1. wearing gloves, place cotton balls in a crisscross pattern on a petri dish, four at regular intervals from the outside, leaving the center empty. -Use gloves when using the phenolphthalein solution and ammonia water to avoid direct skin contact. Ammonia water can cause skin irritation if it comes in contact with the skin. 2. 2. Pour a small amount of phenolphthalein solution onto each cotton ball, allowing enough to drip off. - Phenolphthalein solution is a colorless (clear) solution that turns red when it comes into contact with ammonia (to show that phenolphthalein is colorless). 3. Place a ball of cotton balls in the center of a petri dish. 4. Add a drop of ammonia water, then cover the petri dish and observe the change. 5. The odor is strong and the lid of the petri dish must be covered to prevent the gas from escaping. 6. (Result) Observe that the cotton balls closest to the ammonia water turn red, one after the other.
The cotton balls closest to the ammonia water turn red because the ammonia particles are moving on their own and diffusing in all directions, encountering the phenolphthalein solution on the cotton balls.