Standard X Science Second Mid Term Test 2024 - THENI District - Solved Question Paper

THENI - SECOND MID TERM TEST - 2024

Standard X - SCIENCE - Solved Question Paper

Part - I: Choose the correct answer (10 x 1 = 10)

1. When a sound wave travels through air, the air particles

a) vibrate along the direction of the wave motion

Explanation: Sound waves in air are longitudinal waves, meaning the particles of the medium vibrate parallel to the direction of energy propagation.

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

b) 20 kHz

Explanation: The audible range for a healthy human ear is typically from 20 Hz to 20,000 Hz (or 20 kHz). The other options (50 kHz, 15000 kHz, 10000 kHz) are ultrasonic and well above the human hearing range.

3. Artificial radioactivity was discovered by

b) Irene Curie

Explanation: Irene Curie and her husband Frédéric Joliot-Curie discovered artificial radioactivity in 1934.

4. _____ isotope is used for the treatment of cancer.

b) Radio Cobalt

Explanation: The radioisotope Cobalt-60 (Radio Cobalt) is widely used in radiation therapy to treat cancer.

5. Photolysis is a decomposition reaction caused by

c) light

Explanation: The term 'photolysis' is derived from 'photo' (light) and 'lysis' (splitting). It refers to the decomposition of a chemical compound by light energy.

6. The pH of a solution is 3. Its [OH⁻] concentration is

c) 1 x 10⁻¹¹ M

Explanation: We know that pH + pOH = 14. Given pH = 3, so pOH = 14 - 3 = 11. The concentration of hydroxide ions is given by $[OH⁻] = 10^{-pOH}$. Therefore, $[OH⁻] = 10^{-11}$ M or $1 \times 10^{-11}$ M.

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

c) Jean Baptiste Lamarck

Explanation: Lamarck's theory of evolution, also known as Lamarckism, is based on the principles of use and disuse of organs and the inheritance of acquired characters.

8. Paleontologists deal with

b) Fossil evidences

Explanation: Paleontology is the scientific study of life that existed prior to the Holocene Epoch, based on the study of fossils.

9. DNA fingerprinting is based on the principle of identifying _____ sequences of DNA

d) repetitive

Explanation: DNA fingerprinting identifies differences in specific regions of DNA called repetitive DNA. These are short sequences that are repeated many times, and the number of repetitions varies from person to person.

10. Pusa Komal is a disease resistant variety of

c) cow pea

Explanation: Pusa Komal is a high-yielding, disease-resistant variety of cowpea, specifically resistant to bacterial blight.

Part - II (Answer any 5 questions, Q.No.18 is compulsory) (5 x 2 = 10)

11. What is a longitudinal wave?

A longitudinal wave is a wave in which the particles of the medium vibrate parallel to the direction of the propagation of the wave. These waves consist of regions of compressions (high pressure) and rarefactions (low pressure). Example: Sound waves in air.

12. Match:

Column A	Column B	Correct Match
1. Infrasonic	a) Compressions	c) 10 Hz
2. Echo	b) 22 kHz	d) Ultrasonography
3. Ultrasonic	c) 10 Hz	b) 22 kHz
4. High pressure region	d) Ultrasonography	a) Compressions

Explanation: 1. **Infrasonic:** Frequencies below 20 Hz (e.g., 10 Hz). 2. **Echo:** Reflection of sound, a principle used in Ultrasonography. 3. **Ultrasonic:** Frequencies above 20 kHz (e.g., 22 kHz). 4. **High pressure region:** A characteristic of a longitudinal wave, known as a compression.

13. In Japan, some of the new born children are having congenital diseases. Why?

This is primarily due to the long-term effects of radiation exposure from the atomic bombings of Hiroshima and Nagasaki in 1945. The radiation caused genetic mutations in the reproductive cells of the survivors. These mutations were then passed down to subsequent generations, leading to an increased incidence of congenital diseases and genetic disorders among their children and grandchildren.

14. Define combination reaction. Give example.

Combination Reaction: A reaction in which two or more reactants combine to form a single product is called a combination reaction. The general form is A + B → AB.

Example: The burning of magnesium ribbon in air to form magnesium oxide. $$ 2Mg + O_2 \rightarrow 2MgO $$ (Magnesium + Oxygen → Magnesium oxide)

15. a) Which organism is considered to be the fossil bird? b) What is the study of fossils called?

a) The organism considered to be the fossil bird, and a connecting link between reptiles and birds, is Archaeopteryx.

b) The study of fossils is called Paleontology.

16. What are transgenic organisms?

Transgenic organisms, also known as Genetically Modified Organisms (GMOs), are plants or animals whose DNA has been modified using genetic engineering techniques. This modification typically involves inserting a gene from another species to introduce a new, desirable trait (e.g., disease resistance, higher yield).

17. Name the types of stem cells.

Based on their potential to differentiate, stem cells are of two main types:

Embryonic Stem Cells: These are pluripotent cells derived from the inner cell mass of a blastocyst (an early-stage embryo). They can differentiate into all derivatives of the three primary germ layers.
Adult Stem Cells (Somatic Stem Cells): These are undifferentiated cells found among differentiated cells in a tissue or organ. They are multipotent and primarily act to maintain and repair the tissue in which they are found.

18. (Compulsory) Two observers are stationed in two boats 4.5 km apart. A sound signal sent by one, under water, reaches the other after 3 seconds. What is the speed of sound in the water?

Given:

Distance (d) = 4.5 km = 4500 m
Time (t) = 3 s

Formula for speed:

$$ Speed (v) = \frac{Distance (d)}{Time (t)} $$

Calculation:

$$ v = \frac{4500 \, m}{3 \, s} $$ $$ v = 1500 \, m/s $$

Therefore, the speed of sound in the water is 1500 m/s.

Part - III (Answer any 4 questions, Q.No.25 is compulsory) (4 x 4 = 16)

19. a) Why does sound travel faster on a rainy day than on a dry day? b) Name three animals, which can hear ultrasonic vibrations.

a) Sound travels faster on a rainy day because the presence of moisture (water vapor) in the air decreases its density. The speed of sound is inversely proportional to the square root of the density of the medium. Since humid air is less dense than dry air, sound travels faster through it.

b) Three animals that can hear ultrasonic vibrations are:

Bats
Dolphins
Dogs

20. a) Give the function of control rods in a nuclear reactor. b) What is stellar energy?

a) Function of control rods: The control rods in a nuclear reactor are used to control the rate of the nuclear fission chain reaction. They are made of neutron-absorbing materials like Boron or Cadmium. By inserting the rods into the reactor core, they absorb excess neutrons, slowing down the reaction. By withdrawing them, they allow more neutrons to cause fission, increasing the reaction rate.

b) Stellar energy: Stellar energy is the energy radiated by stars, including our Sun. This immense energy is produced by nuclear fusion reactions occurring in the core of the stars. In the Sun, hydrogen nuclei fuse together under extremely high temperature and pressure to form helium nuclei, releasing a vast amount of energy in the process.

21. Explain a) Precipitation Reactions b) Neutralization Reactions

a) Precipitation Reactions: A precipitation reaction is a type of chemical reaction in which two soluble ionic compounds in an aqueous solution react to form an insoluble solid product called a precipitate. This precipitate separates from the solution.
Example: When a solution of silver nitrate (AgNO₃) is mixed with a solution of sodium chloride (NaCl), a white precipitate of silver chloride (AgCl) is formed. $$ AgNO_{3(aq)} + NaCl_{(aq)} \rightarrow AgCl_{(s)} \downarrow + NaNO_{3(aq)} $$

b) Neutralization Reactions: A neutralization reaction is a chemical reaction between an acid and a base, which results in the formation of a salt and water. The H⁺ ions from the acid react with the OH⁻ ions from the base to form water (H₂O), neutralizing each other's properties.
Example: The reaction between hydrochloric acid (HCl), a strong acid, and sodium hydroxide (NaOH), a strong base, produces sodium chloride (NaCl), a salt, and water. $$ HCl_{(aq)} + NaOH_{(aq)} \rightarrow NaCl_{(aq)} + H_2O_{(l)} $$

22. a) Why is Archaeopteryx considered to be a connecting link? b) How can you determine the age of the fossils?

a) Archaeopteryx is considered a connecting link because its fossil shows features of both reptiles and birds, providing evidence for the evolution of birds from reptilian ancestors.

Reptilian features: It had a long bony tail, teeth in its jaws, and claws on its wings.
Avian (bird) features: It had feathers, wings, and a wishbone (furcula).

This combination of traits strongly suggests it is an intermediate form between these two groups.

b) The age of fossils can be determined primarily by two methods:

Relative Dating: This method determines the relative order of past events without determining their absolute age. It is based on the principle that in undisturbed rock layers (strata), the oldest fossils are found in the lowest layers and the youngest are in the uppermost layers.
Absolute Dating (Radiometric Dating): This method provides a more precise numerical age for fossils. It is based on the decay of radioactive isotopes present in rocks. For example, Carbon-14 dating is used for relatively young fossils (up to about 50,000 years), while methods like Potassium-Argon or Uranium-Lead dating are used for much older fossils.

23. a) Differentiate between Outbreeding and Inbreeding. b) Undifferentiated cells and Differentiated cells

a) Outbreeding vs. Inbreeding

Feature	Inbreeding	Outbreeding
Definition	Mating of closely related individuals within the same breed for 4-6 generations.	Mating of unrelated animals. Can be between individuals of the same breed (but no common ancestors), different breeds, or different species.
Purpose	To increase homozygosity and evolve a pure line. Helps in accumulating superior genes and eliminating undesirable ones.	To produce offspring with desirable qualities (e.g., hybrid vigour), overcome inbreeding depression, and create new breeds.
Disadvantage	Can lead to inbreeding depression, reducing fertility and productivity.	Can be less effective in creating pure lines.

b) Undifferentiated cells vs. Differentiated cells

Feature	Undifferentiated Cells	Differentiated Cells
Definition	Unspecialized cells that have the ability to divide and develop into various specialized cell types.	Specialized cells that have a specific structure and function within a multicellular organism.
Potential	They are pluripotent or multipotent (e.g., stem cells).	They are unipotent, committed to a single cell type.
Function	Growth, repair, and renewal of tissues.	Perform specific functions (e.g., nerve cells transmit signals, muscle cells contract).
Example	Embryonic stem cells, adult stem cells.	Neurons, skin cells, liver cells, muscle cells.

24. What are the effects of hybrid vigour in animals.

Hybrid vigour, or heterosis, is the phenomenon where the offspring of a cross between two different purebred lines or breeds show qualities superior to both parents. The main effects in animals include:

Increased Growth Rate: Hybrid animals often grow faster and reach market weight more quickly.
Higher Productivity: Increased milk production in cattle, higher egg production in poultry, and better wool quality in sheep.
Improved Fertility and Reproduction: Hybrids tend to have better reproductive performance, including higher conception rates and larger litter sizes.
Enhanced Disease Resistance: The offspring often show greater resistance to common diseases and environmental stresses.
Increased Longevity and Survival Rate: Hybrids generally have a better overall survival rate from birth to maturity.

25. (Compulsory) a) A solution has a pOH of 11.76. What is the pH of this solution? b) Calculate the pH of 1.0 x 10⁻⁴ molar solution of HNO₃?

a) To find the pH from pOH, we use the relationship:

$$ pH + pOH = 14 $$

Given, pOH = 11.76

$$ pH = 14 - pOH $$ $$ pH = 14 - 11.76 $$ $$ pH = 2.24 $$

The pH of the solution is 2.24. Since the pH is less than 7, the solution is acidic.

b) Nitric acid (HNO₃) is a strong acid, which means it completely dissociates in water to produce H⁺ and NO₃⁻ ions.

$$ HNO_3 \rightarrow H^+ + NO_3^- $$

Therefore, the concentration of hydrogen ions [H⁺] is equal to the concentration of the HNO₃ solution.

Given, concentration of HNO₃ = $1.0 \times 10^{-4}$ M

So, $[H^+] = 1.0 \times 10^{-4}$ M

The pH is calculated using the formula:

$$ pH = -log[H^+] $$ $$ pH = -log(1.0 \times 10^{-4}) $$ $$ pH = - (log(1.0) + log(10^{-4})) $$ $$ pH = - (0 + (-4)) $$ $$ pH = 4 $$

The pH of the solution is 4.

Part - IV (Answer all the questions in detail) (2 x 7 = 14)

26. a) Compare the properties of alpha, beta and gamma radiations.

Property	Alpha (α) rays	Beta (β) rays	Gamma (γ) rays
Nature	Helium nucleus ($^{4}_{2}He$)	Electron ($^{-1}_{0}e$)	Electromagnetic waves (photons)
Charge	Positively charged (+2e)	Negatively charged (-1e)	Neutral (no charge)
Ionizing Power	Very high (about 100 times β, 10,000 times γ)	Moderate (less than α, more than γ)	Very low
Penetrating Power	Very low (can be stopped by a sheet of paper)	Moderate (can be stopped by an aluminum sheet)	Very high (requires thick lead or concrete to stop)
Speed	About 1/10 to 1/20 of the speed of light	Up to 9/10 of the speed of light	Travels at the speed of light
Effect of Electric/Magnetic Field	Deflected towards the negative plate/pole	Deflected towards the positive plate/pole (more than α)	Not deflected

(OR)

b) What is a chemical equilibrium? What are its characteristics?

Chemical Equilibrium: Chemical equilibrium is a state in a reversible chemical reaction where the rate of the forward reaction (reactants to products) is equal to the rate of the reverse reaction (products to reactants). In this state, the concentrations of reactants and products remain constant over time, and there is no net change in the composition of the system. It is a dynamic state, meaning that both forward and reverse reactions are still occurring, but at the same rate.

Example: The synthesis of ammonia in the Haber process: $$ N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g) $$

Characteristics of Chemical Equilibrium:

Dynamic Nature: Equilibrium is dynamic. The forward and reverse reactions continue to occur at equal rates, so there is no overall change in concentration.
Constant Concentrations: At equilibrium, the concentrations of all reactants and products become constant and do not change with time.
Reversible Reactions: Equilibrium can only be achieved in reversible reactions.
Attainable from Either Direction: Equilibrium can be reached whether the reaction starts with reactants or with products.
Closed System: Chemical equilibrium is only possible in a closed system, where no substances can enter or leave.
Catalyst Effect: A catalyst increases the rates of both the forward and reverse reactions equally. Therefore, a catalyst helps to attain equilibrium faster but does not alter the position of the equilibrium or the equilibrium constant.
Effect of Change (Le Chatelier's Principle): If a change in conditions (like temperature, pressure, or concentration) is applied to a system at equilibrium, the system will shift in a direction that counteracts the change to re-establish equilibrium.

27. a) i) How do you differentiate homologous organs from analogous organs? ii) Natural selection is a driving force for evolution-How?

i) Differentiating Homologous and Analogous Organs

Feature	Homologous Organs	Analogous Organs
Origin	Have a common embryonic origin and similar basic structure.	Have different embryonic origins and different basic structures.
Function	May perform different functions.	Perform similar functions.
Evolutionary Evidence	Indicate a common ancestry and support divergent evolution.	Indicate different ancestry and support convergent evolution.
Example	The forelimbs of a human, a bat, a whale, and a cat. They have the same bone structure but are used for different purposes (grasping, flying, swimming, walking).	The wings of a bird and the wings of an insect. Both are used for flying, but their internal structure and origin are completely different.

ii) Natural Selection as a Driving Force for Evolution

Natural selection, a concept proposed by Charles Darwin, is the primary mechanism and driving force of evolution. It operates on the following principles:

Overproduction: Organisms tend to produce more offspring than can possibly survive.
Variation: Within any population, there is natural variation among individuals. These variations are inherited.
Struggle for Existence: Due to overproduction and limited resources (food, space, mates), individuals must compete with one another to survive.
Survival of the Fittest (Differential Survival and Reproduction): Individuals with variations that are best suited (advantageous) to their environment are more likely to survive, reproduce, and pass on those favorable traits to their offspring. Individuals with less favorable traits are less likely to survive and reproduce.
Speciation: Over many generations, the accumulation of these favorable variations leads to the emergence of new traits and eventually new species that are well-adapted to their environment. This gradual change in a population's genetic makeup over time is evolution.

(OR)

b) i) Differentiate : Somatic gene therapy and Germ line gene therapy ii) Biofortification may help in removing hidden hunger. How?

i) Differentiating Somatic and Germ Line Gene Therapy

Feature	Somatic Gene Therapy	Germ Line Gene Therapy
Target Cells	Therapeutic genes are transferred into somatic (body) cells of a patient (e.g., bone marrow cells, liver cells).	Therapeutic genes are transferred into germ cells (sperm or eggs) or early embryos.
Inheritance	The genetic modification is not heritable and is limited to the individual patient. It will not be passed on to their children.	The genetic modification is heritable and will be passed on to all subsequent generations.
Purpose	To treat genetic disorders in an individual.	To correct a genetic disorder permanently in a family line.
Ethical Status	Generally considered ethically acceptable for treating diseases and is used in clinical trials.	Raises significant ethical concerns regarding safety, consent, and potential impact on the human gene pool. It is currently banned in humans in most countries.

ii) How Biofortification May Help in Removing Hidden Hunger

Hidden hunger refers to micronutrient deficiencies (lack of essential vitamins and minerals like iron, zinc, and vitamin A) where a person may be consuming enough calories but not enough essential nutrients. Biofortification is a scientific process of increasing the nutritional value of food crops through conventional plant breeding or modern biotechnology.

Biofortification helps remove hidden hunger in the following ways:

Increasing Nutrient Content in Staple Foods: It focuses on enriching staple food crops (like rice, wheat, maize, and beans) that are consumed by large, often poor, populations. This ensures that people get essential micronutrients directly from their daily meals without changing their dietary habits.
Cost-Effective and Sustainable: Once a biofortified crop is developed, it can be distributed and grown by farmers year after year. It is a one-time investment that provides a continuous supply of nutrient-rich food, making it a sustainable solution compared to ongoing supplementation programs.
Improved Health Outcomes: By providing essential micronutrients, biofortified foods can help prevent serious health problems. For example:
- Golden Rice (rich in Vitamin A) can prevent blindness.
- Iron-fortified beans and pearl millet can combat anemia.
- Zinc-fortified wheat and rice can boost the immune system and reduce stunting in children.
Wide Reach: It is particularly effective in reaching remote and rural populations who may not have access to diverse diets or healthcare facilities providing supplements.

By making staple foods more nutritious, biofortification provides a powerful and practical strategy to combat hidden hunger on a global scale.

10th Science - 2nd Mid Term Exam 2024 - Original Question Paper | Theni District | English Medium