Indicate with a plus sign (+) any of these processes that require energy and a negative sign (-) any that release energy. (a) arctic ice melting (d) dry ice changing to vapor (b) starting a car (e) blowing up a balloon (c) flash of lightning

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?