A student fills a bag with three different powders and observes the bag. The powders mix, but the three powders are still visible. The student then adds a liquid and seals the bag. The bag expands and the liquid and powder mixture feels warm. Gas bubbles are observed. What is happening in the bag? There is no way to know what is going on in the bag. It is likely a physical change. The liquid is turning into a gas because heat was added. It is likely a chemical change. The liquid and powder mixture are combining into something new.