Saint's Log

Discovery of O, Ar, and H

I am reading my McMurray chemistry textbook and realizing how fascinating the discovery of various elements was. I went looking for videos on the discovery of various elements, the first one being Argon. This video got me to appreciate the importance of publications for disseminating ideas. Rayleigh couldn’t explain the discrepancies between the density of atmospheric nitrogen and nitrogen obtained from a chemical reaction and this puzzle caught Ramsey’s attention. What followed was a series of intricate experiments and hypotheses until the noble gases were well understood years later.

While it’s incredible learning about how many of the elements we know today were discovered because you can see the scientific method at work, it’s fascinating that even scientists struggled to accept new theories that better explained the world than the ones they had long accepted. The story of the discovery of oxygen is one with examples of this phenomenon. The next video goes through the way people probed the inconsistencies in widely accepted ideas (like there being a component of matter called phlogiston that explains why it burns, etc) and how they came up with brilliant experiments to definitively reveal the existence of oxygen.

It’s interesting that oxygen wasn’t even known not that long ago – apparently only about 2 dozen of the 118 elements were known when the declaration of independence was signed. Videos like this are great because they also demonstrate that a good way to combat many anti-science arguments is by acknowledging when they find inconsistencies that aren’t explained by some widely accepted scientific view and observing that such inconsistencies mean that additional research and experimentation is required, not that the scientific method is broken. A basic understanding of the history of science also makes it easier (for me anyway) to study science since it tends to answer a lot of the “why is this important” questions we often have.

I also watched a video on The Origin of Avogadro’s Number and the video below was suggested at end. I was pleasantly surprised to find that it was a serious of almost 2 dozen videos on the history of chemistry. This is the type of background information that makes learning chemistry fun!

Discovery of Neutrons & Radiation

One of the questions I had at the end of the Chemistry Basics II post was about how neurons were discovered. I guess these two channels have become my go to sources for these explanations. The Chadwick and the Neutron video presents a bit more history (e.g. the involvement of Marie Curie’s daughter).

I like the next video because it poses several questions that should be hints that the model without neutrons.

The use of radiation in these experiments naturally raises the question of how these various types of radiation were discovered. Kathy Loves Physics addresses this in her video.

Chemistry Basics II

Chemistry Basics I covered the sections on scientific discovery up to atomic theory. Next is the question of what atoms are made of. Enter JJ Thomson with his CRT experiments. These 3 videos explain his discovery of the electron. I watched multiple just to see different perspectives on the same experiment.

It was after watching the next one that I found myself wondering how you pump all the air out of a glass bottle.

After it had been established that electrons exist and that they have negative charge, it naturally follows that we would want to know what the charge on an electron actually is. This was resolved by Millikan’s oil drop experiment.

This next video on the oil drop experiment was helpful because it showed a similar but modern setup.

The discovery of electrons, combined with the fact that matter is in general electrically neutron implies that there must be positively charged particles. Ernest Rutherford’s gold foil experiment confirms this:

At this point I have several questions that will have to wait for another time.

1. How are magnets made (e.g. the ones used by J.J. Thomson)?
2. How were alpha particles Rutherford was using discovered?
3. How was it shown that the electrons move around the nucleus?
4. How were neutrons discovered?
5. How was the mass of a proton established?

Chemistry Basics I

It’s been over 20 years since I last studied chemistry. I started reading General Chemistry: Atoms First. It has an introductory chapter 0 that goes over concepts like fundamental units and conversion between units. A mention of the amount of volcanic material ejected into the atmosphere by the Krakatoa volcanic erruption piqued my curiosity enough to watch this History channel video.

Digging into chapter one opened my eyes to the fascinating journey of many scientists through the centuries trying to understand the world, and more specifically, elements. Accounting for the similarities between many of the elements was an undertaking that got a breakthrough in Dmitri Mendeleev’s periodic table as explained in the next video.

Reading about the isolation of oxygen from mercury oxide by Joseph Priestley made me curious about how this was done. Thankfully, there are many informative videos on these topics. Here’s one on the isolation of oxygen.

This video has left me wondering where HgO came from – was it a compound they used for something else?

• Antoine Lavoisier soon afterwards demonstrated the law of mass conservation.
• Joseph Proust followed with the law of definite proportions.
• John Dalton capped off the line of inquiry with the law of multiple proportions.

Searching for Joseph Proust on YouTube leads me to this interesting video with some of this history.

I wish I had all these videos as a tool when I was learning chemistry years ago.