Why Does Heating a Flask Change Its Weight?

In summary, the conversation discusses the potential reasons for a slight decrease in weight when heating up a glass flask. It is suggested that it may be due to the ideal gas law and its relationship between mass and temperature. The question is also raised about what would happen if the flask was heated with no air inside, and whether the mass would decrease in that scenario.
  • #1
qrt388
2
0
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?
 
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  • #2
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.
 
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  • #3


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.
 

1. Why does heating a flask cause its weight to change?

When a flask is heated, the particles inside it gain energy and start to move more quickly. This increased motion causes the particles to take up more space, leading to an increase in the volume of the flask. According to the law of conservation of mass, the total mass of a closed system must remain constant, so the increase in volume is accompanied by a decrease in density. This decrease in density results in a decrease in weight, since weight is determined by the mass and the force of gravity acting on it.

2. Is the change in weight of a heated flask permanent?

No, the change in weight of a heated flask is not permanent. Once the flask cools down and returns to its original temperature, the particles inside it will slow down and take up less space, causing the volume to decrease. This increase in density will result in an increase in weight, and the flask will return to its original weight.

3. Does the type of material the flask is made of affect the change in weight when heated?

Yes, the type of material the flask is made of can affect the change in weight when heated. Different materials have different thermal expansion coefficients, which determine how much they expand or contract when heated or cooled. Materials with higher expansion coefficients will experience a more significant change in weight when heated compared to materials with lower expansion coefficients.

4. How does the shape of the flask affect the change in weight when heated?

The shape of the flask can also affect the change in weight when heated. Flasks with thinner walls or a larger surface area will have a greater change in weight when heated compared to flasks with thicker walls or a smaller surface area. This is because thinner walls and larger surface areas allow for more heat transfer, causing a greater change in the particles' energy and resulting in a larger change in volume and weight.

5. Can heating a flask cause it to lose weight?

Yes, heating a flask can cause it to lose weight. As explained earlier, the increase in volume of the flask when heated results in a decrease in density and weight. In extreme cases, if a flask is heated to a high enough temperature, the volume increase may be significant enough to cause the flask to lose weight and even float in the surrounding air due to the decrease in its weight compared to the force of gravity acting on it.

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