10th Science - Second Mid Term Test 2024 Solutions
Complete solutions for the Virudhunagar District Common Second Mid Term Test - 2024 for Standard 10 Science.
Part I: Choose the correct option (8 x 1 = 8)
1) The frequency, which is audible to the human ear is
2) Unit of radioactivity is
3) Photolysis is a decomposition reaction caused by
4) Which of the following is not an "element + element → compound" type reaction?
5) Which of the following are used as anesthetics?
6) The 'use and disuse theory' was proposed by
7) Which method of crop improvement can be practised by a farmer if he is inexperienced?
8) We can cut the DNA with the help of
Part II: Answer ANY SIX questions only (6 x 2 = 12)
Question No. 16 is compulsory.
9) Mention two cases in which there is no Doppler effect in sound.
- Both the source of sound and the listener are at rest.
- The source and the listener move in such a way that the distance between them remains constant.
10) Write any three features of natural and artificial radioactivity.
| Feature | Natural Radioactivity | Artificial Radioactivity |
|---|---|---|
| Occurrence | It is a spontaneous process occurring in nature. | It is an induced (man-made) process. |
| Control | The process cannot be controlled. | The process can be controlled (started, stopped, or altered). |
| Source | Emitted by unstable nuclei of elements with atomic number > 82. | Emitted by bombarding light, stable nuclei with particles like neutrons. |
11) Name the simplest Ketone and give its structural formula.
Name: The simplest Ketone is Acetone (IUPAC name: Propanone).
Molecular Formula: C₃H₆O
Structural Formula:
$$ \begin{array}{ccc} & \large{O} & \\ & \large{\|} & \\ \large{H_3C} & - \large{C} - & \large{CH_3} \end{array} $$12) The degenerated wing of a Kiwi is an acquired character. Why is it an acquired character?
13) Name two maize hybrids rich in amino acid lysine.
- Protina
- Shakti
14) Define Ethnobotany and write its importance.
Definition: Ethnobotany is the scientific study of the relationship between people and plants. It explores how local, indigenous cultures use plants for food, medicine, shelter, and other cultural purposes.
Importance:
- It helps in the discovery of new medicinal plants and potential drugs.
- It provides valuable information for biodiversity conservation and sustainable agriculture.
- It helps in documenting and preserving traditional ecological knowledge which might otherwise be lost.
15) State and applications of DNA fingerprinting technique.
DNA Fingerprinting: It is a laboratory technique used to establish a link between biological evidence and a suspect in a criminal investigation. It identifies individuals based on the unique patterns (polymorphisms) in their DNA.
Applications:
- Forensic Science: To identify criminals from biological samples like blood, hair, or saliva found at a crime scene.
- Paternity and Maternity Tests: To determine the biological parent of a child.
- Personal Identification: To identify victims of disasters or soldiers killed in action.
16) Calculate the pH of 1.0×10-4 molar solution of HNO₃. (Compulsory)
Nitric acid (HNO₃) is a strong acid, so it dissociates completely in water.
The dissociation reaction is:
$$ HNO_3 \rightarrow H^+ + NO_3^- $$Given the concentration of HNO₃ is \( 1.0 \times 10^{-4} \) M.
Since it dissociates completely, the concentration of hydrogen ions [H⁺] will be the same as the concentration of the acid.
$$ [H^+] = 1.0 \times 10^{-4} \, M $$The pH is calculated using the formula:
$$ pH = -\log_{10}[H^+] $$Substituting the value of [H⁺]:
$$ pH = -\log_{10}(1.0 \times 10^{-4}) $$ $$ pH = -(\log_{10} 1.0 + \log_{10} 10^{-4}) $$ $$ pH = -(0 + (-4)) $$ $$ pH = -(-4) = 4 $$The pH of the solution is 4.
Part III: Write any four questions only (4 x 4 = 16)
Question No. 22 is compulsory.
17) What are the factors that affect the speed of sound in gases?
- Effect of Density: The speed of sound is inversely proportional to the square root of the density of the gas. \( (v \propto \frac{1}{\sqrt{d}}) \). As density increases, the speed of sound decreases.
- Effect of Temperature: The speed of sound is directly proportional to the square root of the absolute temperature of the gas. \( (v \propto \sqrt{T}) \). As temperature increases, the speed of sound increases.
- Effect of Relative Humidity: The speed of sound increases with an increase in humidity. This is because the density of moist air is less than that of dry air.
- Effect of Molecular Weight: The speed of sound is inversely proportional to the square root of the molecular weight of the gas. Gases with lower molecular weights (like hydrogen) transmit sound faster than gases with higher molecular weights (like carbon dioxide).
18) Compare the properties of alpha, beta and gamma radiations.
| Property | Alpha (α) rays | Beta (β) rays | Gamma (γ) rays |
|---|---|---|---|
| Nature | Positively charged particles (Helium nucleus, ₂He⁴). | Negatively charged particles (electrons, ₋₁e⁰). | Neutral electromagnetic waves (photons). |
| Charge | +2e | -1e | 0 (No charge) |
| Ionizing Power | Very high (100 times β, 10000 times γ). | Moderate (less than α). | Very low (least ionizing). |
| Penetrating Power | Very low (stopped by a sheet of paper). | Moderate (stopped by a thin aluminum foil). | Very high (can penetrate thick lead). |
19) What is called Homologous series? Give any three of its characteristics.
Homologous Series: A homologous series is a series of organic compounds which have the same functional group and similar chemical properties, in which the successive members differ by a –CH₂ group.
Characteristics of a Homologous Series:
- All members of the series can be represented by a single general formula (e.g., CₙH₂ₙ₊₂ for alkanes).
- Each successive member in the series differs from the next by a –CH₂ group or by 14 amu of mass.
- They show a gradual change in their physical properties, such as melting point, boiling point, and density, as the molecular mass increases.
- They possess similar chemical properties because they contain the same functional group.
20) Natural selection is a driving force for evolution. How?
- Variation: Within any population, there are natural variations in traits among individuals. These variations arise from mutations and genetic recombination.
- Competition: Organisms produce more offspring than can survive, leading to a "struggle for existence" where they compete for limited resources like food, water, and shelter.
- Survival of the Fittest: Individuals with traits that are better suited (advantageous) for their environment are more likely to survive, reproduce, and pass on those advantageous traits to their offspring. Individuals with less suitable traits are less likely to survive and reproduce.
- Gradual Change: Over many generations, the frequency of these advantageous traits increases in the population. This gradual accumulation of favourable traits leads to the evolution of new species.
21) What are the effects of hybrid vigour in animals?
- Increased Productivity: Hybrids often show higher yields in terms of milk, meat, or eggs compared to their parent breeds.
- Faster Growth Rate: Hybrid animals generally grow faster and reach market weight or maturity more quickly.
- Improved Fertility: Hybrids can have higher reproductive rates and better overall fertility.
- Greater Disease Resistance: They often exhibit enhanced resistance to common diseases and parasites, leading to lower mortality rates and reduced need for medication.
- Enhanced Adaptability: Hybrids can be more resilient and better able to cope with environmental stresses like heat or poor-quality feed.
22) (Compulsory)
a) Air temperature in the Rajasthan desert can reach 46°C. What is the velocity of sound in air at that temperature? (V₀ = 331 ms⁻¹)
b) Calculate the amount of energy released when a radio active substance undergoes fusion and results in a mass defect of 2kg.
a) Velocity of sound at 46°C:
The formula for the velocity of sound at a given temperature 't' (in Celsius) is:
$$ v_t = v_0 + 0.61 \times t $$Where:
- \( v_t \) = velocity of sound at temperature t.
- \( v_0 \) = velocity of sound at 0°C = 331 ms⁻¹.
- \( t \) = temperature in °C = 46°C.
Substituting the values:
$$ v_{46} = 331 + (0.61 \times 46) $$ $$ v_{46} = 331 + 28.06 $$ $$ v_{46} = 359.06 \, \text{ms}^{-1} $$The velocity of sound in air at 46°C is 359.06 ms⁻¹.
b) Energy released from mass defect:
According to Einstein's mass-energy equivalence principle, the energy released (E) is related to the mass defect (m) by the equation:
$$ E = mc^2 $$Where:
- \( E \) = energy released (in Joules).
- \( m \) = mass defect = 2 kg.
- \( c \) = speed of light in vacuum ≈ \( 3 \times 10^8 \, \text{ms}^{-1} \).
Substituting the values:
$$ E = 2 \times (3 \times 10^8)^2 $$ $$ E = 2 \times (9 \times 10^{16}) $$ $$ E = 18 \times 10^{16} \, \text{J} $$Or in standard scientific notation:
$$ E = 1.8 \times 10^{17} \, \text{J} $$The amount of energy released is \( 1.8 \times 10^{17} \) Joules.
Part IV: Answer the questions in detail (2 x 7 = 14)
23) What is an echo?
a) State two conditions necessary for hearing an echo.
b) What are the medical applications of echo?
c) How can you calculate the speed of sound using echo?
Echo: An echo is the repetition of sound produced by the reflection of sound waves from a distant, hard surface such as a cliff, a wall, or a building.
a) Conditions necessary for hearing an echo:
- The time interval between the original sound and the reflected sound (echo) must be at least 0.1 seconds. This is the persistence of hearing for the human ear.
- The minimum distance between the source of the sound and the reflecting surface must be 17.2 meters at a standard temperature of 22°C. This distance allows the sound to travel to the reflector and back in 0.1 s.
b) Medical applications of echo:
The principle of echo is used in a technique called ultrasonography. High-frequency sound waves (ultrasound) are sent into the body, and the echoes received from various organs are used to create an image. Key applications include:
- Obstetrics: To monitor the development and health of a fetus in the womb.
- Cardiology: In echocardiography, to visualize the heart's structure, valves, and pumping action.
- Internal Medicine: To examine internal organs like the liver, kidneys, gallbladder, and spleen for abnormalities.
c) Calculation of the speed of sound using an echo:
To calculate the speed of sound, you need to measure two things:
- The distance (d) between the source of the sound and the reflecting surface.
- The time interval (t) between producing the sound and hearing its echo.
The sound travels a total distance of 2d (to the reflector and back). The speed of sound (v) can be calculated using the formula:
$$ \text{Speed (v)} = \frac{\text{Total distance travelled}}{\text{Time taken}} $$ $$ v = \frac{2d}{t} $$(OR)
Explain the types of double displacement reactions with examples.
A double displacement reaction is a type of chemical reaction where two reactant ionic compounds exchange their ions to form two new product compounds. The general form of the reaction is:
$$ AB + CD \rightarrow AD + CB $$There are two main types of double displacement reactions:
1. Precipitation Reaction
In this type of reaction, two aqueous solutions of soluble salts are mixed, resulting in the formation of an insoluble solid product called a precipitate. The precipitate settles down at the bottom of the container.
Example: When an aqueous solution of silver nitrate (AgNO₃) is mixed with an aqueous solution of sodium chloride (NaCl), a white precipitate of silver chloride (AgCl) is formed along with sodium nitrate (NaNO₃) solution.
Reaction:
$$ \underset{\text{(Silver Nitrate)}}{\text{AgNO}_3(aq)} + \underset{\text{(Sodium Chloride)}}{\text{NaCl}(aq)} \rightarrow \underset{\text{(Silver Chloride - precipitate)}}{\text{AgCl}(s)\downarrow} + \underset{\text{(Sodium Nitrate)}}{\text{NaNO}_3(aq)} $$2. Neutralization Reaction
This is a specific type of double displacement reaction that occurs between an acid and a base. The H⁺ ion from the acid reacts with the OH⁻ ion from the base to form water (H₂O), and the remaining ions combine to form a salt.
Example: When hydrochloric acid (HCl), a strong acid, reacts with sodium hydroxide (NaOH), a strong base, they neutralize each other to form sodium chloride (NaCl), a salt, and water (H₂O).
Reaction:
$$ \underset{\text{(Hydrochloric Acid)}}{\text{HCl}(aq)} + \underset{\text{(Sodium Hydroxide)}}{\text{NaOH}(aq)} \rightarrow \underset{\text{(Sodium Chloride - salt)}}{\text{NaCl}(aq)} + \underset{\text{(Water)}}{\text{H}_2\text{O}(l)} $$24) a) How do you differentiate homologous organs from analogous organs?
b) Why is Archaeopteryx considered to be a connecting link?
a) Differentiation between Homologous and Analogous Organs:
| Feature | Homologous Organs | Analogous Organs |
|---|---|---|
| Origin & Structure | They have a common origin and similar basic anatomical structure. | They have different origins and different basic anatomical structures. |
| Function | They are modified to perform different functions. | They are modified to perform similar functions. |
| Type of Evolution | They indicate divergent evolution (evolution from a common ancestor). | They indicate convergent evolution (evolution of similar traits independently). |
| Example | Forelimbs of a man, cheetah, whale, and bat. | Wings of an insect and a bird. |
b) Archaeopteryx as a Connecting Link:
Archaeopteryx is considered a crucial connecting link (or transitional fossil) between reptiles and birds because it possesses a mosaic of features characteristic of both groups. This demonstrates the evolutionary path from one group to another.
- Reptilian Features:
- It had a full set of teeth in its jaws, like a reptile.
- It possessed a long, bony tail (vertebral column), unlike the short, fused tail (pygostyle) of modern birds.
- It had claws on its forelimbs (wings), similar to reptiles.
- Avian (Bird) Features:
- It was covered in well-developed flight feathers, which are a hallmark of birds.
- Its forelimbs were modified into wings.
- It had a wishbone (furcula), which is characteristic of birds.
The presence of both sets of features in a single organism provides strong evidence that birds evolved from reptilian ancestors.
(OR)
Discuss the importance of biotechnology in the field of medicine.
Biotechnology has revolutionized the field of medicine, offering new ways to diagnose, treat, and prevent diseases. Its importance can be discussed under the following key areas:
- Production of Pharmaceuticals:
- Genetically Engineered Insulin: Biotechnology allows for the large-scale production of human insulin using bacteria (like E. coli). This insulin is safer and more effective for treating diabetes than insulin derived from animals.
- Vaccines: Recombinant DNA technology is used to produce safer and more effective vaccines (e.g., Hepatitis B vaccine) by producing only the antigenic protein, avoiding the risk of injecting the actual pathogen.
- Hormones and Enzymes: Production of human growth hormone, interferons (for viral infections and cancer), and various blood clotting factors.
- Gene Therapy:
- This is a groundbreaking technique aimed at correcting genetic disorders at their source. It involves replacing a faulty or missing gene with a normal, functional gene to treat hereditary diseases like cystic fibrosis, sickle cell anemia, and muscular dystrophy.
- Medical Diagnosis:
- DNA Probes and PCR: Polymerase Chain Reaction (PCR) and DNA probes allow for the rapid and accurate detection of infectious diseases (like HIV, COVID-19) and genetic disorders by identifying the pathogen's or the faulty gene's DNA.
- ELISA Test: The Enzyme-Linked Immunosorbent Assay (ELISA) is a biotechnological tool used for detecting the presence of specific antibodies or antigens, widely used in diagnosing HIV.
- Pharmacogenomics (Personalized Medicine):
- This field combines pharmacology and genomics to develop drugs tailored to an individual's genetic makeup. This helps in prescribing drugs that are more effective and have fewer side effects for a particular patient.
- Stem Cell Technology and Regenerative Medicine:
- Biotechnology plays a crucial role in isolating and culturing stem cells. These cells have the potential to differentiate into various cell types and can be used to repair or replace damaged tissues and organs, offering hope for treating conditions like Parkinson's disease, spinal cord injuries, and heart disease.
In conclusion, biotechnology has transformed modern medicine by providing powerful tools for creating novel therapeutics, precise diagnostics, and personalized treatments, significantly improving human health and longevity.