Is spreading butter on bread a chemical change and if so what's the evidence?

Yes, spreading butter on bread is a chemical change. This is so because the butter chemicals become infused with the bread chemicals. Mostly why butter is soaked into bread

this is proven because even after the excess butter is removed, butter is still on/in the bread

1.solid

2.carbon dioxide

3.helium

  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-