Statement A: The temperature of the gas remains unaltered when it undergoes an adiabatic expansion.

Statement B: Heat energy is exchanged between a system and its surrounding during an adiabatic process.

The correct answer is option 4) i.e. Both A and B are false

CONCEPT:

• Adiabatic expansion: An adiabatic process is where no heat is exchanged between the system and surrounding. This causes the compression of the gas.
  • Here, there is a change in volume due to internal work done on the gas.
  • Hence, the work done is negative.

EXPLANATION:

• Heat is not exchanged in an adiabatic process. Statement B is false.

From the first law of thermodynamics, ΔU = Q - W

• In an adiabatic process, the heat exchanged will be zero 

⇒ Q = 0. Thus,  ΔU = -W

Work done by a gas is given by:

W = P × ΔV

Where P is the pressure and ΔV is the change in volume of the gas.

• During adiabatic expansion, the volume increases, and thus, work done increases.
• Therefore, it will have lower internal energy ΔU. Since internal energy is a measure of temperature, the temperature decreases during adiabatic expansion. Statement A is false.
• Thus, both statements are false.