Question

1. as a large helium - filled balloon rises its volume increases greatly with altitude. this increase in volume is most likely due to:

□ a decrease in the pressure of the atmosphere on the balloon.
□ an increase in the pressure of the atmosphere on the balloon.
□ an increase in the temperature of the gas in the balloon.
□ a decrease in the temperature of the gas in the balloon.

Explanation:

According to Boyle's law ($PV = k$, where $P$ is pressure, $V$ is volume and $k$ is a constant at a given temperature and amount of gas), as altitude increases, the atmospheric pressure decreases. For a helium - filled balloon, when the external atmospheric pressure on the balloon decreases, the gas inside the balloon expands, causing an increase in volume. Temperature changes are not the main factor for the volume increase with altitude in this case.

Answer:

A. A decrease in the pressure of the atmosphere on the balloon.