Chuck has a very detailed model of the solar system where each planet is made out of granite rock. since his little sister really liked the model, he spent two weeks in his dad's workshop building her a styrofoam copy. when he picked up the models to take them back inside the house, which physical property would he immediately notice upon picking them up?

He could be blindfolded and know which was his and which was his sister's. All he would need to do is pick them both up and if they were too big then pick them up one at a time. The lumber might make it harder to tell, but this is a question about physical properties.

So there is a change in mass which for the purpose of this question should be  quite different. His sister's ought to be much lighter than his. He would find it easier to pick up.

  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-