topic07

Topic 7 Chemical substances, chemical properties, chemical changes, colloids
Updated: 2008-08-30
Please send comments to: J.Elfick@uq.edu.au
See also: Interesting websites

Table of contents
7.1.0 Chemical changes and physical changes
7.2.0 Pure substances and impure substances
7.2.1 Classify substances, pure substances, mixtures, solutions
7.2.2 Elements and chemical reactions
7.3.0 Metals and non-metals
7.4.0 Melting point, m.p. of solids
7.5.0 Boiling point, b.p. of liquids

7.6.0 Suspensions and precipitates
7.7.0 Solutions, solubility equilibrium, solubility rules
7.8.0 Colloids, sols, emulsions, gels, aerosols, foams, types of colloids
7.9.0 Chemistry terminology
7.10.0 Prefixes and suffixes
19.2.0 Composition of food, vitamins, minerals

7.1.0 Chemical changes and physical changes
7.1.1 Chemical changes, burn magnesium
7.1.1.1 Chemical changes, burn steel wool, combustion of iron wool
7.1.2 Chemical changes, heat organic substances
7.1.3 Chemical changes, heat metals in chlorine
7.1.4 Physical changes, magnetize and demagnetize iron wire
7.1.5 Physical changes, prepare different forms of sulfur, allotropes of sulfur
3.70 Reactions between two elements, iron and sulfur

7.3.0 Metals and non-metals
7.3.1 Properties of metals
7.3.2 Properties of non-metals
2.43 Different metals (Primary)
12.11.3 Flame test to identify metals and their compounds
12.11.3.1 Borax bead test to identify metals in metallic salts and minerals

7.4.0 Melting point, m. p., of solids
3.2 Melting point of naphthalene
3.3 Melting point of naphthalene with a capillary tube
3.4 Impurities affect the melting point of a substance
7.4.1 Melting point and cooling curve of stearic acid
7.4.2 Melting point of different substances
7.4.3 Melting point of ice and freezing point, f.p., of water
7.4.3.1 Temperature at which ice melts
7.4.3.2 Temperature at which ice and salt mixture freezes
7.4.3.3 Lift ice cube with match stick
2.9 Melt substances (Primary)

7.5.0 Boiling point, b.p. of liquids
3.5 Boiling point of water
3.5.1 Boiling point of sodium chloride solution
3.6 Boiling point of inflammable liquids
3.7 Volatility of different liquids
3.8 Pressure affects the boiling point
7.5.0.1 Elevation of boiling point, ebullioscopic constant, k_B
7.5.3 Boiling point of mixture of two liquids, water and alcohol
7.5.4 Boiling points of inflammable liquids, alcohol
7.5.4.1 Boiling points of inflammable liquids, acetone
13.7.13 Simulated boiling

7.1.5 Physical changes, prepare different forms of sulfur, allotropes of sulfur
7.1.5.1 Prepare monoclinic sulfur from powdered sulfur (flowers of sulfur)
7.1.5.2 Prepare monoclinic crystals from roll sulfur
7.1.5.3 Prepare plastic sulfur then rhombic sulfur
12.18.1 Prepare different forms of sulfur

7.2.3 Silicon compounds, glass
7.2.4 Prepare silicon glass
7.2.4.1 Prepare silicon glass in a furnace
7.2.4.2 Prepare coloured glass
7.2.5 Prepare a silicate garden
7.2.6 Silly putty, silicone, bouncing putty (Dow Corning 3179 dilatant compound) "Tricky Putty"

7.1.0 Chemical changes and physical changes
1. In a chemical change, one or more substances changes into one or more new substances, e.g. hydrogen combines with oxygen to form water. The product(s) has different properties from the reactants. For example burning wood forms black ash containing carbon, white ash containing mineral salts, carbon dioxide gas and water vapour. New substances form and the change cannot be reversed. The arrow symbol " --->" represents this type of change.
2H₂(g) + O₂(g) ---> 2H₂O(l)
2. In a physical change, the properties of a substance change, but the substance is still the same. The change can be reversed. The physical properties of water change when water freezes to ice. However, the ice is composed of water molecules and the change can be reversed. When electricity passes through a tungsten filament in a light bulb, the filament becomes hot and emits light. It is still tungsten. When you turn off the light, the tungsten filament is the same as before. Physical or chemical changes may be fast or slow, e.g. hammering iron, wearing away rock by wind erosion, an explosion when hydrogen burns, rusting of iron.
Classify common examples of changes into chemical change or physical change.
Do the following activities and in each case say whether it is a chemical or physical change: 1. Light a match. (chemical change) 2. Turn on the light. (physical change)
3. Let a nail rust. (a chemical change takes place in air causing a gain in weight) 4. Chew food. (physical change for biting and masticating, and a chemical change for the reactions of starch with salivary amylase)

7.1.1 Chemical changes, burn magnesium
Put a piece of magnesium ribbon in a crucible. Weigh the crucible and lid and magnesium ribbon. Burn the magnesium in the nearly closed crucible so that the ash is not lost. Weigh the crucible and lid and ash. The weight of the ash is greater than the weight of the magnesium. The reaction forms a new substance - magnesium oxide. Mg, density 1.74 g / cm³ oxidizes to MgO, density 3.58 g / cm³, so when oxygen attaches to magnesium the volume decreases because of the strength of the Mg²⁺ -- O^2- bond.
2Mg(s) + O₂(g) ---> 2MgO(s)

7.1.1.1 Chemical changes, burn steel wool, combustion of iron wool
Cover the end of a wooden ruler with aluminium foil then note where the ruler balances as a first order lever, see-saw, over a fulcrum. Put the ruler balance on a sink bench. Put 5 g loose steel wool on the aluminium foil end of the ruler then put a weight on the other end of the ruler so that this end is just down. Heat the steel wool with a Bunsen burner flame. The steel wool glows and its side of the balance moves down as the iron becomes iron oxide.

7.1.2 Chemical changes, heat organic substances
1. Often one product is black because carbon forms. Heat the following substances in a hard-glass or Pyrex test-tube. Observe any decomposition of the substances. When smoke appears, leave the test-tube to cool. No chemical change occurs when you heat charcoal. For the following substances, a chemical change occurs and the residue in the test-tube is carbon: 1. wood or saw dust - note the brown substances that stick to the sides of the test-tube and the black substance that remain in the bottom, 2. sugar, 3. bread, 4. fruit, 5. fat or oil, 6. starch or potato or rice, 7. paper, 8. wool or hair or nail clippings, 9. meat.
2. Put a small piece of wood in a Pyrex test-tube. Heat the tube gently then more strongly. The wood decomposes into a black solid and brown liquids and vapours. Stop heating when you see no more dense smoke. Let the test-tube and observe the substances on the sides of the tube. Put any remaining solid substance in another clean test-tube. Heat it gently and then more strongly. You produce no further liquids or gases from this substance. Compare the black substance with a sample of the original wood for colour and can be bent. Place the end of each in a Bunsen flame for a few seconds. Remove and observe them. The black substance does not decompose or burn with a flame but glows red-hot. The black substance is charcoal, i.e. carbon. Heat small quantities of sugar, paper, wool, meat and compare the residue in the test-tubes with the original substance.

7.1.3 Chemical changes, heat metals in chlorine
Be Careful! Chlorine is poisonous. These experiment may not be allowed on your school system. D the experiments in a fume cupboard.
1. Use tongs to heat steel wool in a Bunsen burner flame, then place it in a test-tube containing chlorine gas. Observe whether any heat is given out during the reaction. Iron and chlorine react together to form a brown yellow iron chloride.
2. Using a wire gauze, scrape some powdered antimony from a lump of the element so that it falls into a test-tube of chlorine. The sparks and burning show that a chemical change is taking place. The new white substance is antimony chloride.

7.1.4 Physical changes, magnetize and demagnetize iron wire
When physical changes occur, no new substance forms.
Pull a thick iron wire (fencing wire) through iron filings. The iron does not attract the iron filings. Magnetize the iron by stroking it with a bar magnet. Hold the iron wire in the iron filings. The iron wire now attracts the iron filings. A physical change has occurred. Hammer the iron wire. The iron wire cannot attract the iron filings so strongly. The physical change has been reversed.

7.1.5 Physical changes, prepare different forms of sulfur, allotropes of sulfur
Sulfur is a non-metallic element that occurs in several allotropic forms. Allotropes are variations of the same element with different bonding and crystal structure. Sulfur occurs in three forms: Form 1: Rhombic sulfur is a light yellow powder. At 100^oC it changes to: Form 2: Monoclinic sulfur with a deeper colour. The monoclinic and rhombic forms differ in the arrangement of the S₈ molecules. At 160^oC, it melts to form a sticky dark brown liquid that can be cooled quickly to form red brown plastic sulfur. Form 3: Plastic sulfur contains long chains of S atoms.
Put sulfur powder in a test-tube. Heat the sulfur extremely gently until it slowly melts to a golden yellow liquid. Continue to heat more strongly until a red gas appears above the liquid. Leave the test-tube to cool. Sulfur forms deposits on the sides of the tube and in the bottom of the tube.

7.1.5.1 Prepare monoclinic sulfur from powdered sulfur (flowers of sulfur)
Monoclinic sulfur has a deep yellow colour, m.p. = 119^oC, and density = 1.96.
Heat powdered sulfur extremely gently in an evaporating dish. The sulfur changes to liquid. Add more powdered sulfur. The colour should stay pale yellow. If the sulfur turns dark, you have overheated it. Repeat the experiment with gentler heating. Leave the sulfur to cool, without moving the evaporating dish. Monoclinic crystals form between 96^oC and 114^oC. After a thin crust forms, punch two holes through the crust with a nail. Pour out the hot sulfur through one hole. Remove the crust and note the monoclinic sulfur crystals on the underside.

7.1.5.2 Prepare monoclinic crystals from roll sulfur
Put small pieces of roll sulfur in a test-tube. Heat the test-tube extremely gently until the sulfur melts, m.p. = 114.5^oC. The liquid is lemon yellow. Pour the liquid sulfur into a folded filter paper. A crust forms on the surface. When the crust forms, open the filter paper. Needle-shaped crystals remain on the filter paper.

7.1.5.3 Prepare plastic sulfur then rhombic sulfur
Rhombic sulfur is a yellow powder, m.p. = 119^oC, and density = 1.96.
Put roll sulfur in a test-tube. Heat the test-tube slowly. Note the changes at the melting point from a light yellow colour to a red liquid. The red brown sulfur becomes viscous and it does not flow out if you hold the test-tube upside down. Continue heating until the reaction forms a brown black liquid. Continue to heat until the sulfur boils at 445^oC. BE CAREFUL! Pour the melted sulfur into a beaker of cold water. The reaction forms strands of amorphous sulfur. When the strands are cool, twist them to show that they are elastic. Later the sulfur hardens because it returns to the rhombic form of sulfur as a ring of eight sulfur atoms in tiny crystals. When heated, the ring breaks open to form long chains.

7.2.0 Pure substances and impure substances
1. Pure substances contains only one kind of atom or molecule, e.g. iron, sulfur, water, and oxygen. It can consist of elements or compounds. Elements may be metals or non-metals.
Impure substances contain more than one kind of substance. They may be mixtures, e.g. sulfur and iron filings, or air, or solutions, e.g. sea water. Mixtures in the home include flour, milk, ink, face powder, and tooth paste. Solutions in the home include fruit drinks (although often an emulsion) lemonade, mineral water. You make toffee or candy with a supersaturated sugar solution. French polish is a solution of shellac in methylated spirit.
2. Most compounds are ionic, e.g. common salt (NaCl) or covalent molecular, e.g. CO₂ or H₂O, or covalent network, e.g. SiO₂. Each compound has a name or formula. Compounds with names ending in "-ide" contains two elements. Compounds with names ending in "-ate" or "-ite" contain oxygen, with more oxygen in the "-ate". Compounds found at home include water, sugar, starch, baking soda, cream of tartar (potassium hydrogen tartrate)
3. Inorganic chemistry is the chemistry of the elements and their compounds, including CO₂, CO and carbonates. Organic chemistry is the chemistry of carbon and its compounds.

7.2.1 Classify substances, pure substances, mixtures, solutions
1. Describe materials at home and in the classroom from their observable physical properties: 1. colour (shiny or dull), 2. opaque (or transparent or translucent), 3. shape (or shape of crystals), 4. odour, 5. state (solid, liquid, gas) (change in state when heated or cooled), 6. mass (heavy, light) more dense or less dense than water, 7. taste (sweet, sour, bitter, other), 8. can be magnetized, 9. can conduct heat, 10. can conduct electricity, 11. can absorb liquids, 12. flexibility (can be bent, fragile). Describe the materials used to make different items in the classroom and in the home.
2. Describe materials as pure substance, or solution or mixture
If a solution is a homogeneous mixture of a liquid with a gas or a solid, then you would not classify air as a solution, nor brass as an alloy, unless they were in liquid form. However, if a solution is a homogeneous mixture of two or more components in a single phase, and usually refers to a solution in water (aqueous solution) then perhaps you can classify air and solid alloys as solutions.

Substances	Pure substance	Solution	Mixture
1. Ice floats in water	+	-	-
2. Tincture of iodine	-	+	-
3. Washing powder	-	-	+
4. Tap water	-	+	-
5. Air	-	+ or	+
6. Brass alloys	-	+ or	+

7.2.2 Elements and compounds, descriptions of common elements
1. An element is a substance that cannot be broken down into simpler substances by a chemical change. At room temperature and atmospheric pressure, eleven elements are gases - H₂, He, N₂, O₂, F₂, Ne, Cl₂, Ar, Kr, Xe, Rn. Two elements are liquids at room temperature - Hg and Br. Reactive elements have atoms weakly bound together and have electrons available for bonding, e.g. F.
2. A compound is a substance composed of two or more elements that are chemically united in fixed proportion. Compounds can be broken down to simple substances. For example the compound carbon dioxide can decompose to carbon and oxygen. [Comment: You can break down the carbon dioxide but you are likely to end with carbon and an oxide of something else.]
3. The periodic table has the elements arranged in groups. Some periodic tables using 1a, 2a to 0, suggest there are 18 groups. Other versions have only 8 or 9 groups. Elements in the same group in the periodic table have similar chemical properties because they have the same number of electrons in their outer shells. (This is not true if you group the transition elements together in the table.)
4. Group 1a elements include the alkali metals (Li, Na, K, Rb, Cs, Fr). The alkali metals are all soft, shiny and metallic when cut. They react easily with water, have low melting points and densities, and are good conductors of electricity. They all have one valence electron that they lose easily to form ions. (Some versions of the periodic table include hydrogen in group 1a also. However, today considering hydrogen separately is more usual as it has few of the properties of the alkali metals.)
5. Group 2a elements are the alkaline earth metals (Be, Mg, Ca, Sr, Ba, Ra). They are harder and have higher melting points and boiling points than the alkali metals. They easily lose two electrons to form ions, e.g. Mg²⁺.
6. Group 0 elements are the noble gases (inert gases or rare gases) He, Ne, Ar, Kr, Xe, Rn-222. They are colourless, odourless, monatomic gases and they form very few compounds. Unreactive elements have atoms joined by strong bonds, e.g. diamond. Elements that exist as separate small molecules have low boiling points and melting points, e.g. He, O₂.
Examine samples of iron, carbon, copper, magnesium, mercury in a thermometer and solid sticks of sulfur. Classify each of them according to the following characteristics: 1. Is it a hard solid, a liquid or a gas at room temperature? 2. If the element is a solid, does it shine and have a lustre? If necessary scratch its surface. 3. Can the element be bent or twisted or does it fracture easily? You may require pliers or a vice to do this. 4. Will the element conduct electricity? Place the element between two electrical contacts in a circuit.

7.2.2.1 Descriptions of common elements
[The properties listed below are based on information from IUPAC, International Union of Pure and Applied Chemistry.]
Click on name of element for information in "List of chemicals".

Aluminium, Al, is a silver white metal, with mechanical strength and forms protective oxide layer in air that prevents further oxidation, available as foil, sheet, wire and powder (1396) (FLAM, not safe for school use) extracted from the ore bauxite (Al₂O₃) 8% of the earth's crust, used in "Alfoil" cooking foil, drink-cans, saucepans, cars, duralumin, alloy of Al + Cu, Mg, etc. for aircraft bodies and struts. Aluminium ions form alums that are complex hydrated metal sulfates that contain 12 or 24 H₂O, e.g. aluminium potassium sulfate Al₂(SO₄)₃.K₂(SO₄).24H₂O, alum, potassium alum, used as mordants in dyeing. Reacts with dilute HCl or H₂SO₄ to form H₂ and metal ion, with concentrated oxidizing acids, HNO₃ or H₂SO₄ to produce high oxidation number ions, and sulfur dioxide SO₂ or nitrogen dioxide, NO₂, with steam to give the oxide and hydrogen gas. Heated powder forms oxide. Excess aluminium may cause short term toxicity, e.g. aluminium sulfate in drinking water, corroded cooking utensils used for cooking acidic foods, alum treatment of water. In 1990, The International Union of Pure and Applied Chemistry (IUPAC) confirmed the use of the spelling "aluminium" but people in the U.S.A. are accustomed to use the spelling "aluminum".
Atomic number: 13 | Relative atomic mass: 26.9815 | Density: 2.70 g cm^-3| m.p.: 660^oC | b.p.: 2470^oC | Specific heat capacity: 900 J kg^-1 K^-1 | E 173

Antimony, Sb, blue white metal, burns in air but no reaction with water or dilute acids, attached by halogens and oxidizing acids, poor conductor of heat and electricity, used in alloys for cable covers, pewter and lead cell accumulator plates, donor impurity in silicon chips, radioactive isotopes to produce neutrons, from stibnite Sb₂S₃,
Atomic number: 51 | Relative atomic mass: 121.75 | Density: 6.68 g cm^-3| m.p.: 630.5^oC | b.p.: 1750^oC | Specific heat capacity: 210 J kg^-1 K^-1

Argon, Ar, is a non-metal inert colourless odourless noble gas at room temperature and pressure Ar, 0.93% of the air, extracted from liquid air. Chemically inactive, monatomic gaseous element, used in incandescent light bulbs, fluorescent tubes and lasers, and for welding.
Atomic number: 18 | Relative atomic mass: 39.948 | Density: 1.40 g cm^-3 (87 K) | m.p.: -189^oC | b.p.: -186^oC | Specific heat capacity: 519 J kg^-1 K^-1

Arsenic, As, is a metalloid (or non-metal) poisonous found free and in combined many minerals, main allotrope grey arsenic, and n-type dopant of silicon semiconductors, hardens lead alloys. White arsenic, arsenic (III) oxide, As₄O₆, common in sulfide ore deposits, very toxic, rodenticide. Salvarsan, Erlich's compound 606 (arsphenamine) was the first drug to treat syphilis. The most toxic form of arsenic is As³⁺ which reacts with enzymes in the body. Agricultural use of arsenic kills plants before concentration is toxic enough for humans.
Atomic number: 33 | Relative atomic mass: 74.9216 | Density: 5.72 g cm^-3 | m.p.: 814^oC | b.p.: 613^oC (sublimes) | Specific heat capacity: 326 J kg^-1 K^-1

Barium, Ba, is an alkaline earth metal, brittle and expensive, used to absorb high energy particles, in minerals barytes, BaSO₄ and witherite, BaCO₃, forms poisonous compounds, oxidizes in air and reacts with water and ethanol. Barium sulfate is used for a contrast medium for X-ray examination of intestines.
Atomic number: 56 | Relative atomic mass: 137.33 | Density: 3.51 g cm^-3 | m.p.: 725^oC | b.p.: 1640^oC | Specific heat capacity: 192 J kg^-1 K^-1

Bismuth, Bi, white metallic crystals, from bismuthinite mineral Bi₂S₃ but rare in the earth, very diamagnetic, low thermal conductivity, high electrical resistance, burns in air with blue flame, used in low melting point alloys for fire safety equipment, thermocouples, magnetic flux measurement, liquid metal coolant for nuclear reactors, cosmetics and medicines, e.g. bismuth carbonate for peptic ulcers.Atomic number: 83 | Relative atomic mass: 208.98 | Density: 9.78 g cm^-3 | m.p.: 271.3^oC | b.p.: 1560^oC | Specific heat capacity: 123 J kg^-1 K^-1
Boron, B, is a non-metal or metalloid, yellow brown network solid, brown amorphous form and black metallic form, has metallic lustre, very hard (9.3 Mohs' scale) and strong semiconductor, found in minerals, e.g. tourmaline, and associated with volcanic activity as borates, used in control rods for nuclear reactors and in green flares.
Atomic number: 5 | Relative atomic mass: 10.81 | Density: 2.34 g cm^-3 (amorphous form) | m.p.: 2300^oC | b.p.: 2550^oC | Specific heat capacity: 123 X 10³ J kg^-1 K^-1

Bromine, Br is a red-brown, volatile, poisonous, non-metal liquid between 19^oC and 27^oC, suffocation odour, vapour irritates eyes and throat, strong oxidizing agent, used for many chemical compounds including "anti-knock" petrol additive, 1,2-dibromoethane, scarce element extracted from sea water, 65 ppm, as bromide ion. Silver bromide import for photography. Bromoform, tribromomethane, CHBr₃ used to separate minerals, bromothymol blue indicator, pH 6.0 -7.6, potassium bromide formerly used as sedative and was supposed top be put in army tea to quieten soldiers' sexual urges, bromochlorodifluoromethane, CHBrClF₂, low toxic fire extinguisher for confined spaces. The fat soluble fire retardant PBDE, polybromyldiphenyl ether, in the deca, octa and penta forms has been detected in mothers' milk, fish and the environment. (POISON COR 1744) Br₂ (3.6% bromine) r.d. 3.12 gm cm^-3, b.p. 58.7^oC, solidifies -7^oC (swimming pool sanitation, products from bromine, e.g. BCDMH)
Atomic number: 35 | Relative atomic mass: 79.904 | Density: 3.12 g cm^-3 | m.p.: -7.2^oC | b.p.: 58.78^oC | Specific heat capacity: 448 J kg^-1 K^-1

Cadmium, Cd is a soft blue white metal, toxic at low concentrations, a rare element that occurs in the mineral sphalerite, zinc sulfide, is used for cadmium plating against corrosion, in nuclear reactors and in films sensitive to ultraviolet light, reference voltage in a Western Standard cadmium cell, Cd/ Zn alloys in low melting point solders and aluminium solders, Ni-Cd batteries (Nicad) phosphorescent coating of TV tubes. Cadmium looks like zinc but make a crackling sound like tin when bent. Oysters in polluted water make accumulate cadmium. In former Communist countries that practised collection of "night soil" as a fertilizer, cadmium pollution of low lying agricultural soil has occurred. Cadmium is toxic because it competes with Zn and Ca. Large concentrations cause painful bone ailments. and bone porosity. Our body gets rid of excess Cd by deposition in the kidneys and liver.
Atomic number: 48 | Relative atomic mass: 112.41 | Density: 8.64 g cm^-3 | m.p.: 321^oC | b.p.: 765^oC | Specific heat capacity: 230 J kg^-1 K^-1Calcium, Ca [FLAM 1401] is an alkaline earth metal, granules in liquid paraffin. Reacts with dilute HCl or H₂SO₄ to form H₂ and metal ion, occurs mainly as carbonates, e.g. calcium carbonate, CaCO₃, gypsum, CaSO₄.2H₂O, 3.5% of the earth's crust, essential nutrient element for bones, teeth and muscle contraction in animals and middle lamella of plan cells, extracted by electrolysis of fused calcium chloride. Reacts with concentrated oxidizing acids, HNO₃ or H₂SO₄ to produce high oxidation number ions, and sulfur dioxide, SO₂, or nitrogen dioxide, NO₂. Reacts with cold water and reacts with air to form peroxides. Calcium is the most abundant mineral, and the fifth most abundant element mostly in bone tissue. About 1% is used in nerve transmission, muscle contraction and other functions
Atomic number: 20 | Relative atomic mass: 40.08 | Density: 1.54 g cm^-3| m.p.: 850^oC | b.p.: 1487^oC | Specific heat capacity: 653 J kg^-1 K^-1

Carbon, C, charcoal, lump, powder, lamp black, acetylene black, wood charcoal, activated carbon / charcoal (coke is left when coal is heated without air, for blowpipe work, charcoal may contain wood ash mainly potassium carbonate, soft "lead" pencils) non-metal network solid, has two natural crystalline forms, diamond and graphite. Diamond has strong covalent bonds in three dimensions to four other atoms, is the hardest substance known, transparent, brittle and non-conductor. It is used as gemstones, diamond dust abrasives and rock boring tools. Graphite has covalent bonds that are strong in one dimension but weak between layers, has density 3.5, and is soft and black. slippery with lustre and is good conductor only along its layers, available as graphite mineral, graphite powder and colloidal graphite "Aquadag", occurs as mineral deposits or is made from petroleum, used in the "lead" of soft "B" pencils, as a lubricant and electrical conductor, in cast iron and as coke for heating oildag, plumbago, "black lead", black-lead, graphite.
Atomic number: 6 | Relative atomic mass: 12.011 | Density: 2.25 g cm^-3 (graphite) | m.p.: 3730^oC (sublimes) | b.p.: 4830^oC | Specific heat capacity 711 J kg^-1 K^-1 (graphite) | 519 J kg^-1K^-1 (diamond)

Chlorine, Cl, is a non-metal green yellow, poisonous with irritating smell gas at room temperature and pressure Cl₂, strong oxidizing agent and used in bleaching powder, disinfectant, 1.9% of sea water, produced from electrolysis of brine, used to make many organic products, e.g. chloroform trichloromethane CHCl₃, chlorofluorocarbon refrigerant and aerosol now phased out because of damage to the ozone layer in atmosphere, chlorophenol red pH 4.8 to 6.4 indicator, chloral hydrate sedative, chloric (V) acid, HClO₃ and its salts chlorates (V) powerful oxidizing agents and sometimes explosives. Chloride is a constituent of gastric juice which is about 0.03 M HCl. It is also used for controlling the transport of oxygen and carbon dioxide haemoglobin in red blood cells. Adults require a daily minimum, of 750 mg of chloride.
This gas is very toxic. It can react to cause fires or explosions upon contact with turpentine, ether, ammonia gas, illuminating gas, hydrocarbon, hydrogen and powdered metals. Dissolves readily in water forming highly corrosive solution. Do not prepare chlorine in open room. Use fume cupboard. Direct combination of chlorine and hydrogen in bright light or ignition of the mixture by lighted taper or electric spark. Reactions of chlorine with metals, solid non-metals, hydrocarbon. Use small quantities only.
Atomic number: 17 | Relative atomic mass: 35.453 | Density: 1.56 g cm^-3 (238 K) | m.p.: -101^oC | b.p.: -34.7^oC | Specific heat capacity: 477 J kg^-1 K^-1Chromium, Cr, is a reactive transition metal but forms protective oxide layer in air that prevents further oxidation and forms hard alloys with Ni or Fe. Chromium is available as technical grade chromium, is extracted from chromite (Fe(CrO₂)₂) and is used for chromium plated metal, hard plating Cr₂O_3,catalysts, in stainless steel and in heat resistant steel. Strong reducing agent Cr²⁺ salts blue in aqueous solution, Cr³⁺ salts green in aqueous solution. CrO₄^2- salts yellow, e.g. potassium chromate, K₂CrO₄, and strong oxidizing agent Cr₂O₇^2- orange, e.g. potassium dichromate K₂Cr₂O₇. Chromium deficiency reduces tolerance to glucose.
Atomic number: 24 | Relative atomic mass: 51.996 | Density: 7.19 g cm^-3 | m.p.: 1890^oC | b.p.: 2482^oC | Specific heat capacity: 448 J kg^-1 K^-1

Cobalt, Co, is a transition hard, grey metal, forms complex ions, e.g. [Co(H₂O)₆]²⁺, magnetic below 1075^oC, essential element but toxic in excess, used in alloys radiography, magnets, steel. Cobalt (II) oxide used to colour glass blue. Occurs in the body only as cyanocobalamin, vitamin B12.
(German: kobold, goblin of the mines, because associated with arsenic and sulfur health-damaging impurities)
Atomic number: 27 | Relative atomic mass: 58.9332 | Density: 8.90 g cm^-3 | m.p.: 1492^oC | b.p.: 2900^oC | Specific heat capacity: 435 J kg^-1 K^-1

Copper, Cu (cuprum) is a bright reddish orange, malleable and ductile transition metal, with high electrical and thermal conductivity, obtained form cuprite, Cu₂S, available as filings, foil, powder, turnings, copper nails, copper wire, and copper turnings, is extracted from cuprite (Cu₂S) and malachite (basic copper (II) carbonate, CuCO₃.Cu(OH)₂.H₂O) and used for coin alloys, electrical wiring and heating vessels. Reacts with concentrated oxidizing acids, HNO₃ or H₂SO₄ to produce high oxidation number ions, and sulfur dioxide SO₂or nitrogen dioxide, NO₂. No reaction with dilute HCl or H₂SO₄. or with water. Heated powder forms oxide. Copper deficiency may occur in infants fed only on cow's milk. Copper bracelets my alleviate arthritis. A copper bowl may be preferable for beating cream. Copper poisoning may occur from water standing for a long time in copper pipes or in a copper hot water service. Copper is a cofactor for many enzymes and proteins, and is used in the development of nerve, bone, blood and connective tissue.- Copper competes with zinc for entry from the intestines, so an increase in dietary zinc may result in copper deficiency. The recommended daily allowance, RDA, is 1.5 to 3.0 mg. Copper bracelets do not cure arthritis.
Atomic number: 29 | Relative atomic mass: 63.546 | Density: 8.92 g cm^-3 | m.p.: 1083^oC | b.p.: 2595^oC | Specific heat capacity: 385 J kg^-1 K^-1

Fluorine, F is a non-metal yellow poisonous gas at room temperature and pressure F₂,most reactive element known, never found as free element but in many silicate minerals and fluorite, CaF₂, most electronegative non-metallic element, strong oxidizing agent, combines with carbon to form low friction fluorocarbon polymers, e.g. PYFE, Teflon, used to make CFCs, chlorofluorocarbons, freon, that damages the ozone layer. Fluorine compounds are added to toothpaste and drinking water, e.g. tin (II) fluoride, sodium monofluorophosphate (MFP) sodium fluoride and amine fluorides. In Australia solid sodium silicofluoride is added to drinking water in some places. However, some natural water sources already contain the fluoride ion. The enamel of teeth are formed from the crystalline mineral hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂. The fluoride ion F^- replaces the OH^- to form in the teeth Ca₁₀(PO₄)₆F₂. Fluoride is essential for teeth and bones.
Atomic number: 9 | Relative atomic mass: 18.9984 | Density: 1.11 g cm^-3 (85 K) | m.p.: -220^oC | b.p.: -188^oC | Specific heat capacity: 824 J kg^-1 K^-1

Gold, Au (aurum) is a yellow, lowest meal in activity series so most unreactive transition metal, is found in nature as free element form, available as gold leaf, occurs as the element and is used in coin alloys, electrical components, dentistry alloys, jewellery and as a monetary standard. No reaction with dilute HCl or H₂SO₄, air, water or concentrated oxidizing acids, e.g. HNO₃ or H₂SO₄. Reacts with aqua regia, "royal water" that dissolves gold the "king of metals" (1 part conc. HNO₃ + 3 parts con. HCl) to form AuCl₄. Atomic number: 79 | Relative atomic mass: 196.967 | Density: 19.3 g cm^-3 | m.p.: 1063^oC | b.p.: 2970^oC | Specific heat capacity: 130 J kg^-1 K^-1

Helium, He, is a non-metal noble gas at room temperature and pressure He, with separate small molecules, 0.0005% of the air, superfluid at 2.2 K, lowest boiling point, obtained from natural gas wells, using in diving gases, balloons, welding. Has no known compounds.
Atomic number: 2 | Relative atomic mass: 4.00260 | Density: 0.147 g cm^-3(4 K) | m.p.: -270^oC | b.p.: -269^oC | Specific heat capacity: 5.19 X 10³ J kg^-1 K^-1

Hydrogen, H, is a colourless odourless gas at room temperature and pressure H₂, lightest element, burns to form water, most common element in space, natural isotopes hydrogen and deuterium and manufactured isotope radioactive tritium, product of electrolysis of water, used to fix nitrogen and make ammonia in Haber process, reduction of ore oxides, manufacture of HCl, hydrogenation of oils, elemental gas in balloons and possible potential use as hydrogen fuel in motor cars.
Atomic number: 1 | Relative atomic mass: 1.0079 | Density: 0.070 g cm^-3 (20 K) | m.p.: -259^oC | b.p.: -252^oC | Specific heat capacity: 1.43 X 10⁴ J kg^-1 K^-1

Iodine, I, resublimed [COR 1759] is a non-metal forms violet black solid poisonous scales with special smell, the least reactive of the halogens, most common as iodides, insoluble in water but dissolves in ethanol and a solution containing I^-, 1% in KI, because it forms I₃^-, when heated sublimes to form vapour that irritates the eyes, important for function of the thyroid gland, intense blue colour is test for starch, extracted from unpurified Chile saltpetre (caliche) and seaweed, powerful disinfectant when dissolves in ethanol to form tincture of iodine, as radio iodine isotope Iodine-123 used in nuclear medicine, especially thyroid gland disorders. Strong oxidizing agent and antiseptic. As povidone-iodine in the antiseptic "Betadine". Iodine is used in the muscles and in the thyroid gland as part of the chemicals thyroxine and triiodothyronine. Iodine deficiency causes hyperthyroidism and an enlarged thyroid gland. The recommended daily allowance, RDA, is 150 pg.
Atomic number: 53 | Relative atomic mass: 126.905 | Density: 4.93 g cm^-3 | m.p.: 113.5^oC | b.p.: 184^oC | Specific heat capacity: 218 J kg^-1 K^-1

Iron, Fe (ferrum, ferrum reductum) as powder, iron nails, iron wire, iron filings, steel wool, is a magnetic and strong transition metal, 4.5% of the earth's crust, used for making iron and steel and is the most commonly used metal, available as filings, iron nails and wire, extracted from iron ores, e.g. haematite, Fe₂O₃, reacts with dilute HCl or H₂SO₄ to form H₂ and metal ion, reacts with concentrated oxidizing acids, HNO₃ or H₂SO₄to produce high oxidation number ions, and sulfur dioxide SO₂ or nitrogen dioxide, NO₂, reacts with steam to give the oxide and hydrogen gas. Heated powder forms oxide. The complex haemoglobin molecule has an iron atom in the centre. During rusting, metallic ion changes to Fe(OH)₃.xH₂O. Galvanized iron is Fe with Zn coating, e.g. "tin" roof. Iron is used in the haemoglobin protein that carries oxygen and carbon dioxide in the blood. Pig iron is cast iron, 2-4.3% carbon.
Atomic number: 26 | Relative atomic mass: 55.847 | Density: 7.86 g cm^-3 | m.p.: 1535^oC | b.p.: 3000^oC | Specific heat capacity: 448 J kg^-1 K^-1

Krypton, Kr, is a non-metal colourless odourless noble gas at room temperature and pressure Kr₂, extracted from liquid air, 0.0001% of the air, mixed with other inert gases in fluorescent lamps. Forms few compounds.
Atomic number: 36 | Relative atomic mass: 83.80 | Density: 2.16 g cm^-3 (121 K) | m.p.: -157^oC | b.p.: -152^oC | Specific heat capacity: 247 J kg^-1 K^-1

Lead, Pb (plumbum) as lead shot, fishing sinkers, roof guttering, foil, powder, filings, strip, is a soft dense unreactive metal, available as lead foil, powder and lead shot, extracted from the ore galena (PbS) used in fishing sinkers, solder, lead glazes and X-ray protective shields, holds the pieces of glass together in stained glass windows, ingestion and skin absorption causes lead poisoning (especially in young children sucking lead paint) used in bullets, lead shot, fishing sinkers, building construction, lead cell accumulators, solder, pewter, bearings and alloys. Lead paint formerly contained the white pigment "white lead", basic lead carbonate, Pb(OH)₂PBCO₃ that is now replaced by titanium dioxide, TiO₂. Formerly, ladies used lead carbonate to whiten their faces and some may have died from such use. Reacts with concentrated oxidizing acids, HNO₃ or H₂SO₄ to produce high oxidation number ions, and sulfur dioxide SO₂ or nitrogen dioxide, NO₂. No reaction with dilute HCl or H₂SO₄or with water. Heated powder forms oxide. Inorganic Pb²⁺is an accumulated poison and can replace calcium in bone. A "lead pencil" contains graphite, not lead.
Atomic number: 82 | Relative atomic mass: 207.2 | Density: 11.3 g cm^-3| m.p.: 327^oC | b.p.: 1744^oC | Specific heat capacity: 130 J kg^-1 K^-1

7.2.2.2 Tetraethyl lead, lead tetra-ethyl
Octane (C₈H₁₈) Octane number 16.1.1h | See also 32.5.5.5: Spark plugs, pre-ignition | See also 11.11.2: Petrol-sniffing
The "anti-knock" additive to petroleum, the lead alkyl lead (IV) tetraethyl, Pb(C₂H₅)₄, lessens pre-ignition, "knocking" by inhibiting combustion reactions and so improving its octane rating. This "leaded petrol" is no longer made or used in Australia and other countries because the compound causes lead poisoning and environmental pollution so is replaced by "unleaded petrol" that contains additional aromatic hydrocarbons to improve its octane rating.

Lithium, L is a least dense, soft and shiny, very reactive alkali metal, rare element found in some granite pegmatites, used in Al and Mg alloys, batteries and anti-depressant medicines. Reacts with oxygen and water, on heating reacts with nitrogen and hydrogen. Lithium carbonate is used for a craft flux.
Atomic number: 3 | Relative atomic mass: 6.941 | Density: 0.53 g cm^-3| m.p.: 180^oC | b.p.: 1330^oC | Specific heat capacity: 3.39 X 10³ J kg^-1 K^-1

Magnesium, Mg [FLAM 1418] as powder, ribbon, turnings, wire, photographers' flash bulbs, light bulbs and fire starters is a silver white alkaline earth metal, 2% of the earth's crust, forms protective oxide layer in air that prevents further oxidation, available as powder (FLAM) - dangerous, and ribbon (FLAM) - the safest form for school use that burns in air with intense white light, and as turnings (FLAM) low density, extracted from sea water, found in magnesite, MgCO₃ and dolomite, MgCO₃.CaCO₃, used in aircraft bodies, cars, flashbulbs and alloyed with aluminium. Reacts with dilute HCl or H₂SO₄ to form H₂ and metal ion, reacts with concentrated oxidizing acids, HNO₃ or H₂SO₄ to produce high oxidation number ions, and sulfur dioxide SO₂or nitrogen dioxide, NO₂, reacts with hot water, reacts with halogens, sulfur and nitrogen. Heated powder forms oxide. Magnesium is stored in bones. It is used in many adenosine triphosphate, ATP, reactions. The recommended daily allowance, RDA, is 350 mg for adult males, and 280 mg for adult females. Manganese is a cofactor for many enzymes, but magnesium can usually substitute for it.
Atomic number: 12 | Relative atomic mass: 24.305 | Density: 1.74 g cm^-3 | m.p.: 650^oC | b.p.: 1110^oC | Specific heat capacity: 1.03 X 10³ J kg^-1 K^-1

Manganese, Mn, is a white to reddish colour, hard, brittle transition metal, available as electrolytic flake and manganese (IV) oxide (manganese dioxide) extracted by electrolytic treatment of ores, e.g. pyrolusite (manganese (IV) oxide) used in ferromanganese for alloy steel manufacture.
Atomic number: 25 | Relative atomic mass: 54.9380 | Density: 7.20 g cm^-3 | m.p.: 1240^oC | b.p.: 2100^oC | Specific heat capacity: 477 J kg^-1 K^-1

Mercury, Hg (hydrargyrum) formerly called "quicksilver", is a liquid metal between 19^oC and 27^oC, the lowest melting point of all substances, m.p. = -38.9^oC, dissolves in most metals to produce amalgams, toxic when inhaled or taken internally or absorbed through the skin, free surface mercury not to be used in schools but can be examined in thermometers, extracted from cinnabar (mercury (II) sulfide) used in dentistry amalgams, mercury vapour lamps, electrical switches, interferometer lights and detonators, e.g. mercury fulminate (Hg(CNO)₂). Reacts with concentrated oxidizing acids, HNO₃ or H₂SO₄to produce high oxidation number ions, and sulfur dioxide SO₂ or nitrogen dioxide, NO₂. No reaction with dilute HCl or H₂SO₄ or with water. Heated powder forms oxide.
Mercury (I) nitrate
Millon's Reagent contains mercury (I) nitrate in nitrous acid. Mercurous nitrate, mercury (I) nitrate, formerly used in the manufacture of felt hats, caused tremors in the workers and leading to the term "mad as a hatter", a character in Alice in wonderland by Lewis Carroll.
Atomic number: 80 | Relative atomic mass: 200.59 | Density: 13.6 g cm^-3 | m.p.: -38.9^oC | b.p.: 357^oC | Specific heat capacity: 138 J kg^-1 K^-1

Molybdenum, Mo, silvery solid, transition element, in molybdenite, MoS₂, not affected by most acids, used in steel alloys, in two enzyme systems xanthine oxidase and aldehyde oxidase. Hard water can provide some of the daily intake of molybdenum.

Neon, Ne, is a non-metal inert noble gas at room temperature and pressure, 0.0018% of the air, with very low reactivity, used for high voltage display lighting, has bright orange colour, "neon" lights, strip lighting, high voltage display lighting and in pilot electrodes (starter electrodes to start up sodium vapour discharge lamps) cold cathode tubes, manufactured by recovery from atmosphere.
Atomic number: 10 | Relative atomic mass: 20.179 | Density: 1.20 g cm^-3 (27 K) | m.p.: -249^oC | b.p.: -246^oC | Specific heat capacity: 1.03 X 10³ J kg^-1 K^-1

Nickel, Ni, as foil, powder, is a transition metal that resists corrosion, is obtained from ores containing NiS, is available as sheet, is extracted from NiS ores, isused in shiny coin alloys, nickel plating, and in "silver" cutlery stamped "EPNS" (electroplated nickel silver) that has a shiny metal protective coating, Reacts with dilute HCl or H₂SO₄ to form H₂ and metal ion, reacts with concentrated oxidizing acids, HNO₃ or H₂SO₄ to produce high oxidation number ions, and sulfur dioxide SO₂or nitrogen dioxide, NO₂, reacts with steam to give the oxide and hydrogen gas. Heated powder forms oxide.
The name comes from the German Kupfernickel, copper goblin. The nickel coin in U.S.A is made of a nickel copper alloy.
Atomic number: 28 | Relative atomic mass: 58.69 | Density: 8.90 g cm^-3| m.p.: 1453^oC | b.p.: 2730^oC | Specific heat capacity: 439 J kg^-1 K^-1

Nitrogen, N, is a non-metal gas at room temperature and pressure H₂, 78.8% of the air, forms oxides: Nitrous oxide N₂O, nitric oxide NO, nitrogen dioxide NO₂, dinitrogen tetroxide N₂O₄.
Atomic number: 7 | Relative atomic mass: 14.0067 | Density: 0.808 g cm^-3 (77 K) | m.p.: -210^oC | b.p.: -196^oC | Specific heat capacity: 1.04 X 10³ J kg^-1 K^-1

Oxygen, O, is a non-metal colourless and odourless gas at room temperature and pressure O₂, 20.95% of the air, 47% of the earth's crust, identified by lighting a glowing splint, supports combustion and is necessary for respiration, made in the laboratory by decomposition of hydrogen peroxide with MnO₂ catalyst, manufactured by distillation of liquid air, most abundant element 50% of mass of rocks in earth's crust. Reacts with metals to form basic oxides, reacts with non-metals to form acidic oxides. Oxygen is carried by binding directly to the iron, in its 2+ oxidation state. Monthly loss of iron because of menstruation may average 28 mg. The recommended daily allowance, RDA, is 10 mg for adult males and 15 mg for adult females. Lecithin, diacylphosphatidylcholine is used in cell membranes. The lecithins are mixed esters of glycerol and choline with long chain fatty acids and phosphoric acid.
Atomic number: 8 | Relative atomic mass: 15.9994 | Density: 1.15 g cm^-3(90 K) | m.p.: -218^oC | b.p.: -183^oC | Specific heat capacity: 916 J kg^-1 K^-1

Phosphorus, P, Phosphorus is a non-metal network solid, occurs mainly as phosphates and in many minerals, e.g. apatite, has two main allotropes, white phosphorus, P₄, is waxy, poisonous, very reactive, spontaneously flammable, reacts with oxygen in the air to form P₂O₅, so it is stored under water, red phosphorus red [FLAM 338] is not poisonous, ignites above 300^oC, has phosphorus atoms bound in a covalent network so is less reactive than white phosphorus and can be stored in air, used in match heads and for "doping" semiconductors. Phosphates are important agricultural fertilizers, e.g. NPK. Phosphorescence is the green glow from the slow oxidation of white phosphorus. It is an example of chemiluminescence. Phosphorus occurs as inorganic calcium phosphate in bones and teeth, in tissue and in the ATP molecule. The recommended daily allowance, RDA, is 1200 mg.
See also 8.1.0: Heat sources, light a match
(white) Atomic number: 15 | Relative atomic mass: 30.9738 | Density: 1.82 g cm^-3 | m.p.: 44.2^oC | b.p.: 280^oC | Specific heat capacity: 757 J kg^-1 K^-1
(red) Atomic number: 15 | Relative atomic mass: 30.9738 | Density: 2.34 g cm^-3 | m.p.: 590^oC | b.p.: - ^oC | Specific heat capacity: 670 J kg^-1 K^-1

Platinum, Pt, is a soft, ductile transition metal, resists most chemical agents and does not oxidize at high temperature, available as foil and wire, occurs in free elemental form or in alloys, used for electrical contacts, electrodes and jewellery. No reaction with dilute HCl or H₂SO₄, air, water or concentrated oxidizing acids, e.g. HNO₃ or H₂SO₄, reacts with aqua regia (concentrated HNO₃ + HCl) to form H₂PtCl₆.
Atomic number: 78 | Relative atomic mass: 195.08 | Density: 21.4 g cm^-3 | m.p.: 1769^oC | b.p.: 4530^oC | Specific heat capacity: 134 J kg^-1 K^-1

Potassium, K (kalium) is a soft and shiny white alkali metal, highest metal in activity series so does not occur in the free state, 2.5% of the earth's crust, available as the metal in liquid paraffin and is used widely in chemistry, is the " K" in the common fertilizer NPK, usually as K₂O. Reacts with dilute HCl or H₂SO₄ to form H₂ and metal ion, reacts with concentrated oxidizing acids, HNO₃ or H₂SO₄ to produce high oxidation number ions, and sulfur dioxide SO₂ or nitrogen dioxide, NO_2, reacts with cold water and reacts with air to form peroxides. Potassium has less concentration in extra cellular fluids than in intracellular fluids where it is the primary cation. Potassium ion is lost in sweat along with sodium ion. (FLAM 2257) (in liquid paraffin)
Atomic number: 19 | Relative atomic mass: 39.0983 | Density: 0.86 g cm^-3 | m.p.: 63.7^oC | b.p.: 774^oC | Specific heat capacity: 753 J kg^-1 K^-1

Radium, Ra, is a radioactive alkaline earth metal, used in some cancer therapy, extracted from pitchblende, uraninite, used as a radioactive resource.
Atomic number: 88 | Relative atomic mass: 226.025 | Density: 5.0 g cm^-3 | m.p.: 700^oC | b.p.: 1140^oC | Specific heat capacity: 121 J kg^-1 K^-1

Radon, Rn, is a non-metal noble colourless water-soluble gas at room temperature and pressure Rn₂, formed by decay of radium-226, forms under granite where it may be a health habit to people living in granite houses, has few compounds, used in radiotherapy.
Atomic number: 86 | Relative atomic mass: (222) | Density: 4.4 g cm^-3 (211 K) | m.p.: -71^oC | b.p.: -61.8^oC | Specific heat capacity: 92 J kg^-1 K^-1

Selenium, Se, is a non-metal, obtained from sulfide ores, decolorizes glass, semiconductor that conducts electricity when e.m.f. applied, used in photoelectric cells and light meters. Similar properties to sulfur. The Kjeldahl catalyst is sodium sulfate + selenium. Selenium is a trace mineral used to destroy hydrogen peroxide. The recommended daily allowance, RDA, is 70 mu g for males, and 55 mu g for females.
Atomic number: 34 | Relative atomic mass: 78.96 | Density: 4.81 g cm^-3 | m.p.: 217^oC | b.p.: 685^oC | Specific heat capacity: 322 J kg^-1 K^-1

Silicon, Si, lump [powder FLAM 1346] is a non-metal network solid with many properties similar to carbon. occurs naturally as a brown powder or grey crystals, 28% of the earth's crust, forms a network solid similar to diamond and has valence 4, the second most abundant element mainly in silicates in rocks, prepared by reduction of silica SiO₂ in an electric furnace, used as a semiconductor, conductivity can be increased by increasing its temperature or by adding small quantities of boron or phosphorus, called doping. The common form of silicon dioxide is silica, SiO₂as in quartz. A major component of rocks is the silicate ion, SiO₄^4- as in glass. Silicone greases have a polymer network of silicon and oxygen atoms attached to C and H atoms.
Atomic number: 14 | Relative atomic mass: 28.0855 | Density: 2.33 g cm^-3 | m.p.: 1410^oC | b.p.: 2360^oC | Specific heat capacity: 711 J kg^-1 K^-1

Silver, Ag (argentum) is a silver white transition metal, does not oxidize in air and is the best electrical conductor, available as silver wire, occurs as the element and is used in coin alloys, electrical conductors, photographic emulsions, jewellery and ornaments. Reacts with concentrated oxidizing acids, HNO₃ or H₂SO₄ to produce high oxidation number ions, and sulfur dioxide SO₂ or nitrogen dioxide, NO_2, reacts with concentrated HNO₃ and hot concentrated H₂SO₄. No reaction with dilute HCl or H₂SO₄, air, or water. The "silver paper" usind in wrapping is usually tin foil.
Atomic number: 47 | Relative atomic mass: 107.868 | Density: 10.5 g cm^-3 | m.p.: 961^oC | b.p.: 2210^oC | Specific heat capacity: 234 J kg^-1 K^-1

Sodium, Na (in liquid paraffin) (natrium) (FLAM COR 1428) is a very reactive, soft and shiny alkali metal with a silvery colour, 2.5% of the earth's crust, does not occur in the free state and soon becomes dull in air, available as sodium metal in liquid paraffin, extracted by electrolysis of fused sodium hydroxide, rock salt (halite) and evaporated sea water, used in sodium vapour discharge lamps. Reacts with dilute HCl or H₂SO₄ to form H₂and metal ion, with concentrated oxidizing acids, HNO₃ or H₂SO₄to produce high oxidation number ions, and sulfur dioxide SO₂ or nitrogen dioxide, NO₂, reacts with cold water and reacts with air to form peroxides. Sodium has greater concentration in extra cellular fluids than in intracellular fluids. The level of sodium ion in blood is 310 - 333 mg per 100 mL of serum.
Atomic number: 11 | Relative atomic mass: 22.9898 | Density: 0.97 g cm^-3 | m.p.: 97.8^oC | b.p.: 890^oC | Specific heat capacity: 1.23 X 10³ J kg^-1 K^-1

Strontium, Sr, silver white metallic element, in minerals celestine SrSO₄, strontianite SrCO₃ and spring water, similar properties to calcium, salts used for crimson flame in fireworks, after nuclear explosion fallout contains ⁹⁰Sr that can be absorbed in human bone, strontium chloride in toothpaste for sensitive teeth, e.g. "Sensodyne".
Atomic number: 38 | Relative atomic mass: 87.62 | Density: 2.54 g cm^-3 | m.p.: 800^oC | b.p.: 1300^oC | Specific heat capacity: - J kg^-1 K^-1

Sulfur, S [FLAM 1350] brimstone, sublimed, flowers of sulfur, sulfur sticks, brimstone, is a non-metal occurs as S₈ molecule rings. The main allotropes are as follows: 1. Alpha sulfur, rhombic sulfur, with yellow octahedral crystals, and 2. Beta sulfur with monoclinic prismatic pale yellow crystals. Sulfur is insoluble in water, slightly soluble in ethanol, and soluble in benzene. Above 160^othe S₈ molecule rings break to form long chains of plastic sulfur, polymeric sulfur, that is not soluble in any solvents.
Atomic number: 16 | Relative atomic mass: 32.06 | Density: 2.07 g cm^-3 (Alpha) 1.96 g cm^-3(Beta) | m.p.: 113^oC (Alpha) 119^oC (Beta) | b.p.: 445^oC (Alpha) | Specific heat capacity: -

Tin, Sn (stannum) (tin-plated jam tin) pewter is a ductile, malleable metal, resists corrosion, is available as granules, pellets, foil and powder, is extracted from the ore cassiterite (tin (IV) oxide, SnO₂) and used in alloys and the shiny protective plating of tin cans (tin plate) alloys and solders. It reacts with dilute HCl or H₂SO₄ to form H₂ and metal ion, reacts with concentrated oxidizing acids, HNO₃or H₂SO₄ to produce high oxidation number ions, and sulfur dioxide SO₂ or nitrogen dioxide, NO₂. No reaction with water. Heated powder forms oxide. The "silver paper" usind in wrapping is usually tin foil.
Atomic number: 50 | Relative atomic mass: 118.71 | Density: 7.28 g cm^-3 (white) 5.75 g cm^-3(grey) | m.p.: 232^oC | b.p.: 2270^oC | Specific heat capacity: 218 J kg^-1K^-1

Tungsten, W, white-grey solid, transition element (formerly wolfram) light bulb filaments, from wolframite (MnFe)WO₄, scheelite CaWO_4,not affected by dilute acids, used in steels and lamp filaments, tungsten carbide, WC, black powder, used in cutting tools because has Mohs scale 9.5 The tungsten filament in a light bulb reaches about 2,300^oC. It has the highest melting point of all metals.
Atomic number: 74 | Relative atomic mass: 183.85 | Density: 19.3 g cm^-3 | m.p.: 3,422^oC | b.p.: 5,660^oC | Specific heat capacity: 130 J kg^-1 K^-1

Uranium, U, is a radioactive hard grey metal obtained from pitchblende U₃O₈, ²³⁸U main isotope,²³⁵U used as fuel in nuclear power stations and atomic bombs. Atomic number: 92 | Relative atomic mass: 238.029 | Density: 19.1 g cm^-3 | m.p.: 1130^oC | b.p.: 3820^oC | Specific heat capacity: 117 J kg^-1 K^-1

Zinc, Zn, granulated, zinc foil, dry cell battery case, is a blue white metal, forms protective oxide layer in air that prevents further oxidation, is available as zinc granules, foil, filings and powder (FLAM) extracted from zinc blende (sphalerite, ZnS) used for dry cell battery casings and in the Daniell cell, galvanized iron, alloys and brass, a micronutrient (trace element) required in a very small quantity by living organisms as salts or compounds, not as the pure element. Reacts with dilute HCl or H₂SO₄to form H₂ and metal ion, reacts with concentrated oxidizing acids, HNO₃ or H₂SO₄ to produce high oxidation number ions, and sulfur dioxide SO₂or nitrogen dioxide, NO₂, reacts with steam to give the oxide and hydrogen gas. Heated powder forms oxide. High level of zinc in the diet is undesirable, e.g. from oysters, and zinc deficiency symptoms occur where people live on unleavened bread made from highly extracted wheat flour and no meat or yeast products in the diet. Zinc is a cofactor for about 20 enzymes, e.g. alcohol dehydrogenase that breaks down ethanol and carboxypeptidase that catalyses the hydrolysis of proteins in the small intestine. The recommended daily allowance, RDA, is 15 mg for males and 12 mg for females.
Atomic number: 30 | Relative atomic mass: 65.39 | Density: 7.14 g cm^-3 | m.p.: 420^oC | b.p.: 907^oC | Specific heat capacity: 385 J kg^-1 K^-1
Describe each example.
1. Note the state of matter at room temperature, solid, liquid or gas.
2. Note whether the solid has a shiny surface or has a lustre when the surface is clean.
3. Note whether the metal can be bent or twisted with pliers, or whether it fractures.
4. Note whether the element conducts electricity when held between two alligator clips as electrical contacts.
5. Put a piece of the element on a combustion spoon and set it alight with a burner flame. Examine the burning element.
6. Shake the products of the combustion in a test-tube containing water. Test the solution with moist litmus paper.

Zirconium, Zr, grey-white solid, transition element, in zircon ZrSiO₄, zirconium wire used in photography flash bulbs, camera flash cubes, e.g. "Magicube", nuclear reactor neutron absorber

7.2.3 Silicon compounds, glass
See also 5.14: Quartz | See also 9.3: Egg preservation
1. Silicon is called a metalloid because it has physical properties of metals and chemical properties of non-metals. Silicon is a semiconductor. Silicon does not exist free in nature, but occurs mainly as silicon (IV) oxide (SiO₂) in silica sand, sandstone, clay, quartz and opal. Silicates occur in most rocks and glass. Portland cement is a mixture of calcium and aluminium silicates. In the silicone oils and greases, the silicon atoms form polymers containing a chain of silicon and oxygen atoms with carbon and hydrogen atoms attached to the chain. Silicones repel water. Silica glass is more like a "super cooled liquid" than a crystal because, unlike crystalline substances, it does not have a sharp melting point. However, some chemists say that glass is a disordered solid not a supercooled liquid.
Sodium carbonate is heated with sand to produce sodium silicate, the water-soluble waterglass used as an inorganic builder in detergents, for preserving eggs and for fireproofing materials.
Na₂CO₃(s) + SiO₂(s) --> Na₂SiO₃ + CO₂(g)
sodium carbonate + silicon dioxide --> sodium silicate (waterglass) + carbon dioxide
2. When sodium oxide Na₂O 15%, silicon dioxide SiO₂ 70%, and calcium oxide CaO 10% and other oxides are heated together with temperatures up to 1000^oC, insoluble silica glass forms in which all the crystalline order of the added minerals has been lost. It is also called silica glass or soda lime-silica glass or crown glass. In silica glass, each silicon atom is surrounded by four oxygen atoms as a tetrahedron and each of these is linked to other tetrahedra. When ionic oxides are added in the glass- making melt they get between the Si-O-Si bridges and weaken it. as shown in the transition glass temperatures: silica glass Tg = about 1200^oC, Pyrex Tg = 550^oC, window glass Tg = 550^oC. The glass in high quality wine glasses, called lead crystal, contains lead which gives the glass a ringing sound, higher refractive index and more brilliance. Cobalt gives blue glass, chromium gives green glass, and copper gives red or blue green glass. Boron oxide, B₂O₃, gives shockproof borosilicate glass, "Pyrex", that is resistant to all chemicals except hydrofluoric acid, HF. Flint glass, lead glass, has no colour unlike crown glass that has a slight green to yellow colour due to iron impurity. The 2 distinct constituents of glass are as follows: 1. The network former, i.e. the non-metal as an oxide is usually silicon, but it can be boron, aluminium, or phosphorus. 2. The network modifiers, e.g. sodium, potassium, calcium, and magnesium. Glass may crystallize over a period of many years and then become more brittle, but some glass has remained uncrystallized for 4000 years in Egypt. Sodium sesquicarbonate Na₂CO₃.NaHCO₃.H₂O occurs as a mineral.
1. Collect different drinking glasses, including wine glasses, of roughly the same size. Strike each glass and listen to the ring to identify the existence of modifiers in the glass.

7.2.4 Prepare silicon glass
Pick up sodium carbonate in a nichrome wire loop. Dip the loop into powdered silica and heat over a burner to form a transparent bead of glass.

7.2.4.1 Prepare silicon glass in a furnace
Prepare glass in a crucible by heating a glass mixture in a furnace or over a Meker burner with a hot wide flame. Glass mixture A: 1. 17 g clean sand 2. 4.4 g sodium carbonate 3. 5. 2 g disodium tetraborate (III)-10-water (borax). Glass mixture B: 6 g clean sand, 2 g sodium carbonate, 1 g calcium carbonate

7.2.4.2 Prepare coloured glass
1. Add a metal oxide to the glass mixture.
2. Heat the end of a glass rod to red heat. Dip it into a powdered metallic oxide and heat until the oxide fuses into the glass. Use different salts to colour glass: 1. amethyst use manganese (IV) oxide 2. green use black copper (II) oxide 3. ruby use red copper (I) oxide 4. white use tin oxide.
3. Mix a little silica with an equal quantity of calcium carbonate and about twice as much anhydrous sodium carbonate. Grind them to a powder in a mortar with a pestle. Make a loop in a platinum wire. Heat the loop and place it in the mixture. Reheat the wire with the adhering mixture until the mixture fuses. Cool it. What does the bead look like? Hit it with a hammer. Is it brittle? Does it dissolve in water?

7.2.5 Prepare a silicate garden
1. Mix one part of sodium silicate (IV) (Na₂SiO₃) with four parts of water to make water glass. Gently add crystals of salts to the solution without mixing to make chemical "flowers" grow: 1. Chlorides: Co, Fe, Cu, Ni and Pb 2. Sulfates: Al, Fe, Cu, and Ni 3. Nitrates: Co, Fe, Cu and Ni.
2. Put sand 1 cm deep in a 500 mL jar. Prepare a 1:1 mixture of sodium silicate and water (waterglass) and pour it onto the sand to almost fill the jar. Leave the jar to stand undisturbed for a day. Drop in crystals of metal salts, e.g. metal hydroxides, iron sulfate, copper (II) sulfate, alum, Epsom salts. Observe crystals forming "shoots". Some shoos are directed up by small bubbles. The metal hydroxide skin formed around the crystal is permeable only to water and not the salt. The water diffuses in to balance the concentrations each side of the skin until the skin bursts the skin then forms again further from the crystal.

7.2.6 Silly putty, silicone, bouncing putty (Dow Corning 3179 dilatant compound) "Tricky Putty"
See 3.4.04: Super ball | 3.4.11 Make a slime ball
The silicone polymer in silly putty, polyborosiloxane, have covalent bonds within the molecules, but hydrogen bonds between the molecules. The hydrogen bonds are easily broken. A silicone is chains of OH- Si-O-Si-O-Si-OH with two methyl groups, CH₃ on each of the Si atoms. However, in "Silly putty", boron atoms that can cross link weakly with oxygen atoms in other chains replace some of the silicon atoms.
1. Apply small amounts of stress are slowly to the putty only a few bonds are broken and the putty "flows" and stretches a great distance. Apply larger amounts of stress quickly, many hydrogen bonds are broken, and the putty breaks or tears. Roll it into a ball that you can bounce. Press it onto a pencil drawing so that it lifts off the pencil marks so you can see the drawing on the surface of the silly putty.
2. Mix 55% Elmer's glue solution and 16% sodium borate in a 4:1 ratio. Ingredients: 65% dimethyl siloxane, hydroxy terminated polymers with boric acid, 17% silica, quartz crystalline, 9% thixotrol ST, 4% polydimethylsiloxane, 1% decamethyl cyclopentasiloxane, 1% glycerine, 1% titanium dioxide

7.3.0 Metals and non-metals
1. Metals are elements that form positive ions. Metals may also form complex ions with a non-metal, e.g. chromate ion, CrO₄^2-.
2. Non-metals are elements that form negative ions. Non-metals may also combine with other non-metals, e.g. NO₃^-. The first 105 elements in the periodic table contain 84 metals and 21 non-metals (or metalloids). Metalloids have both metal and non-metal properties, e.g. B, Si, As, Te and Ge, Sb, Bi. 3. Transition elements include, first series - Cr, Mn, Fe, Co, Ni, Cu and perhaps Zn, second series - Mo and Ag, and third series - Pt, Au and perhaps Hg. Transition elements are hard, dense metals with high melting points and boiling points, form coloured ions and compounds and have more than one valence (oxidation number), e.g. copper (Cu¹⁺and Cu²⁺) and chromium (Cr²⁺ and Cr³⁺). The ion Cr²⁺is a strong reducing agent and forms blue salts in solution. Cr³⁺salts are green in solution. CrO₄^2- salts are yellow and Cr₂O₇^2- is a strong oxidizing agent with orange salts, e.g. K₂Cr₂O₇. Transition metals form complex ions and often have catalytic activity, e.g. Fe in the complex haemoglobin molecule, and Fe in the manufacture of ammonia
Examine common metals and non-metals, e.g. aluminium foil, calcium granules, carbon as charcoal, copper foil or wire, iodine crystals, lead foil or lead shot, magnesium ribbon, nickel sheets or plating, red phosphorus, potassium (in liquid paraffin) sodium (in liquid paraffin) sulfur powder or "flowers", tin foil or tin-plating, zinc foil or granulated zinc. List the metallic or non-metallic properties you can observe.

7.3.1 Properties of metals
1. Are usually opaque, hard solids with high density and have shiny, silvery lustre, when cut or scratched.
2. Have strong metallic bonds that make them malleable, ductile and easy to bend. They have high melting points, boiling points and density. You can hammer metals into new shapes because they are malleable. Metals can be drawn into a wire because they are ductile.
3. Have freely moving electrons and thus are good conductors of electricity and heat. 4. May form oxides that turn moist litmus blue. For example, calcium oxide dissolves in water to form the alkali calcium hydroxide. Some metals form a surface layer of oxide that prevents more oxidation, e.g. Al, Cr, Mg and Zn. 5. Reactive metals have stable compounds. Stable metals have compounds that easily decompose.

7.3.2 Properties of non-metals
1. May be monatomic, e.g. Ne, He, polyatomic, e.g. F₂, white phosphorus P, or network solids, e.g. diamond, red phosphorus. 2. May be solids, liquids or gases. 3. Non-metals that are solids, they are usually dull and brittle, and have low density. 4. Are usually poor conductors of electricity and heat. 5. Usually form oxides that turn moist litmus red. For example, carbon dioxide dissolves in water to form the weak acid, carbonic acid (H₂CO₃). 6. Exceptions to the properties of non-metals include graphite carbon that conducts electricity, silicon that has the physical properties of a metal.

7.4.0 Melting point of solids
See also 3.2: Melting point of naphthalene
The melting point, m.p., is the temperature at which a solid starts to liquefy. The melting point and freezing point of a pure substance are the same temperature. Melting is the "solid to liquid" type of phase change. Other phase changes include change from liquid to solid - freezing, solid to gas - sublimation, liquid to gas - evaporation, gas to liquid - condensation. Pure substances melt at constant temperature. Impurities lower the melting point. Impure substances, e.g. alloys, melt over a range of temperature. The melting point graph for a pure substance is horizontal as the solid melts. The melting point graph for an impure substance has an inclined line as the solid melts. Melting points and melting behaviours can be used to identify a substance and decide if it is pure. Melting is also called fusion and the melting point can be called the fusing point.

7.4.1 Melting point and cooling curve of stearic acid
See diagram 7.4.1
Stearic acid (octadecanoic acid) is a safer alternative to using naphthalene for the following experiments. Stearic acid melts at 69^oC.
1. Put 2 cm of the acid in a test-tube with a thermometer. Put the test-tube in a beaker containing water. Heat the beaker tube gently until the acid just melts. Note the time and remove the test-tube from the beaker. Note the temperature every 30 seconds as the substance cools. The acid solidifies again at the same temperature. Heat the test-tube again to free thermometer. Draw the cooling curve of the acid. Plot temperature on the vertical axis and time on the horizontal axis. When the acid is changing from liquid to solid, the curve is horizontal.
2. A more accurate method to measure melting points. Heat one end of a 10 cm capillary tube to seal it. Put octadecanoic acid in the capillary tube. Attach the capillary tube to a thermometer with a rubber band. Put thermometer in a beaker of water. Heat the water while stirring with thermometer. Record the temperature at which the acid melts. Leave the capillary tube to cool. Record the temperature at which the acid solidifies.

7.4.2 Melting point of different substances
Repeat the above experiments with different substances, e.g. candle wax, m.p. = 45^oC - 65^oC, urea, m.p. = 133^oC and hexadecan-1-ol (cetyl alcohol) [CH₃(CH₂)₁₄CH₂OH]. Cetyl alcohol forms the ester cetyl palmitate (C₁₅H₃₁.COO.C₁₆H₃₃), m.p. 42^oC to 47^oC, that is the main component of spermaceti, the white wax found in the head of the sperm whale. The wax was used to make cosmetics and ointments but nowadays we use other chemicals as substitutes to "Save the Whales"!

7.4.3 Melting point of ice and freezing point of water
For pure substances, the melting point, m.p. = freezing point, f.p. For water, m.p. and f.p. = 0^oC. However, freezing mixtures of ice and salt have temperatures below 0^oC. The freezing point of water in motor car radiators is lowered by adding antifreeze solutions, e.g. ethylene glycol (ethane-1,2-diol) that does not freeze above -20.6^oC. Freezing points can be used for detecting water in milk or other adulteration.

7.4.3.1 Temperature at which ice melts
Half fill a beaker with tap water. Note the temperature of the water after five minutes. Put pieces of ice in the water. Note the temperature every five minutes. The temperature drops to zero and remains at zero while ice remains floating in the water. Wait until all the ice melts. The temperature rises again until it reaches room temperature.

7.4.3.2 Temperature at which an ice and salt mixture freezes
See also 19.1.16: Table salt and rock salt
At 0°C, the molecules in pure water form strong bonds to form ice. If sodium and chlorine are between water molecules, it is harder for these bonds to form. Seawater contains about 35 grams of salt per litre and freezes at -1.8°C. Mix crushed ice with salt. Note the temperature after five minutes. The temperature of the ice and salt mixture is below zero.

7.4.3.3 Lift an ice cube with a match stick
Float an ice cube in water. Put a match stick on the ice. Sprinkle a very small amount of salt on to the ice at each side of the match stick. After one minute, lift the ice cube by lifting the match stick. Salt water has a lower melting point or freezing point than pure water. The salt sprinkled on the ice dissolves in the ice lowering its freezing point. The ice around the matchstick melts and the matchstick floats in it. Some of the water may fall off the ice cube but also the salt keeps dissolving in the ice so lowering the concentration of salt around the matchstick and raising the freezing point back towards 0^oC, when it freezes again trapping the matchstick in the ice. The layer of water between the match stick and the ice cube is now frozen so the match stick sticks to the ice.

7.5.0 Boiling point of liquids
See also 3.8: Pressure affects the boiling point
When bubbles of vapour form in a boiling liquid, the vapour pressure of the gas in the bubbles is greater than atmospheric pressure. When the bonds between liquid molecules are strong, only a few molecules can break the bonds to become a vapour. The vapour pressure of that substance is low and the boiling point is high. The boiling point of a liquid is the temperature at which the liquid boils when exposed to the atmosphere. So the boiling point of a liquid is the temperature at which the vapour pressure of the liquid equals the pressure of the atmosphere, 1 atmosphere. At 100^oC, the vapour pressure of pure water is one atmosphere (101.325 KPa, kNm^-2). The boiling point varies with pressure. Boiling chips (anti-bumping granules) are added to chemical reactions to keep the bubbles small and aid steady boiling.

7.5.0.1 Elevation of boiling point, ebullioscopic constant, k_B,
The boiling point of a liquid is raised if substances are dissolved in it. The elevation is proportional to the number of particles or molecules or ions dissolved in the liquid. The elevation in 0C = the molal concentration of the solute in the liquid X a constant. The value of the constant depends on the solvent and is called the ebullioscopic constant, k_B, for that solvent. So if k_B is known, the molecular weight of the solute can be calculated.

7.5.3 Boiling point of a mixture of two liquids, water and alcohol
Use the above method to compare the boiling points of mixtures of water and methylated spirit in different proportions: BE CAREFUL! ALCOHOL IS HIGHLY FLAMMABLE!

Liquids	Solution 1	Solution 2	Solution 3
1. Water	25%	50%	75%
2. methylated spirit	75%	50%	25%

7.5.4 Boiling point of inflammable liquids, ethanol
See also 3.6.0: Boiling point of inflammable liquids
The boiling point of ethanol is 78^oC. Heat water in a kettle. Turn off the gas or extinguish the flame. Pour 2 cm of methylated spirit into a test-tube. Put the test-tube in a beaker. Put a thermometer into the methylated spirit deep enough to cover the bulb. Pour hot water into the beaker so that the water level is higher than the level in the test-tube. Stir gently with thermometer. When boiling starts, record the temperature.

7.5.4.1 Boiling point of inflammable liquids, acetone
Repeat the experiment with propanone (acetone). BE CAREFUL! HIGHLY FLAMMABLE! THE FLASH POINT IS -20^oC! Boil the propanone (acetone) by placing the test-tube in hot water. Do not allow flames in the room. The boiling range of 98% propanone (acetone) is 55.5^oC to 56.5^oC. Nail polish remover formerly contained propanone (acetone) but not in modern manufacture.

7.2.2.3 Mercury and dental amalgam
Statement approved by the 107th session of the National Health and Medical Research Council, Sydney, Australia. "An amalgam is a metal alloy where one component is mercury. Dental amalgam is prepared by mixing silver-tin powder with liquid mercury. The resulting mix then hardens to form a stable solid as mercury forms compounds with the silver and tin.
Dental amalgam is an excellent material for repairing decayed teeth, and for many applications it is still preferable to the alternatives. Amalgam is stronger, and therefore lasts longer than the composite resins (plastics) or synthetic cements. Amalgam is chemically much less damaging to the local tissues than these materials, and it keeps bacteria out extremely well.
As some forms of mercury are toxic, the safety of dental amalgam for dental patients, and for dental care workers, has been thoroughly examined.
The vapour of pure mercury does pose a health hazard if it is inhaled either in very high concentrations for a short time or in moderate concentration for months or years. Mercury vapour crosses the lungs into the blood quite readily, and then moves from the blood into other tissues. This is a possible risk to dental health workers if mercury hygiene is not practised and their workplace becomes contaminated; but it is not a risk to patients receiving amalgam fillings because of them, the exposure to vapour is extremely low and occasional inorganic mercury compounds, such as those formed when dental amalgam is mixed, are poorly absorbed is readily excreted by the kidneys. Mercury compounds are present in many foods in low concentrations and cause no harm.
The health and well being of dental patients who have received amalgam fillings has been studied thoroughly, and the following findings were arrived at:
1. There Is no difference in the incidence of any disease or in the length of life between people who have amalgam fillings and those who do not.
2. People who have amalgam fillings and then have them removed do not experience an improvement in health.
3. People who have no teeth, and therefore no amalgam fillings, are not healthier than people with amalgam filled teeth.
4. Rarely, allergy to amalgam occurs as a local rash on the cheek or tongue next to a filling. For patients with such allergy, material other than amalgam should be used.
Dentists and dental researchers are interested In finding ways to repair teeth without using dental amalgam, because of the industrial risks which amalgam poses to dental care personnel. Patients sometimes ask for fillings made with materials other than amalgam, because of the concerns about safety and appearance. Some alternative materials can be used, but they are often less satisfactory than amalgam from the point of the patient's long term health and well being.
Dental amalgam is still the material of choice for the repair for most medium sized areas of tooth decay in premolar and molar teeth. The goal of the National Health and Medical Research Council is to advise the Australian community on the achievement and maintenance of the highest practicable standards of the individual and public health and to foster research in the interest of improving those standards." [Editorial comment: The research is not very clear and confusing. Properly and accurately mixed amalgams are probably sufficiently stable to not cause any problems over a lifetime. Inaccurately mixed amalgams may leak (leach) enough mercury to cause some minor effects after a long time in a small number of genetically pre-disposed individuals. Another issue for the dental professions was what else to use? It has only been in the past few years that useful alternatives have been available.
About half the current dentists use the alternatives. Previously students studied the interesting chemistry of mercury salts. To my knowledge, there has not been one health problem related to mercury in these thousands of students.]