Why weight change when I put effervescence tablet ?

[Gh778]

I put the bottle in my freezer (home) and I don't forget to wipe the bottle. With second bottle freeze (water => ice), the weight increase too: +0.04g but like I'm waiting more than one hour maybe it's something from balance. And if I heat bottle for have water the height decrease -0.03g. Third and forth bottle no, the weight is always the same with ice. So it's not enough for say something.

PET iirc Coca Cola Co bottles go flat in 3-4 months, and cans in 6-9 months.

ok, but the measure is done in 2 minutes. And the glue ? and the upside down ? and the same lost with different containers ? and proportionnal to the number of tablets ? and with different volumes for gas ? And with glass containers and steel covers ?

It's possible to use the formula of Newton: force=2mv; if top speed is 0.25 m/s the weight losses is 2*0.6/1000*0.25/10 = 0.03 g with 0.6 g of CO2 (it's what I can read on internet about Efferalgan tablet), image show speed that I found on Internet. If it's that, the weight must change with a ball full of air (ping-pong ball) in water. But the CO2 in a tablet is very powerfull, 0.3g give 0.187 liter of CO2, even the ball move faster the volume is not great in a bottle. The ball must be down before close the container. And the gas must relax when the ball reached surface. There is a big difference between gas and a solid. In space, if I accelerate in one direction gas in a chamber, the gas keep the velocity even the walls are heavy, in the contrary it would be possible to move centre of mass. If I replace gas by small solid in each bubble in water, it's not the same case, solid move up from the surface a little and after move down and the momentum is not conserved due to gravity. Under gravity, gas keep momentum until temperature is conserved I think.

 

[Simon Bridge]

I'm afraid your reporting of events is unclear. List what you did and what the result was each time.
Remember, we don't speak each other's native language, so we need to be careful.

The mass-reading goes down by 0.06g = 60mg during the reaction, but increases by 0.04g=40mg after freezing? If you heat the bottle after that, the mass goes down again. But you only see this up-and-down shift for some of your tests not all of them?

How accurate are your scales? What is the smallest unit of mass it can measure?
Have you tried weighing a lump of metal and seeing if the reading is consistent over time, and with subsequent measurements?

Wiping the bottle after freezing is good - but the quantities we are talking about are very small ... how much condensation would 40mg be and how long would it take to form?

Water expands when it freezes - which, in your case, would increase the pressure on the gas at the top. Soe would re-dissolve. There would certainly be less activity so you may have a case for considering it.

The gas bubble in the liquid accelerates, as you have observed, because it is acted on by an unbalanced force. An equal volume of water, then, goes downwards with the same acceleration as the bubble. This water has a greater mass, so it's momentum will be higher. So more momentum gets transferred down than gets transferred up - so how is it that this gives rise to a decrease in force to the scales?

Newtons law for force is F=Δp/Δt which simplifies to F=ma.
"Specific Impulse" is Δp and Δp=2mv in the kind of collision where the object rebounds with the same momentum as it struck. You have to understand the equation before you apply it.

ok, but the measure is done in 2 minutes. And the glue ? and the upside down ? and the same lost with different containers ? and proportionnal to the number of tablets ? and with different volumes for gas ? And with glass containers and steel covers ?

In order:
. You are losing a lot less mass over 2mins than the coke does over 3months - and your bottles have already been used more than once - probably worn, certainly not factory-new.
. Glue, upside down... makes no difference to the diffusion through the walls of the container.
. Diffusion is proportional to the pressure - which is proportional to the number of tablets, so this supports the proposition.
. Pressure also depends on the volume of gas... but you have provided no data on this part.
. The type of cover does not matter - the diffusion is through the walls. Gasses can diffuse through steel too (did you not read the reference I gave you?) That you get the same reading for different materials is problematic but you also have no controls so I cannot tell if the readings are significant: maybe the variation with materials is too small for your scales to measure?

Keep investigating - what is the pressure inside the bottle after the tablet has dissolved?
You'll need to measure it.

Inflate an empty bottle with compressed gas to about that pressure and see if you get significant weight loss afterwards. That'll removing outgassing from the list at least.

 

[Gh778]

Ok for take care about language english, where do you come from ?

For the volume of the gas, I take with same bottle: 5 cl to 1.45 liter (for large as I can, some bottle the max is 0.45, others max is 0.95 and others 1.45) but the result is always the same, for example with a bottle of 1.5l I have tested with volume of gas of: 5cl, 25 cl, 50cl, 75cl, 100cl, 125cl, 145cl.

The mass-reading goes down by 0.06g = 60mg during the reaction, but increases by 0.04g=40mg after freezing?

yes for 2 bottles, I don't have same result for 2 another bottles

How accurate are your scales?

0.01 g. I measure in real time. I read the 0 after too, for watch if it's always to 0.

Gasses can diffuse through steel too (did you not read the reference I gave you?)

Yes I read it yesterday. But with different diameters of cover this don't change the result. And I tested with glass container and glass cover and the result is the same, ok there is a 2mm thickness of gasket but it is compressed and the thickness is around 1mm.

You'll need to measure it.

I will do today

Inflate an empty bottle with compressed gas to about that pressure and see if you get significant weight loss afterwards. That'll removing outgassing from the list at least.

I don't think it's possible with materials I have, it's not easy to do.

how much condensation would 40mg be and how long would it take to form?

I can't measure it

You are losing a lot less mass over 2mins than the coke does over 3months

Are you sure ? if I lost 0.03g in 2 min, after 3 months I would lost 0.03*30*24*30*3 = 2 kg

so how is it that this gives rise to a decrease in force to the scales?

for me the gas inside bubble has a velocity, this velocity is conserved when the gas is mix to another. Sum of force is always 0, because there is always gravity in account and when I put down the tablet, I put down the gas (with its momentum). But after, I close the cover and measure the weight. .

You have to understand the equation before you apply it.

I try to calculate the difference of force due to the gas, the increase temperature would be like +2.9° but after I don't know how to apply for have the force if I consider 0.5g of CO2 for example. Do you know ?

For Archimede's law application, have you good result ? Because it can be the solution

The best is to repeat this experience with laboratory materials. But I don't have.

 

[Gh778]

I try new test:

1/ I put water in small glass/steel container with a tablet in it, upside down, oil on gasket, closed
2/ I place this container in a bigger glass/steel container, oil on gasket, upside down, water inside

The tablet is in water when I return the big container, not before. I close the big container before return it and put in balance like that I have the exact weight. I can see if gas move in big container because this give bubbles (I tested this point).

I measure the weight of all.

The weight decrease of the same value in 2 minutes (like before). Here like the big container don't have a lot of additional pressure because the small container is closed (I don't ear pchiiitttt when I open the big container), I'm not sure it's possible to incriminate the diffusion.

 

[Simon Bridge]

That doesn't look like you are losing mass then.
That leaves one of the other three.

 

[Gh778]

That leaves one of the other three.

could you explain ? It's not possible it's Archimedes effect too.

That doesn't look like you are losing mass then.

not mass, weight

A friend of a friend who works in a Lab for analysis has tested with 2 balances of 0.001 g (Kern PEJ and PBJ, I don't know if it's good but it's pro balances), with a small glass/metal in a big glass/metal like I described before. He has near the same result. The weight decrease 0.0273 g (mean) in 2 minutes. He done 4 measures. At least, I can say it's not my balances, I think it's better to have another measures with different balance. I don't tell to him my results so he don't knew that I'm waiting 0.03 g. He don't use exactly the same effervescent tablet but I think it must be CO2 in it too. If someone has a balance precise enough he can do the tests, because I prefer to have a lot of measures and say that don't come from a problem with balance. If you do the test, don't forget to put all thing in container, like that Archimedes law don't interact more after than before.

Image: red is small glass/steel container, black is big glass/steel container, I use support for don't shock the glass. Tablet is block like that it is in water only when I return all the system. I think like that it's not possible to incriminate Archimedes and diffusion.

I added sensor (mountain watch) for measure the pressure in big container and it's never change with big values (only +1.3% max of pressure). Like that I'm sure it's not diffusion of gas.

What do you think I need to add for understand where the problem come from ? I measure weight while 2 minutes, not only for limited escape of gas.

 

[Buckleymanor]

Hi,

I measure weight of : column of water + water + effervescence tablet + cover (hermetic)

When I put effervescence tablet (give a lot of small bubbles) in water and close very quickly the cover, the weight decrease of 0.2g with a precision of 0.01g for the weight-balance. The weight decrease more and more until -0.2g. When I open the cover I can ear pshiiitttt, this could say no gas has move out. I tried with big column (1 liter) and others smaller. Could you explain where is my error when I do experimentation ?

The weight decreases because of bouyancy. The production off a lot of small bubbles causes a decrease in density this results in an increase in bouyancy.The mass remains the same but the atmosphere does not support the extra gas supply from the effervesence tablet in the same way.
Because the experiment is closed the effect of the tablet is like attaching a helium balloon inside the column resulting in a weight decrease.

 

[Simon Bridge]

OK - things that can lead to a lowered weight reading on a balance:

1. there is less mass sitting on the balance
2. there is an additional force acting on the system being weighed
3. it is an artifact of the weighing process
4. the acceleration of gravity has changed

If you rule out #1, then it must be one of the other three.

One thing that springs to mind is when the object being weighed has some sideways vibration, the weight reading can be lowered. I see this in experiments from people who think they have discovered antigravity using rotating widgets. The wobble from the machine throws the weight off - especially for electronic balances - making it look like the machine's weight is reduced.

I usually overcome the effect by making the machine do some work - like lifting a smaller weight over a pulley (compared with machine switched off). Accounting for any very small vibrations caused by the chemical reaction and bubbles would be difficult... but it would work in well with your observations.

You could mount a mirror on the scale surface and bounce a laser off it to put the spot on a wall some meters away to see if there is much vibration present compared with the initial setup?

 

[Simon Bridge]

The weight decreases because of bouyancy. The production off a lot of small bubbles causes a decrease in density this results in an increase in bouyancy.The mass remains the same but the atmosphere does not support the extra gas supply from the effervesence tablet in the same way.
Because the experiment is closed the effect of the tablet is like attaching a helium balloon inside the column resulting in a weight decrease.

Which would also work - except I'd like to see the math.
The system is closed - so one would naively expect that this means the same mass is occupying the same volume before and after release even though CO2 locked into a solid is less dense than released as a gas.
Can you link to an example?

 

[Gh778]

You could mount a mirror on the scale surface and bounce a laser off it to put the spot on a wall some meters away to see if there is much vibration present compared with the initial setup?

I don't have a laser, but could you explain more ?

For vibration, ok when I walk I can see the weight changed, but this cancel if I don't move. At one time there is no bubble moving up in the water (or I can't see it). One "system" has waited the night and I don't watch movement in the water but the weight never change (-0.03g / tab).

If the acceleration of gravity has changed, 2 solids and 2 liquids I use like "references" (I test my balance with "references" before) must changed its weight, but not.

What is an artifact ?

 

[Simon Bridge]

An "artifact" is the name for an erroneous or false reading caused by the way the equipment works or is used ...
http://oxforddictionaries.com/definition/english/artefact
http://en.wikipedia.org/wiki/Artifact_(error )

Have you tried vigorously shaking the container before weighing for the second time?

Does the weight loss stop when new bubbles stop being made?

 

[Gh778]

Have you tried vigorously shaking the container before weighing for the second time?

yes

Does the weight loss stop when new bubbles stop being made?

Yes, but it's not so simple, because new bubbles coming after 2 min but very low number if I compare when the tablet is always there. I stop measuring after 2 min now but like yesterday I have my new system for measuring, I wait this night, and I can say this morning the weight don't change.

If it's an artifact, I would understand how does it works.

 

[Simon Bridge]

I have my new system for measuring, I wait this night, and I can say this morning the weight don't change.

... you need to be clear: do you mean that if you leave the container overnight, there is no weight lost?

 

[Gh778]

no, sorry for me bad english...yesterday I done a measure, the weight decrease -0.03g, I let all the night and the weight don't change in the night, it is always -0.03g in the morning.

 

[Simon Bridge]

No worries - I've had a go trying attract some people who may be able to help you with your quest.
Meantime - did you discover anything that recovered the lost weight? Freezing or something?

 

[Gh778]

did you discover anything that recovered the lost weight? Freezing or something?

I don't have time for this because I focused on Archimedes and diffusion problems. But tomorrow, I will test with new "water->ice->water" cycle and test weight each time. The problem of condensation will be always there. Even if I tested a "simple" bottle of water to see if I weight the good weight.

I appreciate if someone can test and measure weight for have an external point of view with physician knowledge, maybe I forget something in my test.

 

[dlgoff]

IMO gas is escaping. But I'm jumping in here, as safety could be an issue for other experimenters that may read this thread.

https://www.youtube.com/watch?v=nZHGK37jBp8

Need I say more?




Be Safe

 

[Gh778]

Need I say more?

yes, have you read message #36 and see the image ? Because I put tablet in small glass/steal container, and put it in another bigger glass/steel container, I measure the pressure in big container and maybe one or two percent is added. So this don't change the -0.03g I lost

 

[Simon Bridge]

Well you didn't fill the container completely full either.
Outgassing requires that gas escape both walls. But that may happen if the seals are not as good as you think.

Will you show us a video of your setup in progress?

 

[Gh778]

Will you show us a video of your setup in progress?

sure, tomorrow or wednesday

Well you didn't fill the container completely full either.
Outgassing requires that gas escape both walls. But that may happen if the seals are not as good as you think.

It's possible to have diffusion through wall of the first container, but like pressure in the second container is always the same than external pressure, the diffusion through the big container must be near 0.

Have you datas of the diffusion of CO2 through glass and metal function of time and thickness ? Because when I saw the value on internet I don't read big value and something that can gave 0.03g in 2 minutes with 1 g of CO2. And like I said before even there is diffusion, this is the same value with different containers ?

 

[Buckleymanor]

Which would also work - except I'd like to see the math.
The system is closed - so one would naively expect that this means the same mass is occupying the same volume before and after release even though CO2 locked into a solid is less dense than released as a gas.
Can you link to an example?

http://en.wikipedia.org/wiki/Cartesian_diver
Ok.The diver is submerged in water, though the container is submerged in the atmosphere in a similar way.So unless gas is escapeing as digoff hints the production of bubbles within the container is causing a density change through pressure, allowing more bouyancy to the container within the atmosphere.

 

[Gh778]

@Buckleymanor: If I lost weight when there are bubbles, this can say I can move down a mass m1 I recover m1gh, and at bottom I change weight m2 and move up very quickly (acceleration=1000 m/s²) and recover energy from movement, I lost m2gh, I return to first position and I win energy (m1-m2)*gh, like g and h can be very high (in theory), I can win energy even I lost energy due from the dissolution of the tablet, it's not possible.

 

[Buckleymanor]

@Buckleymanor: If I lost weight when there are bubbles, this can say I can move down a mass m1 I recover m1gh, and at bottom I change weight m2 and move up very quickly (acceleration=1000 m/s²) and recover energy from movement, I lost m2gh, I return to first position and I win energy (m1-m2)*gh, like g and h can be very high (in theory), I can win energy even I lost energy due from the dissolution of the tablet, it's not possible.

Your mass does not change.It is your density that is variable due to the introduction of the tablet.
Look at the diver it's mass remains the same but the air within it changes density due to the pressure applied on the bottle.You are applying pressure on the walls of the container as the tablet produces bubbles the whole thing grows slightly as the pressure increases makeing the contents of the container slightly less dense.Which in turn makes it more bouyant within the atmosphere and weighing less.
Unless it is the gas escapeing from the container, then it is looseing mass to the atmosphere and this will also make it weigh less.

 

[Gh778]

@Buckleymanor: ok, now I understood what you want to explain. True, the system is about the same. Bubbles decrease density, this increase volume and so Archimedes force. The weight decrease. You're right.

But now what's happens with energy ? I can move down the system without bubbles and move up with bubbles at any speed. It's not possible to recover more energy than give.

 

[Simon Bridge]

http://en.wikipedia.org/wiki/Cartesian_diver
Ok. The diver is submerged in water, though the container is submerged in the atmosphere in a similar way. So unless gas is escapeing as digoff hints the production of bubbles within the container is causing a density change through pressure, allowing more bouyancy to the container within the atmosphere.

Where in that link is it demonstrated that the overall weight-reading on a scale decreases?
(Or changes at all?) That's what you need to demonstrate.
All I see in the linnk is that the density of the air inside the stopper changes, changing the buoyancy force on the stopper - not the entire bottle.

In Gh778's setup - the air inside the container increases density because additional gas is being added - even though the bubbles decrease the mean density of the liquid, and there is reduced density from the disintegration of the tablet. The overall volume of the setup does no change and neither does the mass (it has been asserted).Consider: If a bottle of compressed helium is in an evacuated chamber, and the whole is sitting, in air at STP, on a sensitive balance. The bottle is opened (by an automated mechanism, remote control, something) allowing the helium to escape and fill the room. All else remaining equal: what do you think would happen to the reading on the balance?

You can even imagine the mass of the chamber+bottle is lighter than the air it displaces so that, filled with helium, it would normally float in the air... and we tether it to the balance.

 

[Gh778]

Maybe it's easier to understand with a basic problem (image):

1/ the system at start
2/ I add bubble object in water, this don't change the mass of water+gas, but the volume of water increase, the external pressure increase, the volume of bubble decrease...

For the delay of transmission of pressure, if water is at altitude 1 meter in the column, the speed of sound is around 340 m/s. The time for reach up is 0, but for reach the bottom time need 0.003 s.
If pressure increase of 100000 Pa in 2 minutes, the differential pressure is around 2.5 Pa / s. It's enough for create a difference of weight I think, no ?

 

[Buckleymanor]

@Buckleymanor: ok, now I understood what you want to explain. True, the system is about the same. Bubbles decrease density, this increase volume and so Archimedes force. The weight decrease. You're right.

But now what's happens with energy ? I can move down the system without bubbles and move up with bubbles at any speed. It's not possible to recover more energy than give.

When you add bubbles you are also adding the energy the introduction of the tablet and the chemical reaction are supplying energy so you are not getting something for nothing.

 

[Gh778]

reaction are supplying energy so you are not getting something for nothing

I thought about that but the energy of chemical reaction is fixed Ec. But you can accelerate an object like you want, with 1000 m/s² for example, you can find an energy greater than Ec with parameter of acceleration, or even the system can have a high constant velocity 10000 m/s for example before to put in contact of water/tablet.

Another tests:
In one case, if I wait a long time: 3 tests on 4, I can say the weight is always at -0.03g
In other case, if I freeze water to ice: 4 tests on 6, I can say the weight come back to original value. So it's not enough to tell something.

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For the delay of transmission of pressure, if water is at altitude 1 meter in the column, the speed of sound is around 340 m/s. The time for reach up is 0, but for reach the bottom time need 0.003 s. If pressure increase of 100000 Pa in 2 minutes, the differential pressure is around 2.5 Pa / m. It's enough for create a difference of weight I think, no ? And the pressure in water depend of speed of sound in water around 1500 m/s, very different of sound in air, how pressure can do for equilibrate in the same time ?

 

[Simon Bridge]

Maybe it's easier to understand with a basic problem (image):

1/ the system at start
2/ I add bubble object in water, this don't change the mass of water+gas, but the volume of water increase, the external pressure increase, the volume of bubble decrease...

How do you add the bubble?

I'm sorry, this example is more complicated than your original one.

 

[Gh778]

How do you add the bubble?

it's just a theoretical problem for understand how pressure works. But if it's more complicated, let it down.

Do you know how delay change a dynamic pressure ? Delay come from speed of sound in the material ?