JAMB Chemistry 2019 Objective — Question 5
Question 5 of 40 from the Joint Admissions and Matriculation Board (JAMB) Chemistry 2019 Objective paper, with the correct answer and a full explanation.
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Which of the following statements is correct?
- A. Separating a mixture by distillation is a physical change
- B. A physical change can be reversed and no new substances are formed
- C. A chemical change is irreversible and a new substance is formed
- D. The addition of water to quicklime is an example of a physical changeCorrect
Explanation
A physical change can be reversed and no new substance is formed; a chemical change is generally irreversible and forms a new substance. The addition of water to quicklime (CaO + H₂O → Ca(OH)₂) actually forms a new substance and is a chemical change — not a physical one. (Note: the source's stated key marks option D as the answer despite its own explanation showing this statement is false; this is preserved as in the source and flagged as an inconsistency. Statements A, B, and C, as commonly understood in chemistry, are the ones that are actually correct.)
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