Which of the following requires a chemical change? A. Melting chocolate on a graham cracker
B. Toasting a marshmallow over a fire
C. Letting the fizz escape from a soda
D. Blending mustard and ketchup on a bun

C

Explanation:

When you let the fizz out of soda you are making it no longer sodo so a b and d are not correct

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !

c. because step up transformer steps up the input voltage i.e increases the input voltage  

the number of turns are greater on the secondary side of step up transformer  

transformer does not handle dc current