Gold Nuggets in 2019

Between 1850 and 1900, the city of Bendigo in Victoria, Australia, was the centre of a Gold Rush. Central Deborah Gold Mine, the last commercial gold mine to operate in Bendigo, re-opened as a tourist attraction in 1986.
Gold can still be found in the Bendigo area.
On Mothers' Day 2019, a family out walking Lucky their dog on the outskirts of Bendigo walked onto a gold nugget. They took it along to the local IGA supermarket to weigh it. The gold nugget weighed 624 grams (about 20 ounces).
Today, the price of gold in Australia is listed as $65.76 per gram. So, if pure, the gold in this nugget would be worth 624 × $65.76 ≈ $41,000.
How big would this gold nugget be?
We know the mass of the nugget is 624 grams.
We can look up the density of gold in tables, ρ = 19.3 g cm^-3
Since density = mass (g) ÷ volume (cm³)
19.3 = 624 ÷ volume (cm³)
volume (cm³) = 624 g ÷ 19.3 g cm^-3 = 32.3 cm³
Which could be represented by a cube approximately 3.2 cm × 3.2 cm × 3.2 cm
Not very big at all is it!

Ballarat, another Victorian Gold Rush town and site of the historic "Eureka Stockade", was also the place where another spectacular gold nugget was found in June 2019 (and reported nationally in July 2019). This gold nugget weighed about 2 kilograms, or 2,000 grams.
At today's prices, it would have a value of about 2,000 × $65.76 ≈ $130,000
And how big would this nugget be?
density = mass (g) ÷ volume (cm³) volume (cm³)
density = mass (g) ÷ density (g cm^-3) = 2,000 g ÷ 19.3 g cm^-3 = 103.6 cm³
The dimensions of a cube with this volume would be about 4.7 cm × 4.7 cm × 4.7 cm
Which would fit nicely into the palm of your hand as shown in the photograph below

Further Reading:
Density Calculations

Suggested Study Questions:

1.  The density of gold is 19.3 g cm^-3. Calculate the mass of
   • 1 cm³ of gold 
   • 10 cm³ of gold 
   • 1 m³ of gold
2.  The density of gold is 19.3 g cm^-3. Calculate the volume of
   • 1 g of gold
   • 10 g of gold
   • 1 kg of gold 
3.  The density of gold is 19.3 g cm^-3. Calculate the dimensions of a cube of gold which has a mass of
   • 5 g
   • 500 g
   • 5 kg
4. The density of gold is 19.3 g cm^-3. Calculate the diameter of a sphere of gold which has a mass of
   • 2 g
   • 200 g
   • 2 kg
5. A credit card has the approximate dimensions 65 mm × 55 mm × 1 mm. Calculate:
   • volume of the credit card in cm³
   • mass of a gold credit card
   • value of a gold credit card if the cost of gold is $65 per gram
   • Why aren't "gold" credit cards really made out of gold?
6. Gold is one of the few metals that is found in nature as the "native" element (that is, it is found as the element and not in compounds). Explain why gold can be found in nuggets.
7. Name some other metals that can also be found in their native state (that is, found as the element and not as compounds). Explain why these metals can be found in their native state. 
8. Name a metal that is not found on Earth in its native state, and explain why it is not found in nature as the uncombined element.

Titanium Gold Alloy

Titanium is the metal used to replace hip and knee joints because it is strong, resistant to wear, and, is nontoxic.

Before titanium was used to replace hips and knees, stainless steel was used.
The density of stainless steel used to make replacement hips and knees is about 7.8 g cm³. The density of titanium metal is 4.506 g cm³, about half the density of stainless steel. This means that a replacement joint made out of titanium will weigh less than the same replacement joint made out of stainless steel.
Titanium is also strong. The strength of the material used to replace hip and knee joints is important because you do not want your new joint to bend or break or under strain.

Titanium has a melting point of 1670°C and a boiling point of 3287°C, which means it remains solid over the range of temperatures humans are exposed to. This is important because you want your new hip or knee replacement to remain a solid!
Naturally occurring titanium is made up of a number of isotopes, all of which are stable so they do not undergo nuclear decay. This is important because it means that there is no loss of titanium mass due to radioactive decay, and there is no fear of damage to cells from the emission of radiation.

isotope	atomic mass	abundance
46Ti	45.953	8.25
47Ti	46.952	7.44
48Ti	47.948	73.72
49Ti	48.948	5.41
50Ti	49.945	5.18

Titanium metal will react with water, halogens and dilute hydrochloric acid, but only if the temperature is elevated well above body temperature. Similarly, titanium metal will react with oxygen in a combustion reaction at elevated temperatures. Titanium metal does not appear to react with bases at all. Therefore, titanium is unlikely to react with substances found in the human body.

Researchers at Rice University have found that alloying titanium with gold can produce an even better material to use for replacement hips and knees. Mixing titanium and gold in the ratio of 3:1 at high temperature produces an alloy that is 3 times harder than steel and 4 times harder than the pure titanium commonly in use for hip and knee replacements. The atoms of titanium and gold in this alloy are packed in a cubic arrangement, an arrangement that is usually associated hardness. The structure of this alloy is shown below:

This titanium gold alloy has been found to be even more biocompatible that pure titanium.
The researchers intend to undertake further studies to investigate whether using chemical dopants might improve the alloy's hardness even further.

Reference:
Rice University. "Titanium and gold equals new gold standard for artificial joints: Titanium-gold alloy that is 4 times harder than most steels." ScienceDaily. ScienceDaily, 20 July 2016. 

Further Reading
Metals and Non-metals 
Density
Isotopes
Relative Atomic Mass
Alloys

Suggested Study Questions

1. Titanium and gold are both metallic metallic elements.
   • What are the physical properties common to most metallic elements?
   • What are the chemical properties common to most metallic elements?
2. Draw up a table of the physical properties of titanium.
3. A typical knee replacement made out of titanium has a mass of 560 g.
   • Calculate the volume of the titanium knee replacement.
   • Calculate the mass of the same knee replacement if it were made out of stainless steel
4. Define the term isotope.
5. Determine the number of protons in the nucleus of an atom of each of the isotopes of titanium listed in the article above.
6. Determine the number of neutrons in the nucleus of an atom of each of the isotopes of titanium lists in the article above.
7. Which is the most abundant isotope of titanium? Explain your answer.
8. Use the data in the article above to calculate the relative atomic mass of naturally occurring titanium.
9. Given the atomic radius of titanium is  176 pm (1.76 x 10^-10 m) and the atomic radius of gold is 174 pm (1.74 x 10^-10 m), do you think the alloy of titanium and gold discussed in the article above is an interstitial alloy or a substitutional alloy? Explain your answer.
10. Consider the structure of the titanium gold alloy shown in the diagram in the article above.
    • The blue balls represent which atoms of which element?
    • The red balls represent which atoms of which element?

Alloys

What is an alloy?
What kinds of alloys are there?
Are steel, brass and bronze alloys?
How do the properties of an alloy differ from the properties of the elements making up the alloy?

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Queensland Nickel

In January 2016, Queensland Nickel went into voluntary administration, that is, the company was having difficulty meeting its financial obligations. The story's big news in Australia because Queensland Nickel is 100% owned by one of Australia's most colourful characters, Clive Palmer. Palmer is reputed to be worth about $1 billion and has business interests in minerals and property, including the Palmer Coolum Resort which houses animatronic dinosaurs on its golf course which has been rather controversial. Palmer has been involved in politics since the 1970s firstly as a member of the National Party, then of the Liberal-National Party, then in 2013 he formed his own political party, the Palmer United Party or PUP. And yes, Australians did actually vote PUPs into parliament, including Palmer himself who won the seat of Fairfax  (located in Queensland on the Sunshine Coast, just north of Brisbane, created in 1984 and named after the founder of the Country Women's Association, Ruth Fairfax). But enough of the Australian political history lesson, lets get back to the Queensland Nickel problem.

Nickel is an important metal in our society. More than 80% of the nickel produced worldwide goes into alloys. When alloyed with other metals, nickel imparts toughness, strength and resistance to corrosion as well as various magnetic, electrical and heat resistant properties.  About 65% of all nickel produced is consumed making stainless steel which is used to make cars as well as many other consumer and commercial products, including the kitchen sink!

The worlds largest producers of nickel are the Philippines, Indonesia, Russia, Canada and Australia.

Australia exports about $4 billion of nickel per year, making it an important export commodity. Australia has about 17 million tonnes of nickel reserves. Western Australia has about 96% of these reserves, Queensland about 3.8% and Tasmania about 0.2%. At the current rate of production, these reserves should last about 70 years.

In 1974, nickel mining began at Greenvale, 220 km northwest of Townsville. This nickel ore was transported by train to the Palmer owned refinery at Yabulu,  about 25 km north of Townsville. The Greenvale mine closed in 1992, however, commencing in 1986, nickel ore was shipped from New Caledonia, the Philippines and Indonesia to Townsville then transported by rail to the refinery. The refinery produces about 32,000 tonnes of nickel and 19,000 tonnes of cobalt per year.

The Yabulu plant carries out three process:

1. ore processing
2. mixed nickel-cobalt hydroxide processing
3. nickel and cobalt refining

Nickel ore contains nickel oxide, NiO. Ore processing involves blending, drying, and milling to fine powders.
The fine ore powder is then mixed with fuel oil reductant (C) and reduction roasted at  750°C under reducing conditions achieved by the partial combustion of fuel oil to carbon monoxide and the addition of hydrogen gas. We can represent the reduction of NiO by C as:
                750°C 
NiO + C  --->    Ni + CO

 The reduced ore, containing nickel and cobalt, is cooled and then leached in aqueous ammonium carbonate liquor at atmospheric pressure to selectively dissolve nickel and cobalt. This product liquor contains about 12 g L^-1 Ni and 0.6 g L^-1 Co, while the residual solids in the tailings contain carbonates of manganese and magnesium. The solution containing dissolved nickel and cobalt is separated from the solids and the excess ammonia removed. Patented ammoniacal extraction technology selectively extracts nickel which is then precipitated as basic nickel carbonate,  Ni₄CO₃(OH)₆(H₂O)₄

4 Ni²⁺ + CO₃²⁻ + 6 OH⁻ + 4 H₂O --->  Ni₄CO₃(OH)₆(H₂O)₄

This basic nickel carbonate is dewatered and the product can then be calcined in a rotary kiln under reducing conditions to produce nickel. Calcination drives off carbon dioxide and water to produce nickel calcine, approximately 60% nickel and 40% nickel oxide. After further reduction of nickel calcine using hydrogen, a metal is produced that is 99% nickel:
NiO + H₂  --->  Ni + H₂O
The Palmer-owned Queensland Nickel refinery is still operational, and there is no shortage of nickel ore to refine, so why is the business in danger of closing? 
According to Palmer, the financial difficulties Queensland Nickel find itself in result from a fall in nickel prices  and the Queensland Government's refusal to guarantee a $35 million loan. Certainly nickel prices have been in a general decline, In 2007, the price of nickel peaked at about $50,000 per tonne, in 2008 the price of nickel was about $20,000 per tonne, now it is worth less than half that much, probably because the supply of nickel is simply greater than demand for it. So, why is this story getting so much media attention? Is it because 237 workers at the refinery were sacked? Maybe, but the biggest issue in the media surrounds the purported donations made by the Palmer-owned Queensland Nickel to the Palmer-founded and led political party, PUP, to the tune of $15.2 million donated in 2013-14 financial year and another $5.9 million in 2014-15, which could probably have paid 237 workers for quite a few more months.

References:
http://www.abc.net.au/news/2016-01-16/qld-nickel-donated-nearly-$290k-just-2-weeks-before-sackings/7093096
http://www.smh.com.au/federal-politics/political-news/clive-palmers-political-career-on-the-brink-after-business-meltdown-20160118-gm8a0q.html
http://www.smh.com.au/business/mining-and-resources/clive-palmers-queensland-nickel-in-voluntary-administration-20160117-gm7x8r.html

Further Reading:
Metal Extraction Concepts: http://www.ausetute.com.au/metalextract.html
Carbon Reduction Method: http://www.ausetute.com.au/creduction.html
Redox Concepts: http://www.ausetute.com.au/redox.html
Oxidation States (Numbers): http://www.ausetute.com.au/oxistate.html
Percentage Composition: http://www.ausetute.com.au/percentc.html

Suggested Study Questions:

1. What is the oxidation state (oxidation number) of nickel in each of the following:
   • Ni
   • NiO
   • Ni₄CO₃(OH)₆(H₂O)₄


2. In the reaction:      NiO + C  --->   Ni + CO
   • Which species is oxidised?
   • Which species is reduced?
   • Which species is the oxidant?
   • Which species is the reductant?
   • Which species is the reducing agent?
   • Which species is the oxidising agent?
   • Is this a redox reaction? Explain your answer.
3. Nickel oxide, NiO, can also react with hydrogen gas in a similar reaction to the one above in order to produce solid nickel, Ni, and water.
   • Write a balanced chemical equation for this reaction.
   • Which species is oxidised?
   • Which species is reduced?
   • Which species is the oxidant?
   • Which species is the reductant?
   • Which species is the reducing agent?
   • Which species is the oxidising agent?
   • Is this a redox reaction? Explain your answer.
4. Nickel oxide, NiO, can also react with carbon monoxide gas in a similar reaction to the one above in order to produce solid nickel, Ni, and carbon dioxide.
   • Write a balanced chemical equation for this reaction.
   • Which species is oxidised?
   • Which species is reduced?
   • Which species is the oxidant?
   • Which species is the reductant?
   • Which species is the reducing agent?
   • Which species is the oxidising agent?
   • Is this a redox reaction? Explain your answer.
5. The carbon reduction method can also be used to extract zinc metal from zinc oxide.
   • Write a balanced chemical equation for this reaction.
   • Which species is oxidised?
   • Which species is reduced?
   • Which species is the oxidant?
   • Which species is the reductant?
   • Which species is the reducing agent?
   • Which species is the oxidising agent?
   • Is this a redox reaction? Explain your answer.
6. Name one other metal that could be extracted from its oxide using the carbon reduction method and explain why this method could be used for this metal.
7. Name a metal that cannot be extracted from its oxide using the carbon reduction method and explain why this method would not work.
8. Native nickel, that is, nickel found as the element and not in compounds, is rarely found in nature on Earth. Explain why.
9. When native nickel is found on Earth, it occurs as an alloy with iron inside large meteorites. Explain why elemental nickel can be found inside these meteorites that landed on Earth.
10. Calcination is the process of heating a compound to drive off carbon dioxide. Nickel(II) carbonate can be calcined to produce nickel(II) oxide. Write a balanced chemical equation for this reaction.
11. The most common application of  calcination is to convert calcium carbonate in limestone into calcium oxide (called lime) in the production of cement. Write a balanced chemical equation for the calcination of calcium carbonate.
12. Assume a nickel ore is composed of 2% NiO, what mass of ore must be processed annually to produce 32,000 tonnes of nickel metal?
13. In 2014 the price of nickel was an average of about $16,000 per tonne, while in 2015 its price had fallen to about $10,000 per tonne. Assuming Queensland Nickel maintained a steady production rate of 32,000 tonnes per year, what was the change in Queensland Nickel's revenue from 2014 to 2015.
14. What do you think contributed most to the financial difficulties of Queensland Nickel, falling nickel prices or millions of dollars in political donations? Justify your answer.

Ancient Elements

Only about a dozen elements were known to the people living in ancient civilizations.

• Copper beads dating from about 6000 B.C. have been found in Turkey.

• A lead statuette found in an Egyptian temple dates from around 3800 B.C. and golden artefacts have also been found in ancient Egyptian tombs.

• Silver was used by the ancient Greeks and Romans to prevent infection, and was used as an early form of currency.

• There is evidence of the systematic production of iron in Turkey around 2000 B.C. for use in tools and weapons.

• Carbon, in the form of diamonds, was also known in the Ancient world, but, carbon in the form of charcoal was far more important to these early people because it could be used in the production of copper, tin, and therefore bronze (an alloy of copper and tin).

• Sulfur was also known to the Ancient Egyptians and Greeks, who used it as a medicine.

• The ancient Chinese, Indians and Egyptians also knew about mercury, using it in ointments and cosmetics.

• Before 1000 B.C., Indians were extracting zinc from its ores. Ornaments containing 80% or more of zinc have been found.

• During the Bronze Age (an earlier period than the Iron Age), arsenic was included in bronze to make the alloy harder. Ancient people understood that they could produce arsenic by heating certain substances (which we would now call arsenic sulfides and oxides).

• Antimony was used in cosmetics in the Ancient world, notably by the Egyptians who used it around their eyes (known as kohl).

• Chromium has been found in ancient Chinese artifacts. The weapons the Chinese Terracotta Army carry are coated in chromium oxide and date from around the 3rd century B.C.

In fact, these were really the only elements known  until the 17th century A.D.
Today we know of over a 100 elements.
Chemistry has come a long way in the last few hundred years!

Further Reading:
History of the Elements
Metal Extraction Concepts
Periodic Table
Metals and Non-metals
Pure Substances and Mixtures

Suggested Study Questions:

1.  Find each of the elements mentioned above on the Periodic Table.
2. Draw up a table of the name and chemical symbol for each of the elements mentioned above.
3. Draw up a table classifying each of these elements as metals, non-metals or semi-metals (metalloids).
4. Name a mixture mentioned in the article above.
5. Name a compound mentioned in the article above.
6. There are only 3 metallic elements that are not a "silvery" colour. One of these is cesium (or caesium), but if the sample of cesium is very pure it loses its golden colour. Name the other two non-silvery metallic elements.
7. Explain why you often find weapons like swords made of iron, but you never find functional weapons made of gold.
8. Explain why you find ornamental weapons made out of gold, but rarely out of zinc.
9. Ancient people could have produced mercury by heating cinnabar (mercury(II) sulfide). The cinnabar decomposes, producing liquid mercury and sulfur. Write a word equation for the decomposition of cinnabar.

New Metallurgy Resources

AUS-e-TUTE has just added new metallurgy resources.
Tutorials, game, test and drills on the chemistry of deciding how to extract a metal from its ore.
Visit http://www.ausetute.com.au

New Metallurgy Resources

AUS-e-TUTE has just added new tutorials, games, tests, and drills to its metallurgy section.
The new sections include:
Metal + Water Reactions
Metal + Non-oxidizing Acid Reactions
Metal + Oxygen Gas Reactions
Activity Series (metals)

Sunken Silver

In 1941, the British cargo ship SS Gairsoppa was carrying 7,000 tonnes of cargo from Calcutta. The cargo included pig iron, tea and about 200 tonnes of silver. A German U-boat torpedo sunk the SS Gairsoppa as it made its way to Ireland in stormy weather. While only one person out of the 85 crew members on board survived the attack, it is believed its cargo of silver is still at the bottom of the ocean.

Silver is unique because it has the highest electrical and thermal conductivity of any known element. It is a soft metal, just a little harder than gold, and is extremely ductile and malleable meaning it can be bent or beaten into almost any shape.
There were many uses for silver during World War II :

• many electrical connectors and switches were silver plated
• silver bus bars were needed for the new aluminum plants (aluminium aircraft)
• silver replaced large amounts of tin in solder
• silver was used in the reflectors in lights

There are a number of silver alloys:

• Fine silver contains 99.9% by mass silver
• Britannia silver contains 95.84% by mass silver with copper making up the remaining mass
  
• Sterling silver contains 92.5% by mass silver and 7.5% by mass copper.
• Argentium sterling silver is a modern alloy containing 92.5% silver and 7.5% by mass of copper and germanium
• Electrum is a natually occurring alloy of gold and silver. The % by mass of gold can be within the range of 70-90%.

And, silver is present in most coloured carat gold alloys:

• 9 carat gold contains 62.5% silver and 37.5% gold
• 22 carat gold contains 91.7% gold with the remaining mass made up of silver and/or copper
  

Silver is stable in pure air and water, but tarnishes when exposed to air or water containing ozone or hydrogen sulfide. In the presence of oxygen gas and hydrogen sulfide gas, elemental silver forms the dark-coloured silver (I) sulfide and water.

Reference
Shipwreck of SS Gairsoppa reveals £150m silver haul
BBC News Online
http://www.bbc.co.uk/news/uk-15061868

Further Reading
Properties of Metals and Non-metals
Percent by Mass
Writing Ionic Formula
Balancing Chemical Equations

Suggested Study Questions

1. For the element silver, give the
   • chemical symbol
   • atomic number (Z)
   • atomic mass
     
2. For each of the uses given for silver in the article above, explain which physical and/or chemical properties of silver make it ideal for that use.
3. Using the composition of the various silver alloys provided in the article above, place the alloys in order of increasing mass of silver present in a 1kg sample.
4. Using the information contained in the article above, describe the relationship between the mass of gold in a sample and the use of the term carat.
5. Place the following terms in order of decreasing mass of gold: 9 carat gold, 18 carat gold, 22 carat gold and 24 carat gold.
6. Write a word equation to describe the process of tarnishing in air that contains some hydrogen sulfide.
7. Write a balanced chemical equation for the tarnishing of silver in air that contains some hydrogen sulfide.
8. It is thought that the silver being carried by the SS Gairsoppa contained some gold. Which alloy of silver could this be? Explain your answer.
9. The SS Gairsoppa is resting 4,700m below the ocean's surface. Do you expect the silver to be tarnished? Explain your answer.
   

Rhodium

Rhodium, symbol Rh, is the rarest of all non-radioactive metals on Earth, and therefore an expensive metal. On the 22nd July 2011, 1 gram of rhodium cost $(AUD)38 compared to 1 gram of gold which cost $(AUD)31 or 1g of silver for only 78 cents !
Rhodium is a transition metal with a density of 12.41 gcm^-3 and is found in nature as the free metal, or alloyed with similar metals such as platinum or nickel, but not as a chemical compound.
Naturally occurring rhodium is composed of only one isotope, rhodium-103.
Only about 3 tonnes of rhodium are produced in the world each year, and most of this is used for catalyzing chemical reactions.
Approximately 80% of the rhodium produced is used as a reduction catalyst in the three-way catalytic converters of cars.
In a three-way catalytic converter three processes occur simultaneously:

1. Reduction of nitrogen oxides to nitrogen and oxygen: 2NO_x → xO₂ + N₂
2. Oxidation of carbon monoxide to carbon dioxide: 2CO + O₂ → 2CO₂
3. Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water

Other uses of rhodium include :

• plating white gold to make it appear more silvery (white gold is actually an alloy of gold with atleast one other metal such as nickel, manganese, palladium)
• plating sterling silver to make it appear more silvery (sterling silver is an alloy of silver containing 92.5% by mass silver and 7.5% by mass of other metals such as copper)

Queen's University chemists have just discovered that rhodium that is modified using carbon, nitrogen or hydrogen-based complexes changes colour to yellow in the presence of nitrogen, deep blue in the presence of oxygen, and brown in the presence of carbon monoxide. Modified metals, such as modified rhodium, that change colour in the presence of particular gases could warn consumers if packaged food has been exposed to air or if there's a carbon monoxide leak at home. This finding could potentially influence the production of both industrial and commercial air quality sensors.

Reference
Queen's University (2011, July 21). Modified metals change color in the presence of particular gases. ScienceDaily. Retrieved July 23, 2011, from http://www.sciencedaily.com­ /releases/2011/07/110721131159.htm

Further Reading
Periodic Table
Definitions of a Mole
Mass-Mole Calculations
Density
Isotopes
Relative Atomic Mass
Metals & Non-metals
Percentage Composition

Study Questions

1. Locate rhodium in the Periodic Table and give its
   • atomic number
   • relative atomic mass
2. Using the prices per gram of metal given in the story above, calculate
   • the price of the 3 tonnes of rhodium produced in the world each year
     
   • the price of 1 mole of rhodium
   • the price of 10 cubic centimeters of rhodium
   • the mass of $57,000 worth of rhodium
   • the volume of $57,000 worth of rhodium
3. Naturally occurring rhodium has only 1 isotope, rhodium-103. For this isotope give:
   • the number of protons in the nucleus of a rhodium atom
   • the number of neutrons in the nucleus of a rhodium atom
   • the mass number of this isotope of rhodium
   • the atomic number for this isotope of rhodium
4. If naturally occurring rhodium only has 1 isotope why is its relative atomic mass 102.9?
5. List the physical properties you would expect rhodium to have based on its position within the Periodic Table.
6. Why would coating white gold in rhodium make it appear more silvery?
7. A 25 kg sample of sterling silver contains only silver and copper.
   • What mass of silver is present in the sample?
   • What mass of copper is present in the sample?
8. A sample of white gold is found to contain only 1.39 g gold and 0.09g of nickel. Calculate the percent by mass of each element present in the sample.
   
   
   
   
   

Hydrogen: Fuel or Foe?

Hydrogen is being viewed as an eventual alternative to fossil fuels. For metals such as steel, aluminium and magnesium, commonly used in automotive and energy technology, hydrogen is less than ideal.

Hydrogen can permeate the metals when filling the tank, or during various manufacturing processes. It can infiltrate the metal lattice through corrosion, during chromium-plating of car parts, or welding, milling or pressing.

Hydrogen can make these metals brittle and their durability deteriorates leading to sudden failure of parts and components such as the fuel tank, parts of the fuel cell, and even ordinary components like ball bearings.

Scientists at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg are studying hydrogen-induced embrittlement in order to find materials and manufacturing processes that are compatible with hydrogen.

Reference:
Fraunhofer-Gesellschaft (2010, August 21). Hydrogen causes metal to break. ScienceDaily. Retrieved August 22, 2010, from http://www.sciencedaily.com­ /releases/2010/08/100816114831.htm

Study Questions

1. What is meant by the term fossil fuels?
2. Give three examples of commonly used fossil fuels.
3. Why are scientists looking at alternatives to fossil fuels?
4. Describe what is meant by a metal lattice.
5. Explain how hydrogen could infiltrate the metal lattice.
6. Explain how this infiltration of hydrogen into the metal lattice could lead to reduced ductility and brittleness.
7. List other physical properties of metals besides ductility and hardness.
8. List some chemical properties of metals.
   
9. How does steel differ from the other metals mentioned in the article above?
   

Casting : Changes of State

The question of what happens when a material composed of more than one phase or state is heated or cooled is very important.
Many metal parts, for example, are made by casting. In the casting process liquid metal is poured into a mold and solidifies into the shape of the mold. As the liquid metal solidifies it forms tree-like structures called dendrites, and, if one of the dendrites breaks off it can lead to a change in the properties of the solidified material. The airplane industry has spent a long time developing solidification methods to avoid this problem when casting jet turbine blades.
Polymer solar cells use a complicated mixture of two polymers. When heated, the mixture evolves by a process that involves pinching which ultimately alters the properties of the mixture and the efficiency of the solar cell.
Scientists have been observing the heating process during which a rod-like phase or state embedded in another will break up into smaller domains just like droplets at the end of a stream of water, resulting in changes to the properties of the material. They have found that the shape of the interfaces during break up becomes universal, independent of the material used. This now allows them to predict the dynamics of the break-up process in a vast array of materials such as steel and polymers.

Reference:
Aagesen et al. Universality and self-similarity in pinch-off of rods by bulk diffusion. Nature Physics, 2010; DOI: 10.1038/nphys1737

Study Questions

1. Name the phase changes (changes of state) that can occur in each of the following situations:


• heating a solid


• heating a liquid


• cooling a liquid


• cooling a gas




2. Draw a sketch of the temperature-time graph expected for each of the following situations involving pure substances:
   


• heating a solid


• heating a liquid


• cooling a liquid


• cooling a gas




3. Explain why the temperature-time graph for the melting of ice differs from the temperature-time graph for freezing water.
4. Explain why the purity of a solid substance can be determined using its melting point.
5. Do you think the purity of a liquid substance could be determined using its freezing point? Explain your answer.
   
6. Explain what is meant by the term sublimation.
7. Give two examples of pure substances that undergo sublimation.

Galvanizing AUS-e-NEWS

Ever wondered what galvanizing really is?
What is the chemistry behind the process?

The June 2010 issue of AUS-e-NEWS, AUS-e-TUTE's newsletter, takes a look at galvanizing.

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