Question

Which of the following is an example of chemical change?
a. Melting of wax
b. Burning of candle wick
c. Heating of iron rod
d. knitted sweater​

Answer 1

What are chemical changes?

Chemical changes are changes in which a new substance is formed after the reaction.

How do we know a chemical reaction has occured?

• Change in temperature
• Formation of a new substance
• Change is smell
• The change is not reversible

Question :-

Which of the following is a chemical change?

(i) Melting of wax

• It is a physical change as no new substance is formed.

(ii) Burning of a candle wick

• It is a chemical change as new substances such as light, heat and smoke is released.

(iii) Heating of iron rod

• Physical change as no new substance is formed and the heated rod can be cooled down again.

(iv) knitted sweater

• It is a physical change, as there is no change in it's temp., it is reversible, and no new substance is formed.

_____________________________

Therefore, Answer to question,

• Burning of a candle wick is a chemical change.

Answer 2

$\huge\mathfrak\red{Answer}$

B) Burning of Candle

wick√√

Explanation:-

Chemical changes result in the formation of new substances when the composition of the original substance is changed; for example, when a metal reacts with the oxygen of the air it forms a new substance called an oxide . Essential oils can also react with oxygen, which alters their chemical composition and properties.

chemical reactions can be initiated by light and are called photochemical reactions (photo means light). Heat will usually speed up chemical reactions, by increasing the kinetic energy of atoms or molecules so that they collide and interact more frequently.