Which definition is correct?

Under normal conditions, describe how increasing the temperatures effects the solubility of a typical salt

The fact that the total amount of energy in a system remains constant is a(n)

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?