The bending nail is an example of a physical change. Students can see that there is no change in the particles (the smallest parts) of the nail as a result of bending. Their position changes, but not their chemical identity: they are still all iron atoms.
Ask students what they think happens when a nail is exposed to moisture. This is no longer a physical change but a chemical change. The second slide explains a chemical reaction.
Ask students to contrast the types of change.
- “The straight nail is the same color and texture as the bent nail; whereas the nails on this page are different colors and textures.”
- “The particles of the straight nail and the bent nail are the same; however, the particles of the rusty nail are different than those of the iron nail.”
Explain to students that there has been what we call a chemical reaction–the iron from the original nail, oxygen in the air, and water are like the “ingredients” of rust. However, instead of ingredients, we use the more scientific vocabulary “reactants.”