Write answer to the following question:
A student takes an iron rod and a wooden rod of the same length. He fixes a small wax ball at the free end of each rod. He then heats the other end of both rods using a candle flame. After some time, the wax ball on the iron rod falls off first, while the wax ball on the wooden rod remains attached.
1. What does this activity show about iron?
2. Why did the wax ball on the wooden rod remain attached?
3. Two students repeat the activity. One uses a silver rod and the other uses a copper rod. Which student is likely to observe the wax ball falling first?