Uncertainty in gas molecules?

In summary, the conversation discusses the uncertainty involved in observing single molecules in quantum mechanics and how this contradicts the ability to see a collection of molecules, such as I2 gas, as a purple haze. The concept of the uncertainty principle is also brought up and its potential effects on light scattering and absorption processes. The speaker is new to quantum physics and seeking clarification on these concepts.
  • #1
If buckyballs display uncertainty in the double slit experiment, shouldn't iodine gas molecules as well? An I2 molecule is certainly less massive than a buckyball. Yet why can we see I2 gas as a purple haze? I can see it, almost in the same way I can see my pencil, which has a very small uncertainty because it is a large object, yet the I2 molecules should all be independent, with large uncertainties, unlike my unified massive pencil.

Does what I'm saying make sense? And please bear with my ignorance, I'm new to quantum physics.

Thanks :tongue:
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  • #2
What is the setup you are describing? Is it a double slit?
  • #3
No, what I'm trying to say is that from what I've read about quantum mechanics, we shouldn't be able to see a single molecule because of the uncertainty involved with such a small object. Is this incorrect? I use the term "see" loosely because we technically couldn't "see" a single molecule because it couldn't scatter light. In fact, this is probably where I'm going wrong - it is the entire group of I2 molecules that scatters the light collectively, not each individual molecule.

My issue was just that individual molecules are made out by quantum physics to be mysterious wave-particle oddities that defy the laws of classical mechanics that seem so natural and make so much sense. And yet I can look into a flask and see a collection of I2 gas molecules as a purple haze. They are all independent molecules, not one solid object, but I can still observe them and they seem normal enough to me!

Perhaps I'm being ridiculous, but please excuse my lack of knowledge. I've only recently become interested in physics and don't have much experience outside the Physics 1 course I took last year (which was entirely classical, of course).

  • #4
A single molecule can and does scatter light. In fact, you can measure the amount of scattering to determine Avogadro's number.

But you do have an uncertainty in the location of the molecules, and their electronic state and so on. And that affects the scattering and light absorption/emission processes (e.g. natural line-broadening) I'm not sure what effect you're expecting? The uncertainty principle doesn't say you can't measure the position and momentum, it just puts a limit on how accurately they can be known at the same time.

1. What is uncertainty in gas molecules?

Uncertainty in gas molecules refers to the inherent randomness and unpredictability of the movement and behavior of gas molecules. This is due to the constant collisions and interactions between molecules, making it difficult to accurately predict their exact positions and velocities at any given time.

2. How is uncertainty in gas molecules measured?

Uncertainty in gas molecules is typically measured using statistical methods, such as calculating the standard deviation of a large number of measurements or observations of a gas sample. This gives an indication of the range of possible values for a particular aspect of the gas molecules, such as their velocity or position.

3. What factors contribute to uncertainty in gas molecules?

The main factors that contribute to uncertainty in gas molecules include the random thermal motion of the molecules, as well as external factors such as pressure, temperature, and the presence of other molecules or particles that can affect their movement.

4. Why is uncertainty in gas molecules important for scientific research?

Uncertainty in gas molecules is important for scientific research because it affects the accuracy and reliability of experimental results. It is crucial to understand and account for uncertainty in order to draw meaningful conclusions and make accurate predictions based on experimental data.

5. Can uncertainty in gas molecules be eliminated?

No, uncertainty in gas molecules cannot be eliminated completely. However, it can be reduced by controlling external factors and using more precise measurement techniques. Additionally, understanding and accounting for uncertainty can help improve the accuracy and reliability of scientific research.

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