NCERT Solutions Curiosity Chapter 4 Activity 4.7: Let us experiment (demonstration activity) — Substances that Behave Differently from Metals in Air and Water

Book page 52 & 53 Updated on2026-09-05

Q1.
Again, recall the chapter ‘Exploring Substances: Acidic, Basic, and Neutral’. Using an acid-base indicator, check whether the solution obtained after the addition of water to the gas jar is acidic or basic or neutral.
Answer

Burn a little powdered sulfur in a deflagrating spoon, lower it into a gas jar, cover the jar, then after 3 – 4 minutes add a small quantity of water, replace the lid and shake so that the gas dissolves. Test that solution.

Indicator usedWhat you seeWhat it means
Blue litmus paperTurns redAcidic
Red litmus paperStays red (no change)Not basic
China rose indicatorTurns dark pinkAcidic
Caution: this is a demonstration activity for the teacher, and it must be performed in a fume hood or a well-ventilated area. Burning sulfur produces gases which can be harmful if inhaled.
Q2.
What do you observe?
Answer

You observe that the solution is acidic in nature — it turns blue litmus red.

Sulfur + oxygen (air) on burning → sulfur dioxide gas
Sulfur dioxide + water → sulfurous acid
So the oxide of a non-metal gives an acidic solution.
Why it matters: place this beside Activity 4.6 and the whole chapter falls into place. Magnesium (metal) gave a basic oxide; sulfur (non-metal) gives an acidic oxide. The behaviour of an element's oxide is one of the surest ways of telling a metal from a non-metal.
Did you know? The same reaction happens in the open air when fuels containing sulfur are burnt. The sulfur dioxide dissolves in rain and falls as acid rain, which damages crops, buildings and statues.
Was this helpful? Report an error