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A physical change is exemplified by the


Question

A physical change is exemplified by the

Options

A) burning of bush

B) rusting of a metal

C) dissolution of calcium in water

D) heating of ammonium chloride


The correct answer is D.

Explanation:

A physical change does not produce a new substance. Changes in state or phase (melting, freezing, vaporization, condensation, sublimation) are physical changes. Examples of physical changes include crushing a can, melting an ice cube, and breaking a bottle. A chemical change makes a substance that wasn't there before.

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Discussion (6)

  • The answer ought to be C because whenever calcium reacts with water to give calcium hydroxide and water

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  • A physical change does not produce a new substance. Changes in state or phase (melting, freezing, vaporization, condensation, sublimation) are physical changes. Examples of physical changes include crushing a can, melting an ice cube, and breaking a bottle. A chemical change makes a substance that wasn't there before.

    1. When a chunk of calcium metal is dropped into a beaker of distilled water, after a second or so, the calcium metal begins to bubble vigorously as it reacts with the water, producing hydrogen gas, and a cloudy white precipitate of calcium hydroxide. This is a chemical change.

  • Udoyo Ernest

    I think Option D is the correct answer because heating ammonium chloride results to sublimation which is reversible. Note that physical change is usually reversible and no new substance is formed, every other options forms new substance e.g dissolution of calcium in water forms calcium hydroxide and the mass of the product changes compared to the mass of reactants which is the evidence of chemical change.

    1. Ernest, you are in fact correct and an adjustment has been made to the question. However, ammonium chloride doesn't actually undergo sublimation upon heating. It decomposes and forms ammonia gas and hydrogen chloride gas. When they are in contact with cooler surfaces, they recombine to form back ammonium chloride. This gives a false impression that it has undergone sublimation.

  • Olaniyi Olamide

    Physical changes or properties can be define as changes that occur in a substance that is reversible.
    Burning of bush, rusting of a metal and heating of ammonium chloride cannot be reversed to its original form but dissolution of calcium in water can be reversed by heating the mixture to allow the water to evaporate.