Final answer:
The mass of a pot of water decreases after heating due to evaporation. Involving a glass beaker in a calorimeter might minimally affect the temperature change but not fundamentally alter the principle that heating typically leads to mass loss in the system due to escaped water molecules.
Step-by-step explanation:
If a student measures the mass of a pot of water before and after heating it, she should expect to see a decrease in mass after heating. This is because some of the water will evaporate when heated, which means that water molecules are leaving the pot and entering the air as a gas, thus reducing the total mass of the pot and water.
When considering the effect of a glass beaker in a calorimeter on the measurement, the presence of the beaker initially at the same temperature as the water might slightly affect the thermal capacity of the system, leading to a different heat absorption compared to having just water. However, the beaker's mass and specific heat are likely to be much smaller relative to the water, suggesting its overall influence on the temperature change of the system when heated might be minimal.
In all these scenarios, it is important to remember that changes in mass or temperature of water are dictated by the physical principles such as conservation of mass and the relationship between specific heat, mass, and energy transfer.