The symbol `Delta` in reaction signifies ______ is responsible for reaction. [heat/light]

Explanation

To answer the question regarding the symbol `Delta` in a chemical reaction, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Symbol**: The symbol `Delta` (Δ) is commonly used in chemistry to indicate a specific condition under which a reaction occurs.

2. **Identifying the Role of Delta**: In chemical reactions, `Delta` signifies that heat is applied to the reactants. This is important because many reactions require heat to proceed.

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