Ask students: What clues did you have that a chemical reaction occurred in this activity?Bubbling. Tell students that a change in temperature is also a sign that a chemical reaction may be occurring.

Iron oxide, aluminum, and a catalyst are placed in a flowerpot. The reaction is extremely exothermic resulting in molten iron and aluminum dripping into sand below the flowerpot. The demonstration ...

but the number of atoms does not change. A catalyst is a substance that speeds up a chemical reaction. Catalysts are useful because they do not get used up during a reaction. Exothermic and ...