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submitted 4 months ago by fossilesque@mander.xyz to c/science_memes@mander.xyz

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[-] Zachariah@lemmy.world 5 points 4 months ago

I’ve heard this, but then I asked once what speed water molecules in a room temperature glass of water would be going. Are they like walking, driving, flying in a jet, or much faster? I was told my question didn’t have an answer since it didn’t really work that way or something.

I often wondered if the person answering just wasn’t able to make some assumption needed to answer because I didn’t state it in the question, or if saying thermometers measure speed is just wrong.

[-] L3mmyW1nks@lemmy.world 13 points 4 months ago

See figure 3 here: https://en.m.wikipedia.org/wiki/Thermodynamic_temperature

As mentioned above, there are other ways molecules can jiggle besides the three translational degrees of freedom that imbue substances with their kinetic temperature. As can be seen in the animation at right, molecules are complex objects; they are a population of atoms and thermal agitation can strain their internal chemical bonds in three different ways: via rotation, bond length, and bond angle movements; these are all types of internal degrees of freedom.

tl;dr Water be jiggly. Amount of jiggle is hard to put a number on

[-] Zachariah@lemmy.world 3 points 4 months ago

So if I were jiggling, I think I could come up with a speed. I’d figure out how far I'm moving, and how long it takes me to move. So I could measure from far left to far right of the jiggle (let’s say 18in.) and then how far to go from far left to far right and return to the original position. If that’s 2 seconds, then that’s 1½ feet per 2 seconds which can be converted to any other speed such as km/hr.

[-] dohpaz42@lemmy.world 3 points 4 months ago

let’s say 18in.

Show off. 😠

[-] Zachariah@lemmy.world 3 points 4 months ago

I’m rather jiggly.

[-] ninja@lemmy.world 2 points 4 months ago

The jiggly argument is about not all parts moving at once or in one direction. If you jiggled to the right by taking one 18 inch step to the right, sticking your left arm straight left, waiving your right arm in a complete circle, holding your left foot 3 inches off the ground, and squatting down 10 inches how far have "you" moved?

[-] Zachariah@lemmy.world 1 points 4 months ago

How does the thermometer get its answer? I’d measure that part.

[-] FooBarrington@lemmy.world 2 points 4 months ago

The answer by the thermometer is the temperature, which is based on more degrees of freedom. You'll have to define some mapping between the other degrees and velocity.

[-] MeowZedong@lemmygrad.ml 1 points 4 months ago

Here's an experiment that you could try at home:

Takes 2 cups of water of equal volume, one hot and one cold. Put a single drop of food coloring into each cup and time how long it takes for the color to fully disperse throughout the water.

Record your units in SI units like cm or mm, because inches are stupid and scientists have agreed to not like them. You are a scientist now, so you must join the club.

Submit your findings to the journal of Lemmy for peer review. Extrapolate into other forms of measurement if you want.

If you want it to be even better, measure 3 temperatures (in °C, mind you): room temp, hot, and cold. Then you can plot them on a curve of distance vs time.

[-] davidgro@lemmy.world 3 points 4 months ago

It would still be possible to answer the speed question, you just get different answers for different substances (and even phases of the same substance) at the same temperature.

Since something like water does have those additional ways to store energy, my guess is it would be slower at room temp than another liquid with less complex molecules that have about the same mass each. (If there is such a thing)

Also I expect different answers for each of mean, median, and mode speeds.