Friday, August 22nd, 2014

Factoids 2012 – Nuggets of information that may help on the AP and SAT Chemistry Exams

For many years I have been in the habit of attempting to pass on nuggets of information to the kids that I teach, that they might be able to put to use in the AP or SAT Chemistry exams. These are typically pieces of information that every year might be the subject of a few multiple choice questions (perhaps even the odd point here and therein the free response section of the AP),  that might rely on some chemical general knowledge, recent scientific news item or other, largely random, ‘factoid’.

These nuggets of information are unlikely to form any formal part of many, mainstream chemistry course that is designed to prepare you for these exams, but rather they are accumulated by having knowledge of other, related disciplines (maybe biology or physics), reading around the subject, being aware of scientific or chemical issues in current affairs and the news, or perhaps simply are reliant on some general knowledge – the kind of knowledge that might be obtained by reading ‘science’ articles on Wikipedia or reading a chemical encyclopedia!

Here I have attempted to summarize some of these factoids. By their very nature, any attempt at a compilation can NEVER be ‘complete’ or indeed exhaustive, so please view this list in that light. In fact, I wanted to do a blog post rather than a document, since people can comment, and the list can be more dynamic and can evolve. PLEASE understand this is (and always will be), a ‘work in progress’!

I have tried to gather some very generic headings in order to organize the material, but again, by its very nature, the factoid knowledge is diverse and somewhat random, and can be difficult to categorize in a meaningful way – by definition, it’s somewhat fractured and ‘random’. I hope this helps you to score an extra point or two in your tests!

A. Environmental

a. Greenhouse gases – classically CO2, but also H2O and methane. Cause global warming and climate change.

b. Eutriphication – nitrates and phosphates washed into water systems causing excess growth of algae and other organisms and increased stagnation.

c. CFC’s (Chlorofluorocarbons) – Compounds of the halogens, previously used in refrigerants that are known to cause the breakdown of the protective ozone layer around the earth.

d. Hard water – water with calcium and magnesium ions dissolved in it that creates a ‘scum’ with soap and can be difficult to create a lather with. Also buils up ‘limescale’ in pipes leading to blockage, ‘Softened’ by replacing group 2 ions with group 1 ions.

B. Biological

a. Amino acids – Organic molecule important in biological systems. Contains carboxylic acid functional group (-COOH) and amino functional group (-NH2). Can form a ‘zwitterion’ where acid internally donates H+ to NH2.

Amino Acid

Amino Acid

Zwitterion

Zwitterion

b. Proteins – long polymer chains of amino acids. Crucial biological roles

c. Lipids – large group of naturally occurring biological molecules with various functions. Include sterols, waxes and fats

d. Fats – Primarily triglycerides that are tri-esters derived from glycerol (an alcohol) and ‘fatty acids (acids)

e. Carbohydrates – compounds of carbon and H2O, often known as the more generic, ‘sugars’

C. Laboratory Situations (AP)

See separate document, here.

D. Medicine

a. Disinfectants – iodine, hydrogen peroxide

b. Radioactivity – used to attack tumors or track bodily function

E. Qualitative lab tests

a. Gases

(i) CO2 – turns limewater milky. (Will also extinguish a splint, but not definitive – see N2)
(ii) N2 – extinguishes a splint (see CO2)
(iii) O2 – relights a glowing splint
(iv) H2 – ‘squeaky pop’ test with glowing lighted splint

b. Other – see TOPIC 5 notes.

F. Common Colors

See separate document, here.

G. The Elements

a. States – solids at RT, except Br and Hg (liquids) & common gases (H, O, N, F, Cl, noble gases)

b. NOT monatomic

(i) Diatomic (Br-I-N-Cl-H-O-F or H-O-F-Br-I-N-Cl)

(ii) P4 (white/red), S8 (rhombic/monoclinic) (However, generally uncommon to use anything other than single P or S atoms in equations)

c. Abundance – listed in order, most abundant first.

(i) Earth’s crust – O, Si, Al, Fe, Ca, Na, K, Mg

(ii) Sea (not including H and O that make up water) – Cl, Na, Mg, S, Ca, K, Br

d. Names – For common groups, see TOPIC 7 notes. Lanthanides – first row of f-block, Actinides – second row of f block

H. Uses of chemicals in Industry/Commercial

a. Semi-conductors – silicon, germanium and other metalloids

b. Ammonia – in fertilizers/cleaners

c. Explosives – many nitrogen containing compounds (TNT)

d. HF – as glass etcher

I. Definitions

a. Allotropes – different forms of the same element (e.g. diamond and graphite for carbon)

b. Isomer – same formula, different arrangements (different bonds or different 3D- arrangement). Common in organic questions

c. Gravimetric – analysis by weighing

J. Trivial/Common names and household chemicals/applications

a. Caustic soda or (lye) – sodium hydroxide

b. Lime – CaO or calcium hydroxide used to make acidic soil less acidic

c. Epsom Salts – magnesium sulfate used in bathing salts to relieve aches and pains.

d. Milk of magnesia – magnesium hydroxide as an antacid or laxative

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