you heat up hydrochloric acid using a bunsen burner and it start to see bubbles at 100 c whats the melting point? And then you freeze hydrochloric acid and see that it becomes a solid at -17. What’s the boiling point?

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?