The following 20 Multiple Choice Questions (MCQ) are based on
Chapter 5: Changes Around Us: Physical and Chemical from the NCERT Class 7
Science textbook Curiosity. Each question has four options - select the
best answer and click to check.
Instructions: Read each question carefully. Choose the most
appropriate option from (a), (b), (c), or (d). Click
Show Answer to reveal the correct answer with explanation.
Multiple Choice Questions
1A physical change generally:
(a) Does not form a new substance
(b) Always forms a new substance
(c) Cannot change shape
(d) Must be permanent
(a) is correct
Physical properties such as state, size or shape may change while composition remains the same.
2Which is a physical change?
(a) Rusting iron
(b) Burning wood
(c) Curdling milk
(d) Melting ice
(d) is correct
Ice and liquid water are the same substance in different states.
3A chemical change is identified by:
(a) No change in properties
(b) Always being reversible
(c) Formation of one or more new substances
(d) Only a change in size
(c) is correct
Chemical reactions produce substances with new compositions and properties.
4Which is a chemical change?
(a) Melting wax only
(b) Burning magnesium
(c) Folding clothes
(d) Cutting paper
(b) is correct
Magnesium combines with oxygen to form magnesium oxide.
5Curdling of milk is chemical because:
(a) New substances with different properties form
(b) Only its container changes
(c) It can be restored by simple cooling
(d) No composition changes
(a) is correct
The chemical composition and properties of milk change during curdling.
6Rusting is a reaction of iron with:
(a) Only dry air without oxygen
(b) Only salt
(c) Pure nitrogen
(d) Oxygen and moisture
(d) is correct
Hydrated iron oxide forms when iron is exposed to air and water.
7Which method helps prevent rusting?
(a) Scratching off coatings
(b) Adding acid
(c) Painting the iron surface
(d) Keeping it wet
(c) is correct
Paint blocks oxygen and water from reaching the metal.
8Combustion is a process in which a substance:
(a) Is cut into pieces
(b) Burns in oxygen and releases energy
(c) Only melts
(d) Freezes without reaction
(b) is correct
Burning is a chemical reaction that often releases heat and light.
9Burning a candle involves:
(a) Both physical and chemical changes
(b) Only a physical change
(c) Only a chemical change with no melting
(d) No change
(a) is correct
Wax melts physically while wax vapour combusts chemically.
10Mixing baking soda and vinegar produces bubbles of:
(a) Oxygen
(b) Nitrogen
(c) Helium
(d) Carbon dioxide
(d) is correct
Their reaction releases carbon dioxide gas.
11Carbon dioxide turns lime water:
(a) Red
(b) Colourless in every case
(c) Milky
(d) Bright blue
(c) is correct
Insoluble calcium carbonate forms and makes the liquid appear milky.
12Which observation can indicate a chemical change?
(a) Only crushing
(b) Gas production, colour change or temperature change
(c) Only a change in position
(d) Only cutting
(b) is correct
Such evidence may signal new substances, though observations should be interpreted together.
13Freezing water is reversible because:
(a) Ice can melt back into water
(b) A new element forms
(c) Water is destroyed
(d) It produces rust
(a) is correct
The state changes while the substance remains H2O.
14Which change is usually irreversible?
(a) Melting ice
(b) Inflating a balloon
(c) Folding cloth
(d) Burning paper
(d) is correct
The ash and gases cannot be changed back into the original paper by simple means.
15A permanent change is necessarily chemical:
(a) Only in water
(b) Only when heating
(c) No; some permanent changes are physical
(d) Yes, always
(c) is correct
Cutting paper is a largely permanent physical change because no new substance forms.
16Which is a desirable change?
(a) A destructive landslide
(b) Cooking food properly
(c) Spoilage of fruit
(d) Rusting of a bridge
(b) is correct
Desirability depends on human purpose and consequences, and cooking is generally useful.
17Weathering is the:
(a) Breaking down of rocks in place
(b) Transport of rock fragments only
(c) Formation of metal wires
(d) Neutralisation of acids
(a) is correct
Physical and chemical processes gradually break rocks into smaller material.
18Erosion involves:
(a) Only formation of new rock
(b) Melting ice in a glass
(c) Making an electric circuit
(d) Removal and transport of weathered material
(d) is correct
Wind, water and ice can carry soil and rock particles away.
19Soil formation from rocks may involve:
(a) No change
(b) Only melting
(c) Both physical and chemical changes
(d) Only electrical change
(c) is correct
Rocks break physically and minerals also undergo chemical alteration.
20Composting vegetable peels is chemical because:
(a) Only water evaporates
(b) Microorganisms form new substances
(c) The peels are only cut
(d) No decomposition occurs
(b) is correct
Decomposition transforms organic waste into chemically different compost.
