The heat energy exchanged between the system and surroundings at constant temperature and pressure is known as…..

Answer

To solve the question, we need to identify the term that describes the heat energy exchanged between a system and its surroundings at constant temperature and pressure.

### Step-by-Step Solution:

1. **Understanding the Context**: The question asks about the heat energy exchanged between a system and its surroundings under specific conditions: constant temperature and constant pressure.

2. **Identifying the Term**: In thermodynamics, when heat is exchanged at constant temperature and pressure, the term used to describe this energy exchange is known as "enthalpy."

3. **Defining Enthalpy**: Enthalpy (denoted as H) is a thermodynamic quantity that represents the total heat content of a system. It is defined mathematically as:
\[ H = E + PV \]
where:
- \( H \) = Enthalpy
- \( E \) = Internal energy of the system
- \( P \) = Pressure
- \( V \) = Volume

4. **Understanding the Components**: In this equation:
- The internal energy (E) accounts for the energy contained within the system.
- The term \( PV \) accounts for the work done by the system due to its volume and pressure.

5. **Conclusion**: Since the question specifies that the heat energy exchange occurs at constant temperature and pressure, we conclude that the correct answer is **enthalpy**.

### Final Answer:
The heat energy exchanged between the system and surroundings at constant temperature and pressure is known as **enthalpy**.

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