NCERT Solutions Curiosity Chapter 2 –15Section 2.1.3 Turmeric as an indicator — Activity 2.5: Let us prepare
Book page 14 Updated on2026-09-05
Q1.
Take a spoonful of turmeric (haldi) in a petri dish or container and add a little water to make a paste (Fig. 2.9a). Carefully dip a piece of filter paper in the turmeric paste until it gets yellow colour. Take it out and allow it to dry. Cut this yellow paper into thin strips, which are used as ‘turmeric paper’ (Fig. 2.9b). Prepare the turmeric paper.
Answer
Four steps and you have your own indicator paper.
Put a spoonful of turmeric in a petri dish and add a little water — just enough for a thick paste. Fresh turmeric, ground, works equally well.
Dip a piece of filter paper in the paste until it is evenly yellow.
Take it out and let it dry completely.
Cut the dry yellow paper into thin strips — this is turmeric paper. Do this under adult supervision.
Why the paste must be thick and the paper fully dry: a watery paste leaves a pale, patchy yellow that makes a colour change hard to spot, and a damp strip spreads the sample drop all over instead of holding it in one place. An evenly yellow, bone-dry strip gives a sharp red mark the moment a base touches it.
Tip: if filter paper is not available, plain white blotting paper or a piece of an unglazed white sheet will do.
Q2.
What did you observe? Do all samples change the colour of the turmeric paper?
Answer
No. Only some samples change it — and every one of them turns the yellow paper red.
S.No.
Name of the sample
The colour of the turmeric paper after putting a drop of the sample
1.
Lemon juice
No change (stays yellow)
2.
Soap solution
Turns red
3.
Amla juice
No change (stays yellow)
4.
Tamarind water
No change (stays yellow)
5.
Vinegar
No change (stays yellow)
6.
Baking soda solution
Turns red
7.
Lime water
Turns red
8.
Tap water
No change
9.
Washing powder solution
Turns red
10.
Sugar solution
No change
11.
Salt solution
No change
Why it happens: the yellow colour of turmeric changes only in a basic medium. Acids and neutral liquids leave it exactly as it was, so only the four Group B samples show a change.
Q3.
Group the samples which do not change the colour of the turmeric paper. Compare them with the samples in Group A, Group B, and Group C in Table 2.2.
Answer
The samples that leave the turmeric paper yellow are: lemon juice, amla juice, tamarind water, vinegar, tap water, sugar solution and salt solution.
Compared with Table 2.2, that is all of Group A plus all of Group C — acidic and neutral substances lumped together. Only Group B (the bases) is separated out.
Table 2.2 group
Nature
Turmeric paper
Group A
Acidic
No change — stays yellow
Group B
Basic
Turns red
Group C
Neutral
No change — stays yellow
Why this matters: turmeric gives only two possible readings — red or unchanged — but there are three natures to identify. Two answers cannot label three things, so Groups A and C have to share the same reading.
Q4.
Can turmeric paper be used as an indicator for acidic substances? Discuss your observations with your classmates.
Answer
No. Turmeric paper can be used to test basic substances only. It cannot differentiate between acidic and neutral substances, because both leave it yellow.
Turmeric paper turns red → the substance is basic Turmeric paper stays yellow → the substance is acidic or neutral — you cannot say which
What to do instead: if a sample leaves turmeric paper yellow, follow up with blue litmus. If the blue litmus turns red the sample is acidic; if it too shows no change, the sample is neutral. Two indicators used one after the other settle all three cases.
Did you know? This is why a curry stain on a white shirt turns red when soap is applied — the soap is basic and the turmeric in the curry is acting as an indicator on your shirt. Rinse with plenty of water and the red fades back to yellow.