A combstible substance is made up of hydrocarbons (compounds containing carbon and hydrogen). When such a substance is burnt in air, carbon dioxide and water are formed, with the evolution of heat and light.
Explain why any substance undergoing incomplete combustion gives out yellow flame.

Explanation

To explain why any substance undergoing incomplete combustion gives out a yellow flame, we can break down the explanation into the following steps:

### Step-by-Step Solution:

1. **Understanding Combustion**:
- Combustion is a chemical reaction that occurs when a substance reacts with oxygen, producing heat and light. There are two types of combustion: complete and incomplete.

2. **Complete vs. Incomplete Combustion**:
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