Mass Defect & Binding Energy (1 Viewer)

[howcanibesmarter]

How is mass defect, mass difference, energy and binding energy different? I'm kinda confused.

Here's what I do know.
Like I get the definitions, mass defect is difference in mass between nucleons and nucleus, whereas mass difference is difference between mass of products and reactants. binding energy is energy released when a nucleus is formed from its constituent nucleons. binding energy of products > binding energy of reactants means binding energy released or is it just energy?

What i don't get is the distinction between energy and binding energy, are they two separate things? Apparently energy being absorbed means a decrease in total binding energy? And that binding energy is equivalent to change in mass defect?

But doesn't this mean an increase in binding energy (increase in mass since equivalent), results in energy being released (mass difference decreases by E=mc^2), but this doesn't seem to be the case...

 

[wizzkids]

You have to loosen up your thinking, and start to think like Einstein, who told us that mass and energy are interchangeable.
Mass is stored energy.
If you change the potential energy of an object, a particle, an assembly of particles, whatever, then its mass will also change. Sometimes the change of mass will be so small that it is almost undetectable. Energy and binding energy are both measured with the same units, joules or in Chemistry it's joules per mole. In Particle Physics we also use electron-volts eV, or Mega electron-volts MeV because the numbers are more convenient.

The binding energy of an assembly of particles represents the drop in potential energy of the whole, over the parts, which you correctly stated. We cannot directly measure this binding energy, but we can observe its external manifestation, which is the drop in mass of the whole assembly.

Then using the Einstein equation, we can convert the "lost mass" into an equivalent change of potential energy. The assembly becomes more stable when its potential energy decreases, in other words, if the mass of the assembly decreased, then it is more stable compared to its constituent particles.
In nuclear fission of heavy nuclei like uranium U-235, the nucleus splits into two halves, and the combined mass of the two halves is less than the mass of the U-235, therefore a great deal of energy is is released. A chemist might say this is an exothermic transmutation.
In nuclear fusion of light nuclei such as ²₁H + ²₁H --> ⁴₂He the mass of the helium nucleus is less than the combined mass of two protons and two neutrons, and a modest amount of energy is released. This is also an exothermic transmutation.
Does that help?