PLEASE HELP ME! Show your work. Calculate the amount of heat released in the complete combustion of 8.17g of A1 to form A1₂O₃(s) at 25°C and 1 atm. ΔH°f for A1₂O₃(s)=-1680 kJ/mol.

4A1(s)+3O2(g)→2A12O3(s)

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?