Final answer:
As external pressure on a gas increases at a constant temperature, the gas volume decreases and internal pressure increases according to Boyle's Law. Option b is the answer.
Step-by-step explanation:
When the external pressure on a sample of gas increases at a constant temperature, according to Boyle's Law, the volume of the gas decreases, and the internal pressure increases. Boyle's Law states that at constant temperature, the volume and pressure of a gas are inversely related, meaning that as one increases, the other decreases, and vice versa. Therefore, if the volume of a gas is reduced due to increased external pressure, the particles of gas are compressed, and since they have less space to move around, they collide with the walls of the container more frequently, leading to an increase in internal pressure.
Conversely, if the pressure on a gas is decreased, the gas volume will increase. This relationship is observed in weather balloons which expand as they rise to regions of lower atmospheric pressure. In summary, the correct answer to the question is b) The volume decreases, and the internal pressure increases.