Final answer:
Given the temperature change from 15°C to 25°C, balloons should be partially filled with helium in the morning to allow for thermal expansion and prevent bursting as the ideal gas law indicates that volume expands with temperature.
Step-by-step explanation:
When dealing with helium-filled balloons and temperature changes, one must consider the ideal gas law, which states that the product of pressure (P), volume (V), and temperature (T) for a gas is constant if the amount of gas does not change. Since the temperature is rising from 15 degrees Celsius in the morning to 25 degrees Celsius during the parade, the volume of the helium inside the balloons will want to expand as the temperature increases. This could cause the balloons to burst if they are fully inflated at the lower temperature. In practice, when inflating the balloons in cooler temperatures knowing that temperatures will rise, you should partially fill the balloons. This will allow for some expansion when the temperature rises without risking over-inflation and popping. Therefore, the answer to the students' question is B, you will partially fill the balloons with helium in the morning to allow for thermal expansion.
Using the ideal gas law, PV=nRT, where P is the pressure, V is the volume, n is the amount of gas, R is the ideal gas constant, and T is the temperature in Kelvin. When the temperature increases, if the volume is constrained to be constant, the pressure will rise. However, if the balloon is not fully inflated, the volume can increase within the stretchable limits of the balloon, thus accommodating the increased pressure without the balloons popping.