Answer:
The option "New substances formed" best explains why this is considered a chemical change.
Step-by-step explanation:
A chemical change is a process in which one or several substances, called reagents, undergo modification of their molecular structures and are transformed into other substances, called products.
On the other side, a neutralization reaction is one in which an acid (or an acid oxide) reacts with a base (or basic oxide). In the reaction a salt is formed and in most cases water is formed. A salt is an ionic compound formed by the union of ions and cations through ionic bonds.
So:
acid + base ⇒ salt + water
Neutralization reactions are generally exothermic, which means they release energy in the form of heat.
In this case, hydrochloric acid and sodium hydroxide are mixed together to form salt and water. Then it is a neutralization reaction, producing a chemical change that releases energy. In this way, during the reaction, the temperature of the solution increases.
So, the option "New substances formed" best explains why this is considered a chemical change.