* Fizzing and Bubbling: The most obvious sign is the rapid release of gas bubbles (carbon dioxide). This is caused by the reaction between the bicarbonate in the tablet and the citric acid, producing carbon dioxide gas.
* Temperature Change: The reaction is exothermic, meaning it releases heat. You might notice the water getting slightly warmer.
* Change in Appearance: The tablet dissolves and disappears as it reacts. The solution might become cloudy or change color slightly.
* Formation of a New Substance: The reaction creates new substances, including sodium citrate and water. These weren't present before the reaction.
In summary: The fizzing, bubbling, heat production, disappearance of the tablet, and formation of new substances are all clear signs of a chemical reaction taking place.
