Class 10 Board Examination — Physical Science Mock Test Paper — 2 Time: 3 Hours

Class 10 Board Examination — Physical Science Mock Test Paper — 2 Time: 3 Hours | Maximum Marks: 60

General Instructions: 1. Section A contains MCQs (1 mark each) 2. Section B contains Short Answer questions (2 marks each) 3. All questions are compulsory 4. Draw neat diagrams wherever necessary

SECTION A — Multiple Choice Questions

(1 Mark Each | 10 × 1 = 10 Marks)

Q1. Which of the following is a double displacement reaction? (a) Zn + CuSO₄ → ZnSO₄ + Cu (b) 2H₂ + O₂ → 2H₂O (c) AgNO₃ + NaCl → AgCl + NaNO₃ (d) CaCO₃ → CaO + CO₂

Q2. The colour of litmus solution in an acidic medium is: (a) Blue (b) Green (c) Red (d) Yellow

Q3. Which of the following is the strongest acid? (a) Acetic acid (b) Carbonic acid (c) Hydrochloric acid (d) Citric acid

Q4. The process of depositing a thin layer of a desired metal over another metal using electricity is called: (a) Corrosion (b) Electroplating (c) Galvanisation (d) Alloying

Q5. In the Modern Periodic Table, the number of periods is: (a) 5 (b) 6 (c) 7 (d) 8

Q6. The SI unit of electric charge is: (a) Ampere (b) Volt (c) Ohm (d) Coulomb

Q7. Which of the following is NOT a good conductor of electricity? (a) Copper (b) Silver (c) Rubber (d) Aluminium

Q8. A convex mirror always forms an image that is: (a) Real, inverted, and enlarged (b) Virtual, erect, and diminished (c) Real, erect, and same size (d) Virtual, inverted, and enlarged

Q9. The phenomenon responsible for the blue colour of the sky is: (a) Reflection (b) Refraction (c) Dispersion (d) Scattering of light

Q10. Which device converts mechanical energy into electrical energy? (a) Electric motor (b) Generator (c) Transformer (d) Battery

SECTION B — Short Answer Questions

(2 Marks Each | 15 × 2 = 30 Marks)

Q11. What is a combination reaction? Write a balanced chemical equation for one example of a combination reaction.

Q12. What is rancidity? State two methods to prevent rancidity.

Q13. Define pH. What is the pH of the following and what does it indicate: (i) pH = 3 (ii) pH = 11

Q14. What is the difference between a mineral and an ore? Give one example of each.

Q15. State two chemical properties of metals. Write a chemical equation for each.

Q16. State Newlands' Law of Octaves. What was the limitation of this classification?

Q17. Define electric current and potential difference. State their SI units.

Q18. Two resistors of 4 Ω and 6 Ω are connected in series to a 20V battery. Find: (i) The total resistance (ii) The current flowing through the circuit

Q19. State the right-hand thumb rule. How is it used to determine the direction of the magnetic field around a straight current-carrying conductor?

Q20. What is a solenoid? Draw a neat diagram of a solenoid and state its use.

Q21. Define refraction of light. State Snell's Law of refraction in mathematical form.

Q22. An object is placed 20 cm in front of a convex lens of focal length 10 cm. Find the image distance using the lens formula and state the nature of the image.

Q23. What is dispersion of light? Name the colours of the visible spectrum in order.

Q24. Differentiate between step-up and step-down transformers. Give one practical use of each.

Q25. What are the advantages of using AC over DC for long-distance transmission of electrical energy?

ANSWERS

Section A — Answers

A1. (c) AgNO₃ + NaCl → AgCl + NaNO₃

A2. (c) Red

A3. (c) Hydrochloric acid

A4. (b) Electroplating

A5. (c) 7

A6. (d) Coulomb

A7. (c) Rubber

A8. (b) Virtual, erect, and diminished

A9. (d) Scattering of light

A10. (b) Generator

Section B — Answers

A11. A combination reaction is a reaction in which two or more substances combine to form a single new substance.

Example: When quicklime (calcium oxide) reacts with water, it forms calcium hydroxide (slaked lime).

CaO + H₂O → Ca(OH)₂ + Heat

This is also an exothermic reaction as heat is released during the process.

A12. Rancidity is the process by which fats and oils in food get oxidised on exposure to air, causing them to smell and taste unpleasant.

Two methods to prevent rancidity:

Adding antioxidants such as BHA (butylated hydroxyanisole) to food products to prevent oxidation of fats.
Storing food in airtight containers or packaging food in nitrogen gas to prevent contact with oxygen.

A13. pH is a scale used to measure the concentration of hydrogen ions (H⁺) in a solution. It ranges from 0 to 14.

(i) pH = 3 — This indicates an acidic solution. The lower the pH below 7, the stronger the acid. A pH of 3 represents a moderately strong acid (e.g., vinegar or orange juice).

(ii) pH = 11 — This indicates a basic (alkaline) solution. The higher the pH above 7, the stronger the base. A pH of 11 represents a strong base (e.g., lime water or household ammonia).

A14. Mineral: A naturally occurring substance in the earth's crust that contains a metal in combined or free state. Example: Bauxite (Al₂O₃·2H₂O) is a mineral of aluminium.

Ore: A mineral from which a metal can be extracted profitably and conveniently is called an ore. Example: Haematite (Fe₂O₃) is an ore of iron.

Note: All ores are minerals but not all minerals are ores.

A15. Two chemical properties of metals:

Reaction with oxygen: Metals react with oxygen to form metallic oxides which are basic in nature. 4Na + O₂ → 2Na₂O (Sodium oxide)
Reaction with dilute acids: Metals react with dilute acids to produce a salt and hydrogen gas. Fe + H₂SO₄ → FeSO₄ + H₂↑ (Iron reacts with dilute sulphuric acid to form iron sulphate and hydrogen gas)

A16. Newlands' Law of Octaves (1866): When elements are arranged in increasing order of their atomic masses, every eighth element has properties similar to the first, just like the musical notes (do, re, mi, fa, sol, la, ti).

Limitations:

This law was applicable only up to calcium. After calcium, every eighth element did not have properties similar to the first element.
When noble gases were discovered later, they could not be accommodated in Newlands' arrangement, which disturbed the entire order.

A17. Electric current: The rate of flow of electric charge through a conductor is called electric current. I = Q/t SI unit: Ampere (A)

Potential difference: The work done per unit charge to move a positive charge from one point to another in an electric circuit is called potential difference. V = W/Q SI unit: Volt (V)

A18. Given: R₁ = 4 Ω, R₂ = 6 Ω, V = 20V

(i) Total resistance in series: Rₛ = R₁ + R₂ = 4 + 6 = 10 Ω

(ii) Current flowing through the circuit (using Ohm's Law): I = V/R = 20/10 = 2 A

A19. Right-Hand Thumb Rule: If a current-carrying conductor is held in the right hand such that the thumb points in the direction of the current, then the curled fingers around the conductor point in the direction of the magnetic field produced around it.

Application: When a straight conductor carries current upward, the right hand is held with the thumb pointing upward (direction of current). The curled fingers show that the magnetic field forms concentric circles around the conductor in the anticlockwise direction when viewed from the top.

A20. A solenoid is a long coil of wire consisting of a large number of circular turns of insulated copper wire wound closely in the form of a cylinder.

Diagram description (draw the following):

Draw a cylindrical coil with multiple circular loops
Show current direction with arrows on the wire
Draw magnetic field lines emerging from one end (North pole) and entering the other end (South pole)
Label: current in, current out, N pole, S pole, magnetic field lines

Use of solenoid: A solenoid is used to make an electromagnet. When an iron core is placed inside the solenoid, it becomes a powerful electromagnet used in electric bells, cranes, and MRI machines.

A21. Refraction of light: The bending of light when it travels from one transparent medium to another transparent medium of different optical density is called refraction of light. It occurs due to the change in speed of light as it passes from one medium to another.

Snell's Law of refraction: The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for a given pair of media.

sin i / sin r = n (refractive index) = constant

Or: n₁ sin i = n₂ sin r

where n₁ and n₂ are the refractive indices of the two media, i is the angle of incidence, and r is the angle of refraction.

A22. Given: u = −20 cm, f = +10 cm (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 = 2/20 − 1/20 1/v = 1/20 v = +20 cm

The image is formed 20 cm on the other side of the lens. Nature of image: Real, inverted, and same size as the object (since object is at 2F).

A23. Dispersion of light: The splitting of white light into its seven constituent colours when it passes through a prism or any transparent medium is called dispersion of light. It occurs because different colours of light travel at different speeds in a medium and hence refract by different amounts.

The colours of the visible spectrum in order (from violet to red): V I B G Y O R Violet — Indigo — Blue — Green — Yellow — Orange — Red

(Violet bends the most and Red bends the least during dispersion.)

A24.

	Step-up Transformer	Step-down Transformer
Function	Increases voltage, decreases current	Decreases voltage, increases current
Turns ratio	More turns in secondary coil	More turns in primary coil
Practical use	Used at power stations to transmit electricity over long distances	Used at homes and localities to reduce voltage to safe usable levels

A25. Advantages of AC over DC for long-distance transmission:

Voltage can be stepped up easily: Using a transformer, AC voltage can be increased to very high values (e.g., 11,000V or more) for transmission. High voltage means low current, which reduces energy loss due to heating in transmission wires (P = I²R). DC voltage cannot be stepped up easily with a simple transformer.
Less energy loss: Since AC is transmitted at high voltage and low current over long distances, the power loss (I²R loss) in the transmission cables is significantly reduced, making AC far more economical and efficient than DC for power transmission.
Easy to transform: AC can be easily stepped up for transmission and stepped down for safe domestic and industrial use using simple transformers, whereas DC requires more complex and expensive equipment for voltage conversion.

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