To show breakdown of food by using the model of chalkpiece kept in vinegar.
A .1) Break a piece of chalk into two halves.
2) Crush one half to tiny pieces leaving the other as it is.
3) Take two small mineral water bottles (!4 ltr bottle) cut them into two equal halves and discard the upper portion.
4) Now we have two beakers from the lower cut portion.
5) Fill them half with vinegar and add the crushed chalk to one beaker and the other uncrushed half chalk to the other.
6) Observe them after half-an-hour or so.