Science and Technology Part I - March 2024 Solution
Q. 1 (A) Write the correct alternative:
(i) The SI unit of heat is
(A) Calorie (B) Joule (C) Kcal/kg °C (D) Cal/g °C
(ii) We can see the sun even when it is little below the horizon because of
(A) Reflection of light (B) Refraction of light (C) Dispersion of light (D) Absorption of light
(iii) ________ is the functional group of carboxylic acid.
(A) -COOH (B) -CO- (C) -CHO- (D) -OH
(iv) In simple microscope ________ lens is used.
(A) Concave (B) Plano concave (C) Plano convex (D) Convex
(v) In ________ process a layer of molten tin is deposited on metals.
(A) Anodization (B) Tinning (C) Galvanizing (D) Alloying
Q. 1 (B) Answer the following:
(i) Write the name of the atom having the smallest size.
Answer: Helium (He)
(ii) Write the molecular formula of calcium carbonate.
Answer: CaCO3
(iii) Write the use of 'Calorimeter'.
Answer: A calorimeter is used for the measurement of heat exchange during physical or chemical processes.
(iv) Identify the hydrocarbon from the given electron-dot structure:
Answer: The structure (HH HCC:H HH) represents Ethane (C2H6).
(v) Match the Columns:
| Column 'A' | Column 'B' |
|---|---|
| Refractive index of water | 1.33 |
Q. 2 (A) Give scientific reasons (any two):
(i) When the gas formed on heating limestone, is passed through freshly prepared lime water, the lime water turns milky.
Answer: Heating limestone ($CaCO_3$) releases Carbon dioxide ($CO_2$). When $CO_2$ reacts with lime water ($Ca(OH)_2$), it forms Calcium Carbonate ($CaCO_3$), an insoluble white precipitate that makes the water milky.
(ii) Tungsten metal is used to make a solenoid type coil in an electric bulb.
Answer: Tungsten has a very high melting point (approx 3410°C). When current passes through the bulb's filament, it becomes white-hot to emit light; Tungsten's high melting point prevents it from melting at these extreme temperatures.
(iii) On exposure to air, silver articles turn blackish after some time.
Answer: Silver reacts with Hydrogen Sulphide ($H_2S$) gas present in the air to form a layer of Silver Sulphide ($Ag_2S$). This black coating is a result of corrosion.
Q. 2 (B) Answer the following (any three):
(i) State Dobereiner's law of triad. Give one example of it.
Law: When elements with similar properties are arranged in increasing order of atomic masses in a group of three (triad), the atomic mass of the middle element is approximately the average of the other two.
Example: Lithium (6.9), Sodium (23.0), Potassium (39.1).
Example: Lithium (6.9), Sodium (23.0), Potassium (39.1).
(ii) Identify the figure and explain its use:
[Image of an AC Electric Generator]
(iii) What is meant by satellite launch vehicle? Name any one Indian satellite launch vehicle.
Answer: A satellite launch vehicle is a rocket used to place satellites into their respective orbits. Example: PSLV (Polar Satellite Launch Vehicle).
(iv) What is free fall? When is it possible?
Answer: When an object moves solely under the influence of gravity, it is in free fall. It is only truly possible in a vacuum.
(v) The focal length of a convex lens is 20 cm. What is its power?
Answer: $f = 20\text{ cm} = 0.2\text{ m}$.
$P = \frac{1}{f(\text{m})} = \frac{1}{0.2} = +5.0\text{ Dioptre (D)}$.
$P = \frac{1}{f(\text{m})} = \frac{1}{0.2} = +5.0\text{ Dioptre (D)}$.
Q. 3 Answer the following (any five):
(i) Complete the paragraph (Classification of Blocks):
Select the appropriate options and complete the following paragraph :
(Metals, non-metals, metalloids, four, seven, s-block, p-block, d-block, f-block).
On the basis of electronic configuration, elements in the modern periodic table are classified into ...................... blocks. Groups 1 and 2 elements are included in ......................... and all these elements are metals. (except Hydrogen). Group 13 to 18 elements are included in ..................... . This block contains metals, non-metals and metalloids. Group 3 to 12 elements are included in ........................... and all the elements are ............................ elements shown at the bottom of the periodic table i.e. Lanthanides and Actinides constitute .................... and all these elements are metals.
Select the appropriate options and complete the following paragraph :
(Metals, non-metals, metalloids, four, seven, s-block, p-block, d-block, f-block).
On the basis of electronic configuration, elements in the modern periodic table are classified into ...................... blocks. Groups 1 and 2 elements are included in ......................... and all these elements are metals. (except Hydrogen). Group 13 to 18 elements are included in ..................... . This block contains metals, non-metals and metalloids. Group 3 to 12 elements are included in ........................... and all the elements are ............................ elements shown at the bottom of the periodic table i.e. Lanthanides and Actinides constitute .................... and all these elements are metals.
On the basis of electronic configuration, elements in the modern periodic table are classified into four blocks. Groups 1 and 2 elements are included in s-block and all these elements are metals (except Hydrogen). Group 13 to 18 elements are included in p-block. This block contains metals, non-metals and metalloids. Group 3 to 12 elements are included in d-block and all the elements are metals. The elements shown at the bottom of the periodic table i.e. Lanthanides and Actinides constitute f-block and all these elements are metals.
(ii) (a) Factors affecting rate of reaction? (b) Explain one.
Factors: Nature of reactants, size of particles, concentration, temperature, and catalyst.
Explanation (Temperature): Increasing temperature increases the kinetic energy of particles, leading to more frequent and effective collisions, thus increasing the rate of reaction.
Explanation (Temperature): Increasing temperature increases the kinetic energy of particles, leading to more frequent and effective collisions, thus increasing the rate of reaction.
(iii) Observe the graph (Heating curve of water):
(b) Line AB represents Latent heat of fusion (ice turning to water at 0°C).
(c) Line BC represents increase in water temperature from 0°C to 100°C.
(iv) Complete the eye defect table:
| Point/Figure | --- | --- |
|---|---|---|
| Name of the defect | Myopia (Short-sightedness) | Hypermetropia (Long-sightedness) |
| Position of image | In front of retina | Behind retina |
| Lens used to correct | Concave lens | Convex lens |
(v) General properties of ionic compounds.
1. They are crystalline solids.
2. They have high melting and boiling points.
3. They conduct electricity in molten or aqueous states.
2. They have high melting and boiling points.
3. They conduct electricity in molten or aqueous states.
(vi) Newton's Law of Gravitation:
(a) Law: $F = G \frac{m_1 m_2}{d^2}$.
(b) If distance is tripled ($3d$), force becomes 1/9th of original.
(c) If one mass is doubled, force is doubled.
(b) If distance is tripled ($3d$), force becomes 1/9th of original.
(c) If one mass is doubled, force is doubled.
(vii) Satellite revolution time calculation:
$R = 6400 + 35780 = 42180\text{ km}$. Velocity $v = 3.08\text{ km/s}$.
$T = \frac{2\pi R}{v} = \frac{2 \times 3.14 \times 42180}{3.08} \approx 86000\text{ seconds}$ (approx. 24 hours).
$T = \frac{2\pi R}{v} = \frac{2 \times 3.14 \times 42180}{3.08} \approx 86000\text{ seconds}$ (approx. 24 hours).
(viii) What is a solenoid ? Draw a neat diagram and name its various components.
Answer: A copper wire with a resistive coating wound in a chain of loops like a spring is called a solenoid.
[Image of magnetic field lines around a solenoid]
[Image of magnetic field lines around a solenoid]
Q. 4 Answer the following (any one):
(i) Observe the given diagram and answer the question : Observe the prism diagram:
(a) Process: Dispersion of light.
(b) Deviates most: Violet.
(c) Deviates least: Red.
(d) Phenomenon: Rainbow.
(e) Spectrum: The band of colored components of a light beam.
(b) Deviates most: Violet.
(c) Deviates least: Red.
(d) Phenomenon: Rainbow.
(e) Spectrum: The band of colored components of a light beam.
(ii) Observe the acetic acid reaction diagram:
(a) Reactants: Acetic acid and Sodium carbonate.
(b) Gas: Carbon dioxide ($CO_2$).
(c) Lime water: Turns milky.
(d) Alternative chemical: Sodium bicarbonate.
(e) Use: Preserving food (Vinegar).
(b) Gas: Carbon dioxide ($CO_2$).
(c) Lime water: Turns milky.
(d) Alternative chemical: Sodium bicarbonate.
(e) Use: Preserving food (Vinegar).
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