The two changes have the following in common:
- Both conserve mass
While the formation of rust is a chemical change and involves the transformation of iron into iron oxide, the growth of snail shells is also a biological process that involves the deposition of calcium carbonate. Both processes involve the conservation of mass, as the materials involved in each change are rearranged rather than created or destroyed.
The other options do not apply:
- Rust formation is a chemical change, while snails growing shells is more of a biological process, so they are not both only physical or chemical changes.
- They do not represent changes in state (like solid to liquid) but rather transformations in material properties or structures.