ICSE · Grade 6

Ch. 2: Physical Quantities and Measurement

Learn what physical quantities are, why we need standard units, the metric/SI system, and how to measure length and mass carefully — with conversions by powers of 10.

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Meaning of physical quantity and measurement Need for standard units Metric system and SI units Length: tools, precautions, direct/indirect methods Mass vs weight and unit conversions
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Interactive lab — Measurement

Play with units, convert lengths, and remember: every measurement needs a number + unit.

Line up with zero!

Object length: 12.0 cm = 120 mm

Tip: Always place the 0 mark at one end. Read the other end carefully (avoid parallax — eye straight above the mark).

Metric ladder (×10 / ÷10)

km
hm
dam
m ★
dm
cm
mm

3 m = 300 cm

Going down the ladder (bigger → smaller unit) → ×10 each step. Going up → ÷10.

Mass chain: t → kg → g → mg

tonne ×1000 kg ×1000 g ×1000 mg
  • 2.5 kg = 2500 g
  • 2.5 kg = 0.0025 tonne
  • 2.5 kg = 2 500 000 mg

Mass stays the same everywhere. Weight changes with gravity (lighter on the Moon!).

Seven SI base units (flash)

📏
m
metre
length
⚖️
kg
kilogram
mass
⏱️
s
second
time
⚡
A
ampere
current
🌡️
K
kelvin
temperature
🧪
mol
mole
amount
💡
cd
candela
light

Also remember: measurement = magnitude + unit. “35” alone is meaningless!

# Exam tips ## Must know - Definition of physical quantity, measure, measurement - Why standard units? (4 points) - SI seven base units with symbols - 1 km = 1000 m; mm–cm–m conversions - Mass vs weight - Mass conversions ×1000 / ÷1000 - Precautions for ruler use - Direct vs indirect length measurement ## Common traps - Mass changes on Moon ❌ (weight changes) - Measurement is only a number ❌ - 1 m = 100 mm ❌ (1 m = 1000 mm) - Forgetting 0-mark alignment ## Easy formula examples Thickness of card = total stack length ÷ number of cards Wire thickness = coil length ÷ number of turns
Interesting facts Common mistakes Vocabulary Revision notes

Topics in this chapter

  • Physical quantity
    Any physical property that can be measured using numbers (length, mass, time, temperature).…
  • Standardisation
    Measurement = magnitude + unit. Units must be accurate, universal, stable over time and place.…
  • Metric & SI system
    Metric system powers of 10. SI has 7 base units: m, kg, s, A, K, mol, cd.…
  • Length
    Horizontal length, height, width/breadth, distance. Ruler and tape. 0-mark alignment. Direct and ind…
  • Mass and weight
    Mass = amount of matter (kg). Weight = gravity force (changes). Convert t-kg-g-mg by 1000.…
  • Time & temperature
    Time in seconds; clocks. Temperature with thermometer (°C, K).…

Philosophy check

  • What is this civilization?
  • Why was it advanced?
  • How did cities work?
  • Where do we still see these ideas?
  • Exams — what will be asked?