Dry ice is solid carbon dioxide (CO2). When dry ice is dropped into an Erlenmeyer flask with water, it sublimes, i.e. turns to gas directly from solid state. White smoke is a fog or mist of water droplets.
A piece of sodium metal (Na) is dropped into a Petri dish with water (H2O). Sodium melts, moves around and fizzes vigorously, producing bubbles of hydrogen gas (H2) and sodium hydroxide (NaOH): Na + H2O -> NaOH + H2. The presence of the hydroxide is accentuated by phenolphthalein indicator, which turns the solution pink, indicating alkaline solution.
Iodine test is used to determine presence of starch. Here a dropper is used to add few drops of Lugol's solution into a beaker with an aqueous solution of corn starch (0.1% concentration). Lugol's solution (Lugol's iodine) is an aqueous solution of iodine and potassium iodide. Elemental iodine (I2) reacts with starch and produces dark-blue color.
Marble is a metamorphic rock that contains calcium carbonate (CaCO3) and other carbonate minerals. Here a piece of marble is dropped into a beaker with 0.5 M hydrochloric acid (HCl). Carbon dioxide (CO2) bubbles are produced: CaCO3 + HCl -> CaCl2 + H2O + CO2. This is the mechanism by which acid rain erodes marble statues and structures.