Why Does Heating a Flask Change Its Weight?

[qrt388]

If you heat up a glass flask why will the weight of the flask decrease slightly?

The lab we're doing deals with the ideal gas law, so maybe it has to do with the mass being inversely proportional to the temperature? Or is there another reason?

Also, what would happen if you heat up a flask with no air in it that's sealed off from the outside (so inside the flask is like a vacuum)? Would the mass decrease?

 

[Dick]

What do you think? Why on Earth do you think the weight of the flask will decrease, even slightly? The ideal gas law doesn't say mass will decrease. It says the ratio of mass to volume will decrease under constant pressure.

 

[Moetasim]

I can explain why heating a flask can cause a change in its weight. When a flask is heated, the molecules inside the flask gain energy and become more active. This increase in energy causes the molecules to move around more and collide with the walls of the flask more frequently. This increased collision force creates a slight increase in pressure inside the flask, which in turn, causes the flask to expand slightly.

According to the ideal gas law, pressure is directly proportional to temperature, and volume is directly proportional to pressure. Therefore, as the temperature of the flask increases, the volume also increases, causing a decrease in the density of the air inside the flask. This decrease in density results in a decrease in the weight of the flask.

If the flask is sealed off from the outside and there is no air inside, the same process still applies. As the temperature increases, the molecules inside the flask gain energy and move around more, causing the flask to expand. However, since there is no air inside the flask, there is no change in pressure. Therefore, the weight of the flask would remain constant.

In summary, heating a flask causes an increase in volume and a decrease in density, resulting in a slight decrease in weight. This phenomenon can be explained by the ideal gas law and is applicable even in a vacuum environment.