A) Melting of wax is a physical change while burning of wax in a candle is a chemical change.
B) Metals expand on heating while contract on cooling. Both are physical changes.
C) Composition of matter changes during a chemical change while it remains same during a physical change.
D) High and low tides in sea are the examples of non-periodic changes while growth of a tree is a periodic change.
Correct Answer: D
Solution :
Changes which occur again and again after fixed intervals of time are known as periodic changes. For example, change of day and night, occurrence of full moon, beating of heart, oscillation of pendulum of clock, high and low tides in sea, etc. Changes which do not repeat themselves at regular intervals are called non-periodic changes. You cannot predict when will they reoccur. For example, occurrence of earthquake, accidents, sneezing, rusting of iron, growing of a tree, etc.
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