''A hot liquid' remains hot and a cold liquid remains cold in a thermos flask.'' Explain how ?

Explanation

To explain how a hot liquid remains hot and a cold liquid remains cold in a thermos flask, we can break down the explanation into several key points:

### Step-by-Step Solution:

1. **Structure of the Thermos Flask**:
- A thermos flask consists of two walls: an inner wall and an outer wall. Between these two walls, there is a vacuum.

2. **Role of Vacuum**:
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