Iron is malleable (able to be hammered into sheets).

Is this an intensive physical property, extensive physical property, or a chemical property? Why?

This is not a chemical property since you have iron to start and iron at the end. See here for the other two.

https://en.wikipedia.org/wiki/Intensive_and_extensive_properties

The property of iron being malleable is an extensive physical property.

To understand why, let's break down the different types of properties.

Intensive properties are characteristics of a substance that do not depend on the amount of material. Examples of intensive properties include density, boiling point, and color. These properties remain the same regardless of how much of the substance is present.

Extensive properties, on the other hand, do depend on the amount of material being considered. Examples of extensive properties include mass, volume, and length. These properties change as the amount of substance changes.

In the case of iron being malleable, this property is extensive because it does depend on the amount of iron being considered. The ability of iron to be hammered into sheets is directly related to the amount of iron available for shaping. The more iron there is, the more sheets can be made.

So, in conclusion, the malleability of iron is an extensive physical property because it changes based on the amount of iron being considered.