By which methods can the internal energy of an ideal gas be changed ?

Explanation

To determine how the internal energy of an ideal gas can be changed, we can follow these steps:

### Step 1: Understand the Formula for Internal Energy
The internal energy (U) of an ideal gas is given by the formula:
\[ U = n \cdot f \cdot R \cdot T \]
Where:
- \( n \) = number of moles of the gas
- \( f \) = degrees of freedom of the gas molecules
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