Answer :
Final answer:
The observation that indicates an endothermic reaction is occurring is that the beaker feels cool. This is because endothermic reactions absorb heat from their surroundings, leading to a decrease in temperature. Other changes, like color change or solid formation, do not specifically indicate that a reaction is endothermic.
Explanation:
Observing Endothermic Reactions
In an endothermic reaction, heat is absorbed from the surroundings, causing the surroundings to feel cooler. This means that an effective observation to indicate that an endothermic reaction is occurring in a beaker is:
- The beaker feels cool.
When the reaction occurs, the energy is drawn in to break bonds in the reactants, resulting in a cooling sensation. This is typically detected by feeling the beaker or using a thermometer. In contrast:
- If the beaker feels warm, the reaction is exothermic (it releases heat).
- Color changes or solid formation can occur in both types of reactions, but they do not specifically indicate an endothermic process.
- Glowing typically indicates a different kind of reaction or energy release, unrelated to heat absorption.
Thus, the cool sensation when touching the beaker is the clearest indicator of an endothermic reaction.
Learn more about endothermic reactions here:
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