? Drew a ray diagram to justify your answer.

Hints: (1) Image is real, inverted / same size as the object; (2) Concave mirror; (3). Zero; (4). Image will be formed beyond C, It will be larger in size.
Or
A 1.5 cm tall object is placed perpendicular to the principle axis of a convex lens of focal length 15 cm. Distance of object from the lens is 20 cm. Use lens formula to find the nature, position and size of the image. [3]

Answer: 

h₁ = +1.5 cm, f = +15 cm, u = -20 cm
As we know, 1/f = 1/v – 1/u ⇒   1/v = 1/f + 1/u
1/v = 1/(+15) + 1/(+20)  = 1/15 – 1/20 = + 1/60                  ∴  v = +60 cm
Now,  h₁/h₂ = v/u   ⇒   h₂ =  v × h₁/u    =    +60 × 1.5/-20  = -4.5 cm
Nature: Real and inverted.

Question: 15. Local people have a major stake in forest resources. Illustrate giving four examples how conservation of forests is essential for the existence of their life. [3]

Answer: Involvement of local people in the conservation of forests as well as avoiding the exhaustion of the forest resources which fulfill the varied needs of local people such as:

1. Large quantity of firewood, small timber and thatch;
2. Bamboo to make slats for huts and baskets;
3. Wood for making implements for agriculture, hunting and fishing and
4. Leaves for fodder, etc.