Showing 176 to 179

Flashcards

Some principles

<2022-Feb-07>

Network
Make cards that refer to other cards, by mentioning (in passing) a keyword that is the test question for another card. For clozes, this is a bit difficult because the "test question" is an entire sentence or paragraph, but you can reuse specific turns of phrase or reuse references to third-party concepts, e.g. to a person.
  • This is probably useful for linking "sequences" of concepts, that you can use to explain a Big Idea to someone else without losing your train of thought. However, make a general habit of networking cards in this way and you can explain anything, not just a specific sequence.
Importing others' work
  • Be brutal with rejecting bad cards. In Anki, the hotkey for suspending a card is @, press it liberally. This can be good practice because you should also be brutal with your own cards.
  • Don't forget to tag all imported cards as such, even if you edit them. Give each source a tag of its own.
  • See importing as an incremental process. If at any point you want to stop seeing cards from another's deck, you can still keep the cards you liked so far by filtering that deck for the cards with a due date (b/c you've reviewed them), and moving those to your main deck.
Multi-pass reading
You may feel overwhelmed by the spectre of "processing" an entire book, an entire blog archive, or some other collection of material, into flashcards. You can sidestep perfectionist paralysis by processing it beginning-to-end in multiple passes.

What links here

  • 2022-02-07
  • 2022-01-13
  • Artifact: Anki-editor
Created (4 years ago)

Bicycle tires

Measurements are a jungle, not only due to historically dishonest marketing, but also because by convention the inch-measurements go by the expected approximate outside diameter of tires, so a tyre fitting a 622mm wheel is marked as a 28" tyre if it goes on a narrow (road bike) wheel, and marked as a 29" tyre if it goes on a wide (mountain bike) wheel. The wheels themselves have the same diameter.

Minimize confusion by using the ISO standard, which measures wheel diameter in millimeters regardless of the tires. All tires fitting a 622mm wheel are marked the same. And then you see the tyre width as a separate number. If you read a number like 32-622 on a tyre, that means it's about 32 mm wide at full pump. If you read the same number on a wheel, that means it's intended for such tyres (the actual metal rim can be narrower).

Here are the diameters you can expect to see in Swedish outlets today:

  • 559 mm - called 26" on MTB
  • 584 mm - called 27.5" on MTB
  • 622 mm - called 29" on MTB and 28" on road bike

What links here

Created (4 years ago)

Periodic table

Elements list

The Wiki article en.wikipedia.org/wiki/Periodic_table takes up these patterns you can see in the table:

  • Groups
  • Periods
  • Blocks
  • Metals / metalloids / nonmetals
  • Electron configuration
  • Atomic radii
  • Ionization energy
  • Electronegativity
  • Electron affinity
  • Metallic character
  • Linking or bridging groups

The article also takes up

  • history
  • alternative tables
  • open questions
1 H                                 2 He
3 Li 4 Be                     5 B 6 C 7 N 8 O 9 F 10 Ne
11 Na 12 Mg                     13 Al 14 Si 15 P 16 S 17 Cl 18 Ar
19 K 20 Ca 21 Sc 22 Ti 23 V 24 Cr 25 Mn 26 Fe 27 Co 28 Ni 29 Cu 30 Zn 31 Ga 32 Ge 33 As 34 Se 35 Br 36 Kr

The classic periodic table

Rows and columns are called periods and groups.

Group 1: Alkaline metals Lithium group
Group 2: Alkaline earth metals Beryllium group
Group 11: Coinage metals Copper group
Group 12: Volatile metals Zinc group
Group 13: Icosagens Boron group
Group 14: Crystallogens Carbon group
Group 15: Pnictogens Nitrogen group
Group 16: Chalcogens Oxygen group
Group 17: Halogens Fluorine group
Group 18: Noble gases Helium group

Might be most important to remember the groups 1-2 (s-block) and 13-18 (p-block) since they have a lot of periods. The p-block especially has shifting characteristics diagonally: nonmetals, metalloids, metals.

The table can be divided into blocks as seen below, in recognition of the sequence in which the electron shells are filled. Note that the f-block is those elements that are normally offset below the main table.

640px-Periodic table blocks.png

The blocks are named after the electron subshells named s, d, f, p. The s sub-shell can cotain a maximum of two electrons, which explains why the s-block is two columns wide.

The d-block can also be referred to as the transition metals.

Group 18: helium, neon, argon, krypton, xenon, radon. Reactivity increases down the group with radon being the most reactive. Group 17: fluorine (gas), chlorine (gas), bromine (liquid), iodine (solid), astatine (solid).

Created (4 years ago)

Elements

2 He

Helium

The only element without a solid state: it is liquid at absolute zero.

19 K

Potassium (from potash). Starts the fourth period.

Can be made to burn with a lavender-colored flame.

23 V

Vanadium (from Vanadis, another name for Freya).

24 Cr

Chromium (from Greek 'chroma' meaning 'colour').

27 Co

Cobalt (from German 'kobald' meaning goblin, an accusation of miners astray in their search for tin).

28 Ni

Nickel (from German 'kupfernickel' meaning devil's copper or St. Nicholas copper). The discoverer analyzed a mineral which he thought might contain copper.

31 Ga

Gallium (from Gallia). Discovered by a French guy in 1875, see also 32 Ge.

32 Ge

Germanium (from Germania). Discovered by a German guy in 1886, see also 31 Ga.

37 Rb

Rubidium (meaning deepest red). Starts the fifth period.

Few uses. Due to chemical similarity to 19 K (potassium) we absorb it in food. Nontoxic. The average person stores about 500 mg.

41 Nb

Niobium (from Niobe, the daughter of King Tantalus). So named due to its similarity to 73 Ta (tantalum), which is below in the same group.

43 Tc

Technetium (from Greek meaning artificial).

44 Ru

Ruthenium (from Latin meaning Russia).

45 Rh

Rodium (from Greek meaning rose-colored).

46 Pd

Palladium (from the asteroid Pallas, named after Pallas the goddess of wisdom).

47 Ag

Silver (argentum).

It's used in mirrors because it's the best reflector of visible light known.

Silver tarnishes over time, forming a black oxide. Where appearance is important, as in jewelry, we use sterling silver, an alloy with mostly silver.

49 In

Indium (from Latin meaning indigo).

50 Sn

Tin.

51 Sb

Antimony (from Greek meaning 'not alone'). The symbol Sb is from the Latin name stibium. Found in nature as the mineral stibnite AKA antimonite.

A solid metalloid in the nitrogen group.

History: Used in Ancient Egypt as a mascara, in the Middle Ages to harden lead for type (printing press).

Uses: alloys (with lead particularly) in batteries, types, bullets; some electronic devices; some flame-retardant materials.

Toxic.

55 Ce

Cesium (caesius means sky blue and cesium flame is sky blue). Starts the sixth period.

An important use is the cesium clock, i.e. atomic clock, used in mobile phone networks and GPS.

57 La

Lanthanum, the first in the lanthanides (57-71).

58 Ce

Cerium (from the asteroid Ceres, named after Ceres the god of agriculture).

71 Lu

Lutetium (from Lutetia, the old name for Paris). Ends the lanthanides.

72 Hf

Hafnium (from the Latin name for Copenhagen, Hafnia).

74 W

Tungsten. The English name is derived from a Swedish word, but the Swedish name for 74 W is something else altogether (volfram).

Has the highest melting point of any element (3414 C).

Used to be in lightbulbs. Calcium and magnesium tungstenates are still used in fluorescent lighting. Tungsten carbide (tungsten + carbon) is immensely hard, very important to metalworking, and a great material for drills and saws.

77 Ir

Iridium (from Iris the goddess of the rainbow).

Almost as unreactive as gold. The most corrosion-resistant material known.

Discovered together with osmium (76 Os): When crude platinum (78 Pt) was dissolved in aqua regia, it left behind a black residue thought to be graphite, but Smithson Tennant found it to be two new elements, named iridium due to its colourful salts and the other osmium due to its curious odor.

79 Au

Gold. The Latin name is aurum.

Not toxic; chemically unreactive, though it will dissolve in "aqua regia", a mixture of nitric and hydrochloric acid.

80 Hg

Mercury AKA quicksilver (hydrargyrum).

Mercury, and 35 Br, are the only liquid elements at room temperature.

Had many uses in the past, but is highly toxic. Now mostly used as catalyst.

84 Po

Polonium, the first radioactive element (with the exception of 43 Tc), and all following elements are radioactive.

87 Fr

Francium. Starts the seventh period.

Has no uses. Half-life of 22 minutes.

89 Ac

Actinium, the first in the actinides (89-103).

92 U

Uranium (from Uranus).

Most uranium comes in the form of U-238, which is not fissile. Enriched uranium has a greater proportion of U-235, depleted uranium is back to being mostly U-238, with even less 235 than naturally occurring uranium.

Uranium weighs 19.1 g/cm3 which is almost as heavy as gold (19.3 g/cm3).

94 Pu

Plutonium

98 Cf

Californium, the last useful element. Einsteinium (99 Es) and above are only for research as of ~2015.

Used in metal detectors.

What links here

Created (4 years ago)
Showing 176 to 179