In a chemical equation, a triangle (Δ) indicates that heat is applied to the reaction. It signifies that the process is endothermic, meaning that the reaction absorbs heat during the course of the reaction. This can involve heating compounds to initiate a chemical reaction, helping to break bonds or facilitate the transformation of reactants into products.
For example, if we see the equation A + B → C + Δ, it means that when substances A and B react, heat is added, resulting in product C. This symbol is quite useful as it helps chemists understand the energy changes involved in reactions, which is crucial for controlling the conditions under which reactions occur.