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.  

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.