Answer:
A new substance was forming
Explanation:
Two types of changes are undergone by substances involved in a reaction. They are physical changes and chemical changes. Physical changes are those changes that does not involve the synthesis of a new product. On the other hand, CHEMICAL CHANGES alters the chemical composition of the substances involved, and hence, new substances are formed.
Chemical changes are usually characterized by change of temperature, color change, evolution of a gas etc. According to this question, Mia mixed two substances in a test tube and noticed that the test tube became warm. She also noticed gas coming from the test tube. Based on Mia's observations, a CHEMICAL CHANGE, LEADING TO THE FORMATION OF NEW SUBSTANCE, HAS OCCURRED.
