Noah added yeast and sugar to lukewarm water and placed it in a flask. He stretched a balloon over the opening of the flask. After several minutes, he noticed small bubbles rising along the side of the flask as the balloon slowly began to inflate. Noah concluded that —

There was a chemical reaction

Explanation:

there was bubbles on the side of the flask

atomic number of carbon is 6

electronic configuration of carbon is 1s²2s²2p²

orbital diagram of c is as shown here in the image.

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-