If there is 8 g of a substance before a physical change, how much will there be afterwards?
a) 0 g
b) 4 g
c) 8 g
d) 16 g

C) 8 g

Explanation: A physical reaction is defined as the reaction in which a change in shape, size takes place. No new substance gets formed in these reactions.

According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side.

Thus if mass of reactants is 8 g, mass of products is also 8g.

The correct answer is option C, that is, 8 gm.  

Explanation:

A reaction in which a change in size, shape occurs is known as a physical reaction. No formation of novel substances takes place in this kind of reactions.  

On the basis of the law of conservation of mass, mass can neither be destroyed nor be created. Therefore, the mass of the products needs to be equivalent to the mass of the reactants. The number of atoms of every element needs to be similar on both the reactant and product end. Hence, if the mass of reactants is 8 grams, then the mass of products will also be 8 grams.  

a corroding iron, if that's one of your choices