Archive for the 'Basic concepts' category

National Chemistry Week repost: Happy Mole Day! (What's a mole?)

Oct 23 2010 Published by under Basic concepts, Chemistry

This is National Chemistry Week. It's always chosen to coincide with whichever calendar week includes October 23 (or 10/23), since October 23 is "Mole Day".

"Huh? Why would chemists celebrate a furry critter that burrows underground?"

Not that mole. The mole chemists celebrate is a unit.

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National Chemistry Week repost: elements.

Still swamped, but National Chemistry Week must go on. Here's a post from the archives about one of the basic concepts of chemistry, what defines an element.

As far as chemists are concerned, the world is made up of atoms and various assemblies and modifications thereof. Those atoms and modifications of atoms are, in turn, made up of protons, neutrons, and electrons. Protons have a +1 charge and a mass of 1.0073 amu [1]. Neutrons have zero charge and a mass of 1.0087 amu. And electrons have a -1 charge and a mass of 5.49 x 10-4 amu. Various combinations of these three will give you atoms, radicals, and ions [2]. Protons and neutrons hang out together in the nucleus of your atom (or radical or ion), while electrons can be thought of as zipping around the nucleus [3].

An element is defined by the number of protons in the nucleus. The element oxygen has 8 protons in the nuclei of its atoms. Any atom (or radical or ion) that has exactly 8 protons is an oxygen atom, and all oxygen atoms (or radicals or ions) have exactly 8 protons. It doesn't matter how many electrons there are zipping around the nucleus; that determines the net charge. It doesn't matter how many neutrons there are in the nucleus; that determines the atomic mass (and which isotope of oxygen you have). The number of protons in the nucleus is all that counts when you're determining the element you're dealing with.

Lots of compounds (like water) are made up of more than one element (here, hydrogen atoms and oxygen atoms in a ratio of 2:1). Elements, however, have molecules that are made up of a single kind of atom -- elemental hydrogen is H2, while elemental oxygen comes in two forms, O2 and O3 (ozone). Most textbooks will define an element as a substance that can't be broken down into simpler substances. (This means that chemists must view protons, neutrons, and electrons not as substances, but as the building blocks from which substances are made.)
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[1] The abbreviations "amu" stands for atomic mass unit. 1 amu = 1.66056 x 10 -27 kg.

[2] Ions are nuclei (or multinuclear assemblies) where the total number of protons does not equal the total number of electrons — meaning they have a net-positive or net-negative charge. For example, Cl- has one more electron zipping around the Cl nucleus than there are protons in that nucleus.

A radical is a nucleus (or a multinuclear assembly) with an unpaired electron that’s “looking for action” (i.e., is generally highly reactive). For example Cl. has the same number of protons and electrons (i.e., a neutral charge), but one of its 17 electrons is not paired, and thus the radical is “looking” for an opportunity to react with something else that will provide an electron to pair with.

Not to get too anthropomorphic or anything …

[3] Strictly speaking, you really shouldn't think of electrons as having a well-defined location until you go looking for them with a "measurement event". But as far as anyone can tell, they probably don't stray too far from the positive charge concentrated in the nucleus.

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National Chemistry Week repost: How does salt melt snails?

Oct 19 2010 Published by under Basic concepts, Chemistry, Critters, Garden

It should be noted that for some of us, nearly the whole world comes to us through the lens of chemistry, every week of the year. Here's another post from the back-catalogue that brings my chemical sensibilities to the garden:

In light of our recent snail eradication project:

Why does salt "melt" snails and slugs? (And how do people manage to prepare escargot without ending up with a big pot of goo?)

To answer this question, let us consider the snail as seen by the chemist:

Snail1.jpg

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Basic concepts: Truth.

Oct 30 2009 Published by under Basic concepts, Philanthropy, Philosophy

No, I'm not going to be able to get away with claiming that truth is beauty, and beauty, truth.
The first issue in understanding truth is recognizing that truth is a property of a proposition. (What's a proposition? A proposition is a claim.) A proposition that is true has a certain kind of correspondence with the world about which it is making a claim. A proposition that is false does not have this correspondence.
At the most basic level, what we want from this correspondence seems pretty obvious: what the propositions says about the world matches up with how the world actually is.

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How does salt melt snails?

May 11 2009 Published by under Basic concepts, Chemistry, Critters, Garden

In light of our recent snail eradication project:

Why does salt "melt" snails and slugs? (And how do people manage to prepare escargot without ending up with a big pot of goo?)

To answer this question, let us consider the snail as seen by the chemist:

Snail1.jpg

Continue Reading »

9 responses so far

Happy Mole Day! (What's a mole?)

Oct 23 2008 Published by under Basic concepts, Chemistry

This is National Chemistry Week. It's always chosen to coincide with whichever calendar week includes October 23 (or 10/23), since October 23 is "Mole Day".

"Huh? Why would chemists celebrate a furry critter that burrows underground?"

Not that mole. The mole chemists celebrate is a unit.

Continue Reading »

Comments are off for this post

Basic concepts: scientific anti-norms (part 2).

Coming on the heels of my basic concepts post about the norms of science identified by sociologist Robert K. Merton [1], and a follow-up post on values from the larger society that compete with these norms, this post will examine norms that run counter to the ones Merton identified that seem to arise from within the scientific community. Specifically, I will discuss the findings of Melissa S. Anderson [2] from her research examining how committed university faculty and Ph.D. students are to Merton's norms and to the anti-norms -- and how this commitment compares to reported behavior.

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Basic concepts: scientific anti-norms.

A while back, I offered a basic concepts post that discussed the four norms identified by sociologist Robert K. Merton [1] as the central values defining the tribe of science. You may recall from that earlier post that the Mertonian norms of science are:

  • Universalism
  • "Communism"
  • Disinterestedness
  • Organized Skepticism

It will come as no surprise, though, that what people -- even scientists -- actually do often falls short of what we agree we ought to do. Merton himself noted such instances, and saw the criticisms scientists made of their peers who didn't live up to the norms as good evidence that the tribe of science was committed to the norms. Many of the forces Merton saw pulling against the norms of science came from outside the tribe of science. However, it's just as reasonable to ask if there isn't a set of countervailing norms -- or "anti-norms" -- that come from within the tribe of science.

In this post, I consider the forces Merton saw as working in the opposite direction from the norms. In a follow-up post, I will discuss the findings of Melissa S. Anderson [2] probing how committed university faculty and Ph.D. students are to Merton's norms and to the anti-norms -- and how this commitment compares to reported behavior.

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Basic concepts: the norms of science.

Since much of what I write about the responsible conduct of research takes them for granted, it's time that I wrote a basic concepts post explaining the norms of science famously described by sociologist Robert K. Merton in 1942. [1] Before diving in, here's Merton's description:

The ethos of science is that affectively toned complex of values and norms which is held to be binding on the man of science. The norms are expressed in the form of prescriptions, proscriptions, preferences, and permissions. They are legitimatized in terms of institutional values. These imperatives, transmitted by precept and example and reinforced by sanctions are in varying degrees internalized by the scientist, thus fashioning his scientific conscience or, if one prefers the latter-day phrase, his superego. Although the ethos of science has not been codified, it can be inferred from the moral consensus of scientists as expressed in use and wont, in countless writings on the scientific spirit and in moral indignation directed toward contraventions of the ethos. [2]

Let's break that down:

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Audience participation: help me flag good posts for non-scientists trying to understand science.

A regular reader of the blog emailed me the following:

Have you ever considered setting up a section for laymen in your blog where posts related to the philosophy of science, how research is conducted, how scientists think etc. are archived? An example of what I think might be a good article to include would be your post on Marcus Ross.
Part of why I like reading your blog is because you analyze these fundamental issues in science, and I believe that this will help any laymen who stumble upon your blog for the first time quite a bit. It certainly helped me! I had to trawl through tons of posts to get to posts related to these fundamental issues though (not that the other posts are not interesting!).

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