Multiple choice

When an iron nail gets rusted, iron oxide is formed _______.

  1. without any change in the weight of the nail

  2. with an increase in the weight of the nail

  3. with a decrease in the weight of the nail

  4. without any change in the colour or weight of the nail
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When iron rusts, it combines with oxygen from air to form iron oxide (Fe2O3). Since oxygen atoms add to the iron, the total mass increases. This follows the law of conservation of mass - the nail's weight increases by the mass of oxygen atoms that bond with iron.

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