Source: Extra Practice
Rusting of iron objects is a common phenomenon. What is rusting an example of, and what causes it?
Options
Option A
A physical change caused by heat.
Option B is correct
A chemical change caused by reaction with oxygen and water.
Option C
A physical change caused by exposure to light.
Option D
A chemical change caused by friction.
Explanation
Rusting is a chemical change where iron reacts with oxygen and water (moisture) in the air to form hydrated iron(III) oxide, commonly known as rust. This changes the original substance (iron) into a new substance (rust) with different properties, making it a chemical change. Physical changes only alter the form, not the composition. Heat, light, or friction are not the primary causes of rusting. (3 marks = ~75 words)