Advent Calender - H_H

15th

(1) Riddle:

If you add me to the bottom of a water bottle I will make it lighter. If you add me to the top there will be no change in weight. What am I?

Answer to previous: Time

(2) Shout-out:

kotorishion

(3) Fact:

In the twelve days of Christmas song, if you bought (or hired) everything in the song the amount of times it was said, it would cost £1.3 Million.