In basic chemistry, which of the following is a clear example of an endothermic reaction that absorbs energy from its surroundings?

Introduction / Context:
Chemical reactions can either release energy to the surroundings or absorb energy from them. These two broad categories are called exothermic and endothermic reactions. Recognizing whether a process is exothermic or endothermic is a basic skill in school chemistry and is often tested with everyday examples like burning fuel or plant photosynthesis. This question asks you to select an example of an endothermic reaction, which is one that absorbs energy, usually in the form of heat or light, from its environment.

Given Data / Assumptions:

• The options include combustion, mixing quicklime with water, burning coal, and photosynthesis.
• Combustion and burning are typically associated with heat release and flames.
• Photosynthesis in plants is known to use sunlight to convert carbon dioxide and water into glucose and oxygen.
• We assume standard school definitions of exothermic and endothermic reactions.

Concept / Approach:
An exothermic reaction is one that releases energy to the surroundings, often making the environment warmer or producing light and heat. Examples include burning coal, burning wood, or mixing quicklime with water, which generates significant heat. An endothermic reaction, on the other hand, absorbs energy from its surroundings, often causing the surroundings to cool or requiring continuous energy input such as light. Photosynthesis is a classic endothermic process in which green plants absorb energy from sunlight to drive the chemical reaction that builds glucose molecules from carbon dioxide and water. The fact that plants must capture light energy for this process is a clear signal that energy is being absorbed rather than released.

Step-by-Step Solution:
1. Recall that combustion of fuel, such as wood, coal, or gas, releases heat and light and is therefore exothermic.2. Mixing quicklime, which is calcium oxide, with water produces slaked lime and releases a large amount of heat, so this is also an exothermic reaction.3. Burning coal in a furnace is another combustion reaction that clearly gives off heat energy to the surroundings.4. In contrast, photosynthesis in green plants uses light energy from the sun to convert carbon dioxide and water into glucose and oxygen.5. Because photosynthesis needs continuous energy input in the form of sunlight, it is an endothermic process.6. Therefore, among the given options, the correct example of an endothermic reaction is photosynthesis in green plants.

Verification / Alternative check:
The overall photosynthesis equation can be written in words as: carbon dioxide plus water plus energy from sunlight gives glucose plus oxygen. The presence of energy on the reactant side shows that the system must absorb energy for the reaction to proceed. By contrast, for combustion, energy appears on the product side, indicating release of heat and light. Experiments measuring temperature changes in the environment also show that combustion raises the surrounding temperature, while certain endothermic reactions cause cooling if they absorb heat from the surroundings. These observations confirm that photosynthesis is endothermic, while the other listed reactions are exothermic.

Why Other Options Are Wrong:
Option A, combustion of fuel in air, is wrong because combustion is a classic exothermic process that releases energy. Option B, mixing quicklime with water, is incorrect because this reaction produces heat and is often used in heating applications. Option C, burning coal, is another exothermic reaction that releases a large amount of heat and light. None of these three options absorb energy from the surroundings in the way photosynthesis does. They therefore do not qualify as endothermic reactions.

Common Pitfalls:
Students sometimes mix up exothermic and endothermic because both involve energy changes. A helpful memory aid is that exothermic reactions make the surroundings warmer, whereas endothermic reactions make the surroundings cooler or require an external energy source such as sunlight. Another pitfall is to focus only on whether a process takes time, rather than on energy flow. Always think about whether the system is giving energy away or taking energy in when deciding if a reaction is exothermic or endothermic.

Final Answer:
The clear example of an endothermic reaction in this list is photosynthesis in green plants, which absorbs energy from sunlight to form glucose and oxygen.