Effects of Temperature Changes on Mass Measurement in Chemistry Experiments
What is the effect of not allowing a flask to cool completely before final weighing in a chemistry experiment?
1) The measured mass of the flask will be higher than the actual mass
2) The measured mass of the flask will be lower than the actual mass
3) The measured mass of the flask will be the same as the actual mass
4) Cannot be determined without additional information
Answer:
The measured mass of the flask will be lower than the actual mass because the cooling process would cause the gas inside the flask to contract, creating a slight vacuum if the stopper is not removed, resulting in a reduced measured mass.
Explanation: If the flask, sealed with a tiny stopper, has not cooled completely to room temperature, there is still some residual heat in the flask and the gas above the liquid inside it. When a vessel like a flask is sealed while it's containing gas and is warmer than its surroundings, the gas inside will exert more pressure than if it were at room temperature due to the increase in kinetic energy of the gas particles as they heat up.
When the flask is then cooled to room temperature, the gas inside contracts and creates a slight vacuum if the stopper is not removed. This vacuum could reduce the measured mass since there will be a small force pulling the flask upward, against gravity, due to the pressure difference. Therefore, the measured mass will be lower than the actual mass in this scenario. This falls under the principles of calorimetry and gas behavior related to temperature changes.