Philosophy Major Seeking Physics Answers

[i_drank_what?]

Hi everyone, I'm an undergrad philosophy major and I have a few specific physics questions, the answers to which shall help me write my final paper for metaphysics this semester.

The most important question is: if you break something simple like a piece of wood, could you expect that the sum of the mass of the two pieces would be exactly the same as the mass of the original piece of wood?

Also, I'd like to make sure that I am right in assuming that the products of nuclear fission would collectively have less mass than the input.

Thanks in advance,

 

[AstrophysicsX]

The mass would be the same.

 

[Drakkith]

The current way I've seen nuclear fission and fusion described is that the reactions liberate energy and the resulting particles have less mass than the originals.

However, I have recently heard that mass itself doesn't go away or change. (Rest mass)
So unfortunently I actually don't know.

 

[Ryumast3r]

It would be safe to assume that if you broke something that only broke into two pieces that didn't involve more complex things (like the reaction above), that yes, the sum would = the mass of the original (conservation of mass according to Newtonian Mechanics).

 

[gendou2]

If you bend plastic back and forth until it breaks, you heat it up. You might consider this added energy added gravitational mass, but you aren't increasing the rest mass at all...

 

[Drakkith]

If you bend plastic back and forth until it breaks, you heat it up. You might consider this added energy added gravitational mass, but you aren't increasing the rest mass at all...

The breaking of chemical bonds is analogous to the breaking of nuclear bonds. You might say that you made the plastic pieces MORE massive because you had to supply energy to break the bonds in the first place.

 

[Curl]

Well you are adding energy, but it is so small that touching the object will add/remove mass by a few orders of magnitude more than what you changed by breaking the object , so this isn't really a good question.

 

[Drakkith]

Well you are adding energy, but it is so small that touching the object will add/remove mass by a few orders of magnitude more than what you changed by breaking the object , so this isn't really a good question.

Alright. Well, if you break apart a nucleus into two different parts, do those parts have MORE mass than they did as a single nucleus? That would pretty much answer all of this.

 

[Antiphon]

Lots of things going on here. The rest masses of the atoms don't change on heating the wood but the rest mass of the wood most certainly goes up. Hot wood weighs more than cold wood according to general relativity but good luck measuring it.

The before and after masses will be different for sure but by really tiny tiny amounts.

Some atoms and wood fragments will become airborne. This will reduce the mass of the visible peices. The wood itself before breaking is in a continuous mass exchange with the environment. You can smell wood, so wood molecules (or probably a rich set of volatile organic compunds) are leaving the wood and going up your nose.

When you bend the wood to break it some of the bending is inelastic and heats the wood increasing it's mass (internal energy) by a tiny amount. When the fracture ocurrs, more work is done on the wood to effect the fracture. The free surface atoms will quickly form new bonds with water vapor and other atmospheric species (oxygen mainly). This may slightly increase or decrease the surface energy and hence mass of the wood fragments. A whole lot of phonons will rattle around in the pieces and heat it slightly some more.

If you wait a while the wood will eventually reach thermal equilibrium again but even then the masses of the remaining parts will be different than that of the original peice.

There will have been a very tiny (but not zero) amount of gravitational radiation from the quadrupole acceleration of the fracturing parts but one could make the case that all that energy came from the muscles energy breaking the wood, not from an energy change in the wood itself.

The short answer for a philosopy paper is that the mass is changing before, during and after the fracture. Good luck with that one!

 

[i_drank_what?]

First of all, thank you all for your timely and helpful responses,

Perhaps a better question might be "is it theoretically possible that all of the mass be preserved in the process of breaking the wood, while in the same sense impossible for the products of splitting an atom to have the same cumulative mass as the original atom," I guess I am asking if this is a fundamental difference between atoms and other objects.

I want to make an argument along the lines of "you can destroy a boat without destroying any mass, but you cannot destroy an atom without destroying any mass"

 

[Drakkith]

I want to make an argument along the lines of "you can destroy a boat without destroying any mass, but you cannot destroy an atom without destroying any mass"

In effect, you cannot do either. Breaking or making chemical or nuclear bonds WILL alter the mass of the object, even if it is just SLIGHTLY more or less. The lack or excess of mass comes from the energy either liberated or added to break or make the bond. In every case the total energy and mass IS conserved between all particles involved.

 

[i_drank_what?]

In effect, you cannot do either. Breaking or making chemical or nuclear bonds WILL alter the mass of the object, even if it is just SLIGHTLY more or less. The lack or excess of mass comes from the energy either liberated or added to break or make the bond. In every case the total energy and mass IS conserved between all particles involved.

Thank you, that answers my question.

 

[Antiphon]

I want to make an argument along the lines of "you can destroy a boat without destroying any mass, but you cannot destroy an atom without destroying any mass"

It's a matter of degree, not direction. Much more mass is lost when you split a nucleus because the forces involved are much stronger. But rest assured that if you destroy a boat, you have a different mass than when the boat was in one peice.

It takes work to break chemical bonds and when you do it the mass of the resulting system is slightly higher.

You may get work out of a nucleus or you may have to put work in. It depends on the nucleus.

 

[Lsos]

It's a matter of degree, not direction. Much more mass is lost when you split a nucleus because the forces involved are much stronger. But rest assured that if you destroy a boat, you have a different mass than when the boat was in one peice.

It takes work to break chemical bonds and when you do it the mass of the resulting system is slightly higher.

You may get work out of a nucleus or you may have to put work in. It depends on the nucleus.

Wouldn't the mass be slightly LOWER after breaking the chemical bonds, since you liberated energy stored in them?

 

[diazona]

Thank you, that answers my question.

Just a quick interjection: I'd suggest replacing the word "mass" with "energy." The word "mass" is sort of defined in different ways for different objects, e.g. when you talk about the mass of a piece of wood, you're not actually talking about the same sort of physical quantity as the mass of an elementary particle. If you say "energy" instead, it removes that ambiguity.

 

[Mapes]

Wouldn't the mass be slightly LOWER after breaking the chemical bonds, since you liberated energy stored in them?

Nope; compounds are at a lower energy level than their constituent atoms; that's why chemical bonds form. You aren't liberating energy when you break bonds, you're supplying it. Of course, if an even more stable compound exists, you may get that energy back and then some. Trivia: The N-N triple bond in N₂ is exceptionally stable. Many explosives contain non-diatomic nitrogen so that diatomic nitrogen can be formed during detonation, which releases all that energy.

 

[S_Happens]

Trivia: The N-N triple bond in N₂ is exceptionally stable. Many explosives contain non-diatomic nitrogen so that diatomic nitrogen can be formed during detonation, which releases all that energy.

That's an answer I was looking for a long time ago. I was asking if the nitrogen was simply for stability of the explosive and/or ease of breaking that bond or if it served another purpose. Of course now that I know what I'm looking for, the returns on searches are plentiful.

 

[KingNothing]

I'm confused by this thread. If you break something, thereby putting it in a 'higher' energy state, wouldn't that energy just come from the work you did to break it?

 

[KingNothing]

Also, I'd like to make sure that I am right in assuming that the products of nuclear fission would collectively have less mass than the input.

Yes.

 

[Buckleymanor]

Nope; compounds are at a lower energy level than their constituent atoms; that's why chemical bonds form. You aren't liberating energy when you break bonds, you're supplying it. Of course, if an even more stable compound exists, you may get that energy back and then some. Trivia: The N-N triple bond in N₂ is exceptionally stable. Many explosives contain non-diatomic nitrogen so that diatomic nitrogen can be formed during detonation, which releases all that energy.

So the broken parts become more massive?

 

[Mapes]

So the broken parts become more massive?

To a minuscule degree.

 

[KingNothing]

To a minuscule degree.

Mapes, could you perhaps explain this in a different way? I don't get it.

Essentially what I'm hearing is: you add energy to the system (by applying force) and when it breaks, the system is at a higher energy state. It sounds to me like a simple energy transfer.

 

[renzagliarobb]

Hi everyone, I'm an undergrad philosophy major and I have a few specific physics questions, the answers to which shall help me write my final paper for metaphysics this semester.

The most important question is: if you break something simple like a piece of wood, could you expect that the sum of the mass of the two pieces would be exactly the same as the mass of the original piece of wood?

Also, I'd like to make sure that I am right in assuming that the products of nuclear fission would collectively have less mass than the input.

Thanks in advance,

If you break something...you will lose some atomic mass in the process (almost nothing but the mass does change)

When nuclear fission occurs...mass is exchanged for heat energy.

 

[renzagliarobb]

First of all, thank you all for your timely and helpful responses,

Perhaps a better question might be "is it theoretically possible that all of the mass be preserved in the process of breaking the wood, while in the same sense impossible for the products of splitting an atom to have the same cumulative mass as the original atom," I guess I am asking if this is a fundamental difference between atoms and other objects.

I want to make an argument along the lines of "you can destroy a boat without destroying any mass, but you cannot destroy an atom without destroying any mass"

If you destroy an atom...the mass changes to energy. You cannot destroy energy or mass, you can only convert it back and forth. The mass is changed to energy so...yes mass changes at the atomic level.

 

[Drakkith]

If you break something...you will lose some atomic mass in the process (almost nothing but the mass does change)

When nuclear fission occurs...mass is exchanged for heat energy.

When you break something you have added energy to it, increasing its mass.

The 2nd part is correct.

 

[renzagliarobb]

When you break something you have added energy to it, increasing its mass.

The 2nd part is correct.

The energy created is from a chemical reaction, The energy comes from the mass of the object. Energy can only be created from mass. If the energy is created from "breaking something" where is the energy coming from? What mass has created the energy?

 

[Drakkith]

The energy created is from a chemical reaction, The energy comes from the mass of the object. Energy can only be created from mass. If the energy is created from "breaking something" where is the energy coming from? What mass has created the energy?

Whatever is breaking the object, in our case a person, applies force and does work to break it. That is where the energy comes from to break those chemical bonds.

 

[renzagliarobb]

Whatever is breaking the object, in our case a person, applies force and does work to break it. That is where the energy comes from to break those chemical bonds.

How does energy or work exerted from a person change to mass? If I go running in the park and do not break anything...where does the energy go? Does it just convert to mass somewhere? Am I changing the mass of the earth?

 

[Drakkith]

How does energy or work exerted from a person change to mass? If I go running in the park and do not break anything...where does the energy go? Does it just convert to mass somewhere? Am I changing the mass of the earth?

Your body consumes fuel in the form of food and oxygen. The byproducts of this, CO2 and other things, have LESS mass than they did before they were used. Some of this energy is converted into heat, which is why you heat up and sweat when you exercise. Some of that energy goes into the actual moving of your muscles and is expended that way.

Now the key here is that when you BREAK something you have broken the bonds of the atoms and molecules that make up that object. After you broke them they did not reform and bind with something else like the fuel in your body does. If I break a piece of wood in half and then throw it into the fire, the wood burns and releases energy. If you could measure every particle from that wood before and after the fire you would find that it has less mass than they did before.

Also, remember that energy can be converted to light as well. That is why a fire is visible.

Edit: When I say "Energy is Expended" I mean that it is converted to another form and cannot be used for further work. NOT that it simply dissapears.

 

[epenguin]

Hi everyone, I'm an undergrad philosophy major and I have a few specific physics questions, the answers to which shall help me write my final paper for metaphysics this semester.

The most important question is: if you break something simple like a piece of wood, could you expect that the sum of the mass of the two pieces would be exactly the same as the mass of the original piece of wood?

Also, I'd like to make sure that I am right in assuming that the products of nuclear fission would collectively have less mass than the input.

Thanks in advance,

I've heard of incommunication between disciplines but this is ridiculous! The answers to these questions are in every pop physics book aimed at 10-year olds!

I don't think mass is a metaphysical concept, it is a physical one. Specifically it is an invariant of motion, that is, a physical concept probably more abstract than metaphysics which I guess is still stuck with rather naive, or falsely concrete, concepts of 'substance' etc. It has the remarkable property of being, within well understood limitations, constant, but I guess something has to be or there could be no science, probably no thought or nervous systems. I don't know if this last statement is also metaphysics but I think it is independent of any metaphysics, and I suspect that the constancy of any particular thing scientific laws declare to be constant is metaphysically contingent.

If you think this means I'm hostile to philosophy I'm not - wait till you hear the others! Hostile to metaphysics maybe, sorry.