10th Science Second Mid Term Test 2024 - Full Question Paper with Solutions
SECOND MID TERM TEST - 2024 | Standard - X SCIENCE | Solutions
Part - I: Choose the correct answers (9 × 1 = 9)
1) When a sound wave travels through air, the air particles
a) vibrate along the direction of the wave motion
b) vibrate but not in any fixed direction
c) vibrate perpendicular to the direction of the wave motion
d) None of the above
Answer: a) vibrate along the direction of the wave motion
2) The frequency which is audible to the human ear is
a) 50 KHz
b) 20KHz
c) 15,000 KHz
d) 10,000 KHz
Answer: b) 20KHz (The audible range for humans is 20 Hz to 20,000 Hz or 20 kHz)
3) _______ isotope is used for the treatment of cancer
a) Radio Iodine
b) Radio Cobalt
c) Radio Carbon
d) Radio Nickel
Answer: b) Radio Cobalt (Cobalt-60 is used in radiotherapy)
4) Photolysis is a decomposition reaction caused by
a) heat
b) electricity
c) light
d) Mechanical energy
Answer: c) light
5) The ionic product of water at 25°C is
a) \(1.00 \times 10^{-14} \text{ mol}^2\text{dm}^6\)
b) \(1.00 \times 10^{14} \text{ mol}^{-2}\text{dm}^6\)
c) \(1.00 \times 10^{-14} \text{ mol}^2\text{dm}^{-6}\)
d) \(1.00 \times 10^{14} \text{ mol}^2\text{dm}^{-6}\)
Answer: c) \(1.00 \times 10^{-14} \text{ mol}^2\text{dm}^{-6}\)
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) The term Ethnobotany was coined by
a) Khorana
b) J.W. Harshberger
c) Ronald Ross
d) Hugo de vries
Answer: b) J.W. Harshberger
8) We can cut the DNA with the help of
a) Scissors
b) Restriction Endonucleases
c) Knife
d) RNAase
Answer: b) Restriction Endonucleases
9) DNA fingerprinting is based on the principle of identifying ________ sequence of DNA.
a) Single stranded
b) mutated
c) polymorphic
d) repetitive
Answer: d) repetitive (It identifies variations in repetitive DNA sequences)
Part - II: Answer any four questions. (Q.No.15 is compulsory) (4 × 2 = 8)
10) Why does sound travel faster on rainy days than on a dry day?
The speed of sound in air increases with the increase in humidity. On rainy days, the humidity is higher than on dry days. The density of moist air is less than that of dry air. Since the speed of sound is inversely proportional to the square root of the density of the medium, sound travels faster in less dense moist air. Therefore, sound travels faster on rainy days.
11) Write true or false:
a) On dipping a pH paper in a solution, it turns into yellow. Then the solution is basic.
Answer: False. A yellow color on a universal pH indicator paper indicates a weakly acidic solution (pH around 5-6). Basic solutions turn the paper blue or violet.
b) Sound can travel through solids, liquids, gases and even vacuum.
Answer: False. Sound is a mechanical wave and requires a medium (like solid, liquid, or gas) to propagate. It cannot travel through a vacuum.
12) Why is Archaeopteryx considered to be a connecting link?
Archaeopteryx is considered a connecting link because it has features of both reptiles and birds, providing evidence for the evolution of birds from reptiles.
- Reptilian characters: Presence of teeth in the jaw, a long bony tail, and claws on its wings.
- Avian (bird) characters: Presence of feathers on the body, wings (modified forelimbs), and a beak-like jaw.
13) Name the types of stem cells.
Stem cells can be classified based on their potency (ability to differentiate):
- Totipotent stem cells: Can differentiate into any cell type, including the placenta, forming a complete organism.
- Pluripotent stem cells: Can differentiate into any cell type of the body, but not the placenta.
- Multipotent stem cells: Can differentiate into a limited range of cell types.
14) i) When and where was the first nuclear reactor built?
The first nuclear reactor, Chicago Pile-1 (CP-1), was built in 1942 at the University of Chicago, USA.
14) ii) Which radioactive material is present in the ore of pitchblende?
The primary radioactive material present in the ore of pitchblende is Uranium.
15) Calculate the pH of 1×10⁻⁴ molar solution of NaOH. (Compulsory)
NaOH is a strong base and dissociates completely in water.
\[ \text{NaOH} \rightarrow \text{Na}^+ + \text{OH}^- \]
Given, concentration of NaOH = \(1 \times 10^{-4}\) M.
Therefore, the concentration of hydroxide ions, \([OH^-] = 1 \times 10^{-4}\) M.
First, we calculate the pOH: \[ \text{pOH} = -\log_{10}[OH^-] \] \[ \text{pOH} = -\log_{10}(1 \times 10^{-4}) \] \[ \text{pOH} = 4 \] We know that at 25°C, \( \text{pH} + \text{pOH} = 14 \). \[ \text{pH} = 14 - \text{pOH} \] \[ \text{pH} = 14 - 4 = 10 \] The pH of the solution is 10.
First, we calculate the pOH: \[ \text{pOH} = -\log_{10}[OH^-] \] \[ \text{pOH} = -\log_{10}(1 \times 10^{-4}) \] \[ \text{pOH} = 4 \] We know that at 25°C, \( \text{pH} + \text{pOH} = 14 \). \[ \text{pH} = 14 - \text{pOH} \] \[ \text{pH} = 14 - 4 = 10 \] The pH of the solution is 10.
Part - III: Answer any three questions. (Q.No.20 is compulsory) (3 × 4 = 12)
16) State Soddy and Fajan's displacement law.
Soddy and Fajan's displacement laws describe the changes in the atomic number (Z) and mass number (A) of a nucleus during radioactive decay.
- Alpha Decay: When a nucleus undergoes alpha decay, it emits an alpha particle (\(_{2}^{4}\textrm{He}\)). The atomic number of the daughter nucleus decreases by 2, and its mass number decreases by 4. \[ _{Z}^{A}\textrm{X} \rightarrow _{Z-2}^{A-4}\textrm{Y} + _{2}^{4}\textrm{He} \] The daughter element is displaced two positions to the left in the periodic table.
- Beta Decay: When a nucleus undergoes beta decay, it emits a beta particle (\(_{-1}^{0}\textrm{e}\)). The atomic number of the daughter nucleus increases by 1, and its mass number remains unchanged. \[ _{Z}^{A}\textrm{X} \rightarrow _{Z+1}^{A}\textrm{Y} + _{-1}^{0}\textrm{e} \] The daughter element is displaced one position to the right in the periodic table.
17) i) Differentiate reversible and irreversible reaction.
| Feature | Reversible Reaction | Irreversible Reaction |
|---|---|---|
| Direction | Proceeds in both forward and backward directions. | Proceeds only in the forward direction. |
| Completion | Never go to completion; attain a state of equilibrium. | Proceed to completion. |
| Symbol | Represented by a double arrow (\(\rightleftharpoons\)). | Represented by a single arrow (\(\rightarrow\)). |
17) ii) Among these two reactions, which one is feasible?
2NaCl(aq) + F₂(g) → 2NaF(aq) + Cl₂(g)
2NaF(aq) + Cl₂(g) → 2NaCl(aq) + F₂(g)
The feasibility of these reactions depends on the reactivity of the halogens. The reactivity order is F₂ > Cl₂ > Br₂ > I₂. A more reactive halogen can displace a less reactive halogen from its salt solution.
- In the first reaction, Fluorine (F₂) is more reactive than Chlorine (Cl₂), so it can displace Chlorine from NaCl. Therefore, the first reaction is feasible.
- In the second reaction, Chlorine (Cl₂) is less reactive than Fluorine (F₂), so it cannot displace Fluorine from NaF. Therefore, the second reaction is not feasible.
18) Define Ethnobotany and write its importance.
Definition: Ethnobotany is the study of the relationship between plants and people, particularly the traditional knowledge of indigenous cultures regarding the use of plants for various purposes like medicine, food, shelter, and rituals.
Importance:
Importance:
- It helps in documenting and preserving traditional botanical knowledge which might otherwise be lost.
- It provides valuable clues for the discovery of new plant-based drugs and medicines.
- It plays a crucial role in the conservation of plant biodiversity and cultural heritage.
- It supports local economies by promoting the sustainable use of plant resources.
19) Match the following:
- Wood park - Thiruvakkarai (National Fossil Wood Park)
- Insulin - First hormone produced using rDNA technique
- pH of human blood - 7.35 (The normal range is 7.35-7.45)
- C-14 - Age of fossil (Used in carbon dating)
20) \(^{238}_{88}\text{Ra}\) experiences three \(\alpha\)-decay. Find the number of neutrons in the daughter element. (Compulsory)
Initial Nucleus: \(^{238}_{88}\text{Ra}\)
Atomic Number (Z) = 88, Mass Number (A) = 238.
An alpha decay (\(\alpha\)) involves the emission of a Helium nucleus (\(_{2}^{4}\text{He}\)). In one \(\alpha\)-decay, Z decreases by 2 and A decreases by 4.
For three \(\alpha\)-decays:
Atomic Number (Z) = 88, Mass Number (A) = 238.
An alpha decay (\(\alpha\)) involves the emission of a Helium nucleus (\(_{2}^{4}\text{He}\)). In one \(\alpha\)-decay, Z decreases by 2 and A decreases by 4.
For three \(\alpha\)-decays:
- Total decrease in Z = \(3 \times 2 = 6\)
- Total decrease in A = \(3 \times 4 = 12\)
- New Atomic Number (Z') = \(88 - 6 = 82\)
- New Mass Number (A') = \(238 - 12 = 226\)
Part - IV: Answer in detail (3 × 7 = 21)
21) a)
i) 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 20,000 Hertz (20 kHz). These high-frequency sound waves are inaudible to humans but can be detected and used by certain animals and in various technological applications.
ii) State three uses of ultrasonic vibration.
- Medical Field: Used in ultrasonography for imaging internal body organs, monitoring fetal development, and in echocardiography to view the heart.
- Industrial Applications: Used for cleaning delicate parts, drilling holes in hard materials, and for non-destructive testing to detect flaws or cracks in metal structures.
- Navigation and Communication: Used in SONAR (Sound Navigation and Ranging) systems on ships and submarines to measure the depth of the sea and locate underwater objects.
iii) Name three animals which can hear ultrasonic vibration.
Three animals that can hear or use ultrasonic vibrations are:
- Bats (use it for echolocation to navigate and find prey)
- Dolphins (use it for echolocation in water)
- Dogs (can hear frequencies up to 45 kHz)
OR
21) b) Compare the properties of alpha, beta and gamma radiation.
| Property | Alpha (α) Radiation | Beta (β) Radiation | Gamma (γ) Radiation |
|---|---|---|---|
| Nature | A stream of Helium nuclei (\(_{2}^{4}\textrm{He}\)) | A stream of fast-moving electrons (\(_{-1}^{0}\textrm{e}\)) | High-energy electromagnetic waves (photons) |
| Charge | Positive (+2e) | Negative (-1e) | Neutral (0) |
| Ionizing Power | Very high (about 100 times that of beta) | Moderate | Very low |
| Penetrating Power | Very low (can be stopped by a sheet of paper) | Moderate (can be stopped by a thin aluminum sheet) | Very high (requires thick lead or concrete to stop) |
| Effect of Electric/Magnetic Fields | Deflected | Deflected (more than alpha particles) | Not deflected |
22) a) Explain the factors influencing the rate of a reaction.
The rate of a chemical reaction is influenced by several factors:
- Nature of the Reactants: The rate depends on the chemical nature of the reacting substances. For example, reactions involving ionic compounds are generally faster than those involving covalent compounds because less energy is needed to break bonds.
- Concentration of the Reactants: According to the law of mass action, the rate of a reaction is directly proportional to the concentration of the reactants. Higher concentrations lead to more frequent collisions between particles, increasing the reaction rate.
- Temperature: Increasing the temperature generally increases the reaction rate. A rise in temperature increases the kinetic energy of the molecules, leading to more frequent and more energetic collisions that are effective in forming products.
- Presence of a Catalyst: A catalyst is a substance that increases the rate of a reaction without being consumed itself. It provides an alternative reaction pathway with a lower activation energy, allowing more reactant molecules to convert into products.
- Surface Area of Reactants: For reactions involving solids, the rate increases with an increase in surface area. Grinding a solid reactant into a fine powder increases the surface area available for reaction, leading to more collisions and a faster rate.
- Pressure (for gaseous reactions): Increasing the pressure of a gaseous reaction increases the concentration of the gas molecules, leading to more frequent collisions and a higher reaction rate.
OR
22) b) How does pH play an important role in everyday life.
pH plays a vital role in various aspects of our daily lives:
- Human Body: Our body functions within a narrow pH range. Human blood must be maintained at a pH of about 7.35-7.45. Our stomach produces hydrochloric acid, creating a highly acidic pH (1.5-3.5) which is essential for digesting food.
- Agriculture: Plants require a specific soil pH for optimal growth. Farmers test the soil pH and amend it using substances like lime (to reduce acidity) or gypsum (to reduce alkalinity) to ensure healthy crop yields.
- Tooth Decay: When we consume sugary foods, bacteria in our mouth produce acids. If the pH in the mouth falls below 5.5, the tooth enamel (made of calcium phosphate) begins to demineralize, leading to tooth decay. Using toothpaste, which is typically basic, helps neutralize this acid.
- Acid Rain: Atmospheric pollutants like sulfur dioxide and nitrogen oxides dissolve in rainwater to form sulfuric and nitric acids, lowering the pH of the rain (acid rain). This harms aquatic life, damages forests, and corrodes buildings and monuments.
23) a) i) How do you differentiate homologous organs from analogous organs?
| Feature | Homologous Organs | Analogous Organs |
|---|---|---|
| Origin | Have a common embryonic origin. | Have different embryonic origins. |
| Structure | Similar basic anatomical structure. | Different basic anatomical structure. |
| Function | May perform different functions. | Perform similar functions. |
| Evolution | Indicate divergent evolution (common ancestry). | Indicate convergent evolution (adapted to similar environments). |
| Example | Forelimbs of a human, a whale's flipper, and a bat's wing. | Wings of an insect and wings of a bird. |
23) a) ii) a) _________ is often referred as Goldilock zone for life.
Habitable Zone (or Earth)
23) a) ii) b) The theory of natural selection for evolution' was proposed by _______.
Charles Darwin
OR
23) b)
i) Define Genetic Engineering. (2)
Genetic engineering is the technology that involves the direct manipulation, alteration, and modification of an organism's genetic material (DNA). This is done to change the characteristics of an organism or to introduce new traits by inserting, deleting, or modifying genes.
ii) Name two maize hybrids rich in amino acid lysine. (2)
Two maize hybrids rich in the amino acid lysine are:
- Protina
- Shakti
iii) Differentiate Somatic gene therapy and germ line gene therapy. (3)
| Feature | Somatic Gene Therapy | Germ Line Gene Therapy |
|---|---|---|
| Target Cells | Targets the somatic (body) cells of an individual (e.g., lung cells, muscle cells). | Targets the germ cells (sperm or egg cells) or the zygote. |
| Heritability | The genetic modification is not heritable and is not passed on to the next generation. | The genetic modification is heritable and is passed on to all subsequent generations. |
| Ethical Status | It is used in clinical trials to treat genetic diseases in individuals. It is considered more ethically acceptable. | It is highly controversial due to major ethical concerns and is not currently performed on humans. |