Examkin

Question

Difficulty: EasyProperties of Matter

An automotive technician performs several actions on a piece of iron: cutting it to size, polishing its surface, heating it to bend it into shape, and leaving an unpainted scrap outside where it eventually forms reddish-brown rust. Which of these actions results in a chemical change?

  1. A
    Cutting the iron to a smaller size
  2. Rusting after being exposed to outside airAnswer
  3. C
    Heating the iron until it bends
  4. D
    Polishing the surface to make it smooth and shiny

Answer

Rusting after being exposed to outside air
Rusting is a chemical change because iron atoms react with oxygen in the atmosphere to create an entirely new compound, iron oxide.

Step-by-Step Solution

1
Define the difference between physical and chemical changes.
A physical change alters form, shape, or appearance without changing the underlying chemical identity. A chemical change produces one or more new substances with different chemical properties.
Understanding the fundamental criteria distinguishes changes in state/shape from chemical reactions.
2
Evaluate cutting, polishing, and heating/bending.
These actions modify only the size, surface texture, and shape of the iron, while the substance remains pure iron (FeFe).
Changes in dimensions and mechanical deformation do not alter chemical bonds.
3
Evaluate the process of rusting.
Iron exposed to moisture and oxygen undergoes oxidation to form iron(III) oxide (Fe2O3Fe_2O_3), a completely new substance.
The creation of a new compound with distinct chemical properties defines a chemical change.

Key Concept

Physical versus Chemical Changes in Matter
Rate this question

Topics

Properties of Matter

More questions from this topic