Which of the following changes is a physical change? MCQ with Answer and Explanation

Which of the following changes is a physical change?
A. Curdling of milk
B. Burning of coal
C. Boiling of water
D. Rusting of iron
Answer: Option C
Solution (By JKExamLibrary)
Boiling water changes state from liquid to gas, but the chemical composition (H₂O) remains unchanged – physical change. Others form new substances.

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Practice More chemistry Questions

Question #1
The pH of human blood is approximately:
A. 5.5
B. 2
C. 7.4
D. 9

Correct Answer: Option C


Explanation:
Blood pH is slightly alkaline, maintained between 7.35 and 7.45. Deviation can cause acidosis or alkalosis.

This question belongs to: Science chemistry
Question #2
Detergents are better than soaps because they:
A. Are natural products
B. Are cheaper
C. Work well in hard water
D. Have no environmental impact

Correct Answer: Option C


Explanation:
Synthetic detergents (like alkyl sulfates or sulfonates) form soluble calcium and magnesium salts, so they lather well even in hard water. Soaps form scum. Detergents are usually derived from petrochemicals, can be non-biodegradable if branched, and may cause pollution.

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Question #3
The law of multiple proportions was proposed by:
A. Jöns Jacob Berzelius
B. Joseph Proust
C. Antoine Lavoisier
D. John Dalton

Correct Answer: Option D


Explanation:
John Dalton formulated the law of multiple proportions: If two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other are in ratios of small whole numbers. Lavoisier gave law of conservation of mass. Proust gave law of definite proportions. Dalton's atomic theory explained these laws.

This question belongs to: Science chemistry