Gluesticks

Which of these is an example of a physical change?

a. A peach spoils. b. A copper bowl tarnishes. c. A piece of jewelery turns your skin green. d. A hot glue-gun melts a glue stick.

Public Comments

1. d. It is what materials science folks call a phase transformation, like ice melting into water. In a, b, and c the objects are changing chemically. You can't unspoil a peach, but if you cool the melted glue, it will turn solid again and be the same as when you started.