Nios Previous Year Science And Technology Solved Question Paper Class 10
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Nios Science And Technology 2024 Question Paper
(212)
Time: 2 ½ Hours] [ Maximum Marks: 85
Note:
(i) This question paper consists of 43 questions in all.
(ii) All questions are compulsory.
(iii) Marks are given against each question.
(iv) Section – A consists of
(a) Q.No. 1 to 17 – Multiple Choice type questions (MCQs) carrying 1 mark each. Select and write the most appropriate option out of the four options given in each of these questions. An internal choice has been provided in some of these questions. You have to attempt any one of the given choices in such questions.
(b) Q.No. 18 to 28 – Objective type questions. Q.No. 18 to 27 carry 2 marks each (with 2 subparts of 1 mark each) and Q.No. 28 carries 5 marks (with 5 sub-parts of 1 mark each). Attempt these questions as per the instructions given for each of the questions 18 to 28.
(v) Section – B consists of
(a) Q.No. 29 to 34 – Very Short Answer type questions carrying 2 marks each to be answered in the range of 30 to 50 words.
(b) Q.No. 35 to 41 – Short Answer type questions carrying 3 marks each to be answered in the range of 50 to 80 words.
(c) Q.No. 42 to 43 – Long Answer type questions carrying 5 marks each to be answered in the range of 80 to 120 words.
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SECTION – A
- No. 1 to 17 are the Multiple-Choice Questions of 1 mark each. An internal choice has been provided in some of these questions. You have to attempt only one of the given choices in such questions.
- In ancient times people used to make measurements by using their: 1
(A) thumb (B) hand-span (C) first finger (D) all of the above
Ans. (D) all of the above.
- Someone has written the mass of a body as given below in different ways. Which of these is written correctly as per rules? 1
(A) 100 mg (B) 100 mg (C) 100/mg (D) 100 mgs
Ans. (A) 100 mg
- (i) In respect of ionic compounds, which one of the following properties is incorrect?
(A) they are solid and hard.
(B) their melting and boiling points are high.
(C) they are soluble in organic solvents.
(D) they are good conductor of electricity in molten state.
Ans. (C) they are soluble in organic solvents.
OR
(ii) If two chlorine atoms share one of their electrons, they both attain the stable configuration of a noble gas which is :
(A) Neon (B) Argon (C) Krypton (D) Xenon
Ans. (B) Argon
- (i) Identify which of the following is formed by transfer of electrons : 1
(A) Oxygen (B) Nitrogen (C) Hydrogen (D) Sodium chloride
Ans. (D) Sodium chloride
OR
(ii) Consider the formation of a compound in the following manner + ® X, X in the above reaction is :
(A) solid sodium chloride (B) liquid sodium chloride (C) gaseous sodium chloride (D) molten sodium chloride
Ans. (A) solid sodium chloride
- Which of the following atoms has the largest atomic radius? 1
(A) C (B) N (C) O (D) F
Ans. (A) C
Ans. (B) suggests that setup A has less friction than setup B, which is correct because the glass surface will offer less friction than the sand surface.
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Ans. (C) ms⁻²
- Which one of the following statements is not correct in regard of energy transformation? 1
(A) Photosynthesis : Solar energy ® Chemical energy of food
(B) Electric bulb : electric energy ® Light energy
(C) Loudspeaker : electric energy ® Sound energy
(D) Physical exercise : Chemical energy of food ® Kinetic energy
Ans. (B) Electric bulb : electric energy ® Light energy
- Rate of doing work is called __________. 1
(A) Force (B) Displacement (C) Power (D) Motion
Ans. (C) Power
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- A mirror always forms a diminished image of an object, wherever you place the object in front of it.
The mirror is : 1
(A) Plane (B) Concave (C) Convex (D) None of these, as there is no mirror like this
Ans. (C) Convex
- (i) Which of the following is not a digestive gland? 1
(A) Liver (B) Gastric gland (C) Pancreatic islets (D) Wall of intestine
Ans. (C) Pancreatic islets
OR
(ii) Which one of the following blood group is a universal donor?
(A) A (B) B (C) AB (D) O
Ans. (D) O
- (i) Which of the following is used as a male contraceptive device? 1
(A) Vasectomy (B) Tubectomy (C) Copper T (D) Hypophysectomy
Ans. (A) Vasectomy
OR
(ii) Which of the following human reproductive organ is not present in pair?
(A) Vas deferens (B) Fallopian tube (C) Cervix (D) Ovary
Ans. (C) Cervix
- Which of the following is not a method of artificial propagation in plants? 1
(A) Cutting (B) Layering (C) Gootee (D) Budding
Ans. (C) Gootee
Ans. (A): CH₃CH₂OH + CO₂.
OR
Ans. The correct matches are:
(A) 1 → Meth
(B) 2 → Eth
(C) 3 → Prop
(D) 4 → But
- (i) A four carbon containing compound Butanone has the functional group: 1
(A) −COOH (B) −CHO (C) −CO− (D) −OH
Ans. (C) −CO−
OR
1
Ans. (A) C₆H₁₄
- (i) Which one of the following statements is incorrect in respect of adaptive features in aquatic plants? 1
(A) They have reduced root system.
(B) The leaves are thin and narrow.
(C) The shoot system is well organised
(D) Upper surface of leaf is coated with wax.
Ans. (C) The shoot system is well organised
OR
(ii) Fins of fish help to:
(A) Swim (B) Steer (C) Maintain Balance (D) All the above
Ans. (D) All the above
- (i) The trapping of a layer of cool air at the ground level by an overlying layer of warm and stagnant air is called: 1
(A) Thermal inversion (B) Global warming (C) Incineration (D) Biological magnification
Ans. (A) Thermal inversion
(ii) Which one of the following is not an example of natural environmental problems? 1
(A) Earthquakes (B) Floods (C) Tsunami (D) Afforestation
Ans. (D) Afforestation
Questions No. 18 to 27 are the objective questions of 2 marks each. Some of these questions have 4 sub-parts. You have to do any 2 sub-parts out of 4 sub-parts in such questions.
- Match Column – I statements with the right option of Column – II. 1×2
Column – I Column – II
(i) SI unit of Pressure (P) Kelvin
(ii) SI unit of Temperature (Q) Celsius
(R) Pascal
(S) Candela
Ans.
Here is the correct matching:
| Column I | Column II |
| (i) SI unit of Pressure | (R) Pascal |
| (ii) SI unit of Temperature | (P) Kelvin |
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- Complete the following sentence by given options below. 1×2
[Attempt any 2 Parts from the following (i to iv)]
(loss, chemical bonding, bad conductor, good conductor, gain)
(i) Atoms of elements in a molecule are held together by __________ .
(ii) Metals form cations by __________ of electrons.
(iii) Formation of anions by non-metals takes place with the __________ of electrons.
(iv) Ethyl alcohol is a __________ of electricity in its aqueous solution.
Ans.
Here is the correct filling of blanks:
(i) Atoms of elements in a molecule are held together by chemical bonding.
(ii) Metals form cations by loss of electrons.
(iii) Formation of anions by non-metals takes place with the gain of electrons.
(iv) Ethyl alcohol is a bad conductor of electricity in its aqueous solution.
- Write TRUE (T) for correct statement and FALSE (F) for incorrect statements. 1×2
[Attempt any two parts from following questions (i to iv)]
(i) The electronic configuration of Argon is 2, 8, 8
(ii) In the formation of sodium chloride, sodium atom gains one electron and chlorine atom looses one electron.
(iii) Covalent bond is formed by mutual sharing of equal number of electrons between two atoms.
(iv) Ethyl alcohol produces H+ ions in its aqueous solution.
Ans.
Here are the statements with TRUE (T) or FALSE (F) designations:
(i) The electronic configuration of Argon is 2, 8, 8. — False (F)
(The correct configuration is 2, 8, 8 for Neon, Argon is 2, 8, 8, 8 for a total of 18 electrons.)
(ii) In the formation of sodium chloride, sodium atom gains one electron and chlorine atom loses one electron. — False (F)
(Sodium loses one electron, and chlorine gains one electron.)
(iii) Covalent bond is formed by mutual sharing of an equal number of electrons between two atoms. — True (T)
(iv) Ethyl alcohol produces H+ ions in its aqueous solution. — False (F)
(Ethyl alcohol does not dissociate to produce H+ ions; it’s not an acid.)
Ans. (i) The blood vessels that carry blood from the heart are termed as arteries, and those that bring blood from various parts of the body to the heart are termed as veins.
(ii) The thin structures that allow the exchange of materials between blood and tissues are called capillaries.
- Read the Passage and answer the Questions (i) and (ii) that follow it. 1×2
RTIs refer to infections of reproductive organs. These illnesses may occur due to poor genital hygiene. For example, Poor menstrual hygiene among girls. Importantly, RTIs include the illness that are transmitted from one Person to another Person during sexual contact and are known as STDs.
(i) Which one of the following is not STDs ?
(A) Syphilis (B) Gonorrhea (C) AIDS (D) Goitre
(ii) HIV/AIDS is not transmitted by :
(A) Unprotected sexual intercourse (B) Infected blood (C) Infected mother to her baby (D) Kissing and hugging
Ans. (i) Which one of the following is not an STD?
(D) Goitre
(ii) HIV/AIDS is not transmitted by:
(D) Kissing and hugging
- Write TRUE (T) for correct statement and FALSE (F) for incorrect statement. 1×2
[Attempt any two Parts from the following questions (i to v)]
(i) HENRY MOSELEY, an English Physicist discovered that the ‘atomic mass’ and not the ‘atomic number’ is the most fundamental property of elements.
(ii) F, Cl, Br, I and At are the non-metallic elements called halogens.
(iii) Metallic character increases in a Period from left to right.
(iv) 1 pm = 10−12 m
(v) If the electronic configuration of an element is 2, 8, 1 then it is a non-metal.
Ans.
(i) HENRY MOSELEY, an English Physicist discovered that the ‘atomic mass’ and not the ‘atomic number’ is the most fundamental property of elements. — False (F)
(Henry Moseley discovered that the atomic number is the most fundamental property, not atomic mass.)
(ii) F, Cl, Br, I, and At are the non-metallic elements called halogens. — True (T)
(iii) Metallic character increases in a Period from left to right. — False (F)
(Metallic character decreases from left to right in a period.)
(iv) 1 pm = 10−12 m. — True (T)
(v) If the electronic configuration of an element is 2, 8, 1, then it is a non-metal. — False (F)
(The configuration 2, 8, 1 corresponds to sodium, which is a metal.)
Ans.
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- Fill in the blanks. 1×2
Attempt any two parts from the following questions (i to iv).
(i) A close interaction between two or more different organisms of different species living
in close physical association is termed as __________.
(ii) The __________ rate of a population is the number of individuals dying per thousand
per unit time.
(iii) The process of conversion of ammonia into nitrates is known as __________.
(iv) __________ is the inter-connected food chains.
Ans. (i) A close interaction between two or more different organisms of different species living in close physical association is termed as symbiosis.
(ii) The mortality rate of a population is the number of individuals dying per thousand per unit time.
(iii) The process of conversion of ammonia into nitrates is known as nitrification.
(iv) Food web is the inter-connected food chains.
- Write TRUE (T) for correct statement and FALSE (F) for incorrect statements. 1×2
[Attempt any two parts from the following questions (i to iv)]
(i) Fish and aquatic invertebrates like prawns have gills for respiration.
(ii) Penguins have a hump to store fat.
(iii) Population growth curves are either J-shaped or S-shaped.
(iv) Abiotic components are the organisms which include plants, animals and microorganisms in an eco-system.
Ans. (i) Fish and aquatic invertebrates like prawns have gills for respiration. — True (T)
(ii) Penguins have a hump to store fat. — False (F)
(Penguins do not have a hump to store fat. This is a characteristic of camels.)
(iii) Population growth curves are either J-shaped or S-shaped. — True (T)
(iv) Abiotic components are the organisms which include plants, animals, and microorganisms in an ecosystem. — False (F)
(Abiotic components are the non-living factors, not organisms; organisms are part of the biotic components.)
Now attempt any two parts from the following questions (i to iv) :
(i) What is the force of gravity acting on an object of mass 2000 kg at the earth’s surface?
(A) F = 1.962 N (B) F = 19.62 N (C) F = 1962 N (D) F = 19620 N
Ans.
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Ans.
(iii) G is known as universal gravitational constant. Why ?
(A) Its value vary from place to place
(B) Its value is same everywhere
(C) The value of G is very large
(D) The value of G is very small
Ans.
Ans.
- Read the passage and answer the questions that follow it (i to vii). 1×5
Given below is the circuit diagram to study relationship between Voltage and Current.
(i) In the circuit diagram the voltmeter is connected :
- in series (B) in parallel (C) in mixed combination (D) in no particular combination
Ans. (B) in parallel
A voltmeter is always connected in parallel across the component (in this case, the resistor RRR) whose voltage is to be measured. This is because it measures the potential difference between two points without significantly affecting the circuit.
(ii) Which one of the following sets includes devices that are used in electrical circuits for their safety ?
(A) Switch, tester and fuse (B) Tester, fuse and MCB (C) Switch, fuse and MCB (D) MCB, switch and tester
Ans. (C) Switch, fuse, and MCB
- Switch: Used to open or close the circuit, controlling the flow of electricity and providing a basic safety mechanism.
- Fuse: Protects the circuit by breaking the connection if the current exceeds a safe limit, preventing potential damage or fire hazards.
- MCB (Miniature Circuit Breaker): Automatically turns off the circuit during overload or short circuit conditions, providing a safer and more modern alternative to fuses.
These devices are commonly used for safety in electrical circuits.
Ans. (B) Rheostat
The symbol depicts a variable resistor (rheostat). A rheostat is used to control the current by varying the resistance in the circuit. The arrow on the resistor indicates that it can be adjusted, which is a characteristic feature of a rheostat.
(iv) Which law, the above circuit diagram represents ?
(A) Joule’s Law of heating effect (B) Kirchhoff’s Law (C) Ohm’s Law (D) Coulomb’s Law
Ans. (C) Ohm’s Law
This circuit is designed to study the relationship between voltage and current, which is the essence of Ohm’s Law. Ohm’s Law states that the current I through a conductor between two points is directly proportional to the voltage V across the two points, provided the temperature remains constant. The mathematical form is V=IR, where R is the resistance.
(D) Joule
The Joule is the standard SI unit of energy, including electrical energy. While kilowatt-hour (kWh) is a commonly used unit for electrical energy in practical terms (e.g., billing electricity usage), it is not the SI unit. One joule is the energy transferred when one watt of power is used for one second.
- 1 Joule = 1 Watt second (C)
(vi) For the Verification of Ohm’s Law in laboratory, which of the following items are required ?
(A) cells, key, resistance wire, voltmeter, galvanometer
(B) cells, key, resistance wire, ammeter, galvanometer
(C) cells, key, resistance wire, voltmeter, ammeter
(D) cells, key, resistance wire, galvanometer
Ans.
(C) cells, key, resistance wire, voltmeter, ammeter
To verify Ohm’s Law, you need:
- Cells to provide the voltage.
- Key (switch) to open and close the circuit.
- Resistance wire to study the voltage-current relationship.
- Voltmeter to measure the voltage across the resistor.
- Ammeter to measure the current flowing through the circuit.
A galvanometer is used to detect small currents, but it is not necessary for verifying Ohm’s Law.
(vii) Which one of the following is the unit of potential difference?
(A) Joule/Coulomb (B) Volt/Coulomb (C) Ampere/second (D) Ohm meter
Ans.
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SECTION – B
- (i) Write the balanced chemical equation for the following statements. 2
(a) Sodium element reacts with oxygen to form sodium oxide.
(b) Iron reacts with steam to form iron oxide and hydrogen gas.
Ans.
OR
(ii) What is rust? Mention any two important conditions required for rusting.
Ans.
- Write the molecular formula and draw the structures of the following compounds. 2
(i) Formic acid (ii) Propanone
Ans.
(i) Formic acid:
- Molecular formula: HCOOH
- Structure:
H−C(=O)−OH
Formic acid is the simplest carboxylic acid with one carbon atom.
- Write any two postulates proposed by Niel’s Bohr in Bohr’s Model of hydrogen atom. 2
Ans.
Niels Bohr proposed the following two key postulates in his model of the hydrogen atom:
- Quantized Orbits: Electrons in an atom move in specific, fixed orbits or energy levels around the nucleus without emitting radiation. These orbits are quantized, meaning the electron can only occupy certain allowed orbits, each corresponding to a specific energy level.
- Energy Absorption and Emission: An electron can transition between these fixed orbits by absorbing or emitting a quantum of energy. The energy absorbed or emitted corresponds to the difference in energy between the two orbits. This principle explains the discrete spectral lines observed in atomic spectra.
OR
State any two results of α-ray scattering experiment explained by Rutherford.
Ans.
Rutherford’s α-ray scattering experiment (also known as the Rutherford gold foil experiment) led to several significant results:
- Nucleus Existence: The experiment demonstrated that an atom has a small, dense nucleus at its center. This was inferred from the fact that a small fraction of the α-particles were deflected at very large angles, which could only be explained if there was a small, positively charged nucleus repelling the positively charged α-particles.
- Atom’s Mostly Empty Space: Most of the α-particles passed through the gold foil with little or no deflection, indicating that the majority of the atom is empty space. This result showed that the dense nucleus occupies only a tiny fraction of the atom’s volume, while the rest of the atom is relatively empty.
- Explain how a person can get rid of suffering from ‘acidity’ i.e. irritation and occasional pain in the stomach.
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Ans.
Acidity occurs when there is an excess production of stomach acid, which can lead to irritation and pain. This is often caused by factors such as diet, lifestyle, and other conditions.
Ways to Manage Acidity:
- Dietary Changes:
- Avoid Spicy and Fatty Foods: Foods that are spicy or high in fat can increase stomach acid production. Try to eat bland foods that are less likely to irritate your stomach.
- Eat Smaller Meals: Instead of having three large meals, eat smaller, more frequent meals to reduce the amount of acid produced and prevent overloading the stomach.
- Lifestyle Adjustments:
- Don’t Lie Down After Eating: After eating, wait for at least 2-3 hours before lying down. This helps in preventing acid from flowing back into the esophagus.
- Elevate the Head of Your Bed: If acidity is a problem at night, try elevating the head of your bed to prevent acid from flowing back into the esophagus while you sleep.
- Hydration:
- Drink Water: Drinking plenty of water can help dilute stomach acid and aid in digestion. Avoid drinking too much water right after meals.
- Avoid Smoking and Alcohol:
- Quit Smoking: Smoking can increase acid production and weaken the lower esophageal sphincter (LES), making acid reflux worse.
- Limit Alcohol Intake: Alcohol can also increase stomach acid and contribute to acid reflux.
- Over-the-Counter Medications:
- Antacids: These can neutralize stomach acid and provide quick relief.
- H2 Blockers and PPIs: These medications reduce the production of stomach acid and are available over-the-counter or by prescription.
If the acidity persists or becomes severe, it is important to consult a healthcare professional for further evaluation and treatment.
- What is a solenoid? Draw a sketch to show the magnetic field pattern produced by a current carrying solenoid.
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Ans.
A solenoid is a long, cylindrical coil of wire wound in a helical shape. When an electric current passes through the wire, the solenoid produces a magnetic field similar to that of a bar magnet, with distinct north and south poles.
Magnetic Field Pattern of a Current-Carrying Solenoid
- Inside the Solenoid: The magnetic field inside a solenoid is uniform and parallel to the axis of the solenoid. It is strong and concentrated within the coil.
- Outside the Solenoid: The magnetic field lines outside the solenoid resemble those of a bar magnet, forming closed loops from one end of the solenoid to the other. The field is weaker outside the solenoid compared to the inside.
Here is a sketch to illustrate the magnetic field pattern of a current-carrying solenoid:
Explanation of the sketch:
- Inside the Solenoid: The magnetic field lines are parallel and closely spaced, indicating a strong and uniform magnetic field.
- Outside the Solenoid: The field lines curve from the north pole (N) to the south pole (S), similar to a bar magnet.
The magnetic field lines inside the solenoid run parallel to the axis, creating a uniform field, while outside, they form loops that return to the opposite end, creating a pattern similar to that of a bar magnet.
- Define the terms: 2
(i) Osmoregulation (ii) Dialysis
Ans.
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(i) Osmoregulation: Osmoregulation is the process by which living organisms maintain the balance of water and electrolytes (such as sodium, potassium, and chloride) in their bodies. This involves the regulation of water and salt concentrations to ensure that cells and tissues operate efficiently. Osmoregulation helps to prevent dehydration or excessive water accumulation, which can disrupt cellular functions. In humans, osmoregulation is primarily controlled by the kidneys, which filter blood and adjust the concentration of urine.
(ii) Dialysis: Dialysis is a medical procedure used to remove waste products and excess fluids from the blood when the kidneys are not functioning properly. It involves passing the blood through a machine or a special filter that separates waste and excess fluids from the blood, which is then returned to the body. There are two main types of dialysis:
- Hemodialysis: Blood is circulated through a machine that filters it and returns it to the body.
- Peritoneal Dialysis: A special solution is introduced into the abdominal cavity through a catheter, where it absorbs waste products and excess fluids, which are then removed.
Dialysis is essential for patients with severe kidney failure to maintain their health and balance bodily fluids.
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Ans. Test Tube A contains diluted NaOH (sodium hydroxide) and phenolphthalein indicator is being added to it.
- Test Tube B contains diluted NaOH and diluted HCl (hydrochloric acid) is being added.
Now, let’s answer the questions:
(a) What color change will you observe in test tube A?
- Phenolphthalein is an indicator that turns pink in a basic solution. Since Test Tube A contains NaOH, a basic substance, the solution will turn pink after adding phenolphthalein.
(b) What would happen in test tube B?
- In Test Tube B, diluted HCl (an acid) is added to the basic NaOH solution. The HCl will neutralize the NaOH, causing the pH to decrease. When the solution becomes neutral or slightly acidic, the pink color (due to phenolphthalein) will disappear, and the solution will turn colorless.
(c) What is the process occurring in test tube B called?
- The process occurring in Test Tube B is called neutralization, where an acid (HCl) reacts with a base (NaOH) to form water and salt, and the pH moves towards neutral.
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(ii) Name the constituents of Baking Powder. Why Baking Powder is used but not used Baking Soda in bakery?
Ans. Constituents of Baking Powder:
Baking powder is a mixture of:
- Baking Soda (Sodium Bicarbonate, NaHCO₃)
- Tartaric Acid or another acidifying agent (e.g., cream of tartar)
- A drying agent (such as cornstarch) to prevent premature reactions by absorbing moisture.
Why Baking Powder is used instead of Baking Soda in bakery:
- Baking Soda (NaHCO₃) is a base, and it requires an acidic ingredient (like lemon juice, vinegar, or buttermilk) to react and release carbon dioxide gas, which causes the dough to rise. If there is no acidic component in the recipe, baking soda won’t work effectively, and the final product might have a soapy or bitter taste.
- Baking Powder, on the other hand, contains both an acid (like tartaric acid) and a base (baking soda). It can work on its own without needing additional acidic ingredients. This makes it more versatile in baking, ensuring a consistent rise and proper texture in baked goods.
In bakery, baking powder is preferred because:
- It gives consistent results without depending on external acidic ingredients.
- The reaction occurs in two stages: first when it is mixed with the dough (at room temperature) and then again during baking (at high temperature), allowing a more controlled rise.
- (a) Write the molecular formula and chemical name of Bleaching Powder. 3
(b) Name the two materials used in the manufacture of Bleaching Powder.
(c) Write the chemical equation that takes place in the manufacture of Bleaching powder in Hasen-Clever Plant.
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Ans.
The molecular formula and chemical name of bleaching powder are as follows:
- Molecular Formula: {Ca(OCl)2}
- Chemical Name: Calcium Oxychloride
Bleaching powder is commonly used as a disinfectant and bleaching agent in various industries.
(b) Name the two materials used in the manufacture of Bleaching Powder.
The two materials used in the manufacture of bleaching powder are:
- Calcium Hydroxide (Slaked Lime) – {Ca(OH)_2}
- Chlorine Gas – {Cl_2}
This reaction produces calcium oxychloride (bleaching powder) and water.
(c) Write the chemical equation that takes place in the manufacture of Bleaching powder in Hasen-Clever Plant.
Ans.
- 3
Ans.
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- (i) Draw the generalized structure of a neuron (nerve cell) and label the following parts 3
on it.
(a) Dendrites (b) Cell body (c) Axon (d) Nucleus
Ans. Here is the diagram of a neuron (nerve cell) with the labeled parts: dendrites, cell body, axon, and nucleus.
OR
(ii) (a) Name the hormone released by thyroid gland. What is its function in our body?
(b) Define hyperthyroidism
(c) Define hypothyroidism
Ans.
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- With the help of a line diagram show the chromosomal basis of sex determination in humans. 3
Ans. Here is the line diagram showing the chromosomal basis of sex determination in humans. It illustrates how the male can contribute either an X or Y chromosome, while the female always contributes an X chromosome, resulting in either a female (XX) or male (XY) offspring.
- What is meant by Population dispersal? Explain in brief about the two types of Population dispersal. 3
Ans. Population dispersal refers to the movement or spreading of individuals from their place of origin or high population density to other areas. This process is important for species survival, gene flow, and colonization of new habitats. Population dispersal helps organisms find resources, avoid competition, escape predators, and adapt to environmental changes.
There are two main types of population dispersal:
- Emigration (Outward dispersal):
- Definition: Emigration is the movement of individuals out of a population to settle in a new area. This results in a decrease in the size of the original population.
- Example: Animals migrating to a new habitat due to scarcity of food or unfavorable living conditions in their current environment.
- Immigration (Inward dispersal):
- Definition: Immigration is the movement of individuals into a new population or area from another location. This increases the population size in the new area.
- Example: When animals from a surrounding area move into a forest that offers better food and shelter.
Both types of dispersal can occur due to various factors like resource availability, environmental conditions, or human activities, and they help maintain genetic diversity and species survival.
- (i) State the term bio-magnification. 3
(ii) DDT is widely used for crop protection. How is it responsible for the decreased population of pelicon birds?
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Ans. (i)
Bio-magnification refers to the process by which the concentration of harmful substances, such as pesticides or heavy metals, increases as you move up the food chain. These substances accumulate in the bodies of organisms and become more concentrated in predators at higher trophic levels. For example, if small fish consume contaminated algae, and then larger fish eat those small fish, the concentration of the harmful substance increases in the larger fish. This can have detrimental effects on the health of the entire ecosystem, including humans who consume these top predators.
Ans. (ii) DDT (dichlorodiphenyltrichloroethane) is a pesticide that was widely used for crop protection and to control insect-borne diseases. However, it had unintended environmental consequences, particularly for bird populations like pelicans.
DDT is known to cause a phenomenon called “biomagnification,” where it accumulates in the tissues of organisms higher up the food chain. When pelicans, which are at the top of the food chain in their habitat, consume fish contaminated with DDT, the concentration of the chemical becomes much higher in their bodies.
One of the most severe impacts of DDT on pelicans and other birds was the thinning of their eggshells. DDT interferes with calcium metabolism in birds, leading to eggshell thinning. This made the eggs more fragile and prone to breaking before hatching. As a result, fewer eggs successfully hatched, leading to a decline in the pelican population.
The decline in pelican populations due to DDT was a significant ecological issue, highlighting the broader environmental impact of certain pesticides.
- (i) (a) Define dispersion of white light through a glass prism. Draw a diagram to illustrate it. 5
(b) Which of the colours bends least and which one bends the most?
(c) Why does prism show dispersion of white light?
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Ans. (a) Dispersion is the process by which white light is separated into its constituent colors when it passes through a glass prism. White light is composed of various colors, each with a different wavelength. When white light enters the prism, it slows down and bends due to the change in medium. Different colors bend by different amounts because they travel at different speeds in the glass. This causes the colors to spread out and form a spectrum. The result is a display of colors ranging from red to violet.
Here’s a simplified description of the process:
- Entry of White Light: White light enters the prism at an angle.
- Refraction: As the light passes from air into the glass prism, it slows down and bends.
- Dispersion: The different colors (wavelengths) of light bend by different amounts, spreading out into a spectrum.
- Exit from Prism: The separated colors emerge from the other side of the prism, continuing to spread out due to their different angles of refraction.
In the diagram:
The colors typically observed in the spectrum are red, orange, yellow, green, blue, indigo, and violet, often remembered by the acronym ROYGBIV.
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(b) Which color bends least and which one bends the most?
- Red: Bends the least. Red light has the longest wavelength among the visible spectrum colors, so it refracts (bends) the least when passing through the prism.
- Violet: Bends the most. Violet light has the shortest wavelength among the visible spectrum colors, so it refracts (bends) the most.
(c) Why does a prism show dispersion of white light?
A prism shows dispersion of white light due to the phenomenon of refraction, which occurs because different colors of light travel at different speeds when they pass through a medium such as glass. Here’s a detailed explanation:
- Refraction: When white light enters the prism, it slows down and bends due to the change in speed as it moves from air (a less dense medium) into the glass (a denser medium). The amount of bending depends on the wavelength of the light.
- Different Speeds for Different Wavelengths: In the glass prism, different colors of light have different wavelengths and therefore different speeds. Shorter wavelengths (like violet) slow down more and bend more compared to longer wavelengths (like red). This difference in bending causes the colors to spread out.
- Separation of Colors: As light exits the prism, the different colors emerge at different angles. This separation of colors creates the spectrum observed, with red light bending the least and violet light bending the most.
Thus, the prism effectively separates white light into its component colors through refraction and dispersion.
OR
(a) Draw diagrams of the following lenses : 2
Double Convex, Plano Convex, Double Concave, Convexo Concave
(b) Draw diagrams showing the following : 3
– myopic eye
– hypermetropic eye
– relaxed eye
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Ans. Double Convex, Plano Convex, Double Concave, Convexo Concave
Double Convex Lens:
- A double convex lens is thicker at the center and thinner at the edges, converging light rays to a focal point.
Plano Convex Lens:
- A plano convex lens has one flat (plano) surface and one convex surface, focusing parallel light rays to a focal point.
Double Concave Lens:
- A double concave lens is thinner in the middle and thicker at the edges, diverging light rays.
Convexo Concave Lens:
- A convexo concave lens has one convex surface and one concave surface, often used for correcting vision.
(b) Diagrams of Eyes:
Myopic Eye (Nearsighted):
- In a myopic eye, light rays focus in front of the retina, making distant objects appear blurry. A concave lens is used to correct this condition.
Hypermetropic Eye (Farsighted):
- In a hypermetropic eye, light rays focus behind the retina, making nearby objects appear blurry. A convex lens is used to correct this condition.
Relaxed Eye:
- A relaxed eye has light rays converging directly on the retina, resulting in a clear image. This is the normal state of the eye when viewing objects at a comfortable distance.
These diagrams help visualize how lenses and eye conditions affect the focus of light and vision.
Ans.
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(ii) (a) Why do elements of the same group have similar properties?
(b) How does the atomic size of elements vary in a period with increase in atomic number? State reason.
Ans. (ii) (a) Why do elements of the same group have similar properties?
Elements in the same group of the periodic table have similar properties due to their similar electronic configurations, specifically in their valence shell. Here’s why:
- Valence Electrons: Elements in the same group have the same number of valence electrons. For example, all elements in Group 1 (alkali metals) have one valence electron, while elements in Group 17 (halogens) have seven valence electrons.
- Chemical Behavior: The number of valence electrons determines how an element will bond with other elements and its reactivity. Since elements in the same group have the same number of valence electrons, they exhibit similar chemical behaviors. For instance, alkali metals are highly reactive and form similar compounds with halogens.
- Periodic Trends: Similar properties arise from the consistent way these valence electrons interact with other elements and their surroundings.
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(ii) (b) How does the atomic size of elements vary in a period with an increase in atomic number? State the reason.
In a period (row) of the periodic table, the atomic size generally decreases as the atomic number increases. This trend occurs due to the following reasons:
- Increasing Nuclear Charge: As you move across a period from left to right, the number of protons in the nucleus increases. This increase in positive charge (nuclear charge) attracts the electrons more strongly.
- Constant Electron Shells: Although the number of electrons increases across a period, they are added to the same principal energy level (or shell). Thus, the distance between the nucleus and the outermost electrons decreases because the effective nuclear charge (the net positive charge experienced by the electrons) increases.
- Effective Nuclear Charge: The stronger attraction between the nucleus and the electrons pulls the electron cloud closer to the nucleus, reducing the atomic radius.
In summary, the atomic size decreases across a period due to the increase in nuclear charge, which pulls the electrons closer to the nucleus despite the addition of more electrons.
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OR
(iii) (a) The Modern Periodic table has been evolved through the early attempts of Dobereiner, Newland and Mendeleev. List one advantage and one limitation of all the three attempts.
(b) Define atomic number ‘Z’ of an element.
(c) State Modern Periodic Law.
Ans.
(a) Advantages and Limitations of Early Attempts at Periodic Classification:
- Dobereiner’s Triads:
- Advantage: Dobereiner’s triads were among the first attempts to classify elements based on their properties, leading to the discovery of patterns and relationships between elements.
- Limitation: Dobereiner’s triads were limited to only a few elements and could not accommodate all known elements or predict the properties of elements beyond the triads.
- Newlands’ Law of Octaves:
- Advantage: Newlands’ Law of Octaves was an early attempt to organize elements based on their properties and atomic masses, which highlighted the periodic nature of elements.
- Limitation: The law of octaves only worked well for the first 16 elements and did not account for elements discovered later. It also did not fit well with the transition metals.
- Mendeleev’s Periodic Table:
- Advantage: Mendeleev’s table organized elements based on increasing atomic mass and grouped them by similar chemical properties. It successfully predicted the properties of elements that had not yet been discovered.
- Limitation: Mendeleev’s table had some discrepancies due to the use of atomic mass, leading to incorrect placements for some elements. Additionally, it could not accurately explain the placement of isotopes and elements with similar properties but different atomic masses.
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(b) Define Atomic Number ‘Z’ of an Element:
The atomic number Z of an element is defined as the number of protons in the nucleus of an atom of that element. It determines the element’s identity and its position in the periodic table. The atomic number also equals the number of electrons in a neutral atom.
(c) State the Modern Periodic Law:
The Modern Periodic Law states that:
“The properties of elements are a periodic function of their atomic numbers.”
This means that when elements are arranged in order of increasing atomic number, their physical and chemical properties show a periodic pattern, or recurring trends, which is the basis for the structure of the modern periodic table.
