In the context of your question, an endothermic reaction is one that absorbs energy (usually in the form of heat) from its surroundings.
Among the options you provided:
-
Water freezing - This is an exothermic process because heat is released when water changes from a liquid to a solid state.
-
An egg cooking - This is also an exothermic process as it involves the absorption of heat, but the energy is supplied from an external source (e.g., heat from a stove).
-
A candle burning - This process is exothermic because it releases heat and light as the wax combusts.
-
Iron rusting - This reaction is typically considered to be exothermic as well, as it is a slow oxidation process that can release some heat, particularly when large amounts of iron oxidize.
Given these options, none of them are actually "endothermic reactions" in their natural course. However, if we interpret "activation energy" in the sense of energy input required to initiate an endothermic reaction, none of the reactions listed would directly be categorized as endothermic.
For clarity:
- An example of an endothermic reaction would be photosynthesis or the dissolution of certain salts in water, which absorb heat from their surroundings.
If your question meant to ask which reaction is the least exothermic or relates to a higher activation energy (needing some energy to begin), "an egg cooking" could involve activation energy, but it is not strictly an endothermic reaction; rather, it is a process that requires heat from an external source.
So, technically, none of the provided options lead to an endothermic reaction based solely on activation energy considerations.