Final answer:
Boiling water and crystallization of sugar are physical changes, while ripening of a fruit and decomposing of organic matter are chemical changes. The commonality is that they all represent state transitions, but they differ in terms of the molecular or chemical transformations involved.
Step-by-step explanation:
The changes a) boiling water, b) ripening of a fruit, c) decomposing organic matter, and d) crystallization of sugar all involve a transition from one state to another, but they differ in that some are physical changes and others are chemical changes.
a) Boiling water is a physical change, as it involves the transition from liquid to gas without altering the molecular structure of water (H₂O).
b) Ripening of a fruit is a chemical change, because it involves complex processes like the conversion of starches to sugars, which changes the fruit's chemical composition.
c) Decomposing organic matter is also a chemical change, as it involves the breakdown of organic material into simpler substances due to biological or chemical processes.
d) Crystallization of sugar is a physical change, as it refers to the change of state from a dissolved sugar solution to solid sugar crystals without altering the chemical identity of the sugar (C₁₂H₂₂O₁₁).