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NCERT Solutions Curiosity Chapter 2 Projects and further exploration — Exploratory Projects

Book page 22 Updated on2026-09-05

Q1.
Create rangoli using acidic or basic substances and natural indicators.
Answer

The idea is to let the colour appear by itself as you spray, instead of using coloured powders.

  1. Make the base. Spread a thin layer of turmeric powder, or brush turmeric paste in a design on a large sheet of white paper, and let it dry. You now have a golden-yellow rangoli.
  2. Draw with a base. Using a cotton bud or a squeeze bottle, draw lines, petals and dots with soap solution, baking soda solution or lime water. Every stroke turns red the moment it touches the turmeric.
  3. Add a second colour. On another part of the sheet spread a layer soaked in red rose extract or purple cabbage extract, then draw with lemon juice for red and with soap solution for green.
  4. Show the science. Write a small card beside the rangoli listing which substance made which colour, and why.
Base layerDrawn withColour that appears
TurmericSoap or baking soda solutionRed
Purple cabbage extractLemon juiceReddish pink
Purple cabbage extractWashing soda solutionGreen
Red rose extractLime waterGreen
Tip: work on newspaper, keep the liquids in labelled droppers, and wash your hands afterwards. Do this rangoli on paper, not on a floor you will have to scrub.
Q2.
You may discuss in your class the acidic, basic, or neutral nature of water obtained from various sources. You may like to test the water samples available from sources such as rain, taps, rivers, etc.
Answer

What a good project must contain: clean labelled bottles, the same test done the same way on every sample, a table of results, and one honest conclusion.

  1. Collect samples in clean bottles and label each with the source, date and place — rainwater, tap water, river or pond water, hand-pump water, boiled water, bottled water.
  2. Test each with blue litmus and then with red litmus, using a fresh strip every time.
  3. Record the results in a table and discuss them with your class.
Source of waterBlue litmusRed litmusNature
Tap waterNo changeNo changeNeutral
Rainwater (collected in the open)Slightly redNo changeSlightly acidic
Pond waterNo changeNo changeNeutral
River water near a drainNo changeSlightly blueSlightly basic
Why rainwater is often slightly acidic: as it falls, rain dissolves carbon dioxide and other gases from the air. Near factories and heavy traffic there are more such gases, so the rain is more acidic — the phenomenon called acid rain.
Check it yourself: collect the first rain of a shower and the rain from half an hour later in two separate bottles. The first sample is usually the more acidic of the two, because it has washed the dust and gases out of the air.
Q3.
Collect a soil sample of your area and find out whether it is acidic, basic, or neutral in nature.
Answer

Method

  1. Dig out a little soil from about 10 cm below the surface — not the loose dusty top layer. Take samples from two or three spots in the field or garden and mix them.
  2. Put two spoonfuls in a glass, add clean water to about three times the height of the soil, and stir well.
  3. Let it stand until the soil settles and the water above is fairly clear.
  4. Touch the clear water with a blue litmus strip and then with a red litmus strip.
Blue litmus → red = acidic soil → treat with lime (chuna)
Red litmus → blue = basic soil → treat with manure or composted leaves
Neither changes = neutral soil → poor growth would mean a nutrient deficiency

Sample answer: "Soil from our school garden turned neither litmus paper, so it is neutral. Soil collected from the field behind the school turned blue litmus faintly red, so that field is slightly acidic and would benefit from a little lime."

Why use settled water and not the soil itself: litmus reads a liquid. Wet mud smeared on the paper hides the colour change under a brown stain, so you must let the soil release its dissolved substances into water and test that water.
Tip: use rainwater or distilled water if you can. Tap water in some areas is itself slightly basic and would shift your reading.
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