I have no idea what this means help

What is the molar mass of potassium nitrate, kno3

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?

The organs inside the body and how they function together