MG SCHOOL EDUCATION: KSEEB MQP 3 Key Answer

KSEEB - SCIENCE MQP - 3 2024-25

KEY ANSWER

PART A - PHYSICS

I. MCQ 2 × 1 = 2

1. The S.I. unit of electric current is

(A) coulomb (B) volt (C) ampere (D) watt

Ans: (C) ampere

2. The change in focal length of an eye lens is controlled by

(A) Ciliary muscles (B) Pupil (C) Retina (D) Iris

Ans: (A) Ciliary muscles

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

3. Write the symbols of the following components used in an electric circuit. i) Electric cell ii) Rheostat

Ans;

4. What problems will occur when live and neutral wires are connected directly to the household electrical appliances from the electric pole ?

Ans: overloading and short circuit

III. Answer the following questions : 3 × 2 = 6

5. Connecting resistors in parallel in domestic circuits is better than connecting them in series. How? Explain.

Ans:

★ Reduced Total Resistance

★ Increased Current Capacity

★ Same voltage supply,

★ allowing them to operate independently,

★ If one appliance fails, the others continue to function (Any four)

6. How do magnetic field lines appear when electric current passes through a circular loop of conducting wires?

Ans:

★ The magnetic field lines appear as concentric circles around the loop.

★ Lines becoming nearly straight and perpendicular to the plane of the loop at the center,

Explain the function of earth wire in domestic circuits.

Ans:

★This provides a low resistance conducting path for the current

★ Any leakage of current in the appliances keeps its potential to that of the earth and the user may not get a severe electric shock

7. Observe the following figure. Answer the question given below :

Whether this phenomenon can be observed on the moon surface? Justify the answer.

Ans:

No, because

★ No Atmosphere

★ No water droplets present to refract and disperse sunlight

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

8. Explain an activity to verify Fleming’s left hand rule.

Ans:

★ Take a small aluminium rod and suspend it horizontally using connecting wires.

★ Place a strong horse-shoe magnet in such a way that rod lies between the two poles with the magnetic field directed upwards.

★ Connect the aluminium rod in series with a battery, a key and a rheostat.

★ Now pass the current through the aluminium rod in one particular direction.

★ The rod displaces towards one side.

★ Reverse the direction of current flowing through the rod. The rod displaces towards the opposite side.

9. Draw the ray diagram for the image formation in a convex lens when the object is placed between optical centre (O) and principal focus (F1). Mention the position and the nature of the image formed.

Ans:

Position of the image : same side of the object

Nature of the image : virtual and erect

10. Observe the figure given below. Name the defect of the eye depicted in the figure. What causes this defect? How can this defect be corrected?

Ans:

Hypermetropia

Cause:

★ The focal length of the eye lens is too long

★ The eyeball has become too small.

Stars twinkle but planets do not twinkle. Why? Explain.

Ans:

★ Planets are closer to Earth than stars , their light has to travel through less of the atmosphere

★ The light from stars are considered as point source of light and travel through more of the Earth's atmosphere

★ Light from planets are considered as extended source of light. So the light from the planets nullify the twinkling effect.

V. Answer the following questions : 2 × 4 = 8

11. A convex mirror that has a radius of curvature 4 m is used in a bus. If a car is located at the distance of 10 m from the mirror, then find the image distance. Mention the nature and the size of the image formed.

Ans:

Given:

R = 4m, u = 10m, v = ?

f = R/2 = 4/2 = 2m

1/v + 1/u = 1/f

1/v = 1/2 + 1/10

1/v = 5+1/10

1/v = 6/10

v = 10/6

v = 1.66m

Nature of the image is virtual and erect

Size of the image is diminissed

12. a) State Ohm’s law.

b) Mention the factors on which the resistance of a conductor depend.

c) Resistivity of a material A is 10¹² Ω m and the resistivity of a material B is 2・63 × 10⁻⁸ Ω m. Which of these two materials can becused as an insulator?

Ans:

a) The potential difference V across the ends of a given metallic wire in an electric circuit is directly proportional to the current flowing through it at constant temperature.

b) Factors on which resistance of a conductor depends :

★ Length of a conductor

★ Area of cross-section of a conductor

★ Nature of the material

★ Temperature.

c) A

P ART – B ( CHEMISTRY )

VI. MCQ 3 × 1 = 3

13. A salt used to remove the permanent hardness of water is

(A) calcium sulphate hemihydrate (B) calcium oxychloride

Ans: (C) sodium carbonate

14. As the pH value of a neutral solution decreases, then

(A) concentration of H+ ions decreases

(B) concentration of H+ ions increases

(D) concentration of H+ and OH− ions equalises

Ans: (B) concentration of H+ ions increases

15. Electronic configurations of the elements A, B and C respectively are 2, 8, 2 ; 2, 8 and 2, 8, 7. Among these the elements that can react each other to form an ionic compound are

(A) Elements A and B (B) Elements B and C

Ans: (C) Elements A and C

VII. Answer the following questions : 3 × 1 = 3

16. What is galvanisation?

Ans: It is the process of coating of zinc on iron or steel to prevent rusting

17. Hydrogen gas is not evolved when a metal reacts with nitric acid. Why?

Ans: Nitric acid is a strong oxidizing agent that oxidizes the hydrogen gas to water.

18. Name the organic compounds that have below given structural formula :

Ans:

i) Formaldehyde

ii) Bromo ethane

VIII. Answer the following questions : 3 × 2 = 6

19. What is the reason for tooth decay? Explain. How can this be prevented?

Ans:

★ Bacteria in your mouth that metabolize sugars and starches from food and produces acids which cause tooth decay.

★ Use toothpaste that contains base which neutralize the acid

20. On heating crystals of copper sulphate its blue colour disappears. Give the reason for this change. How can the blue colour of copper sulphate be restored?

Ans:

★ Because the water molecules are lost on heating.

★ Add water to the white powder, blue colour reappear.

21. Write the electron dot structure of the following molecules : i) Hydrogen ii) Ethane.

Ans:

ii)

IX. Answer the following questions : 3 × 3 = 9

22. a) Balance the following chemical equations :

i) NaOH + H2SO4 → Na2SO4 + H2O

ii) K + O2 → K2O

b) ZnO + C → Zn + CO Identify the reactant that is oxidised and the reactant that is reduced in this reaction.

Ans:

i) 2NaOH + H2SO4 → Na2SO4 + 2H2O

ii) 2K + O2 → K2O

★ Oxidized reactant - C,

★ Reduced reactant - ZnO

Mention the meaning of following chemical reactions :

i) Thermal decomposition ii) Displacement reaction iii) Rancidity.

Ans:

i) Breaks down a single substance into two or more products when heated.

ii) More reactive element replaces a less reactive element in a compound.

iii) The oxidation of oils and fats in foods resulting into a bad smell and bad taste is called rancidity.

23. What is neutralization reaction ? How can sodium chloride be obtained by neutralisation method ? Write the balanced chemical equation for this reaction.

Ans:

★ Chemical reaction between an acid and a base that produces water and salt.

★ Hydrochloric acid and sodium hydroxide react to form sodium chloride.

★ HCl + NaOH → NaCl + H2O.

24. Draw the diagram of the apparatus arranged to show the action of steam on metal and label the following parts :

i) Delivery tube ii) Hydrogen gas

Ans:

X. Answer the following question : 1 × 4 = 4

25. a) Explain the cleansing action of soaps.

b) What is esterification ? Mention the uses of esters.

Ans:

★ The molecules of soap are sodium or potassium salts of long chain carboxylic acids.

★ The ionic end of soap interacts with water while the carbon chain interacts with oil.

★ The soap molecules thus form structure called micells. This forms an emulsion in water.

★ The soap micelles thus helps in pulling out the dirt in water and we can wash our clothes clean.

★ Alcohol and an organic acid combine to form an ester and water is called esterification.

Uses:

★ Flavoring agents

★ Perfumes and cosmetics

a) List any two differences between saturated and unsaturated carbon compounds.

b) What are structural isomers? Write the structures of butane isomers.

Ans:

Saturated carbon compounds.	Unsaturated carbon compounds.
Single bond between carbon atoms Less reactive Give clean flame Ex: Alkanes, Cycloalkanes	double or triple bond between carbon atoms More reactive Give yellow/black flame Ex: Alkenes, Alkynes

b) Same molecular formula but different structure is called structural isomers.

PART – C ( BIOLOGY )

XI. MCQ 3 × 1 = 3

26. Rhizopus : Spore formation :: Spirogyra :

(A) Fragmentation (B) Regeneration

Ans: (A) Fragmentation

27. Osmotic pressure in plants is necessary for

(A) the transportation of materials to the tissues that have low pressure

(B) the transportation of water from root to shoot

(D) the elimination of the difference in the concentration of ions between root and soil

Ans: (A) the transportation of materials to the tissues that have low pressure

28. The correct pathway of movement of male gamete in a flower is

(A) Ovary → Stigma → Pollen tube

(B) Stigma → Pollen tube → Ovary

(D) Style → Pollen tube → Ovary

Ans: (B) Stigma → Pollen tube → Ovary

XII. Answer the following questions : 3 × 1 = 3

29. Surgical method of contraception is better than oral method of contraception. Why?

Ans: Because it is a permanent method and no side effect.

30. What is ozone? What is the advantage of this layer to the organisms on the earth?

Ans:

★ Ozone (O3) is a molecule made of three oxygen atoms.

★ It Prevent entry of UV radiation and reduce the risk of skin cancer in human.

31. Exact copies of the progenies of the parent organism cannot be produced in sexual reproduction. Justify.

Ans: Because both parents contribute genetic material to the offspring.

XIII. Answer the following questions : 2 × 2 = 4

32. What are biodegradable and non-biodegrable substances? Give an example for each.

Ans:.

★ The substances which are break down by microorganisms are called Biodegradable substances

★ The substances which are do not break down by microorganisms are called non- Biodegradable substances.

Examples

★ Biodegradable : plant and animal waste

★ Non - biodegradable: plastics, glass, metals

How do energy and harmful materials travel in the trophic levels of a food chain?

Ans:

★ Energy travels upwards through trophic levels from producers (plants) to consumers,

★ Energy decreasing at each level due to loss as heat due to metabolic processes.

★ Harmful materials tend to accumulate and concentrate at higher trophic levels through a process called biomagnification.

33. Draw a diagram to show the structure of nephron and label Bowman’s cup.

Ans:

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

34. How are the complex molecules of food converted into the simplest forms in the small intestine of human digestive canal?

Ans:

★ It receives pancreatic juice and bile juice. Bile juice makes the food alkaline.

★ Bile salts emulsify the fats in the small intestine.

★ Trypsin present in pancreatic juice helps to digest the proteins.

★ Lypase breaks down the emulsified fats.

★ Enzymes present in the small intestinal juice convert proteins into amino acids, complex carbohydrates into glucose and fats into fatty acids and glycerol.

What is the role of arteries and capillaries in the circulation of blood in our body? Mention the importance of double circulation.

Ans:

★ Arteries carry oxygenated blood away from the heart to various organs of the body

★ Capillaries helps to exchange of material between the blood and surrounding

importance of double circulation.

★ it ensures a complete separation of oxygenated and deoxygenated blood,

★ it enables them to maintain a constant body temperature by supplying sufficient oxygen.

35. Draw the diagram of the human brain. Label the following parts : i) Pons ii) Cerebellum.

Ans:

36. Roles of the ‘uterus’ and ‘placenta’ are complementary to each other in the development of a child. How ? Explain.

Ans:

★ The uterus provides a nourishing environment for the fertilized egg to implant and grow.

★ Placenta embedded in the uterine wall which provides oxygen and nutrients to a developing fetus, and removes waste from its blood.

★ The uterus and placenta have complementary roles in supporting fetal development, regulating growth, and preparing for birth.

“Position of the testis in the human male reproductive system and the role of prostate gland are complementary to each other.” How? Explain.

Ans:

★The position of the testes outside the body in the scrotum.

★ Prostate gland which adds fluid to the semen that helps nourish and protect the sperm.

★ The testes produce the sperm while the prostate provides the optimal environment for their survival and mobility.

XV. Answer the following question : 1 × 4 = 4

37. Red flowering tall pea plant ( TtRr ) is hybridised with white flowering, dwarf pea plant ( ttrr ). Draw a checker board to show the result of plants obtained in F2 generation. What is the phenotypic ratio of the plants produced in F2 generation?

Ans: