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NCERT Solutions for Class 5th The World Around Us Chapter 2 Sugar and oil in two glasses of water — Activity 3

Book page 29–30 Updated on2026-09-19

Q1.
Take two clear glasses of water. Add a spoonful of sugar in one and a spoonful of cooking oil in the other. Stir both well and observe. What do you observe? Which one appears clear?
Answer

What you will see: the sugar disappears completely and that glass looks clear, like plain water. The oil does not mix at all — it breaks into small yellow drops and then floats back to the top as a shiny layer. The glass with the sugar appears clear.

How to do it:

  1. Take two clean glasses. Fill both about three-fourths with clear water. Keep them side by side.
  2. Add one spoonful of sugar to the first glass.
  3. Add one spoonful of cooking oil to the second glass.
  4. Stir each glass well for about half a minute, with a clean spoon.
  5. Now leave both glasses still for two minutes and look at them again from the side, against the light.
What I look atGlass 1 — sugarGlass 2 — cooking oil
While stirringThe white grains get smaller and smallerThe oil breaks into many small round drops
Just after stirringNo grains left at allTiny drops spread all through, water looks cloudy
After two minutesWater is completely clearAll the drops have risen and joined into a shiny layer on top
Is anything visible?No — but taste one drop and it is sweet, so the sugar is still thereYes — you can clearly see the oil floating
Which appears clear?The glass with sugarNot clear — oil is visible on top
Why it happens: Sugar dissolves in water. That means its tiny grains break up and spread evenly through the water, so small that your eyes cannot see them any more. Oil does not dissolve. Oil is also lighter than water, so after stirring, all its drops slowly rise and join together on top. The sugar is hiding in the water; the oil is only sitting on it.
Why the chapter does this experiment: to prove one warning — clear water is not the same as clean water. Harmful chemicals and soapy water dissolve just like the sugar. You cannot see them, but they are there, and they can hurt living beings.
Q2.
Can you list a few things that: Dissolve in water
Answer

Things that dissolve in water — they mix in completely and disappear from sight:

  1. Sugar — the water turns sweet but stays clear.
  2. Salt — the same; taste is the only proof it is there.
  3. Glucose powder and sugar candy (mishri).
  4. Lemon juice and vinegar.
  5. Milk powder, drinking chocolate, coffee powder.
  6. Detergent powder and liquid soap — they dissolve and make the water frothy.
  7. ORS powder and most medicines that are meant to be taken in water.
  8. Fertiliser and urea — this is why fertiliser from the fields gets carried into a river so easily.
  9. Alum (phitkari), used to clean drinking water.
Water + sugar → water still looks clear → but the sugar is still in there
How to test any new thing: put a small spoonful in half a glass of water, stir for a minute, and let it stand. If nothing is left at the bottom and nothing floats on top, and the water is clear, then it has dissolved.
The important lesson: the harmful things in a river — soap, chemicals from factories, fertiliser from fields — belong to this list. They dissolve. That is exactly why a river can look clean and still be unsafe to drink.
Q3.
Can you list a few things that: Do not dissolve in water
Answer

Things that do not dissolve in water — they can still be seen after stirring, either floating on top or lying at the bottom:

  1. Cooking oil — floats and makes a shiny layer on top.
  2. Sand and mud — sink to the bottom.
  3. Chalk powder — makes the water milky, then settles.
  4. Small stones and pebbles — sink at once.
  5. Plastic pieces, wrappers and bottle caps — float and never rot.
  6. Wood, thermocol, dry leaves — float.
  7. Iron filings, pins and nails — sink and rust.
  8. Wheat flour (atta) — makes a paste, then settles at the bottom.
  9. Ghee and butter — float, like oil.
GroupExamplesWhere it goes in the glass
Lighter than waterOil, ghee, thermocol, plastic, dry leaves, woodFloats on top
Heavier than waterSand, mud, chalk, stones, iron pins, attaSettles at the bottom
Why they behave like this: These things do not break up into tiny bits that can spread through the water. They stay as they are. So the only question left is weight — anything lighter than water floats, anything heavier sinks. Nothing here disappears.
Good news and bad news: Things that do not dissolve are easier to remove from a river — a net or a filter can take them out. Things that dissolve are the hard ones, because no net can catch them. That is why it is better to stop them from entering the river at all.
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