If an ideal gas is heated at constant pressure :

Options

A. the volume increases
B. the mass of gas remains same
C. the kinetic energy of the molecules increases
D. attraction forces between gas particles increases

Explanation

To solve the question "If an ideal gas is heated at constant pressure," we can follow these steps:

### Step 1: Understand the Ideal Gas Law
The Ideal Gas Law is given by the equation:
\[ PV = nRT \]
where:
- \( P \) = pressure
- \( V \) = volume
- \( n \) = number of moles of the gas
- \( R \) = universal gas constant
- \( T \) = temperature (in Kelvin)

### Step 2: Analyze the Conditions
Since the problem states that the gas is heated at constant pressure, we can denote this condition:
- \( P \) is constant.

### Step 3: Determine the Relationship Between Volume and Temperature
From the Ideal Gas Law, if pressure \( P \) is constant, we can rearrange the equation to show the relationship between volume and temperature:
\[ V = \frac{nRT}{P} \]
Since \( n \) and \( R \) are constants, we can see that:
\[ V \propto T \]
This means that the volume \( V \) is directly proportional to the temperature \( T \).

### Step 4: Evaluate the Statements
Now we can evaluate the provided statements based on our analysis:
1. **Volume increases with temperature**: This statement is true because \( V \propto T \).
2. **Mass of gas remains the same**: This statement is true because the mass of the gas does not change with temperature or pressure.
3. **Kinetic energy of molecules increases**: The kinetic energy of an ideal gas is given by:
\[ KE = \frac{3}{2} nRT \]
Since \( T \) increases, the kinetic energy also increases. This statement is true.
4. **Attraction forces between gas particles increase**: This statement is false. As the volume increases (due to increased temperature), the distance between gas particles increases, which generally leads to a decrease in the attractive forces between them.

### Conclusion
The correct statements are:
- A: Volume increases with temperature (True)
- B: Mass of gas remains the same (True)
- C: Kinetic energy of molecules increases (True)
- D: Attraction forces between gas particles increase (False)

Thus, the correct answer is A, B, and C.