Answer:
A compound
Explanation:
Chemical compound can be regarded as any substance made up of identical molecules which consists atoms of two or more than two chemical elements. For example four hydrogen atoms bonds with a carbon atom to give methane molecule which is a compound. It should be noted that A compound is a new substance with unique chemical and physical properties formed when two or more elements are chemically bonded during a physical reaction.
Answer:
The correct answer is in an exothermic reaction the energy of the product is less than the energy of the reactants.
Explanation:
Exothermic reaction is a type of reaction that generates heat.As a result in case of an exothermic reaction the energy of the reactant is more than the energy of the product.
That"s why the enthalpy change in an exothermic reaction is always positive .
The answer is A...matter cannot disappear and reappear