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NCERT Solutions for Class 7th Science Chapter 5 Table 5.1: Some changes observed around us — Activity 5.1: Let us think and reflect

Book page 58 Updated on2026-09-19

Q1.
You might have observed various changes happening around you. Some of them are listed in Table 5.1, you may notice that something is changing in each case. Take a moment to reflect on the changes in each case. Record your observations in Table 5.1.
S.No.ChangeObservation(s)
1.Melting ice cubes 
2.Chopping vegetables 
3.Boiling water 
4.Making popcorn from corn 
5.Cutting a piece of paper 
6.Adding beetroot extract to water 
7.Burning wood 
8.Drying wet clothes 
9.Making small balls of dough 
10.Rolling small balls of dough into chapatis 
11.Any other 
Table 5.1, page 58: Some changes observed around us — the Observation column is left blank for you to fill in.
Answer

Here is Table 5.1 filled in. Look carefully at what exactly changes in each case — that is what the observation column is asking for.

S.No.ChangeObservation(s)
1.Melting ice cubesHard, solid ice slowly turns into liquid water. Only the state changes; the substance is still water.
2.Chopping vegetablesOne big piece becomes many small pieces. Only size and shape change; it is still the same vegetable.
3.Boiling waterBubbles rise, steam comes out, the level of water falls. Liquid water becomes water vapour — a change of state.
4.Making popcorn from cornThe kernel bursts with a pop, becomes white, soft and fluffy, and smells different. New substances are formed.
5.Cutting a piece of paperSize and shape change. Every piece is still paper.
6.Adding beetroot extract to waterThe colourless water turns pink or deep red. The colour spreads through the water; no new substance is made — it is a mixture.
7.Burning woodFlame, heat, light, smoke, and grey ash are left behind. New substances are formed and the wood is gone for ever.
8.Drying wet clothesThe water in the cloth evaporates into the air. The cloth becomes lighter and dry; the cloth itself does not change.
9.Making small balls of doughOnly the shape of the dough changes; it is still dough.
10.Rolling small balls of dough into chapatisThe ball becomes a flat, round disc. Again only the shape changes — the raw chapati can be rolled back into a ball.
11.Any other — an iron nail left in the rainA rough, brown, flaky layer (rust) appears on the shining nail. A new substance has formed.
Check it yourself: Read down your observation column. Wherever you have written words like new smell, new colour, ash, cannot be undone, you are almost certainly looking at a chemical change.
Q2.
Can you think of some other changes that happen in your surroundings? Make a list of those changes too.
Answer

Yes. Here is a list you can add to Table 5.1, sorted so that you can see the pattern.

  • Changes in the kitchen: milk setting into curd, grinding wheat into atta, kneading atta into dough, baking a chapati on the tawa, roasting groundnuts, boiling milk, dissolving sugar in tea, cutting an apple and watching it turn brown.
  • Changes at home and school: sharpening a pencil, tearing an old notebook, folding a paper boat, breaking a piece of chalk, a wet blackboard drying, an iron gate rusting, a candle burning, an LPG stove burning.
  • Changes in nature: a seed germinating, a leaf turning yellow and falling, fruits ripening, dew forming on grass in winter, clouds forming and rain falling, a river making pebbles smooth, dead leaves rotting into compost.
  • Changes in ourselves: our height increasing, hair and nails growing, a wound healing, digestion of the food we eat.
Why it happens: Every one of these can be sorted with the same single test — is a new substance formed? Sharpening a pencil, folding paper and dew forming are physical. Curd setting, rusting, burning, ripening, rotting and digestion are chemical.
Q3.
Can we arrange these changes into categories?
Answer

Yes. Changes can be grouped in more than one useful way, and the same change can appear in several groupings.

Basis of groupingCategoriesExamples
Is a new substance formed?Physical change / Chemical changeMelting ice (physical) · Burning wood (chemical)
Can the original be brought back?Reversible / IrreversibleBoiling water (reversible) · Making popcorn (irreversible)
Do we want it to happen?Desirable / UndesirableMilk to curd (desirable) · Rusting of iron (undesirable)
How fast is it?Fast / SlowBurning of magnesium (fast) · Weathering of rocks (very slow)
What made it happen?Natural / Man-madeRipening of fruits (natural) · Chopping vegetables (man-made)

The grouping this chapter uses is the first one: physical change and chemical change.

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