Heat = Mass

bob_46

I think Bill Henry was correct , heat has mass .

icesailor

Mass stores heat or cold.

bob_46

"icesailor">Mass stores heat or cold.

That's true Ice but isn't my point. Heat has mass.
What has more mass an alarm clock wound up or one that's run down ?

RobG

Does a dead battery weigh less than a fully charged one?

bob_46

RobG said:

Does a dead battery weigh less than a fully charged one?

Yes

Jamie Hall

If it does -- the battery that is -- the difference isn't much (for most batteries -- there are exceptions).

A mass of some material can store heat; the amount stored (relative to some other temperature) is related to the heat capacity of the material and the difference in temperature between that material and some reference temperature, assuming that there is no phase change between the temperature of the material in question and the reference temperature).

A "hot" object -- that is, a mass which is perceived to be at a significantly higher temperature than some reference -- will have exactly the same mass as a cooler one. No difference.

If you go much beyond that, friends, you are venturing off into the wilds of thermodynamics -- which is fascinating, but can be complicated...

Tinman

Just borrowed this from a Physics Forum:

Heat, being a transfer or energy, does not have mass. Temperature is derived from the average energy of particles in the medium, and has no effect on mass, nor does it have mass.

bob_46

When you heat something the molecules speed up . When things speed up they gain mass . As you approach the speed of light the molecule approaches infinite mass. E=MC^2 . Or ∆M=∆E/C^2

Jamie Hall

I told you not to get involved in that sort of thing. What you say is true, but your equation is, I regret to say, not. What you are looking at there is the Lorenz-Fitzgerald relationship, which states, in one form, that M = Mrest / (1 - v^2/c^2)^1/2. For velocities in the more or less normal range of molecules, the effect (while theoretically present) is of no practical relevance, since c is 3 x 10^8 meters per second, and "normal" velocities are on the order of 10^3 meters per second. The apparent mass does, indeed, approach infinity as a limit as the velocity approaches c.

bob_46

Wow Jamie! The reason I started this thread is that Dan in his news letter said Henry was wrong and heat doesn't have mass.
I just happen to be reading a book for the fifth time ,on (you guessed it) thermodynamics ,not easy . The book states that heat does have mass and gave the equations I posted. They did say that in ordinary circumstances it would be impossible to measure .
How about giving me your quick definition of entropy . S=k logW ?

Abracadabra

bob said:

RobG said:

Does a dead battery weigh less than a fully charged one?

Yes

Depends on the battery chemistry. Some gain mass when they discharge and others lose mass when they discharge.. but we are talking extremely tiny amounts of mass compared to the mass of the battery.

Jamie Hall

Enntropy, broadly put, is a measure of the disorder present in a system. To decrease entropy it is necessary to do work on the system; in a closed system, if work is extracted the entropy will increase... there has been some very interesting theoretical work done on extending the concept of entropy to information science as well as thermodynamics.

Someone once stated the three laws of thermodynamics as:

1. You can't win (you can't get more energy out of a system than you put into it)

2. You can't even break even (the efficiency of a closed system cannot equal 100% or, put another way, you can not extract in the form of work all the energy which is in a system -- some will always show up as an increase in entropy)

3. You have to start with a pot of zero (the entropy of a system at absolute zero is zero).

Tinman

Jamie Hall = Good Will Hunting?

bob_46

Thanks for your replies Jamie. Where did you pick up your knowledge of thermodynamics ,school or on your own ?

Rich_49

Like my Granpa said , " Ritchie , believe nothing you hear and only half of what you see " . Granpa was pretty smart , a hell of a boiler man too .

Jamie Hall

bob said:

Thanks for your replies Jamie. Where did you pick up your knowledge of thermodynamics ,school or on your own ?

You're welcome! Where did I pick it up? My dad was a professor of Mechanical Engineering, specializing in thermodynamics and heat flow... kind of couldn't help it!

Techman

To Jamie Hall- "I like the way you talk"

icesailor

FWIW or for what it is ALL worth, I recently saw something that showed a way to test good and bad charged and discharged alkaline batteries, If fully charged, and you stand them on their end, they will stay upright. But if they are discharged, they fall over. Or the other way around. It was a photo demonstration. I haven't tried it.

FWIW

ChrisJ

Interesting thread.
I started reading a huge thermodynamics book a while back but got side tracked. I need to get back to that.

What I did find is the reason steam pipes expand when they get hot is because they are storing energy and it takes up space. And then, when they cool you get 100% of that energy back and they shrink back to their normal size.

Any pipe rubbing against wood or a bracket as it expands or contracts in theory wastes energy, though how much I have no idea but it's probably very little. So I guess the end result is you likely get 99% of it back.

Gordy

ChrisJ said:

Interesting thread.
I started reading a huge thermodynamics book a while back but got side tracked. I need to get back to that.

What I did find is the reason steam pipes expand when they get hot is because they are storing energy and it takes up space. And then, when they cool you get 100% of that energy back and they shrink back to their normal size.

Any pipe rubbing against wood or a bracket as it expands or contracts in theory wastes energy, though how much I have no idea but it's probably very little. So I guess the end result is you likely get 99% of it back.

Keeping it simple it's thermal expansion. The molecules are moving more rapidly in the piping material as they heat up, and taking up more space. Thus the material increases, or decreases in size proportionally to the change in temperature. We use the coefficient of linear expansion for all kinds of design criteria. Linear expansion when not controlled properly can create all kinds of issues in all kinds of differing facets of construction.

One of those that most witness is pavement failure in the heat of the summer. Bridge expansion joints. Materials are moving all the time with temperature change.

100% of that heat is going somewhere depending on how well insulated the pipes are. Even pipes that are not insulated, or conducting its heat to wood, or a hanger is still giving heat to the structure, but maybe not where it is going to be most effective.

ChrisJ

Gordy said:

ChrisJ said:

Interesting thread.
I started reading a huge thermodynamics book a while back but got side tracked. I need to get back to that.

What I did find is the reason steam pipes expand when they get hot is because they are storing energy and it takes up space. And then, when they cool you get 100% of that energy back and they shrink back to their normal size.

Any pipe rubbing against wood or a bracket as it expands or contracts in theory wastes energy, though how much I have no idea but it's probably very little. So I guess the end result is you likely get 99% of it back.

Keeping it simple it's thermal expansion. The molecules are moving more rapidly in the piping material as they heat up, and taking up more space. Thus the material increases, or decreases in size proportionally to the change in temperature. We use the coefficient of linear expansion for all kinds of design criteria. Linear expansion when not controlled properly can create all kinds of issues in all kinds of differing facets of construction.

One of those that most witness is pavement failure in the heat of the summer. Bridge expansion joints. Materials are moving all the time with temperature change.

100% of that heat is going somewhere depending on how well insulated the pipes are. Even pipes that are not insulated, or conducting its heat to wood, or a hanger is still giving heat to the structure, but maybe not where it is going to be most effective.

I was talking about the heat being converted into kinetic energy from the pipe rubbing against something. Like I said I'm sure it's very tiny, but it's still happening none the less.

SWEI

The beauty of classical mechanics: First order effects predominate to the point where we can usually ignore the other bits.

Jamie Hall

SWEI said:

The beauty of classical mechanics: First order effects predominate to the point where we can usually ignore the other bits.

Thank goodness...!

nicholas bonham-carter

Has NASA developed a new rocket engine, based on the Amish heater?--NBC

http://www.nasaspaceflight.com/2015/04/evaluating-nasas-futuristic-em-drive/