Class 10 Science Second Midterm Exam 2024 Solved Question Paper | Thanjavur District

Class 10 Science Second Midterm Exam 2024 Solved Question Paper

Matric Hr. Sec. School, Kumbakonam - Thanjavur District

Part I: Choose the best answer (10 X 1 = 10)

1. The frequency, which is audible to the human ear is

a) 50 kHz
b) 20 kHz
c) 15000 kHz
d) 10000 kHz

Answer: b) 20 kHz
The audible range for humans is from 20 Hz to 20,000 Hz (or 20 kHz).

2. Gamma radiations are dangerous because

a. it affects eyes & bones
b. it affects tissues
c. it produces genetic disorder
d. it produces enormous amount of heat

Answer: c. it produces genetic disorder
Due to their high penetrating power, gamma rays can damage DNA within cells, leading to mutations and genetic disorders.

3. In the nuclear reaction \(_6^{12}X \xrightarrow{\alpha \text{ decay}} _Z^AY\), the value of A & Z.

a. 8, 6
b. 8, 4
c. 4, 8
d. cannot be determined with the given data

Answer: b. 8, 4
An alpha decay emits an alpha particle (\(_2^4He\)).
New mass number (A) = 12 - 4 = 8.
New atomic number (Z) = 6 - 2 = 4.

4. Reaction between carbon and oxygen is represented by \(C(s) + O_2(g) \rightarrow CO_2(g) + \text{Heat}\). In which of the type(s), the above reaction can be classified?

(i) Combination Reaction (ii) Combustion Reaction (iii) Decomposition Reaction (iv) Irreversible Reaction

a. i and ii
b. i and iv
c. i, ii and iii
d. i, ii and iv

Answer: d. i, ii and iv
(i) It's a combination reaction as C and O₂ combine to form CO₂.
(ii) It's a combustion reaction as carbon burns in oxygen.
(iv) It's an irreversible reaction as it proceeds in one direction.

5. TFM in soaps represents _____ content in soap.

a. mineral
b. vitamin
c. fatty acid
d. carbohydrate

Answer: c. fatty acid
TFM stands for Total Fatty Matter, which is a measure of the fatty acid content and quality of a soap.

6. The 'use and disuse theory' was proposed by

a. Charles Darwin
b. Ernst Haeckel
c. Jean Baptiste Lamarck
d. Gregor Mendel

Answer: c. Jean Baptiste Lamarck

7. Organisms with modified endogenous gene or a foreign gene are also known as

(a) transgenic organisms
(b) genetically modified
(c) mutated
(d) both a and b

Answer: (d) both a and b

8. Which type of cancer affects lymph nodes and spleen?

a) Carcinoma
b) Sarcoma
c) Leukaemia
d) Lymphoma

Answer: d) Lymphoma
Lymphoma is a cancer that originates in the lymphatic system, which includes the lymph nodes and spleen.

9. A renewable source of energy is

a) petroleum
b) coal
c) nuclear fuel
d) trees

Answer: d) trees
Trees are a renewable resource because they can be replanted and regrown, unlike fossil fuels.

10. Green house effect refers to

a) cooling of earth
b) trapping of UV rays
c) cultivation of plants
d) warming of earth

Answer: d) warming of earth
The greenhouse effect is the process by which greenhouse gases in the atmosphere trap the sun's heat, causing the Earth's surface to warm.

Part II: Write any 5 questions (5 X 2 = 10)

(Question no 18 is compulsory)

11. Why does sound travel faster on a rainy day than on a dry day?

Sound travels faster on a rainy day because the humidity of the air is higher. The density of air decreases as humidity increases because water vapour molecules (\(H_2O\)) are lighter than the nitrogen (\(N_2\)) and oxygen (\(O_2\)) molecules they displace. Sound travels faster in a less dense medium, hence it travels faster on a rainy (humid) day.

12. Define one Roentgen.

One Roentgen is defined as the quantity of radioactive substance which produces a charge of \(2.58 \times 10^{-4}\) coulomb in 1 kg of air under standard conditions of pressure, temperature, and humidity.

13. Differentiate soaps and detergents.

Soaps	Detergents
They are sodium or potassium salts of long-chain fatty acids.	They are sodium salts of long-chain sulphonic acids.
They are not effective in hard water and form scum.	They are effective in both hard and soft water.
They are biodegradable.	Most of them are non-biodegradable.
They have weak cleansing action.	They have strong cleansing action.

14. Why is Archaeopteryx considered to be a connecting link?

Archaeopteryx is considered a connecting link because it possesses characteristics of both reptiles and birds.

Reptilian features: Presence of teeth in its jaw, a long tail with vertebrae, and claws on its fingers.
Avian (bird) features: Presence of feathers on its body and wings, and a bird-like skull.

This indicates that birds evolved from reptiles.

15. State the applications of DNA fingerprinting technique.

Applications of DNA fingerprinting include:

Forensic Science: To identify criminals by analyzing DNA samples from crime scenes (blood, hair, etc.).
Paternity Testing: To resolve disputes of parentage.
Medical Diagnosis: To identify and diagnose inherited genetic disorders.
Conservation: To study the genetic diversity of endangered species for conservation efforts.

16. What are psychotropic drugs?

Psychotropic drugs are chemical substances that act on the central nervous system (CNS) and alter brain function. They can change a person's mood, thinking, perception, and behaviour. Examples include sedatives, stimulants, hallucinogens, and tranquillizers.

17. What is the environmental effect caused by sewage?

Untreated sewage released into water bodies causes several environmental problems:

Water Pollution: It contaminates water sources, making them unfit for drinking and other uses.
Eutrophication: The nutrients in sewage promote excessive growth of algae, which depletes oxygen in the water, harming aquatic life.
Spread of Diseases: Sewage contains pathogens that can cause water-borne diseases like cholera, typhoid, and dysentery.

18. Calculate the amount of energy released when a radioactive substance undergoes fusion and results in a mass defect of 2 kg.

According to Einstein's mass-energy equivalence principle, the energy released (E) is related to the mass defect (m) by the equation:
\[ E = mc^2 \] Given:

Mass defect, \(m = 2 \text{ kg}\)
Speed of light, \(c = 3 \times 10^8 \text{ m/s}\)

Calculation: \[ E = 2 \times (3 \times 10^8)^2 \] \[ E = 2 \times 9 \times 10^{16} \] \[ E = 1.8 \times 10^{17} \text{ Joules} \] The amount of energy released is \(1.8 \times 10^{17}\) J.

Part III: Write any four questions (4 X 4 = 16)

(25th question is compulsory)

19. Compare any four properties of alpha, beta and gamma radiations.

Property	Alpha (\(\alpha\)) Rays	Beta (\(\beta\)) Rays	Gamma (\(\gamma\)) Rays
Nature	Helium nucleus (\(_2^4He\))	Electron (\(_{-1}^0e\))	Electromagnetic waves
Charge	Positive charge (+2e)	Negative charge (-1e)	No charge (neutral)
Ionizing Power	Very high (100 times \(\beta\), 10,000 times \(\gamma\))	Moderate (less than \(\alpha\))	Very low
Penetrating Power	Very low (stopped by a sheet of paper)	Moderate (stopped by a thin aluminium foil)	Very high (stopped by a thick block of lead)

20. What is a chemical equilibrium? What are its characteristics?

Chemical Equilibrium: It is a state in a reversible chemical reaction where the rate of the forward reaction is equal to the rate of the reverse reaction. At equilibrium, the concentrations of reactants and products remain constant over time.

Characteristics of Chemical Equilibrium:

Dynamic Nature: Equilibrium is dynamic because both forward and reverse reactions are still occurring, but at the same rate.
Constant Concentrations: The concentrations of all reactants and products become constant at equilibrium.
Attained from either direction: Equilibrium can be reached whether starting with reactants or products.
Requires a Closed System: Equilibrium can only be achieved in a closed system where no substances can enter or leave.
Catalyst Effect: A catalyst speeds up both forward and reverse reactions equally, so it helps to attain equilibrium faster but does not change the equilibrium position.

21. Define Ethnobotany and write its importance.

Ethnobotany: It is the scientific study of the relationship between people (especially traditional or indigenous cultures) and plants. It explores how people use plants for food, medicine, shelter, rituals, and other purposes.

Importance of Ethnobotany:

Discovery of New Drugs: Traditional knowledge of medicinal plants can lead to the discovery of new and effective modern medicines.
Conservation of Biodiversity: It helps in identifying and conserving important plant species and traditional agricultural practices.
Preservation of Traditional Knowledge: It documents and preserves the valuable knowledge of indigenous communities before it is lost.
Economic Development: It can provide economic opportunities for local communities through the sustainable use of plant resources.

22. Discuss the importance of biotechnology in the field of medicine.

Biotechnology plays a crucial role in modern medicine in several ways:

Production of Pharmaceuticals: Genetically engineered bacteria are used to produce vital medicines like human insulin (for diabetes), human growth hormone, and interferons (for viral infections and cancer).
Vaccine Development: Recombinant DNA technology is used to create safer and more effective vaccines (e.g., Hepatitis B vaccine).
Gene Therapy: It aims to correct genetic disorders by replacing or inactivating faulty genes. It offers potential cures for diseases like cystic fibrosis and sickle cell anemia.
Diagnostic Tools: Biotechnology has led to the development of highly sensitive diagnostic kits (like ELISA) and DNA probes to detect diseases and genetic predispositions quickly and accurately.
Monoclonal Antibodies: These are used for targeted cancer therapy, diagnosis of diseases, and preventing organ transplant rejection.

23. a) How is a cancer cell different from a normal cell?

Normal Cell	Cancer Cell
Undergoes controlled cell division.	Undergoes uncontrolled and rapid cell division.
Shows contact inhibition (stops dividing when it touches other cells).	Lacks contact inhibition and piles up to form a tumor.
Cells are differentiated and have specific functions.	Cells are often undifferentiated and non-functional.
Remains in its original location.	Can metastasize (spread to other parts of the body).

23. b) Differentiate between Type-1 and Type-2 diabetes mellitus.

Feature	Type-1 Diabetes	Type-2 Diabetes
Cause	Autoimmune destruction of beta cells in the pancreas, leading to no insulin production.	The body either becomes resistant to insulin or doesn't produce enough insulin.
Onset	Usually occurs in childhood or adolescence (Juvenile diabetes).	Usually occurs in adults, often over the age of 40.
Body Weight	Patients are often of normal weight or thin.	Patients are often overweight or obese.
Treatment	Requires insulin injections for survival.	Can be managed with lifestyle changes, oral medication, and sometimes insulin.

24. How do rainwater harvesting structures recharge ground water?

Rainwater harvesting structures are designed to capture rainwater runoff and allow it to seep into the ground, thereby recharging groundwater aquifers. They work as follows:

Collection: Structures like rooftop collection systems, check dams, and percolation tanks collect rainwater that would otherwise flow away into drains.
Percolation: The collected water is directed into recharge structures like pits, trenches, or borewells.
Filtration: These structures are often filled with layers of gravel, sand, and charcoal which filter the water as it percolates downwards.
Recharging: The filtered water slowly seeps through the soil and rock layers, eventually reaching and replenishing the underground water table. This raises the groundwater level and improves water availability in wells and borewells.

25. a) Calculate the pH of 0.001 molar solution of HCl.

HCl is a strong acid, so it completely ionizes in water.
\[ HCl \rightarrow H^+ + Cl^- \] The concentration of \(H^+\) ions will be the same as the concentration of the HCl solution.
Given, [HCl] = 0.001 M = \(10^{-3}\) M.
Therefore, \([H^+] = 10^{-3}\) M.
The formula for pH is: \[ pH = -\log_{10}[H^+] \] \[ pH = -\log_{10}(10^{-3}) \] \[ pH = -(-3) = 3 \] The pH of the solution is 3.

25. b) The hydroxide ion concentration of a solution is \(1 \times 10^{-11}\) M. What is the pH of the solution?

First, calculate the pOH from the hydroxide ion concentration \([OH^-]\).
Given, \([OH^-] = 1 \times 10^{-11}\) M.
The formula for pOH is: \[ pOH = -\log_{10}[OH^-] \] \[ pOH = -\log_{10}(1 \times 10^{-11}) \] \[ pOH = -(-11) = 11 \] The relationship between pH and pOH at 25°C is: \[ pH + pOH = 14 \] \[ pH = 14 - pOH \] \[ pH = 14 - 11 = 3 \] The pH of the solution is 3.

Part IV: Write all the questions

26. a) What do you understand by the term 'ultrasonic vibration'?

Ultrasonic vibrations (or ultrasound) are sound waves with frequencies higher than the upper audible limit of human hearing, which is approximately 20 kilohertz (20,000 Hz).

26. b) State three uses of ultrasonic vibrations.

Three uses of ultrasonic vibrations are:

Medical Imaging: Used in ultrasonography to create images of internal body organs, monitor fetal development, and diagnose medical conditions.
SONAR: Used in ships and submarines for navigation, mapping the seabed, and detecting underwater objects (like other submarines or schools of fish).
Industrial Cleaning: Used to clean delicate and intricate parts (like jewelry, electronic components) by creating tiny bubbles that dislodge dirt and contaminants.

26. c) Name three animals which can hear ultrasonic vibrations.

Three animals that can hear ultrasonic vibrations are:

Bats
Dolphins
Dogs

27. Give the balanced chemical equation of the following reactions:

(i) Neutralization of NaOH with ethanoic acid.

\[ \underset{\text{(Sodium Hydroxide)}}{NaOH} + \underset{\text{(Ethanoic Acid)}}{CH_3COOH} \rightarrow \underset{\text{(Sodium Ethanoate)}}{CH_3COONa} + \underset{\text{(Water)}}{H_2O} \]

(ii) Evolution of carbon dioxide by the action of ethanoic acid with NaHCO₃.

\[ \underset{\text{(Ethanoic Acid)}}{CH_3COOH} + \underset{\text{(Sodium Bicarbonate)}}{NaHCO_3} \rightarrow \underset{\text{(Sodium Ethanoate)}}{CH_3COONa} + \underset{\text{(Water)}}{H_2O} + \underset{\text{(Carbon Dioxide)}}{CO_2} \]

(iii) Oxidation of ethanol by acidified potassium dichromate.

\[ \underset{\text{(Ethanol)}}{CH_3CH_2OH} + 2[O] \xrightarrow{K_2Cr_2O_7 / H_2SO_4} \underset{\text{(Ethanoic Acid)}}{CH_3COOH} + \underset{\text{(Water)}}{H_2O} \]

(iv) Combustion of ethanol.

\[ \underset{\text{(Ethanol)}}{C_2H_5OH} + 3O_2 \rightarrow 2CO_2 + 3H_2O + \text{Heat} + \text{Light} \]

(OR)

28. a) Natural selection is a driving force for evolution-How?

Natural selection is a primary driving force for evolution because it explains how species adapt and change over time. The process works as follows:

Variation: Within any population, individuals exhibit variations in their traits (e.g., color, size, resistance to disease).
Struggle for Existence: Organisms produce more offspring than can survive, leading to competition for limited resources like food, water, and space.
Survival of the Fittest: Individuals with traits that are better suited (more advantageous) to their environment are more likely to survive, reproduce, and pass those favorable traits to their offspring.
Gradual Change: Over many generations, these advantageous traits become more common in the population, leading to a gradual change in the species, which is the essence of evolution.

28. b) Differentiate between outbreeding and inbreeding.

Feature	Inbreeding	Outbreeding
Definition	Mating of closely related individuals within the same breed for 4-6 generations.	Mating of unrelated individuals. It can be between individuals of the same breed or different breeds.
Genetic Effect	Increases homozygosity (uniformity).	Increases heterozygosity (genetic variation).
Consequence	Can lead to the expression of harmful recessive traits and loss of vigor (inbreeding depression).	Often results in offspring with superior qualities than parents (hybrid vigor or heterosis).
Purpose	Used to develop pure lines and preserve desirable traits.	Used to introduce new desirable traits and overcome inbreeding depression.