Class 7 ICSE Physics Chapter 1 solutions

✅ Lakhmir Singh Science Physics (ICSE Class 7)
Chapter: Physical Quantities and Measurement
Complete Solved Answers

All questions from the provided pages (Objective, Fill in the blanks, True/False, Match, Subjective, Numericals & Picture-based) solved with step-by-step explanations.

A. Choose the correct option

1. Volume of liquids can be measured by using different instruments which includes:
a. measuring cylinders   b. measuring cups   c. burettes or pipettes   d. all of them

Answer: d. all of them

2. 1 litre is equivalent to
a. 100 ml   b. 1000 ml   c. 10 mm   d. 10 L

Answer: b. 1000 ml

3. The diagram below shows 3 graduated cylinders. The contents of cylinders X and Y are poured into cylinder Z. Which letter represents the amount of liquid that will be in container Z?

Answer: C (Volume of X + Volume of Y = Volume shown in Z after pouring)

B. Fill in the blanks

1. Volume of a container is also known as capacity.
2. SI unit of area is square metre (m²).
3. The density of water is greater than wood.
4. The mercury kept in vessel undisturbed, the upper surface of the liquid is convex.
5. Burette is used in titration / accurate measurement of volume.
6. Speedometer is used to measure speed of the vehicle.
7. The SI unit of density is kg/m³.
8. Odometer is an instrument used to measure the distance travelled by a vehicle.

C. Write T for true and F for false statements

1. Area is the amount of space occupied by a substance. F (Volume is space occupied)
2. If a car is running slow, we say that its speed is low. T
3. The SI unit of area is square metre. T
4. Burette is a tube similar to measuring jar, with a pitch cock provided at the bottom. T
5. The mass per unit volume of a substance is called its density. T
6. Equal volumes of iron and aluminium will have same densities. F
7. The volume of a cube of side 7 cm is 149 cm³. F (7³ = 343 cm³)
8. The speed of train A covering 200 km in 4 hours is more than train B covering the same distance in 6 hours. T

D. Match the following

Physical Quantity	Measuring Device
1. Volume	d. Measuring cylinder
2. Area	c. Graph paper
3. Mass	a. Beam balance
4. Speed	b. Speedometer

E. Arrange the following speeds in increasing order (keeping the least speed first)

(i) An athlete running with a speed of 10 m/s.
(ii) A bicycle moving with a speed of 200 m/min.
(iii) A scooter moving with a speed of 30 km/h.

Bicycle (≈3.33 m/s) < Scooter (≈8.33 m/s) < Athlete (10 m/s)

F. Answer the following questions in short

1. What is volume? Write its SI unit.
   Volume is the space occupied by a substance. SI unit = m³
2. Write formulae for volume of a cylinder, cube and a sphere.
   Cylinder: πr²h   Cube: a³   Sphere: (4/3)πr³
3. How density of a substance can be determined?
   Density = Mass / Volume
4. Write the formula to find the area of a square and a rectangle.
   Square: side²   Rectangle: length × breadth
5. How will you measure the area of an irregular shape?
   Using graph paper (count full squares + half squares)
6. How will you find the density of a solid?
   Mass / Volume (for irregular solid use displacement method)
7. Name the physical quantity obtained by dividing ‘Distance travelled’ by ‘Time taken’ to travel that distance.
   Speed
8. What does the following measure in a car? (a) Speedometer (b) Odometer
   (a) Instantaneous speed   (b) Total distance travelled
9. Name the physical quantity which gives us an idea of how slow or fast a body is moving. Explain.
   Speed — it is distance travelled per unit time
10. Define speed. What is its SI unit of speed?
    Speed = Distance / Time; SI unit = m/s

H. Solve the following numericals

1. Flask weighs 345.8 g, filled with 225 mL CCl₄ total weight 703.55 g. Calculate density of carbon tetrachloride.

Mass of CCl₄ = 703.55 − 345.8 = 357.75 g
Volume = 225 mL = 225 cm³
Density = 357.75 / 225 = 1.59 g/cm³

2. Odometer changes from 67931.0 km to 70962.0 km in 1 h 40 min (8:30 PM to 10:10 PM).

Distance = 70962 − 67931 = 3031 km
(a) Speed = 3031 km / 100 min = 30.31 km/min
(b) Speed in km/h = 30.31 × 60 = 1818.6 km/h

3. Area of floor = 132 m², length = 12 m. Find breadth.

Breadth = 132 / 12 = 11 m

4. Area of rectangle = 117 m², width = 9 m. Find length.

Length = 117 / 9 = 13 m

5. Bus travels 54 km in 90 min. Calculate speed.

90 min = 1.5 h → Speed = 54 / 1.5 = 36 km/h

6. Cork volume = 25 cm³, density = 0.25 g/cm³. Find mass.

Mass = 0.25 × 25 = 6.25 g

7. Density of air = 1.3 kg/m³, room = 2.5 m × 4 m × 10 m. Mass of air?

Volume = 2.5 × 4 × 10 = 100 m³
Mass = 1.3 × 100 = 130 kg

8. Stone mass 30 g, water level rises 50 cm³ → 60 cm³. Density of stone?

Volume = 10 cm³ → Density = 30 / 10 = 3 g/cm³

9. Change 6 m/s into km/h.

6 × 3.6 = 21.6 km/h

10. Bus X: 360 km in 5 h; Bus Y: 476 km in 7 h. Which is faster?

X: 72 km/h   Y: 68 km/h → Bus X is faster

11. Snail: 100 m in 50 h. Average speed in km/h?

100 m = 0.1 km → Speed = 0.1 / 50 = 0.002 km/h

12. Tortoise: 100 m in 15 min. Average speed in km/h?

15 min = 0.25 h → 0.1 km / 0.25 h = 0.4 km/h

13. Sprinter: 100 m in 9.83 s. Average speed in km/h?

Speed = 100 / 9.83 ≈ 10.17 m/s → 10.17 × 3.6 ≈ 36.61 km/h

14. Block 30 cm side, density 2.8 g/cm³. Weight of block?

Volume = 27,000 cm³ → Mass = 2.8 × 27,000 = 75,600 g = 75.6 kg

15. Box volume 36 cm³, base 6 cm × 2 cm. Height?

Base area = 12 cm² → Height = 36 / 12 = 3 cm

16. Delhi–Agra 200 km, average 70 km/h. First 100 km at 50 km/h. Speed for next 100 km?

Total time = 200/70 = 20/7 h
Time for first 100 km = 2 h
Time left = 6/7 h
Speed = 100 × 7/6 = 116.67 km/h

17. Train: 15 km @30 km/h, 75 km @50 km/h, 10 km @20 km/h. Average speed?

Total distance = 100 km
Total time = 0.5 + 1.5 + 0.5 = 2.5 h
Average speed = 100 / 2.5 = 40 km/h

18. Car travels 150 m in 5 s.

(a) Average speed = 150/5 = 30 m/s
(b) In 1 s = 30 m
(c) In 6 s = 180 m
(d) Time for 240 m = 240/30 = 8 s

19. (a) Rock A: 15 cm³, 45 g → Density = 3 g/cm³
(b) Rock B: 30 cm³, 60 g → Density = 2 g/cm³
(c) Rock B is heavier (60 g > 45 g)
(d) Rock A is denser

20. Cylinder r=2 cm, h=7 cm, density 3.1 g/cm³. Mass?

Volume = π×4×7 = 28π cm³
Mass = 3.1 × 28π ≈ 273.0 g (using π≈3.14)

21. Aquariums: 6×4×2 + 8×9×3 = 264 m³

Picture-based Questions

1. Density experiment (mass = 100 g). Read initial and final volume from figure.

Volume of object = Final reading − Initial reading (displaced volume)
Density = 100 g / displaced volume (in cm³) = value in g/cm³
(Read scale from your book figure; typical value ≈ 2 g/cm³ if difference is 50 cm³)

2. Volume of the shapes:

Left cuboid (9 cm × 9 cm × 1 cm) = 81 cm³
Right cube (3 cm × 3 cm × 3 cm) = 27 cm³

3. Area of figures (ladybug, butterfly, umbrella)

Use graph paper method or count squares as per your book figure. (No numerical value given in text; follow book scale)

Prepared by Abhinav Sir•