The Museum of West Namibia wants to know if the Mesosaurus fossils were separated in one or a series of quick, huge movements, or if the separation was the result of slow and steady movement.

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?