When heat is absorbed during a chemical reaction, the reaction is said to be

Analysis

The question asks for the specific term used to describe a chemical reaction that absorbs heat from its surroundings.

Concept Explanation

In chemistry, reactions are classified based on their heat exchange with the environment:

1. Exothermic Reactions: These reactions release heat energy into the surroundings. As a result, the temperature of the surroundings usually increases. The enthalpy change ($\Delta H$) for these reactions is negative.
2. Endothermic Reactions: These reactions absorb heat energy from the surroundings. Because they "take in" heat, the surroundings lose energy and often feel cooler. The enthalpy change ($\Delta H$) for these reactions is positive.
3. Isothermal: This refers to a process that occurs at a constant temperature, not necessarily one that absorbs heat.
4. Thermodynamic: This is a broad branch of science dealing with heat, work, and energy, not a specific type of reaction classification.

Step-by-Step Solution

• Step 1: Identify the key phrase: "heat is absorbed."
• Step 2: Recall the prefix meanings: "Exo-" means "out" (releasing heat), while "Endo-" means "in" (absorbing heat).
• Step 3: Match the definition to the options. Since the reaction absorbs heat, it is classified as endothermic.

Conclusion

Exam Tip: To remember this easily, think of an "Endo"-skeleton (inside) vs. an "Exo"-skeleton (outside). An Endothermic reaction takes heat in, while an Exothermic reaction lets heat out.