Question

chemical and physical changes

1. images: i (pipes exposed to air for six months, then rusted); ii (water kept in a freezer for a few months, then ice)

part a
consider the images depicting change. which statement accurately describes a change taking place in one of the images?
a the water in image ii is undergoing a chemical change because there is a change in phase.
b the pipes are undergoing a physical change because they are still pipes, nothing new is formed.
c a chemical change is occurring in image ii because heat energy is being removed from liquid water.
d the pipes in image i are going through a chemical change called rusting; the evidence is the color change.

Explanation:

• Option A: Phase change (like water freezing or melting) is physical, not chemical. So A is wrong.
• Option B: The pipes in Image I show rust (color change, new substance iron oxide formed), so it's chemical, not physical. B is wrong.
• Option C: Image II is water (liquid) to ice (solid), a phase change (physical), and heat is removed, but it's physical, not chemical. C is wrong.
• Option D: Rusting is a chemical change (iron + oxygen + water → iron oxide). The color change (from silver to brown) shows a new substance, so D is correct.

Answer:

D. The pipes in image I are going through a chemical change called rusting; the evidence is the color change