What is always formed if a chemical reaction takes place?
An element or compound.
Yes, chemical reactions always involve chemical changes. The definition of a chemical reaction is a chemical change that takes place when combining two or more chemical substances. Of course, not every substance present for a reaction will necessarily undergo a chemical change: some may exit the reaction as the same material, even if their presence serves to catalyze the reaction.
Chemical Changes As opposed to a physical change, chemical changes are present when the substance undergoes a chemical reaction and produces a new substance. A chemical change is a chemical reaction that will always take place for there to be a chemical change. Signs that a reaction is taking place: Formation of gases (bubbles), Color change, production of heat or light, and the formation of a solid. a change in composition and characteristics of matter…
Reaction is the change that takes place when two or more substances interact to form new substances?
A physical reaction is when no new substances are formed, there is a change of state eg ice melting to a liquid. A chemical change is when the reaction forms a new substance. eg gas bubbles. An acid reaction can be both. You need to look at the reaction taking place, look for change of state (physical) or any colour change or gas bubbles (chemical).