MODEL Use mathematical models, in the form of sketches, example problems, or calculations, to illustrate why density is a quantity that does not depend on the size of the
sample tested

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?