Starting an element collection

In the spirit of the wonderful photobook The Elements by Theodore Gray (which I have previously blogged about), starting a collection of elements is a great way of introducing yourself (or your children) to basic chemistry. Here are some suggestions, and a list of 24 elements to start with….

2: Helium (He)

Helium is lighter than air, so balloons are often filled with helium.

6: Carbon (C)

Carbon is most easily added to your collection in the form of charcoal. Zinc–carbon batteries have a carbon rod at the centre.

7: Nitrogen (N)

Air is about 78% nitrogen. To add nitrogen to your collection, just fill a small bottle with air.

8: Oxygen (O)

Air is about 21% oxygen. To add oxygen to your collection, just fill a small bottle with air.

9: Fluorine (F)

Fluorine is a toxic gas. But octahedral fluorite crystals (calcium fluoride, CaF2) make a great addition to a collection.

11: Sodium (Na)

Sodium is a reactive metal which will spontaneously catch fire when in contact with water. But sodium chloride (ordinary table salt, NaCl) is perfectly safe.

12: Magnesium (Mg)

Magnesium is a flammable metal, but you can substitute crystals of Epsom salts (magnesium sulfate, MgSO4), which can be obtained from a pharmacy.

13: Aluminium (Al)

Aluminium (aluminum in the USA) is most easily available as aluminium foil.

14: Silicon (Si)

Silicon is widely used in transistors and integrated circuits (chips).

15: Phosphorus (P)

The side of a box of matches is largely composed of phosphorus.

16: Sulfur (S)

Sulfur powder, also called “flowers of sulfur,” is available from pharmacies.

17: Chlorine (Cl)

Chlorine is a toxic yellowish-green gas. But sodium chloride (ordinary table salt, NaCl) is perfectly safe.

20: Calcium (Ca)

Calcium is a reactive metal, but you can substitute crystals of calcite (calcium carbonate, CaCO3) or gypsum (calcium sulfate, CaSO4).

24: Chromium (Cr)

Chromium is used for plating (“chrome plating”) to prevent rusting. Also, “stainless steel” is between about 16% and 25% chromium.

26: Iron (Fe)

Iron is one of the most widely used metals. Iron nails are easy to add to your collection. Like nickel and cobalt, iron is attracted by a magnet.

28: Nickel (Ni)

The United States “nickel” coin is actually only 25% nickel (and 75% copper), but objects made of pure nickel can be found. Indeed, Canadian “nickel” coins from 1955–1981 are almost pure nickel.

29: Copper (Cu)

Copper pipes are widely used in plumbing. You can buy copper plumbing fittings, or get offcuts of pipe from a plumber. Copper electrical wire is also easy to find.

30: Zinc (Zn)

Galvanised iron is coated with zinc to prevent rusting. Also, filing off the copper coating on a US penny reveals a coin made mostly of zinc.

47: Silver (Ag)

A silver coin, or a piece of silver jewellery, would make a fine addition to your collection.

53: Iodine (I)

Iodine is a dark solid, but is sold in pharmacies as a brown solution in alcohol, called “tincture of iodine.”

60: Neodymium (Nd)

Neodymium is one of the “rare earth” elements. Neodymium magnets are the most common form of strong magnet. They are made of an alloy of neodymium, iron and boron (Nd2Fe14B).

74: Tungsten (W )

The filament in an incandescent light bulb is made from tungsten (but because of the danger of broken glass, only an adult should attempt to remove the filament, and then only with very great care).

79: Gold (Au)

A gold coin, or a piece of gold jewellery, would make a truly wonderful addition to your collection. Alternatively, for under $10, science museums will sell impressive-looking bottles of gold leaf floating in liquid.

82: Lead (Pb)

A fishing sinker is probably the easiest lead object to find.

So there you are. Those could be the first 24 elements in your collection!


Sunset on a flat earth

Earlier, I wrote a post on why people know that the earth is round. Evidence such as star movement, the obscuring of distant objects by the earth’s curvature, and aircraft flight times shows that the earth is not flat:

In this post, I want to temporarily put on the “hat” of a flat-earther. They claim that the sun is a “spotlight” which travels across a circular flat earth like this:

That is at least a well-defined model, crazy though it might be, and therefore can be tested. Here is a computer render of the spring sun at sunset on that assumption (as seen from, say, San Francisco, at the moment that the sun disappears from view):

Three obvious problems with the flat-earth model are visible in this picture:

  • The sun is much too small: only 40% of its noontime diameter (because it is 2.5 times as far away as at noon)
  • The sun appears oval, rather than circular, because the “spotlight” is being seen obliquely (click to zoom if you can’t see the shape)
  • The sun is much too high in the sky (24° above the horizon)

In reality, of course, the sun at sunset is a circular disk that gradually slips under the horizon. Oops. No, the earth is not flat.

Something different

This picture illustrates the ill-fated expedition to Australia described in H.P. Lovecraft’s horror story The Shadow Out of Time. The images in the montage are edited versions of public-domain pictures, and include this copy of the Necronomicon. The complete image is © Anthony Dekker.

… On July 10, 1934, there was forwarded to me by the Psychological Society the letter which opened the culminating and most horrible phase of the whole mad ordeal. It was postmarked Pilbarra, Western Australia, and bore the signature of one whom I found, upon inquiry, to be a mining engineer of considerable prominence. Enclosed were some very curious snapshots. I will reproduce the text in its entirety, and no reader can fail to understand how tremendous an effect it and the photographs had upon me. …

The “Pilbarra” in this story (and on the map) is presumably Pilbara Road District, an old name for what is now the town of Port Hedland, Western Australia (although the address given by Lovecraft matches a no longer extant street in the nearby ghost town of Cossack). Lovecraft’s story also refers to a precise geographical location: 22° 3′ 14” S, 125° 0′ 39” E. See more on the Australian aspects of the story at Trollunteer. Propnomicon also did some really good props a few years back.

Snakes and Ladders

Snakes and Ladders board, dated 1966, from the Auckland Museum (credit)

Snakes and Ladders is an ancient board game originating in India. It is totally random, and hence not very interesting. If players start on square #1, then after one turn, they have equal probabilities of being on squares #2, #3, #4, #5, #6, and #7. This image shows the probability distribution:

After two turns, the probability distribution is as follows (the most likely total of two dice rolls is 7, taking a player to square #8 and up a ladder to #26:

After 8 turns, players would be scattered all over the board. There is a 1% chance that any given player has won:

After 19 turns, there is a 24.7% chance that any given player has won:

This probability grows to 50.4% after 35 turns. But no matter how long you play, it remains possible (though increasingly unlikely) that nobody has won yet. Yet another reason why children tend to rapidly tire of the game.

For an alternative view of the probability analysis, see this animation:

American Solar Challenge Construction Progress

As I watch the lead-up to the American Solar Challenge next July, the chart above (click to zoom) shows the teams currently registered, with my estimate of current construction progress (based on a combination of social media reports and official paperwork). Team colours in the chart are my best guess in some cases. The University of Minnesota (Team 35) is in the lead (with an existing car and with most of the race paperwork done). Among teams building new cars, Italian team Onda Solare (559) and Canadian team Poly Montreal (55) lead the pack.

My ASC race information page will be updated from time to time with information on the progress of these and all the other teams. It also decodes the team numbers.

Render of Esteban9, the solar car being built by Polytechnique Montréal (picture credit)