KREIS - SSLC Science Model Question Paper – 1 Key Answer (2020-21)

Key Answer

MGSS

KREIS - SSLC SCIENCE MODEL QUESTION PAPER – 1 

Sub: Science                 Sub. Code: 83E                   Time: 3.15 Hour             Max Marks: 80

PART A: PHYSICS

I. Four alternatives are given for each of the following questions. Choose the correct alternative and write the complete answer along with its letter of alphabet. 4 x 1 = 4 

1. The phenomenon of electromagnetic induction is 

(a) the process of charging a body. 

(b) the process of generating magnetic field due to a current passing through a coil. 

(c) producing induced current in a coil due to relative motion between a magnet and the coil. 

(d) the process of rotating a coil of an electric motor. 

Ans: (c) producing induced current in a coil due to relative motion between a magnet and the coil. 

2. Which of the following is not an example of a bio-mass energy source? 

(a) wood         (b) gobar-gas              (c) nuclear energy                (d) coal 

Ans:  (c) nuclear energy 

3. The equation form of Joule’s law of heating is 

a) V = IR              b) H=I²RT           c) H = RT                   d) I = HT 

Ans: b) H=I²RT  

4. The resistance of a wire of length “l” is “2R”. If the length of the wire is increased to “2l” then the resistance of the wire is 

a) R/2                     b) 4R                    c) 2/R                             d) R

Ans:  b) 4R  

II. Answer the following questions:                                  2 x 1 = 2 

5. What is meant by emergent ray? 

Ans:  

Emergent Ray  is the ray that comes out of a refracting medium.

6. When is the force experienced by a current–carrying conductor placed in a magnetic field largest?  

Ans: 

The force experienced by a current-carrying conductor is the maximum when the direction of current is perpendicular to the magnetic field's direction.

III. Answer the following questions:                                          2 x 2 = 4 

7. Draw the diagram of the electric circuit which has resistors in series. 

Ans:

8. State any two limitations associated with a wind mills? 

Ans: 

• It is Dependent on the Availability of Wind.
• Wind Turbines Kill Birds.
• The Energy that is Produced Can't Be Stored in Large Scale.

IV. Answer the following questions:                    3 x 3 = 9 

 9. Draw a ray diagram and write the position, relative size and nature of image when object is placed in between two principal foci of a convex lens. 

Ans:

Position of the image beyond 2f2

Nature real, inverted and enlorged 

10. What are the advantages of connecting electrical devices in parallel with the battery instead of connecting them in series? 

Ans:

• the voltage remains constant in the parallel connection. 
• We can use one appliance without using other appliances.
• The potential difference across each appliance is equal to the supplied voltage.
• Other components will function even if one component breaks down, each has its own independent circuit.

11. Several electric bulbs designed to be used on a 220V electric supply line, are rated 5W. How many lamps can be connected in parallel with each others across the two wires of 220V line if the maximum available current is 3A? 

Ans:

voltage supply V= 220V

maximum available current I = 3A

Rating of an electric bulb P = 5W

Resistance of each electric bulb 

R₁ = V²/P

R₁ = (220)²/5 

R₁ = 9680Ω

According to ohms law 

V=IR

 R is total resistance of the circuit for x number electric bulbs

R=V/I

R=220/3

R=73Ω

Resistance of each electric bulb is R₁ = 9680Ω

R=1/R₁ + 1/R₂  + ..... upto x times

R=1/R₁ +x

x = R₁ /R

x = 9680Ω / 73Ω

x = 133

number of bulbs connected in parallel are 133

                                                        OR 

 An electric lamp where resistance is 30Ω and a conductor of 8Ω resistance are connected in series to a 9V battery calculate

a) The total resistance of the circuit 

 b) The current through the circuit and 

 c) The potential difference across the electric lamp and conductor. 

Ans: 

Given 

Resistance of electric lamp: 30Ω 

 Resistance of conductor: 8Ω 

 Voltage of battery V: 9V 

a) The total resistance of the circuit is 

 R= R1+R2 

R=30+8 = 38Ω 

b) The current through the circuit is 

I = V/R 

I = 9/38 

I = 0.23A 

c) The potential difference across the electric lamp and conductor. 

 potential difference across the electric lamp is 

V = I R 

V = 0.23 × 30 

V = 0.9V

  potential difference across the conductor is 

V = I RC 

V = 0.23 × 8 

V = 1.84V

V. Answer the following questions:                                     1 x 4 = 4 

 12. Consider the path of a ray of light passing through a rectangular glass slab for different angles of incidence.

 (i) Which one is greater: angle of incidence or angle of refraction? 

 (ii) What happens to the emergent angle on increasing the incident angle at air-glass interface? 

(iii) State the conditions when no bending occurs. 

Ans: 

i. angle of incidence and angle of refraction equal

 ii. Angle of emergence also increases. 

iii. The light ray falls along the normal or the refractive index of the two optical media are equal.

                                                                OR 

 A 2.0 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 10 cm. The distance of the object from the lens is 15 cm. Find the nature, position and size of the image. Also find its magnification.

Ans:

VI. Answer the following question :                                      1 x 5 = 5 

 13. Suppose your parents have constructed a two room house and you want that in the living room there should be a provision of one electric bulb, one electric fan, a refrigerator and a plug point for appliances of power up to 2 kilowatt. Draw a circuit diagram showing electric fuse and earthing as safety devices. 

Ans: 

(i) Four components should be labelled. 

(ii) All of them should be in parallel and there should be a fuse for safety.

 (iii) Live and earth wires should be there.

PART B: CHEMISTRY 

VII. Four alternatives are given for each of the following questions. Choose the correct alternative and write the complete answer along with its letter of alphabet.      2 x 1 = 2 

 14. The correct pair of the metals that react with dil HCl is 

 a) lead, copper                       b) copper, iron 

 c) gold, silver                        d) Zinc, Calcium 

Ans:  d) Zinc, Calcium 

 

15. The alkane having six hydrogen atoms is : 

a) ethane    b) propane     c) butane     d) pentane

Ans: a) ethane 

VIII. Answer the following questions:                                 4 x 1 = 4 

16. What are micelles? 

Ans: 

The hydrocarbon part of the soap molecule links itself to the oily (dirt) drop and ionic end orients itself towards water and forms a spherical structure called micelles. The soap micelles helps in dissolving the dirt in water and wash our clothes.

17. Define Mendeleev’s periodic table law. 

Ans:

Mendeleev's Periodic Law states that the physical and the chemical properties of the elements are a periodic function of their atomic masses.

18. Calcium, Strontium and Barium are Dobereiner’s triads. Find the atomic mass of Strontium if atomic masses of Calcium and Barium are 40 and 137. 

Ans:

according to Dobereiner's triad

atomic mass of strontium =Ca+Ba/2

=137+40/2 = 177/2 = 88.5 

19. How is the concentration of hydrogen (H+ ) affected when a solution of an acid is diluted?

Ans: 

 The concentration of hydronium ions decreases when an acid is diluted because on adding water the H⁺ ions of the acid and hydroxyl ions of water react to form water molecules and the concentration of hydronium ions decreases.

X. Answer the following questions:                                  3 x 3 = 9 

 23. What is meant by electrolytic refining? Draw a neat labelled diagram of Electrolytic refining of copper. 

Ans: 

Electrolytic refining is the process of refining impure metals by using electricity. In this process impure metal is made as the anode and a strip of pure metal is made the cathode. A solution of a soluble salt of the same metal is taken as the electrolyte.

24. Define soap. Briefly describe the mechanism of cleaning by soap. 

Ans:

Soap is a sodium salt or potassium salt of long chain fatty acids having cleansing action in water. 

soaps and detergents cantains two parts. A long hydrocarbon part which is hydrophobic (water repelling) in nature and a short ionic part which is hydrophillic (water attracting) in nature.
The hydrocarbon part of the soap molecule links itself to the oily (dirt) drop and ionic end orients itself towards water and forms a spherical structure called micelles. The soap micelles helps in dissolving the dirt in water and wash our clothes.

                                                                        OR 

Explain the addition and substitution reactions carbon compound. 

Ans:

Addition Reaction: Addition of dihydrogen with unsaturated hydrocarbon in the presence of catalysts such as nickel or platinum or palladium are known as Hydrogenation (addition) reaction.

Substitution Reaction: Replacement of one or more hydrogen atom of an organic molecule by another atom or group of the atom is known as Substitution Reaction.

 25. Draw a diagram showing the reaction of zinc granules with dilute sulphuric acid and testing hydrogen gas by burning and label the following parts.

 a) hydrogen gas bubbles b) dil. sulphuric acid

Ans:

XII. Answer the following questions:                          1 x 4 = 4 

26. Explain the formation of magnesium chloride with electron transfer and electron dot structure.  

Ans: 

• Magnesium chloride (MgCl₂) is formed by the ionic bond formed between magnesium and chlorine atoms.

• The electronic configuration of Mg is 2,8,2. Hence, magnesium needs to loose 2 electrons to become stable. Electronic configuration of chlorine is 2,8,7. Hence, chlorine needs to gain 1 electron to become stable.

• Therefore, during the formation of the ionic bond, a single magnesium atom loses two electrons. On the other hand, two chlorine atoms gain one electron each.

Mg - 2, 8, 2

Cl - 2, 8, 7

PART C: BIOLOGY 

XII. Four alternatives are given for each of the following questions. Choose the correct alternative and write the complete answer along with its letter of alphabet. 2 x 1 = 2 

27. The animal hormone among the following : 

 a) Gibberellins     b) Auxins     c) insulin    d) cytokinins 

Ans: c) insulin 

 28. Which of the following is the full form of UNEP? 

(a) United Kingdom of Africa 

(b) United State of America

(c) United Nations Environment programme 

(d) Union English programme 

Ans: (c) United Nations Environment programme 

XIII. Answer the following questions:                                  2 x 1 = 2 

29. How ozone layer is formed? 

Ans: 

The UV radiations split apart some molecular oxygen (O2) into free oxygen (O) atoms which then combine with the molecular oxygen (O2) to form ozone (O3).

O2   -->O + O

O + O2 --> O3 (ozone).

30. What are 5 R’s to save the environment?

Ans:

The 5 R's: Refuse, Reduce, Reuse, Repurpose, Recycle.

XIV. Answer the following questions:                               3 x 2 = 6 

31. How the plants excrete their wastes from the body. 

Ans: 

• Plants produce two gaseous waste products i.e. oxygen during photosynthesis and carbon dioxide during respiration. Excretion of gaseous waste in plants takes place through stomatal pores on leaves..
• Excess of water is also excreted from the plant body through the stomatal pores and from the surfaces of fruits and stems. 
• The gums, oils, latex, resins, etc. are some waste products stored in plant parts like barks, stems, leaves, etc. Eventually, plants shed off these parts. 

                                                        OR 

 Mention any two main functions of nephrons. 

Ans:

• regulates water and soluble substances in the blood by filtering the blood,
• reabsorbing what is needed, and excreting the rest as urine.
• filter out wastes and toxins, and return needed molecules to the blood. 

32. Draw a labeled diagram of the germination of pollen on stigma. 

Ans:

 33. List the advantages of conservation of forest.

Ans:

• It prevents soil erosion and floods. 
• It helps to maintain the water cycle. 
• It produces huge amounts of raw materials for the industries.
• It preserves different kinds of species and thus, maintains the species diversity.

XV. Answer the following questions:                                        3 x 3 = 9 

 34. Draw a neat diagram showing the structure of human excretory system and label the following parts. i) Left kidney ii) Urinary bladder iii) Venacava iv) Urethra 

Ans:

35. Explain the different types of contraceptive methods. 

Ans:

1. Barrier method: Barriers are available for both males and females. Condoms are barriers made of thin rubber that are used to cover penis in males and vagina in females.
2. Oral contraceptives: In this method, tablets or drugs are taken orally. These contain small doses of hormones that prevent the release of eggs and thus fertilization cannot occur.
3. Implants and surgical methods: Contraceptive devices such as the loop or Copper-T are placed in the uterus to prevent pregnancy. Some surgical methods  includes the blocking of vas deferens to prevent the transfer of sperms known as vasectomy. Similarly, fallopian tubes of the female can be blocked so that the egg will not reach the uterus known as tubectomy.

                                               OR 

 What are the functions of performed by testes and ovary in human beings? 

Ans:

Functions of testis: 

(a) Formation of sperms by the process of spermatogenesis. 

(b) Secretion of testosterone hormone. 

Functions of ovary: 

(a) Formation of ova by the process of oogenesis. 

(b) Secretion of female hormones like estrogens, progesterone and relaxin.

36. How do birds and bats differ with wings? Explain which type of organs they have and the type of evolution they show. 

Ans:

• Wings of bats are skin folds stretched mainly between elongated fingers. But the wings of birds are a feathery covering all along the arm. 
• Wing of a bat and wing of a bird can be considered as analogous organs because they have different basic structure, but have similar appearance and perform similar functions. 
• Wings of bird and bat wings are analogous and wings of Birds and bats did not inherit from a common ancestor. 

                                                           OR 

 Explain the sex determination in human beings.

Ans:

The males have XY sex chromosomes. They produce two types of gametes having X and Y chromosome. The females have XX chromosome. They produce only one type of gamete having X chromosome. If sperm is having X chromosome, then the child will be a girl. If sperm is having Y chromosome, then the child will be a boy. 

XVI. Answer the following questions:                                                             2 x 4 = 8 

 37. Which hormone: 

 a. prepares the body for action? 

 b. controls the amount of sugar (glucose) in blood? 

c. brings about changes in boys at puberty? 

d. brings about changes in girls at puberty? 

Ans: 

a. Adrenaline

b. insulin 

c. testosterone

d. Estrogen 

38. Draw and explain with the help of checker board the independent inheritance of two separate traits shape and color of seeds (Dihybrid Experiment).

Ans:

In a dihybrid cross between two plants having round yellow (RRyy) and wrinkled green seeds (rrYY) two traits are considered the colour of seed and shape of the seed. In this four types of gametes (RY, Ry, rY, ry) are produced. Each of these segregate independent of each other, each having a frequency of 25% of the total gametes produced. Thus the characters for the colour of the seed segregate independently from the characters of the shape of the seed.