In Mrs. Farstaff's Science class, they are holding a contest. She has a glass bottle, and a............How did he do it?

Question

In Mrs. Sharma's Science class, they are holding a contest. She has a glass bottle, and a little bronze ball, the size of which is the exact same as the hole in the bottle. Mrs. Sharma is giving the student who can put the ball in the bottle, without breaking the glass or destroying the ball somehow and get an iPOD.

In her room there is a microwave, petroleum jelly, a stove, and a freezer.

Six of her seven students attempted this feat, but with no luck.

After the sixth student, the seventh, Gagan, comes up to the bottle and the ball. He thinks of using one of the tools in Mrs. Sharma's room at his disposal, and uses one (not the jelly as it was already proven to not work) and five hours later, gets the ball in the bottle and his free iPOD.

How did he do it?

Answer 1

Bronze has a positive thermal expansion coefficient which means it always grows on size with increase in temperature.
The ball was big to get into the glass bottle so only thing that would work is the freezer which would reduce the temperature enough for its size to be small enough to get in.