Conservation of matter states the matter can not be created nor destroyed but yet as a group of 6 middle school teachers from Maine we were attempting to develop a demonstration of this law and were stumped. Can you help us?
The details:
What we tried
Materials: 1000ml flask with 500ml water covered with a balloon containing 2 crushed Alka Seltzer tablets.
Procedure:
1) place the closed system on a balance with the unreacted Alka Seltzer tablet held above the flask in the balloon.
2) Mass the system
3) Tip the balloon, dropping the Alka Seltzer into the water causing the gas-producing reaction
4)Remass the system
What we found:
1) Every time we did this, the system lost between 0.2 to 0.6 g of mass.
What we have already thought of and accounted for:
Air escaping- we tried less porous plastic bags (we also found that an inflated balloon and flask has a mass of air of only 0.1 g - so 0.5g loss doesn't make sense).
Bouyancy of the surrounding air- was disproven with a control system
2006-07-26 07:28:38 · 9 answers · asked by ape54321 2 in Science & Mathematics ➔ Physics
There is no such thing as conservation of mass.
Take the simplest example, a radioactive material
losses mass as it radiates energy.
2006-07-26 10:03:48 · answer #1 · answered by PoohP 4 · 0⤊ 1⤋
it's got to be the buoyancy of the balloon. The problem is that even with a balance scale, you are measuring the force exerted downward by the system on the scale (measuring its weight). Imagine putting a helium filled balloon on the scale--it would register as massless (or maybe even negative mass), even though we can all see the balloon. If you wanted to take buoyancy out of the equation, you would need a system that didn't change volume when the state changed--that is, do the experiment inside a rigid container. The buildup of pressure inside something like a glass jar would be too dangerous for a classroom, but if you had some kind of a well-sealed plexiglass box it might work...
2006-07-26 09:05:08 · answer #2 · answered by mch 1 · 0⤊ 0⤋
the alka-seltzer is creating higher pressure inside the balloon, meaning that according to the kinetic theory of gases, it is constantly moving, and some of the gas is pushing up at the top of the balloon, creating the discrepancy you experienced. yes the air does escape, but its an indetectable amount if any.
the energy from creating the gas essentially turned it into a hot air balloon, by pushing up with a small but detectable force.
what was the control system you used to test for buoyancy? try doing that again.
2006-07-26 07:44:35 · answer #3 · answered by Anonymous · 0⤊ 0⤋
Now first of all i think this question should'nt arise at this level. I mean any middle school student and teacher should take things as they are. The scientists made these laws coz according to me they are right
As far as your experiment is concerned, the loss of mass is practically due to loss of air, but take it this way, the mass of air that escpaed went into the atmosphere. Nothing new was created and therefore the mass of the whole universe is still constant and conserved
And also, take a wood piece like a 2 by 4. Weight it and then burn it. It will turn black producing coal. Now obviously when you weigh the coal it will be lesser in mass than the original piece of wood. This loss is due to the carbon dioxide and other gases produced by the burning wood.
Here the law still holds true, explanation being that the mass that was lost by the wood ( in the form of carbon dioxide ) went into the atmosphere. And as a result the total mass of the universe remains constant. I hope you get it....!
2006-07-26 07:40:04 · answer #4 · answered by Hey squidward :) 1 · 0⤊ 0⤋
With a 1000mL flask, and 500mL of water, I am guessing that the system would weigh more than a few grams... maybe a few hundred. In this case, the measurement error in the balance would be greater than a single gram of mass. A simple fix might be to check the specs on the balance (it might say +/- 0.2g or something like that).
2006-07-26 08:10:58 · answer #5 · answered by Loulabelle 4 · 0⤊ 0⤋
keep the tablets tied to the cap and close the cap airtight.
weigh it.
then tilt the flask and wait. after the reaction weigh it. It should be the same.
In your previous experiment only thing i can think of ( which you have already accounted for) is air escaping, buoyancy
With airtight cap and conducting the experiment you can avoid both.
Believe me the conservation of mass is true.
I can suggest another experiment which will be more fun to the kids.
During Christmas season I see ad ad for a miracle toys. when you put some water over it and leave it vegetation grows over them.
Buy them put them inside jar ( reasonably big to supply enough air for couple of days, 1 gallon or 2). Add water put inside this jar close airtight and weigh it.
after the the growth weigh it again. the weight will be same.
You can leave it over the balance and kids can watch continuously.
2006-07-26 07:30:39 · answer #6 · answered by Dr M 5 · 0⤊ 0⤋
couldnt the the ballon have made it more bouyant or somthing? i know that alkeselters makes an endothermic reaction when put in water.
2006-07-26 07:35:15 · answer #7 · answered by dr_jeckyl1 2 · 0⤊ 0⤋
I would have to see exactly what you used to mass your system. your system probably estimates somewhere.
2006-07-26 07:33:28 · answer #8 · answered by James F 4 · 0⤊ 0⤋
It can be because of error in measuring instrument!
2006-07-26 07:34:53 · answer #9 · answered by Vanchit S 2 · 0⤊ 0⤋