Chemical indicators give off a visible sign when certain molecules are present. A common use of indicators is in determining the pH of a solution. Adding drops of methyl yellow to a basic solution turns the liquid yellow... More »

Harper College explains that forming a precipitate, color changes, gas formation and temperature change are signs of a chemical change. The University of California, Davis adds that the presence of odor also indicates a ... More »

Five indicators of a chemical change are color change, temperature change, precipitate formation, gas bubble formation and smell or taste change. Since some chemical products are poisonous, detecting a chemical reaction ... More »

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Flame photometers work by separating a chemical sample into its constituent atoms and molecules and then analyzing the colors emitted by the chemicals as they absorb and then release energy. Flame photometers are most co... More »

Chemical reactions that release energy are described by as exothermic reactions, and their equations follow the form: reactants = products + energy. Examples of exothermic reactions are explosions, such as ... More »

In a lab, Lugol's solution is typically used as an indicator for the presence of starch in a solution. Lugol's solution, also called Lugol's iodine, is a solution of elemental iodine and potassium iodide in water that ge... More »

Phenolphthalein is an indicator that turns from clear to pink in a basic solution, according to In a strongly acidic solution, the indicator is orange, but in the pH range of 0 to 8.2 it is clear. The indi... More »