Ethan is observing chemical and physical properties of a substance. He heats a substance and observes that the substance turns from a brown solid to a black
powder. He refers to several chemistry journals that claim this represents a chemical
reaction. From his observation and research, he concludes that the substance goes
through a chemical change when heated. How can Ethan best defend his conclusion?
A. by demonstrating that the substance will eventually melt if the temperature
continues to increase
B. by verifying that the substance is now made up of different molecules than
before it was heated
C. by verifying that the substance is made up of only one type of element
D. by demonstrating that the substance is less dense after it is heated

the answer is b beacuse the substance changed

the law of conservation of mass states that in a chemical reaction, the total mass of reactants is equal to the total mass of products. because atoms are only rearranged in a chemical reaction, there must be the same number of sodium atoms and chlorine atoms in both the reactants and products

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.