Unit 3: Matter (Density & Atoms) Reading
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Energy is things moving over a distance against a force. When it comes to electromagnetic energy those moving things are electrons. “What’s an electron?” you ask? Well, that’s what this lesson is all about. We need to wander into the world of quantum physics for a bit and take a look at the teeny and the mysterious world of atoms.
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Sorry for that – sometimes our spell checker gets overly excited! Thanks for your eagle eye!
Everything, from piano’s to pistachio’s are made from the same set of 90 different Lego’s!
Check the spelling here!!!! Great explanation though. Thanks
Here it is – it is also called “linear accelerator“
I cant find the gauss rifle experiment, can you show me?
Thank You!
I’ve always wondered that and I thought it might be the electrons and now I know it is!
Thanks a bunch.
~Rian
Atomic weight of a proton is always 1.
Atomic weight of a neutron is always 1.
The atomic weight, or atomic mass, is protons + neutrons + electrons. The atomic mass is more than the sum of protons + neutrons because while electrons have a relatively insignificant weight, but they weigh something all the same.
Here’s an example:
A normal He (Helium) atom:
Atomic number is 2
Atomic number is equal to the number of protons, so the atomic weight is 4.0026
Atomic weight equals approximately the number of protons plus neutrons (the small difference is the mass of the 2 electrons)
Round down the atomic weight to 4
Adjusted atomic weight (4) – number of protons (2) = number of neutrons (2)
4 – 2 = 2
Therefore: The atomic weight of a proton and a neutron always equal 1, and the reason the atomic weight is not a whole number is due to the relatively insignificant mass of the 2 electrons orbiting outside the nucleus.
If the atomic weight of a proton is 1, and the atomic weight of a neutron is 1, and you find the number of neutrons by subtracting the protons from the atomic weight then why is the atomic weight not a whole number, since protons and neutrons both equal 1?
And do protons and neutrons always equal 1?
You can make your own with the ‘gauss rifle’ experiment (use the search box to find it). Otherwise, you;ll need a nuclear reactor in your basement (not advised).
where can i get a particle accelerator
The question, “what’s the difference between an atom and an element?”, has caused a lot of confusion among my students. Elements are specific kinds of atoms. If I say, “there’s a bunch of atoms in that cup”. That doesn’t tell you much. But if I say, “there’s a bunch of Mercury (a type of element) in that cup.” you know (if you have your handy pocket periodic table with you) exactly what kind of atom it is, what the weight of each atom is, what it’s atomic number is and due to that, you know how many protons, neutrons, and electrons it probably has. By the way, Mercury is very poisonous so if I said “there’s a bunch of Mercury in that cup”, RUN!!!
If I say, there’s a bunch of dogs in that room. You don’t know if I’m talking about chihuahua’s or rottweilers. Dogs, like atoms, are a broad term. Neither word describes things specifically. Now if I said, there’s a bunch of rottweilers in that room, you would know that entering that room would be a very bad idea!
what is the difference between an atom and an element?
~ Liam F.
Yay! Now I understand why water expands when it freezes! Thanks!
~Anna
Whoops! Our superscript formatting went right out the window when we uploaded the content! That’s for your eagle eye! I’ve updated both the website and the download so it makes (math) sense. Sorry for the confusion. ~Aurora
When reading the materials on density, we had a little difficulty understanding the equation for the number of electrons in the shells and answering the question in the exercises. When we printed it out (from a mac) and I looked at it on the PC, the equation looks like 2n2 or 2xnx2. So in the example for the seventh shell it reads like 2×72 = 98. Of course, I knew that made no sense, so I figured out the math should be 2 n squared (since 2 x 7 squared does = 98), and that the exponent wasn’t being written in a superscript.
(From the mom)
Water is one of the few things that expand when it freezes. It’s got to do with the structure of the crystals inside. Do you see how there are major HOLES in the picture above? That’s why it expands, because when the molecules lock together, they leave big spaces between each other (it has to do with the way the water molecule is built).
Most things shrink when frozen, so when the molecules lock together, they slip and slide into each other, squashing together like the image below:
p.s. my key board still isn’tworking, so sorry aboutthe sentances that are all one word.
~Anna
I’d like to say a big “thank you!” because you FINALLY explained the states of matterin a way that I can fully understand. You gave me the definition and WHY they are different! When I went to publicschoolsall they gave mewas the they HOW, and then when I would ask why they wouldeithergetmadandtell me thatIshouldpay betterattention, or just repeat themselves. THANK YOU!!! I also have a question: when water freezes, it expands. How is this possible? I’ve tried looking it up before and I haven’t been able to find an actual explanation for it other than maybe a 20 page long essay that also talked aboutconcepts that I haven’t leared yet. Thanks again!
~Anna,12
If you change the number of protons inside the core of an atom, the atom itself changes. Hydrogen has one proton, and oxygen has eight. So if you stuff seven more protons into the core, it will change into hydrogen…. but this requires a HUGE nuclear power plant or a supernova (largest of the dying stars that explode). In other words, it’s REALLY hard to do.
However, atoms do spontaneously change what’s inside their core on their own, and when it’s done in nature, it’s called radiation. Uranium is a good example of this. For more details, have a look at the reading for Chemistry, Unit 8.
Can elements change from one kind to another kind. such as Hydrogen changing into oxygen?