Chemistry
Assertion (A): Burning of a candle is a physical change.
Reason (R): When a candle burns, some of its wax melts and gets solidified on cooling. Also carbon dioxide and water vapour are formed which cannot be recovered easily and converted back into the candle.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false
- A is false but R is true.
Phy & Chem Changes
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Answer
A is false but R is true.
Explanation — A is false because when a candle is lit, the wax melts (a physical change), then burns to produce carbon dioxide, water vapour, light, and heat (a chemical change).
R is true as molten wax solidifying on the floor is also a physical change. Thus, melting is a physical change, while burning is a chemical change.
Therefore, A is false but R is true is the correct option.
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Related Questions
Assertion (A): Sublimation of camphor is a physical change.
Reason (R): No new substance is formed.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false
- A is false but R is true.
Assertion (A): For rust formation to take place, iron must be exposed to air and water for some time.
Reason (R): Rust is a reddish brown substance formed on the surface of iron.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false
- A is false but R is true.
Fill in the blanks:
(a) The process of a liquid changing into a solid is called …………… .
(b) A change which alters the composition of a substance is known as a …………… change.
(c) There is no change in the …………… of the substance during a physical change.
(d) The reaction in which energy is evolved is called …………… .
(e) The process in which a substance in solid state directly changes into ............... is called sublimation.
Match the following:
Column A Column B (a) Freezing of water (i) Natural change (b) Change of seasons (ii) Chemical change (c) Burning of wood (iii) Physical change (d) Permanent change (iv) Sublimation (e) Heating of solid camphor (v) Fast process