**Step-by-Step Solution:**
1. **Definition of Heat**:
- Heat is defined as a form of energy that is transferred between systems or objects due to a temperature difference.
2. **Understanding Temperature Difference**:
- When two objects are at different temperatures, heat flows from the object at a higher temperature to the object at a lower temperature. For example, if one end of a metal bar is at a higher temperature (T1) and the other end is at a lower temperature (T2), heat will flow from T1 to T2.
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