Which factor increases the rate at which a liquid boils besides external pressure?

• A. Larger surface area
• B. Higher impurities
• C. Lower heat input
• D. Slower agitation

Answer: (A)

The key idea is how fast energy can get into the liquid. Boiling happens when the liquid gains enough energy to change into vapor, so the rate at which heat is transferred to the liquid controls how quickly boiling occurs. A larger surface area provides more contact with the heat source, so heat can flow into the liquid more quickly. With heat coming in faster, the liquid reaches its boiling point sooner and boils more rapidly, creating bubbles more quickly.

The other factors don’t inherently speed up this heat transfer. Higher impurities can alter boiling behavior and often raise the boiling point, which doesn’t help boiling speed. Lower heat input obviously slows energy delivery, and slower agitation reduces convective heat transfer, also slowing boiling.