4. Screw on the bottle lid and insert
the straw through it into the water,
making sure that the straw does
not touch the base of the bottle.
5. Seal around the hole in the lid using play dough, thereby fixing
the straw in place. The seal must be completely airtight.
6. Place one hand on the upper part
of the bottle. What happens to the
liquid in the straw, and why?