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Which of the following is an example of a chemical change?

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CHEMISTRY

Which of the following is an example of a chemical change?

A. dissolution of salt in water

B. rusting of iron

C. melting of ice

D. separating a mixture by distillation

QUICK ANSWER…

B

SOLUTION…  

A chemical change is said to occur when new substances are formed. In physical changes, no new substance is formed.

Now for the right answer to the above question:

  1. Option A is incorrect. dissolution of salt in water is a mere physical change, as the salt can easily be reobtained from the mixture by physical evaporation and not chemical means.
  2. Option B is correct. Rusting of iron is a chemical change, this is because during rusting, water and air react with iron to produce complex ferrous compounds.
  3. C is incorrect. melting of ice is a physical change, mere application of lower temperatures returns the water to ice.
  4. D is not the correct answer. Using distillation to separate a mixture is not a chemical change but a physical manipulation of temperature changes and solubilities.
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QUICK TIPS…

You may please note these/this:

  • In chemical changes, new substances are usually formed.
  • In physical changes, no new substance is formed.

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/ culled from 2018 JAMB-UTME Chemistry question 35 /

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