MG SCHOOL EDUCATION: KREIS Science Model Question Paper

Key Answer

KARNATAKA RESIDENTIAL EDUCATIONAL INSTITUTIONS SOCEITY,

BANGALURU

Model Question Paper – 3 2020-21

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/incomplete statements. Choose the correct alternative and write the complete answer along with its letter of alphabet. 3 x 1 = 3

1. The commercial unit of electric charges is :

a. joule b. watt c. ampere d. Kilo watt hour

Ans: d. Kilo watt hour

2. The concave lens produces a magnification of +3. The object is placed :

a. at the focus b. between the focus and pole

c. between the focus and center of curvature d. beyond the center of curvature

Ans: b. between the focus and pole

3. The pattern of the magnetic field produced by the straight current carrying wire is:

a. in the direction opposite to the wire b. in the direction parallel to the wire

c. concentric circles around the wire d. in the same direction of current

Ans: c. concentric circles around the wire

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

4. if the magnification of an object of 3m is 5, find the height of the image.

Ans:

Height of object = h = 3 m
Height of image = h' = ?
Magnification = m = 5
we know that,
m = h'/h
5 = h'/3
h' = 15m
Height of image is 15 metres

5. A ray of light bends when it travels from one medium into another. Why?

Ans:

A ray of light bends while going from one medium to another because of the phenomena of refraction. When the ray of light travels from one medium to another as the velocity of the light ray will either increase or decrease depending on the optical density of the material.

III. Answer the following questions. 3 x 2 = 6

6. Draw the ray diagram to show the formation of image by a convex lens when the object is kept at 2F.

7. a. Name the material used for making the filament of a bulb.

Ans: Tungsten is used for making filament of an electric bulb

b. Name two gases which are usually filled to prolong the life of filament of bulb.

Ans: Electric bulbs are usually filled with chemically inactive gases like nitrogen and argon

8. List two differences between ‘voltmeter and ammeter’.

Ans:

Ammeter	Voltmeter
It is used to measure current	It is used to measure voltage across two points
It is denoted by a symbol A	It is denoted by a symbol V

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

9. Draw the diagram of an electric motor and Label the following parts. (i) Split rings (ii) Carbon brushes

10. A Concave lens has focal length of 20cm. At what distance from the lens a 5cm tall object be placed so that it forms an image at 15cm from the lens? Also calculate the size of the image formed.

An object 5cm in length is held 25cm away from a converging lens of focal length 10cm. find the position, size and nature of the image formed.

Given that

The height of object = 5cm

Position of object, u = – 25cm

The focal length of the lens, f = 10 cm

We need to find

The position of the image, v =?

We know that

1/v – 1/u = 1/f

Substituting the known values in the above equation we get,

1/v + 1/25 = 1/10

=> 1/v = 1/10 – 1/25

=> 1/v = (5 – 2)/50

Hence, 1/v = 3/50

So, v= 50/3 = 16.66 cm

Therefore, the distance of the image is 16.66 cm on the opposite side of the lens.

Now, we know that

Magnification = v/u

Hence, m = 16.66/-25 = -0.66

Also, we know that

m= height of image/height of the object

Or, -0.66 = height of image / 5 cm

Hence, height of image = -3.3 cm

The negative sign of the height of the image depicts that an inverted image is formed.

So, the position of image = At 16.66 cm on the opposite side of the lens

Size of image = – 3.3 cm at the opposite side of the lens

Nature of image – Real and inverted

11. a. Why is thermal power plants setup near coal or oil fields?

b. List any four characteristic of good sources of energy

Ans:

a. Thermal power plants required coal and oil, which they burn to generate the required power. Since transmission of electricity is more efficient than transporting coal or oil over the same distance, So thermal power plants are generally located near coal fields.

It should provide large amount of energy per unit mass .
It should be easily accessible .
It should provide energy for maximum period of time and it should be renewable.
It should be sustainable and safe for surrounding individual.

V. Answer the following questions. 2 x 4 = 8

12. a. State the rule to determine the direction of a

(i) Magnetic field produced around straight conductor – carrying current.

(ii) Force experienced by a current carrying straight conductor placed in a magnetic field which is perpendicular to it.

(iii) Current induced in a circuit by changing magnetic flux due to motion of a conductor.

Ans:

b. Why is a fuse wire made of tin – lead alloy and not copper?

Ans:

A fuse wire is made of tin alloy because it has low melting point, so that it may melt easily, whereas a copper wire cannot be used as a fuse wire because it has a high melting point due to which it will not melt easily when a short circuit takes place.

a. What precautions should be taken to avoid the over loading of domestic electric circuits?

b. How does a solenoid behave like a magnet? Can you determine north and south poles of a current carrying solenoid using a bar magnet? Explain.

Ans:

· Should not connect too many appliances to a single socket.

· Too many appliances should not be used at the same time.

· Faulty appliances should not be connected to the circuit.

· The fuse should be connected to the circuit in series.

13. a) List the factors on which the resistance of a conductor in the shape of a wire depends.

Ans:

The cross-sectional area of the conductor.
Length of the conductor.

b) Differentiate between electric energy and electric power (any two).

Ans:

Electrical energy defines the energy generated due to the movement of charge carriers in a conductor. While electrical power specifies the rate of consumption of electrical energy by a device. The SI unit of electrical energy is Joules. But electrical power is measured in Watts (or KWh).

PART B: CHEMISTRY

VI. Four alternatives are given for each of the following questions/incomplete statements. Choose the correct alternative and write the complete answer along with its letter of alphabet. 3 x 1 = 3

14. Silver article become block on prolonged exposure to air. This is due to the formation of :

a. Ag₂CO₃ b. Ag₂O c. Ag₂S d. AgNO₃

Ans: c. Ag₂S

15. Which of the following will undergo addition reaction?

a. C3H8 b. C5H12 c. CH4 d. C4H8

Ans: d. C4H8

16. In the Mendeleev’s periodic table gaps were left for the element to be discovered later. Which of the following element found a place in the periodic table later?

a. Germanium b. Silicon c. Nitrogen d. Argon

Ans: a. Germanium

VII. Answer the following questions. 3 x 1 = 3

17. What change will you observe, if you test soap with litmus paper (red or blue).

Ans:

When soap is dissolved in water, the solution is alkaline in nature due to the formation of alkali NaOH or KOH. The solution changes the colour of red litmus to blue.

18. Lithium, Sodium and potassium forms a Dobereiner’s triads. The atomic masses of lithium and potassium are 7 and 39 respectively. Predict the atomic mass of Sodium.

Ans:

19. Aluminum is a highly reactive metal, yet it is used to make utensils for cooking. Give reason.

Ans:

This is because aluminium reacts with oxygen present in air to form a thin layer of aluminium oxide. This oxide layer is very stable and prevents further reaction of aluminium with oxygen.

VIII. Answer the following questions. 3 x 2 = 6 20. Write the Structural formula and IUPAC name of the following compounds. i) A carboxylic acid with five C- atoms ii) An alcohol having two C- atoms.

VIII. Answer the following questions. 3 x 2 = 6

20. Write the Structural formula and IUPAC name of the following compounds. i) A carboxylic acid with five C- atoms ii) An alcohol having two C- atoms.

Ans:

I. Structural formula of a carboxylic acid with five C- atoms

IUPAC Name: Pentanoic acid

I. Structural formula of an alcohol having two C- atoms.

IUPAC Name: ethanol

Complete the following equation for ‘X’ and identify ‘Y’

X + acidified K₂Cr₂O₇ (heat) -------> Y

Ans:

IX. Answer the following questions. 3 x 3 = 9

23. The position of three elements X , Y and Z in the periodic table is given below

Answer the following questions with suitable reason.

i) Out of ‘Y’ and ‘Z’ which element will be more metallic?

ii) Will atomic size of ‘Z’ be smaller or larger than that of ‘X’?

iii) Out of ‘Y’ and ‘Z’ which element will be more electro negativity?

Ans:

i) Out of ‘Y’ and ‘Z’, Z element will be more metallic

ii) atomic size of ‘Z’ be smaller than that of ‘X

iii) Out of ‘Y’ and ‘Z’, Y element will be more electro negativity

24. Explain the mechanism of cleaning action of soap.

Ans:

Soaps and detergents contain 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.

Differentiate between the saturated and unsaturated hydrocarbons.

Ans:

Saturated hydrocarbons:

Saturated hydrocarbons containing only single covalent bonds. These are also known as alkanes.
These compounds are less reactive.
Saturated hydrocarbons burns with blue flame

Unsaturated hydrocarbons:

Unsaturated hydrocarbons are the straight chain compounds containing double or triple covalent bonds are known as alkenes and alkynes.
These compounds are more reactive.
Unsaturated hydrocarbons burn with sooty flame.

25. Draw the diagram to show the reaction of zinc granules with dilute sulphuric acid and testing hydrogen gas by burning. Label the following parts a) Zinc granules b) Soap solution

X. Answer the following question. 1 x 4 = 4

26. a) Write the four properties of Ionic compounds.

Ans:

They have high melting points and high boiling points.
They're hard and brittle.
They conduct electricity when they are dissolved in water.
They're good insulators.

b) What is thermite reaction? Write its balanced chemical question.

Ans:

The thermite reaction is an exothermic reaction between the metal and metal oxide. For example the reaction between the aluminium with the metal oxides, where aluminium acts as a reducing agent. The aluminium reduces the metal oxide most probably an iron (lll) oxide to produce ferrous and aluminium oxide. During the reaction, large amount of energy is released.

Fe2O₃ + 2Al → 2Fe + Al2O₃ + heat

PART C: BIOLOGY

XI. Four alternatives are given for each of the following questions/ incomplete statements. Choose the correct alternative and write the complete answer along with its letter of alphabet. 2X1=2

27. Government launched the “Ganga action plan” (GAP) in 1985. The main purpose of this project was to

a) utilize the river water for irrigation purpose

b) improve the quality of water

c) promote the quality of aquatic life like Fish

d) build new dams over the Ganga river

Ans: b) improve the quality of water

28. Which of the following radiation is responsible for the conversion of atmospheric oxygen to ozone?

a) gamma radiation b) cosmic radiation

c) infrared radiation d) ultra violate radiation

Ans: d) ultra violate radiation

XII. Answer the following questions. 3x1=3

29. Why is ozone layer getting depleted at the higher level of the atmosphere?

Ans:

Ozone layer is getting depleted at the higher levels of the atmosphere due to effect of chlorofluorocarbons CFCs which are used as refrigerants and in fire extinguishers.

30. Suggest two consequences due to the loss of biodiversity.

Ans:

(a) decline in plant production,
(b) lowered resistance to environmental perturbations such as drought

31. Give an example where sex is determined by environmental factor.

Ans:

Incubation temperature determines sex in some of the animals like crocodiles, where the high temperature incubates maleness and low temperature produces femaleness.

XIII. Answer the following questions. 2x2=4

32. Draw the diagram showing the germination of pollen on stigma and label ‘Pollen tube’.

33. Write the flow chart showing ‘Reflex arc’

Write the name and functions of two parts of ‘human hind brain’.

Ans:

Two main parts of hind-brain are — Medulla and Cerebellum.

Their functions are:

Medulla : Involuntary actions such as blood pressure salivation and vomiting.

Cerebellum : It is responsible for precision of voluntary actions and maintaining the posture and balance of the body.

XIV. Answer the following questions. 3x3=9

34. How is sex of a child determined 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.

What is speciation? List four factors that could be lead to speciation.

Ans:

Speciation is an process of forming a new species from other existing species.

Factors that lead to speciation:

· Geographical isolation.

· Genetic drift.

· Natural selection.

· Reproductive isolation.

35. What is placenta? Describe its structure, state its two function in pregnant human female.

Ans:

Placenta is a special tissue connection between embryo and uterine wall. It acts as an endocrine gland.

Placenta is a disc like structure that forms a connection between the embryo and the uterine wall. It possesses villi that increase the surface area for absorption of nutrients.

Role of placenta:

Facilitates passage of nutrition and oxygen to embryo from mother through blood.
Waste substances produced by embryo are removed through placenta into mother’s blood.

Why does menstruation occurs?

Ans:

The ovary releases one egg every month and the uterus prepares for the implantation of the zygote by thickening its walls. The thick wall is not necessary if the egg is not implanted. Thus , the uterine lining slowly breaks down and comes out through the vagina as blood and mucus. This cycle takes place roughly every month and is known as menstruation and lasts for about two to eight days.

36. A blue color flower plant denoted by ‘BB’ is cross bred with that of white colour flower plant denoted by ‘bb’

a) State the colour of flower you would expect in their ‘F1’generation plant

b) What must be the percentage of white flower plants in ‘F2’ if flowers of ‘F1’ plants are self pollinated?

c) Write the expected ratio of the genotypes ‘BB’ and ‘Bb’ in the F2 progeny.

Ans:

a) the colour of flower you would expect in their ‘F1’generation plant is blue

b) be the percentage of white flower plants in ‘F2’ if flowers of ‘F1’ plants are self pollinated is 25%

c) the expected ratio of the genotypes ‘BB’ and ‘Bb’ in the F2 progeny is 1:2

XV. Answer the following questions. 1x4=4

37. Draw the diagram showing the longitudinal section of the human brain. Label the following parts. a) cerebrum b) Medulla

XVI. Answer the following questions. 1x5=5

38) a) Write the characteristics and functions of three types blood vessels.

Arteries:

Arteries are the main blood vessels that carry and transport oxygenated blood or oxygen-rich blood from the heart to other parts of the body. They are the strongest blood vessels with thicker walls and are muscular in nature.

Veins:

Veins are thin, tube-like elastic blood vessels and carry impure or deoxygenated blood from all parts of the body to heart.

Capillaries:

Short and tiny blood vessels and bring about the exchange of substances between blood and tissues.

b) What is translocation? How does it take place in plants?

Ans:

Transport of soluble product of photosynthesis or food from leaves to other parts of plants is called translocation.

For translocation, food molecules enter the part of the phloem called the sieve tubes where they can be transported upwards or downwards to all the parts of the plant including roots.

Translocation is achieved by utilising energy from the ATP that provides osmotic pressure required for upward and downward movement of food.