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Why is a tumbler never made of cloth, and why are shop jars usually transparent? Chapter 6 of Class 6 science is about choosing materials by their properties. This post covers each property the chapter tests, a worked calculation with volume units, the unit-writing rules that lose easy marks, and a practice routine.
Where is this chapter?
"Materials Around Us" is Chapter 6 of Curiosity, NCERT's Class 6 science book marked Reprint 2026-27. The chapter PDF defines a material as "any substance that is used to create an object" and calls arranging objects into groups by a common property classification.
Which properties does the chapter use?
Appearance. Shiny materials are lustrous, and are usually metals: iron, copper, aluminium, gold. Metals can turn dull in air and moisture, so lustre is easiest to see on a freshly cut surface. But not every shiny thing is a metal; polish or a plastic or wax coat can make wood or paper shine.
Hardness. Hard materials are difficult to compress or scratch; soft ones compress or scratch easily. The book stresses this is relative: rubber is harder than sponge but softer than iron.
Seeing through. Transparent materials let you see clearly (glass, water, air). Translucent ones let you see, but not clearly (butter paper, frosted glass). Opaque ones block the view (wood, cardboard, metal).
Solubility in water. Sugar and salt dissolve and seem to disappear; chalk powder, sand and sawdust do not. Some liquids mix with water and some form a separate layer, and some gases, like oxygen, dissolve in water.
Mass and volume. Mass is the amount of matter, measured in grams and kilograms. Volume is the space it takes up, measured in litres and millilitres.
Anything that has mass and occupies space is matter. That is why air counts as matter, even though you cannot see it.
How should you write units?
The chapter has a box on this, and it costs marks every year.
Kilogram is kg: lower case, no space between k and g, no full stop, no "s" for plural. Write 7 kg, not 7 kgs.
Litre is L (capital) and millilitre is mL. Write 500 mL.
Leave a space between the number and the unit.
The SI unit of volume is the cubic metre, m³, and 1 m³ = 1000 L.
These are international conventions. The BIPM, which maintains the SI, lists kg for the kilogram and m for the metre among the base unit symbols, and NIST notes that the cubic metre is the SI unit of volume while the litre, one cubic decimetre, is accepted for use with the SI.
Worked example: how many bottles fill a tank?
A school water tank holds 1.5 m³. How many 500 mL bottles could it fill?
Convert the tank to litres: 1.5 m³ × 1000 L per m³ = 1500 L.
Convert the bottle to litres: 500 mL = 500 ÷ 1000 = 0.5 L.
Divide: 1500 L ÷ 0.5 L = 3000 bottles.
Check by working in millilitres instead: 1500 L = 1,500,000 mL, and 1,500,000 ÷ 500 = 3000. Same answer. The common slip is dividing 1.5 by 500 without converting, which gives a tiny number that cannot be right. Before you divide, put both quantities in the same unit.
Which mistakes cost marks?
"All shiny things are metals." The book says "all that glitters is not gold".
"Air is not matter." It has mass and takes up space.
Calling frosted glass transparent. You see through it, but not clearly, so it is translucent.
Saying a material is "hard" without comparison. Hardness is relative.
Writing kgs, Kg, ml or 7kg.
Confusing mass and volume. Two cups can be equally full (same volume) and still weigh differently, as Activity 6.8 with water, sand and pebbles shows.
Why predict before you test?
Activities 6.7 and 6.8 ask you to predict which materials will dissolve and which cup will be heavier before you check. That is worth doing honestly. In a classroom study, students who predicted a demonstration's result understood it significantly better than students who just watched.
A one-week practice routine
Day 1: Collect 20 objects at home and classify them three ways: by lustre, by transparency and by hardness.
Day 2: Test five kitchen solids in water (sugar, salt, rice flour, sand, sawdust if you have it). Write predictions first.
Day 4: Convert without notes: 2 m³ to litres (2000 L), 750 mL to litres (0.75 L), 3.5 L to millilitres (3500 mL).
Day 7: Pick a chair, a lunch box and a raincoat. For each, name two properties its material needs.
When a conversion keeps going wrong, the Fermi Problem Library has a step-by-step solver that explains the reasoning, so you can see where your units slipped. Two later chapters build on this one: states of water and methods of separation.
Today, find three objects at home that are transparent, translucent and opaque, and write the material each is made of.
