Mass remains constant in a closed system

Steps:

• Gas is trapped in a container, forming a closed system with no matter exchange.
• Compression reduces volume at constant temperature (isothermal process).
• Boyle's law (PV = constant) applies, linking pressure and volume changes.
• Mass is invariant since no gas enters or leaves.

Why B is correct:

• Law of conservation of mass states that mass remains constant in a closed system with no addition or removal of matter.

Why the others are wrong:

• A: Pressure increases as volume decreases (Boyle's law: P ∝ 1/V).
• C: Frequency of particle collisions increases due to higher density from reduced volume.
• D: Density increases as mass stays constant while volume decreases (ρ = m/V).

Final answer: B