manual

How to do it:
1) Cut the eraser (or raisins)
into pieces that are about
the size of grains of rice.
2) Fill the cup with half a cup
of vinegar and a pinch of
baking soda. Then add the
eraser or raisin pieces.
3) The pieces at the bottom will
come up to the surface, then
sink, then come back up again.
T
o continue this experiment
later or to make it go on longer,
add a little more vinegar and
baking soda.
You need:
27
plastic cup
an eraser
(or some raisins)
vinegar
baking soda