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## Tamil Nadu Samacheer Kalvi 10th Science Model Question Paper 2 English Medium

General Instructions:

1. The question paper comprises of four parts
2. You are to attempt all the questions in each part. An internal choice of questions is provided wherever applicable.
3. All questions of Part I, II, III and IV are to be attempted separately.
4. Question numbers 1 to 12 in Part I are Multiple Choice Questions of one mark each.
These are to be answered by writing the correct answer along with the corresponding option code.
5. Question numbers 13 to 22 in Part II are of two marks each. Any one question should be answered compulsorily.
6. Question numbers 23 to 32 in Part III are of four marks each. Any one question should be answered compulsorily.
7. Question numbers 33 to 35 in Part IV are of seven marks each. Draw diagrams wherever necessary.

Time: 3 Hours
Maximum Marks: 75

Part – I

(i) Answer all the questions.  [12 × 1 = 12]
(ii) Choose the most suitable answer and write the code with the corresponding answer.

Question 1.
To produce a displacement _________ is required.
(a) Acceleration
(b) Force
(c) Velocity
(d) Momentum
(b) Force

Question 2.
The refractive index of a transparent medium is always greater than_________.
(a) two
(b) three
(c) one
(d) four
(c) one Question 3.
Velocity of sound in a gaseous medium is 330 ms-1. If the pressure is increased by 4 times without causing a change in the temperature, the velocity of sound in the gas is _________.
(a) 330 ms-1
(b) 660 ms-1
(c) 156 ms-1
(d) 990 ms-1
(a) 330 ms-1

Question 4.
Neon shows zero electron affinity due to _________.
(a) stable arrangement of neutrons
(b) stable configuration of electrons
(c) reduced size
(d) increased density
(b) stable configuration of electrons

Question 5.
A solution is a _________ mixture.
(a) homogeneous
(b) homogeneous and heterogeneous
(c) heterogeneous
(d) Non homogeneous
(a) homogeneous

Question 6.
Powdered CaCO3 reacts more rapidly than flaky CaCO3 because of _________.
(a) large surface area
(b) high pressure
(c) high concentration
(d) high temperature
(a) large surface area Question 7.
A patient with blood group O was injured in an accident and has blood loss. Which blood group the doctor should effectively use for transfusion in this condition?
(a) A group
(b) B group
(c) O group
(d) AB group
(c) O group

Question 8.
_________ is the ATP factory of the cell.
(a) Mitochondria
(b) Nucleus
(c) Ribosomes
(d) Chloroplast
(a) Mitochondria

Question 9.
The Anemophilous flowers have _________.
(a) Sessile stigma
(b) Small smooth stigma
(c) Coloured flower
(d) Large feathery stigma
(d) Large feathery stigma

Question 10.
A person who met with an accident lost control of body temperature, water balance and hunger. Which of the following part of brain is supposed to be damaged?
(a) Hypothalamus
(b) Pons
(c) Cerebrum
(d) Medulla oblongata
(a) Hypothalamus

Question 11.
_________ is the raw material which plays an important role in evolution.
(a) Fossilization
(b) Variation
(c) Preservation
(d) Sedimentation
(b) Variation Question 12.
The centromere is found at the centre of the _________ chromosome.
(a) Telocentric
(b) Metacentric
(c) Sub-metacentric
(d) Acrocentric
(b) Metacentric

Part – II

Answer any seven questions. (Q.No: 22 is compulsory) [7 × 2 = 14]

Question 13.
Define dispersion of light.
When a beam of white light or composite light is refracted through any transparent media such as glass or water, it is split into its component colours. This phenomenon is called as ‘dispersion of light’.

Question 14.
What is meant by equilibrant?
A system can be brought to equilibrium by applying another force, which is equal to the resultant force in magnitude, but opposite in direction. Such force is called as ‘Equilibrant’. Question 15.
Why does an empty vessel produce more sound than a filled one?
The intensity of sound is directly proportional to the square of amplitude of vibration. I ∝ A2 since, the amplitude of vibration of air molecules (empty vessel) is greater than liquid molecules (filled vessel), therefore empty vessel produces louder sound than the filled vessel.

Question 16.
Differentiate ore and mineral.

 Ore Mineral 1. A mineral from which a metal can be economically extracted. 1. A mineral may be a single compound or complex mixture of various compounds of metals found in the earth. 2. All ores are minerals. 2. All minerals are not ores. 3. Eg. Bauxite is an ore of aluminium. 3. Clay is a mineral.

Question 17.
How do detergents cause water pollution?
Some detergents having a branched hydrocarbon chain are not fully biodegradable by micro organisms present in water. So, they cause water pollution.

Question 18.
Define reflex arc.
The pathway taken by the nerve impulse to accomplish reflex action is called Reflex arc. Question 19.
The complete events of cardiac cycle last for 0.8 sec. What is the timing for each event?
The events during a single cardiac cycle involves

• Atrial Systole – Contraction of auricles – (0.1 sec)
• Ventricular Systole – Contraction of ventricles – (0.3 sec)
• Ventricular diastole – Relaxation of Ventricles – (0.4 sec)

Question 20.
What will you do to prevent leaf fall and fruit drop in plants?
Treating plants with auxin will prevent leaf fall and fruit drop. Auxin prevent the formation of abscission layer in plants.

Question 21.
Draw and label the structure of the ovule. Question 22.
Calculate the momentum of a toy car of mass 200g moving with a speed of 5 m/s.
Mass of the toy car (m) = 200 g = 0.2 kg
Speed (v) = 5 m/s
Momentum (p) = m × v
= 0.2 × 5 = 1 kg m/s

Part – III

Answer any seven questions (Q.No: 32 is compulsory) [7 × 4 = 28]

Question 23.
Explain the process of controlled and uncontrolled chain reactions.
Controlled chain reaction:

• In the controlled chain reaction the number of neutrons released is maintained to be one. This is achieved by absorbing the extra neutrons with a neutron absorber leaving only one neutron to produce further fission.
• Thus, the reaction is sustained in a controlled manner. The energy released due to a controlled chain reaction can be utilized for constructive purposes.
• Controlled chain reaction is used in a nuclear reactor to produce energy in a sustained and controlled manner.

Uncontrolled chain reaction:

• In the uncontrolled chain reaction the number of neutrons multiplies indefinitely and causes fission in a large amount of the fissile material.
• This results in the release of a huge amount of energy within a fraction of a second.
• This kind of chain reaction is used in the atom bomb to produce an explosion. Question 24.
What are the factors that affect the speed of sound in gases?
Effect of density: The velocity of sound in a gas is inversely proportional to the square root of the density of the gas. Hence, the velocity decreases as the density of the gas increases.
v ∝ $$\sqrt{\frac{1}{d}}$$

Effect of temperature:
(i) The velocity of sound in a gas is directly proportional to the square root of its temperature.
(ii) The velocity of sound in a gas increases with the increase in temperature, v ∝ $$\sqrt{\mathrm{T}}$$ Velocity at temperature T is given by the following equation:
vT = (v0 + 0.61 T) ms-1

Here, v0 is the velocity of sound in the gas at 0° C. For air, v0 = 331 ms-1. Hence, the velocity of sound changes by 0.61 ms-1, when the temperature changes by one degree Celsius.

Effect of relative humidity: When humidity increases, the speed of sound increases. That is why we can hear sound from long distance clearly during rainy seasons.

Question 25.
(i) Classify the types of force based on their application.
Based on the direction in which the forces act, they can be classified into two types as:

1. Like parallel forces
2. Unlike parallel forces.

1. Like parallel forces:
Two or more forces of equal or unequal magnitude acting along the same direction, parallel to each other are called like parallel forces.

2. Unlike parallel forces:
If two or more equal forces or unequal forces act along opposite directions parallel to each other, then they are called unlike parallel forces.

(ii) Which instrument is used to measure the electric current? How should it be connected in a circuit?

• Ammeter is used to measure the current.
• An Ammeter is connected in series with the circuit.
• The Ammeter is a low impedance device connecting it in parallel with the circuit would cause a short circuit, damaging the Ammeter or the circuit. Question 26.
Write the characteristics of organic compounds.

• Organic compounds have a high molecular weight and a complex structure.
• They are mostly insoluble in water, but soluble in organic solvents such as ether, carbon tetra chloride, toluene etc.
• They are highly inflammable in nature.
• Organic compounds are less reactive compared to inorganic compounds. Hence, the reactions involving organic compounds proceed at slower rates.
• Mostly organic compounds form covalent bonds in nature.
• They have lower melting point and boiling point, when compared to inorganic compounds
• They exhibit the phenomenon of isomerism, in which a single molecular formula represents several organic compounds that differ in their physical and chemical properties.
• They are volatile in nature.
• Organic compounds can be prepared in the laboratory.

Question 27.
The electronic configuration of metal A is 2, 8, 18, 1.
The metal A when exposed to air and moisture forms B a green layered compound. A with con. H2SO4 forms C and D along with water. D is a gaseous compound. Find A,B,C and D.
(i) The electronic configuration of metal (A) is 2, 8, 18, 1.  ∴A is copper (Z = 29)
(ii) (A) Copper exposed to air and moisture forms green layered compound (B) that is copper carbonate. (iii) Copper (A) reacts with con.H2SO4 to give copper sulphate (C) and Sulphur dioxide (D). A Copper Cu B Copper carbonate CuCO3. Cu(OH)2 C Copper sulphate CuSO4 D Sulphur dioxide SO2

Question 28.
A pure tall plant (TT) is crossed with pure dwarf plant (tt), what would be the F1 and F2 generations?
In a monohybrid cross, if a pure tall plant (TT) is crossed with pure dwarf plant (tt). All plants were tall (Tt) in F1 generation. F1 → Tt Tt Tt Tt (Tall heterozygous)
Ratio : 3 : 1
During the selling of F1 generation 3 different types of plants were produced. Tall Homozygous – TT (Pure) – 1
Tall Heterozygous – Tt – 2
Dwarf Homozygous – tt – 1
Ratio : 1 : 2 : 1 Question 29.
(i) What are the external and internal factors affecting photosynthesis
(a) External Factors:

• Light
• Carbon dioxide
• Temperature
• Water
• Mineral elements

(b) Internal Factors:

• Pigments
• Leaf age
• Accumulation of carbohydrates
• Hormones

(ii) Why is vegetative propagation practiced for growing some type of plants?
Vegetative propagation is the only method of multiplication in plants like banana, seedless grapes and orange that have lost their capacity to produce seeds through sexual reproduction and vegetative propagation helps us to introduce plants in new areas where seed germination fails to produce plants.

Question 30.
(i) Solar energy is a renewable energy. How?
Solar energy is renewable, free source of energy, that is sustainable and totally inexhaustible.

(ii) How is the circulatory system designed in leech to compensate the heart structure?
The circulation in Leech is Haemocoelic system. There are no true blood vessels. The blood vessels are replaced by channels called Haemocoelic channels or canals filled with blood like fluid. The coelomic fluid contain Haemoglobin. There are four longitudinal channels. One channel lies above (dorsal) to the Alimentary canal, one below (ventral) to the Alimentary canal.

The other two channels lie on either (lateral) side of the Alimentary canal, which serves as a heart and have inner valves. All the four channels are connected together posteriorly in the 26th segment. Thus the circulatory system is designed in Leech to compensate the heart structure.

Question 31.
(a) What are the contributing factors for obesity?
Obesity is due to genetic factors, physical inactivity, overeating and endocrine factors.

(b) State the importance of biofertiliser.

• Biofertilisers are easy to produce in abundance and are available at low X cost to the marginal farmer.
• It increases the soil fertility without causing any damage to the soil. E.g: Rhizobium, Azospirillium, Azotobacter. Question 32.
(i) Draw a ray diagram of formation of images by the convex lens.
Ray diagram for object placed between F and 2F (ii) The hydroxide ion concentration of a solution is 1 × 1011 m. What is the pH of the solution?
[OH] = 1 × 10-11m
pOH = -log10[OH] = – log10[10-11]
= -[-11 × log10 10]
= -(-11) = 11
pH + pOH = 14
pH = 14 – pOH
pH = 14 – 11 = 3

Part – IV

(1) Answer all the questions. [3 × 7 = 21]
(2) Each question carries seven marks.
(3) Draw diagram wherever necessary.

Question 33.
(a) (i) Define One roentgen.
One roentgen is defined as the quantity of radioactive substance which produces a charge of 2.58 x 10-4 coulomb in 1 kg of air under standard conditions of pressure, temperature and humidity.

(ii) What is a nuclear reactor? Explain its essential parts with their functions.
A Nuclear reactor is a device in which the nuclear fission reaction takes place in a self-sustained and controlled manner to produce electricity. Components of a Nuclear reactor:
The essential components of a nuclear reactor are

1. fuel
2. moderator
3. control rod
4. coolant and
5. protection wall.

(1) Fuel: A fissile material is used as the fuel. The commonly used fuel material is uranium.
(2) Moderator: A moderator is used to slow down the high energy neutrons to provide slow neutrons. Graphite and heavy water are the commonly used moderators.
(3) Control rod: Control rods are used to control the number of neutrons in order to have sustained chain reaction. Mostly boron or cadmium rods are used as control rods. They absorb the neutrons.
(4) Coolant: A coolant is used to remove the heat produced in the reactor core, to produce steam. This steam is used to run a turbine in order to produce electricity. Water, air and helium are some of the coolants.
(5) Protection wall: A thick concrete lead wall is built around the nuclear reactor in order to prevent the harmful radiations from escaping into the environment.

[OR]

(b) (i) An object is placed at a distance 20 cm from a convex lens of focal length 10 cm.
Find the image distance and nature of the image.
u = -20 cm
f = 10 cm  Nature of the image real enlarged and inverted image.

(ii) A ball of mass 1 kg moving with a speed of 10 ms-1 rebounds after a perfect elastic collision with the floor. Calculate the change in linear momentum of the ball.
Given mass = 1 kg, speed =10 ms-1
∴ Initial momentum = mu = 1 × 10 = 10 kg ms-1
Final momentum = mv = -10 kg ms-1
Change in momentum = final momentum – initial momentum
= mv – mu
= -10 -10
Change in momentum = -20 kg ms-1 Question 34.
(a) (i) Calculate the number of moles in 12.046 × 1023 atom of copper.
12.046 × 1023 atoms of copper
6.023 × 1023 atoms of copper = 1 mole (ii) How many grams are there in two moles of H2O
No. of moles = $$\frac{\text { Mass }}{\text { Molar mass }}$$
Mass = No. of moles x molar mass
Molar mass of H2O = (2 × 1) + 16 = 18
Mass = 2 × 18 = 36 g

(iii) In magnesium sulphite, the ration by mass of Mg and S is 3 :4. What is the ratio of the number of Mg and S atoms?
Formula of magnesium sulphide = MgS
Ratio by mass Mg and S = 3 : 4 (b) (i) Explain the mechanism of cleansing action of soap.
A soap molecule contains two chemically distinct parts that interact differently with water. It has one polar end, which is a short head with a carboxylate group (- COONa) and one non polar end having the long tail made of the hydrocarbon chain.

The polar end is hydrophilic (Water loving) in nature and this end is attracted towards water. The non-polar end is hydrophobic (Water hating) in nature and it is attracted towards dirt or oil on the cloth, but not attracted towards water. Thus, the hydrophobic part of the soap molecule traps the dirt and the hydrophilic part makes the entire molecule soluble in water.

When a soap or detergent is dissolved in water, the molecules join together as clusters called ‘micelles’. Their long hydrocarbon chains attach themselves to the oil and dirt. The dirt is thus surrounded by the non-polar end of the soap molecules. The charged carboxylate end of the soap molecules makes the micelles soluble in water. Thus, the dirt is washed away with the soap.

(ii) Differentiate soaps and detergents.
Soaps:

• It is a sodium salt of long chain fatty acids.
• Its effectiveness is reduced when used in hard water.

Detergents:

• It is a sodium salt of sulphonic acids.
• It is effective even in hard water.
• Most of the detergents are non-biodegradable. Question 35.
(a) (i) Explain the functions of the thyroid hormones?
(ii) How are stem cells useful in regenerative process?
(iii) What is palaeontology?
(i) Functions of the thyroid hormone:

• Increases oxygen consumption in tissues.
• Production of energy by maintaining the Basal Metabolic Rate (BMR) of the body.
• Helps to maintain normal body temperature.
• Controls growth of the body, bone formation and development of gonads.
• Essential for normal physical, mental and personality development. Hence also known as personality hormone.

(ii) Stem cells useful in regenerative process:
Sometimes cells, tissues and organs in the body may be permanently damaged or lost due to genetic condition or disease or injury.

In such situations, stem cells are used for the treatment of diseases, which is called stem cell therapy.
In treating neurodegenerative disorders like Parkinson’s disease and Alzheimer’s disease neuronal stem cells can be used to replace the damaged or lost neurons.

(iii) The study of fossils is known as Palaeontology.

[OR]

(b) Explain with an example the inheritance of dihybrid cross. How is it different from monohybrid cross?
The dihybrid cross involves the inheritance of two pairs of contrast characteristics, round – yellow seeds and wrinkled – green seeds.

When pea plants having round- yellow seeds cross bred with pea plant having wrinkled – green seeds, in the first generation (F1), only round yellow seeds were produced.

No wrinkled – green seeds were obtained. Round yellow colour seeds were dominant and wrinkled-green seeds were recessive.

When round-yellow seeds were cross bred by self-pollination, four types of seeds having different combinations of shape and colour were obtained in F2 generation. They were
round yellow, round green
wrinkled yellow, wrinkled green
The phenotypic ratio in F2 generation is 9 : 3 : 3 : 1
i.e. 9 – Yellow, round
3 – Yellow, wrinkled
3 – Green, round
1 – Green, wrinkled  Monohybrid cross:

• Monohybrid cross is a genetic cross that involves a singles pair of genes which is responsible for one trait
• Monohybrid ratio in F2 generation is 3 : 1

Dihybrid cross:

• Dihybrid cross is a genetic cross that involves two pairs of genes which is responsible for two trait
• Dihybrid ratio in F2 generation is 9 : 3 : 3 : 1