10th Science Quarterly Exam 2024 - Question Paper with Solutions
Part - I (12 x 1 = 12)
i) Answer all the questions.
ii) Choose the most appropriate answer from the given 4 alternatives and write the option code and the corresponding answer.
1) Which is formed during anaerobic respiration?
2) The body of leech has
3) Which one of the following shows correct composition of blood
4) Bipolar neurons are found in
5) Which one is referred as "Master Gland"?
6) If the Earth shrinks to 50% of its real radius its mass remaining the same, the weight of a body on the Earth will
7) Where should an object be placed so that a real and inverted image of same size is obtained by a convex lens
8) If a substance is heated or cooled, the change in mass of that substance is
9) SI unit of resistance is
10) The volume occupied by 1 mole of a diatomic gas at S.T.P is
11) The process of coating the surface of metal with a thin layer of zinc is called
12) Which of the following is the universal solvent?
Part - II (7 x 2 = 14)
Note: Answer any 7 questions.
13) Define inertia. Give its classification.
Inertia: The inherent property of a body to resist any change in its state of rest or the state of uniform motion, unless it is influenced by an external unbalanced force, is known as inertia.
Classification:
- Inertia of rest: The resistance of a body to change its state of rest.
- Inertia of motion: The resistance of a body to change its state of uniform motion.
- Inertia of direction: The resistance of a body to change its direction of motion.
14) Define dispersion of light.
Dispersion of light: The phenomenon of splitting of a beam of white light into its seven constituent colours (VIBGYOR) when it is passed through a transparent medium like a glass prism is called dispersion of light.
15) State Boyle's law.
Boyle's Law: It states that when the temperature of a gas is kept constant, the volume of a fixed mass of gas is inversely proportional to its pressure.
Mathematically, P ∝ 1/V
16) What happens to the resistance, as the conductor is made thicker?
The resistance of a conductor is inversely proportional to its area of cross-section (R ∝ 1/A). When a conductor is made thicker, its cross-sectional area (A) increases. Therefore, its resistance decreases.
17) What is Molar volume of a gas?
Molar Volume: The volume occupied by one mole of any gas at Standard Temperature and Pressure (STP) is called Molar Volume. Its value is constant for all gases and is equal to 22.4 litres/mole (or 22.4 dm³/mole).
18) What is rust? Give the equation for formation of rust.
Rust: Rust is a reddish-brown hydrated ferric oxide (Fe₂O₃·xH₂O) formed on the surface of iron when it is exposed to moist air.
Equation:
4Fe + 3O₂ + xH₂O → 2Fe₂O₃·xH₂O (Rust)
19) What is aqueous and non-aqueous solution?
- Aqueous solution: A solution in which water acts as the solvent is called an aqueous solution. Example: Sugar dissolved in water.
- Non-aqueous solution: A solution in which any liquid other than water acts as the solvent is called a non-aqueous solution. Example: Sulphur dissolved in carbon disulphide.
20) Why should the light dependent reaction occur before the light independent reaction?
The light-dependent reaction must occur first because it captures light energy and converts it into chemical energy in the form of ATP (Adenosine Triphosphate) and NADPH (Nicotinamide adenine dinucleotide phosphate). These energy-rich molecules are essential to power the subsequent light-independent reactions (Calvin cycle), where CO₂ is converted into glucose.
21) What does CNS stand for?
CNS stands for Central Nervous System.
22) What is the importance of valves in the heart?
The valves in the heart are crucial for maintaining the unidirectional flow of blood. They open to allow blood to pass from one chamber to another or into the great arteries, and they close tightly to prevent the backflow of blood. This ensures efficient pumping of blood throughout the body.
Part - III (7 x 4 = 28)
Note: Answer any 7 questions. (Q.No. 32 is compulsory)
23) A pure tall plant (TT) is crossed with pure dwarf plant (tt), what would be the F1 and F2 generations? Explain.
When a pure tall plant (TT) is crossed with a pure dwarf plant (tt):
F1 Generation:
- All the plants in the F1 generation will be heterozygous tall (Tt).
- Genotype: All Tt
- Phenotype: All Tall
- This is because the allele for tallness (T) is dominant over the allele for dwarfness (t).
F2 Generation (Self-pollination of F1):
When the F1 generation (Tt) is self-pollinated, the F2 generation shows the following results, which can be illustrated with a Punnett square:
| Gametes | T | t |
|---|---|---|
| T | TT (Tall) | Tt (Tall) |
| t | Tt (Tall) | tt (Dwarf) |
- Genotypic Ratio: 1 (TT) : 2 (Tt) : 1 (tt)
- Phenotypic Ratio: 3 (Tall) : 1 (Dwarf)
24) A 100 watt electric bulb is used for 5 hours daily and four 60 watt bulbs are used for 5 hours daily. Calculate the energy consumed (in kWh) in the month of January.
Given: Month is January (31 days)
1. Energy consumed by the 100 W bulb:
- Power (P₁) = 100 W = 0.1 kW
- Time (t) = 5 hours/day
- Number of days (d) = 31
- Energy (E₁) = P₁ × t × d = 0.1 kW × 5 h × 31 = 15.5 kWh
2. Energy consumed by the four 60 W bulbs:
- Total Power (P₂) = 4 × 60 W = 240 W = 0.24 kW
- Time (t) = 5 hours/day
- Number of days (d) = 31
- Energy (E₂) = P₂ × t × d = 0.24 kW × 5 h × 31 = 37.2 kWh
3. Total energy consumed:
- Total Energy (E) = E₁ + E₂ = 15.5 kWh + 37.2 kWh = 52.7 kWh
The total energy consumed in the month of January is 52.7 kWh.
27) An object is placed at a distance 20cm from a convex lens of focal length 10cm. Find the image distance and nature of the image.
Given:
- Object distance (u) = -20 cm (by sign convention)
- Focal length (f) = +10 cm (for a convex lens)
Using the lens formula: 1/f = 1/v - 1/u
1/10 = 1/v - (1/-20)
1/10 = 1/v + 1/20
1/v = 1/10 - 1/20
1/v = (2 - 1) / 20 = 1/20
Therefore, v = +20 cm
Nature of the image:
- Since the image distance (v) is positive, the image is real.
- Magnification (m) = v/u = 20 / -20 = -1. Since the magnification is negative, the image is inverted.
- Since the magnitude of magnification is 1, the image is of the same size as the object.
Result: The image is formed at a distance of 20 cm on the other side of the lens. It is a real, inverted, and same-sized image.
32) The electronic configuration of metal A is 2,8,18,1. The metal A when exposed to air and moisture forms B a green layered compound. A with con.H₂SO₄ forms C and D along with water. D is gaseous compound. Find A,B,C and D.
Finding A: The electronic configuration 2, 8, 18, 1 corresponds to an atomic number of 29 (2+8+18+1). The element with atomic number 29 is Copper (Cu).
A = Copper (Cu)
Finding B: When Copper (A) is exposed to air (O₂, CO₂) and moisture (H₂O), it forms a green layer of basic copper carbonate.
B = Basic Copper Carbonate (CuCO₃·Cu(OH)₂)
Finding C and D: Copper (A) reacts with concentrated sulphuric acid (con. H₂SO₄) to form copper sulphate (C), sulphur dioxide gas (D), and water.
Reaction: Cu + 2H₂SO₄ (conc.) → CuSO₄ + SO₂↑ + 2H₂O
C = Copper Sulphate (CuSO₄)
D = Sulphur dioxide (SO₂) gas
Part - IV (3 x 7 = 21)
Note: Answer all the questions.
33) a) Define Mole and Give the salient features of "Modern atomic theory".
Mole:
A mole is defined as the amount of substance which contains Avogadro's number (6.022 x 10²³) of particles (atoms, molecules, or ions). It is also the amount of substance containing as many elementary entities as there are atoms in exactly 12 grams of the Carbon-12 isotope.
Salient Features of Modern Atomic Theory:
- An atom is no longer considered indivisible. It is composed of subatomic particles: protons, neutrons, and electrons.
- Atoms of the same element may not be identical in all respects. They can have different masses, known as isotopes (e.g., ¹H, ²H, ³H).
- Atoms of different elements may have the same atomic mass, known as isobars (e.g., ⁴⁰Ar, ⁴⁰K, ⁴⁰Ca).
- An atom is the smallest particle that takes part in a chemical reaction.
- The mass of an atom can be converted into energy according to Einstein's equation, E = mc².
- Atoms of one element can be transmuted (changed) into atoms of another element through nuclear reactions.
b) i) State the reason for addition of caustic alkali to bauxite ore during purification of bauxite. ii) Along with cryolite and alumina, another substance is added to the electrolyte mixture. Name the substance and give one reason for the addition.
i) Reason for adding caustic alkali (NaOH):
In the Baeyer's process for purifying bauxite ore (Al₂O₃·2H₂O), caustic alkali (sodium hydroxide) is added to digest the powdered ore. Bauxite is amphoteric and dissolves in the hot concentrated NaOH solution to form soluble sodium aluminate (NaAlO₂). The impurities like ferric oxide (Fe₂O₃) and silica (SiO₂) are insoluble and can be filtered off. This step is crucial for separating pure alumina from its impurities.
ii) Substance added to electrolyte mixture:
- Name of the substance: Fluorspar (Calcium Fluoride, CaF₂).
- Reason for addition: It is added to the electrolyte mixture of molten cryolite and alumina to further lower the fusion (melting) temperature of the electrolyte and to increase its electrical conductivity, making the electrolytic process more energy-efficient.
35) a) i) State Newton's laws of motion. ii) Deduce the equation of a force using Newton's second law of motion.
i) Newton's Laws of Motion:
- First Law (Law of Inertia): Every body continues to be in its state of rest or of uniform motion along a straight line unless it is acted upon by an external unbalanced force.
- Second Law (Law of Force): The rate of change of momentum of a body is directly proportional to the external unbalanced force applied on it, and the change in momentum takes place in the direction of the force.
- Third Law (Law of Action and Reaction): For every action, there is an equal and opposite reaction.
ii) Deduction of F = ma:
According to Newton's second law of motion, the force (F) applied on a body is directly proportional to the rate of change of its momentum (p).
F ∝ (Change in momentum) / time taken
Let a body of mass 'm' have an initial velocity 'u'. Let a force 'F' act on it for time 't', changing its velocity to 'v'.
Initial momentum = mu
Final momentum = mv
Change in momentum (Δp) = Final momentum - Initial momentum = mv - mu = m(v - u)
Rate of change of momentum = m(v - u) / t
We know that acceleration (a) = (v - u) / t. Substituting this, we get:
Rate of change of momentum = ma
From the second law, F ∝ ma. Introducing a constant of proportionality 'k', we get:
F = kma
The unit of force (the newton) is defined as the force which produces an acceleration of 1 m/s² in a body of mass 1 kg. By choosing this unit, the value of the constant k becomes 1.
Therefore, F = ma.
b) i) Explain the construction and working of a 'Compound Microscope' ii) Why does the sky appear in blue colour?
i) Compound Microscope:
Construction: A compound microscope consists of two convex lenses. The lens with a shorter focal length placed near the object is called the objective lens. The lens with a larger focal length and aperture placed near the observer's eye is called the eyepiece. Both lenses are fitted in a narrow tube with an arrangement to adjust the distance between them.
Working:
- The object is placed just beyond the focal point of the objective lens.
- The objective lens forms a real, inverted, and magnified image (Image A) inside the tube.
- This first image (Image A) acts as the object for the eyepiece.
- The eyepiece is adjusted so that Image A falls within its focal length.
- The eyepiece, acting like a simple microscope, produces a final, virtual, inverted, and highly magnified image (Image B) at the least distance of distinct vision (25 cm).
ii) Why the sky appears blue:
The blue color of the sky is due to a phenomenon called Rayleigh scattering.
- When sunlight enters the Earth's atmosphere, it is scattered in all directions by the tiny gas molecules and dust particles present in the air.
- According to Rayleigh's scattering law, the amount of scattering is inversely proportional to the fourth power of the wavelength of the light (Scattering ∝ 1/λ⁴).
- Sunlight is a mixture of seven colors (VIBGYOR). Blue and violet light have the shortest wavelengths, while red light has the longest wavelength.
- Because of their shorter wavelengths, blue and violet light are scattered much more strongly than the other colors.
- Our eyes are more sensitive to blue light than violet light. Therefore, when we look up at the sky, we see this scattered blue light coming from all directions, which makes the sky appear blue.