_1. what is the systematized body of knowledge based on facts,
experiments, observations and study?

What is the subscript for oxygen in its molecular formula

How do you know when a chemical reaction has occurred

When the chemicals iron sulfide (fes) and hydrochloric acid (hcl) are combined, bubbles appear from the mixture. 1. does the appearance of bubbles indicate a physical or chemical change? 2. why do the bubbles indicate this change? 3. what property is this?