NECO 2003 Physics · Question 8

Which of the following statement(s) is/are correct? I. When a liquid expands its density falls II. When a…

Question

Which of the following statement(s) is/are correct? I. When a liquid expands its density falls II. When a mercury-in-glass thermometer is placed in a hot liquid, the mercury level first descends and then rises. III. The apparent expansion of a liquid is greater than its real expansion.

A.I only
B.II only
C.III only
D.I and II only
E.II and III only

Answer: D. I and II only

Explanation written with AI and checked against the answer key

Analyzing the question: We must judge each statement on its own and then pick the option that matches the true ones. Statement I: "When a liquid expands its density falls." Density = mass ÷ volume. When a liquid expands, its mass stays the same but its volume increases, so its density decreases. True. Statement II: "When a mercury-in-glass thermometer is placed in a hot liquid, the mercury level first descends and then rises." The glass bulb is heated first, so it expands before the mercury gets warm. The bulb's volume increases, so the mercury level drops briefly. Then the heat reaches the mercury, which expands much more than glass, and the level rises. True. Statement III: "The apparent expansion of a liquid is greater than its real expansion." Apparent expansion is the expansion observed when the container also expands. Real expansion = apparent expansion + expansion of the container. So the real expansion is greater than the apparent expansion, which makes this statement False. Conclusion: Only I and II are correct. Exam tip: Remember "Real = Apparent + Container." The real expansion is always the bigger one. Any statement that says apparent is greater than real is a trap. For the thermometer, think "glass first, mercury later" to recall the dip-then-rise behaviour.

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