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Radiation, Binding Energy and Mass Defect

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molo ma

on 7 October 2015

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Transcript of Radiation, Binding Energy and Mass Defect

Protons are all +ve and repel each other!!!
Why would they come together and cram into the nucleus???
Back to why protons stay close together??? Something counteracts the electrical force of repulsion...its the Strong Nuclear Force.
A nucleus can be unstable when the electrical repulsion overcomes the strong nuclear force and it breaks apart. This can happen in large atoms like Uranium...WHY though?
Well, SNForces are only really really strong to particles that are extremely close...in fact the objects must be less than a hundred thousand billionths of a metre away from each other for them to work!!!
Any further apart, and the forces are almost zero (luckily though the protons and neutrons in a small atom are this close together)
Can you think of why a larger atom like uranium is unstable now???
This is a model of a uranium atom
That's right, some of the nucleons are further apart than 100 000 000 000 000ths of a metre!!! So the SNFs cannot act on all nucleons, however electrically repulsive forces act on all protons!!!
Believe it or not after an atom is smashed, the separate protons and neutrons actually weigh more than the nucleus did as a whole. Think about this for a minute...Why is it strange? Its called the MASS DEFECT. This is very odd as normally matter cannot be created! What's going on???
You may not know that Einstein told us that energy and matter can be interchangeable in his famous formula E = mc ^2
The mass of separated components of a helium atom (2 protons and 2 neutrons)is more than that of the atom. The difference arises from the energy put into the system to separate the tightly bound nucleus.
a very small mass can provide you with a very large amount of energy!!! This is the reason why nuclear power can be very useful + also why nuclear weapons are extremely powerful!!! Look at this test done underwater in the pacific during the 50s
If we can control this it will be awesome!!!
(Not to blow stuff up but to use as energy as Nuclear power)
The bomb dropped on Hiroshima was equivalent to 20 000 tons of TNT!
It will require a much bigger amount of coal to get the same energy as a little bit of uranium, as they are completely different ways of releasing energy!!!
Finding the difference in mass of the separate components, and the whole nucleus will tell us how much binding energy was holding the nucleons together (in eV)
E is measured in electron volts eV (unit for energy much smaller than a joule) SI units are Joules. Like any eqn in Physics, calculations should be done in SI units.

m is measured in u (Atomic mass units). This is approx. one proton's mass = 1 AMU or 1 AMU is 1/12th the mass of a carbon-12 atom. A helium nucleus is 4 AMUs.

c is speed of light in a vacuum 3x10 to power 8 m/s

What this tells us is that mass can appear out of energy being put in!!!
The binding energy can be cashed out as mass on the other side therefore the binding energy is calculated by knowing the differences in masses
remember the terms BINDING ENERGY and MASS DEFECT
The main points you must take from this prezi are:
1. Nuclear energy can be harnessed by controlling the incredible energy released by the SNFs in trillions of atoms of a substance
2. The mass of the protons, electrons and neutrons separately minus the mass of the nucleus = mass defect which = binding energy
Large naturally occurring radioactive elements in our Earth (like Uranium) formed approx. 4 billion years ago when our solar system formed.

It formed when a giant molecular cloud collapsed, as a result of a supernova (when a star explodes)...
All of the naturally occurring elements larger than iron (Fe) are made in supernovae (NASA, 2001).
Identify these on the periodic table!
The pressure and heat in supernovae is so great it's almost unimaginable...A Supernova's temperature is about 100 billion degrees Celsius - 6000x greater than the Sun (Filimenko, 2004)...This energy squashes protons and neutrons together
IO Supernova (Bluekai, 2009)
Year 9 Science, Term 2
Why does radioactivity occur?
Large atoms formed this way are very unstable and spend most of their lifetime, trying to reduce their number of protons and neutrons, to get smaller. Different atoms do this in different ways.
This process is known as radioactive decay.
Different forms of elements that undergo this process are known as
radioactive isotopes.

Radioactive substances are identified by this symbol:
These substances can either be harmful OR helpful to our health
This is a model of a Uranium-235 nucleus
(Take note of the in-text referencing throughout this presentation, as your assignment will need the same referencing)
As a general rule, you must reference everything that you would not have known yourself, E.g.
If your assignment has info like this:
In the early 1900s, it was discovered that cancer patients exposed to radiation, had a much greater chance of survival. (American Cancer Society, 2013)
You must reference it! It is clear you got it from somewhere!
If it has info like this:
Your company must consider systemic radiation therapy because it will have massive health and financial benefits.
You DO NOT need to reference this!
A note on referencing...
So where have radioactive elements come from?
80% of geothermal heat comes from
radioactive isotopes decaying
(Turcotte, 2002) and all of the naturally occurring
Uranium, Plutonium, Radium etc
in our Earth was made when the Solar System was made...
Summary points:
All information that you have not thought of must be referenced
All naturally occurring radioactive isotopes found on Earth, formed in the supernova that created our solar system
Large nuclei are unstable due to repulsive forces protons
Radioactive decay is a process to reduce the size of nuclei and release energy
It can be harmful to our cells (including cancer cells)
Year 11 Physics Term 4,
Binding energy and SNF
The following video shows an animation of what a supernova actually looks like...
Imagine the HEAT needed to make this amazing lava flow! Where does it come from?
Full transcript