Multiple choice

When iron rusts, its weight __________.

  1. increases

  2. decreases

  3. no change

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When iron rusts, it combines with oxygen from the air to form iron oxide (rust). Since oxygen is being added to the iron, the total weight increases. This is contrary to what many might intuitively think, as rust often appears flaky and worn away, but chemically, mass is being added to the iron.

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