What a physical change is
One question settles it.
A change where only physical properties like shape, size or state alter, and no new substance is formed. Ask whether something new has appeared. No means physical.
📚 Chapter Learning Kit
Changes Around Us: Physical and Chemical · Class 7 Science · Curiosity
English 5 topics 175 leveled MCQs 85 flashcards 5 games Free
Shared by a Veda teacher · Generated with Veda AI · Oct 2026
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Veda Bites are swipeable micro-lessons — each one teaches exactly one idea. Here's a taste from this kit; the app has the full deck.
Folding a sheet
Still paper afterwards.
Fold sheets into boats and planes. The shapes are new and the paper is not. Unfold one and your sheet is back, perhaps a little creased.
The balloon
Bigger, then smaller again.
An inflated balloon is hugely bigger than it was, and letting the air out brings it back. The rubber sheet was rubber throughout.
What a chemical change is
One sentence to hold.
A change that makes at least one substance which was not there before. Something is there at the end that was missing at the start.
Blowing into lime water
Two glasses, one result.
Blow through a straw into tap water and into lime water. The tap water only bubbles. The lime water turns cloudy, then milky white.
Blow out, never in
Read this before you start.
Never suck the liquid up the straw, especially the lime water. Take the straw out of your mouth before you breathe in.
📖 Smart notes
What you'll study, topic by topic
1
Physical Changes
Fold paper, blow up a balloon, crush chalk: the shape or size alters but the material is the same afterwards. A change like that, with no new substance made, is a physical change.
- In a physical change only physical properties such as shape, size or state alter.
- No new substance is formed during a physical change.
- Folded paper is still paper, so folding it is a physical change.
~35 min · full explanation, examples & memory tricks in the app
2
Chemical Changes
Blow through a straw into lime water and it turns milky. A white solid has appeared that was not there before. When a change makes a new substance, we call it a chemical change.
- A chemical change forms one or more new substances.
- The process by which the new substances form is a chemical reaction.
- A chemical equation is a short way of writing down what a reaction does.
~40 min · full explanation, examples & memory tricks in the app
3
Burning and the Fire Triangle
Burning is a chemical change: the substance takes up oxygen and gives out heat as it goes. A fire needs three things at once, and taking any one of them away puts it out.
- Rusting forms a new brown substance called rust, so it is a chemical change.
- Burning magnesium ribbon leaves a white powder and gives dazzling light.
- Magnesium + Oxygen gives Magnesium oxide + Heat + Light.
~45 min · full explanation, examples & memory tricks in the app
4
A Candle Does Both, and Can It Be Undone?
One burning candle shows both kinds of change at the same time. And once you can tell them apart, a second question becomes worth asking: can the change be brought back?
- A burning candle shows a physical and a chemical change at the same time.
- Wax melting near the flame is a physical change, since it is still wax.
- Molten wax running down and setting solid again is also physical.
~40 min · full explanation, examples & memory tricks in the app
5
Wanted Changes, Unwanted Changes and Very Slow Ones
Curd is a change we want and rust is one we do not, and the same change can be either depending on where it happens. Some changes are so slow that they shape mountains.
- Milk turning to curd, fruit ripening and food cooking are desirable changes.
- Rusting of iron and the decay of food are undesirable changes.
- Decomposition is unwanted in a store room and wanted in a compost pit.
~45 min · full explanation, examples & memory tricks in the app
❓ Leveled MCQ practice
Try the smart MCQs from this kit
175 questions laddered from warm-up to topper-level, each with an explanation. A taste:
A physical change is one in which
Beginner
A one or more entirely new substances are produced from the old ones
B the substance is always destroyed
C no new substance is formed
D heat must always be given out
Show answer & explanation
no new substance is formed
The defining feature is that no new substance appears.
Which of these alter in a physical change?
Beginner
A Shape, size or state
B The substance itself, which becomes a different material altogether
C Nothing at all can alter
D Only the mass of the object
Show answer & explanation
Shape, size or state
Physical properties such as shape, size and state are what alter.
Folding a sheet of paper into a boat is a physical change because
Beginner
A the boat can be unfolded again without any trouble at all
B paper is a very light material
C folding needs no heat at all
D the paper is still paper afterwards
Show answer & explanation
the paper is still paper afterwards
The material is unchanged, which is what makes it physical.
A balloon is pricked with a pin and bursts. This is
Intermediate
A a chemical change, because the balloon cannot possibly be mended now
B a physical change, since the rubber is unaltered
C neither kind of change at all
D both kinds at the same time
Show answer & explanation
a physical change, since the rubber is unaltered
No new substance appeared, so it is physical despite being impossible to undo.
🃏 Flashcards
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Categorization
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Sequence Builder
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Speed Quiz
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