Question

A metallic syringe is taken with its piston at the mid position. The space inside is filled up with air. Now we seal its open end and heat it. Select the most appropriate observation.

• A. The piston will start moving in.
• B. The piston will start moving out.
• C. The piston will first move out and then in.
• D. The piston will first move in and then out.

Answer 1

The correct option is B

The piston will start moving out.

Heating a gas in a container increases its pressure. Initially, the piston of the syringe is in equilibrium because the pressure inside and outside is the same, i.e atmospheric pressure. Heating causes the inside pressure to increase and the equilibrium is disturbed. So the piston moves out to reach equilibrium once again. The piston continues to move out as we continue to heat the trapped air.