New AUS-e-TUTE Resources

AUS-e-TUTE has added new tutorials, games, tests and exams on the following chemistry topics:

• Types of Chemical Reactions

• Chemical and Physical Properties of Alkenes

• cis-trans (geometric) Isomers of Alkenes

• Structural (constitutional) Isomers of Haloalkanes (alkyl halides)

• Thin Layer Chromatography

The following syllabus study guides have also been updated:

• HSC chemistry
• VCE chemistry
• SACE chemistry
• AP chemistry
• A.C.T. chemistry
• QLD chemistry

Year 12 students preparing for the HSC, VCE or WACE  should also log-in to the Test Centre and use the exam preparation resources available for these courses.

6 Random Questions Answered

1/ Question From USA, "How do you calculate density for chemistry?"
Answer: density = mass/volume
(http://ausetute.com.au/density.html)

2/ Question from Canada, "What is the main functional group in aspirin?"
Answer: Aspirin (acetylsalicylic acid) contains a carboxyl and an ester functional group. The carboxyl group is responsible for the acidic properties of aspirin.
(http://ausetute.com.au/aspirin.html)

3/ Question from USA, "What is the magnetic quantum number for iron?"
Answer: Magnetic quantum number, m_l,  has a value from -l to +l
For iron (Z=26), m_l can have values of -2, -1, 0, +1, +2
(http://ausetute.com.au/quantum.html )

4/ Question from Australia, "What is the enthalpy of combustion of ethanol?"
Answer: 1367 kJ/mol
(http://ausetute.com.au/members/alkanolp.html)

5/ Question from Australia, "What is enthalpy of combustion?"
Answer: Enthalpy (or heat) of combustion of a substance is the amount of energy released when 1 mole of the substance combusts (burns) in excess oxygen at constant pressure.
(http://ausetute.com.au/members/heatcomb.html)

6/ Question from Australia, "How do you tell a non reducing sugar?"
Answer: Reducing sugars can be oxidised by mild oxidising agents, non-reducing sugars can not be oxidised by mild oxidising agents.
(http://ausetute.com.au/members/redsugar.html)

Spelling Mistakes vs Incorrect Science

It's that time of year in Australia when tens of thousands of students get ready to sit their final exams.
For many of these students it will be the first time they have sat an external assessment, that is, these exams will not be marked by teachers who know them. This time there will be no kindly teacher marking the exam paper and thinking, "oh dear, well I know what Chris really meant ....", this time a complete stranger will be sitting in front of your paper, and not only that, a complete stranger who has by now had to try to read and mark thousands of papers, and this stranger is only going to give you a mark based on exactly what you did write NOT on what he/she thinks you might have meant!

Which brings me to the subject of this discussion. 
When is a spelling mistake (typo) going to be marked as wrong on a Chemistry exam paper?
A spelling mistake will be marked wrong if it introduces ambiguity into your answer or if it makes what you are saying scientifically incorrect.

Spelling mistakes that will be probably not be marked as wrong include misplaced apostrophes, for example it's instead of its, or misspelling non-science-specific-words like using 'their' instead of 'there', as long as this does not alter the scientific meaning of what you have written.

Spelling mistakes that will definitely be marked wrong are those that make your answer scientifically "wrong".
In chemistry, changing just one letter in a word can have an enormous impact!
For example, ethane has the molecular formula C₂H₆ and is a saturated, and not very reactive, hydrocarbon. On the other hand, ethyne has the molecular formula C₂H₂ and is an unsaturated, and very reactive, hydrocarbon. Changing one letter, an a to a y, has a huge impact on the formula and properties of the compound! If you start writing about the addition of bromine to ethane instead of ethyne you will, and certainly should be, marked wrong.
Then there is the problem of capitalization, which is very important when writing chemical formula.
If you write Co then you have given the chemical symbol for the transition metal cobalt, but if you write CO you have given the molecular formula for the covalent compound carbon monoxide. Just using a lowercase letter instead of a capital (uppercase) letter  has changed the substance from a metallic element to a covalent compound! So, if you start talking about the metallic bonding of CO in the solid state at room temperature and pressure, you will be marked wrong.

After you have written an answer to an exam question, read the question again. Then read your answer. Make sure you have written an answer to the question that was asked, and, make sure that your answer says what you meant it to say! Be on the look-out for those spelling mistakes (typos) that could lose you marks.

Nobel Prize in Chemistry 2013

Martin Karplus, Michael Levitt and Arieh Warshel have been awarded the 2013 Nobel Prize in Chemistry "for the development of multiscale models for complex chemical systems", that is, they have made it possible to model complex chemical reactions using computers.

When light hits the retina in your eye, the free electrons in retinal are filled with energy, which changes the shape of the molecule. This is the first stage in the process of your sense of sight.
In 1972, Karplus and Warshel modelled retinal by developing a computer program that used quantum  physics when it performed calculations on free electrons and then used classical physics for all electrons and all atomic nuclei. This was the first time that anyone had managed to bring about a chemically relevant collaboration between classical and quantum physics.

Enzymes are crucial to life, but in order to simulate the reactions of enzymes, a computer program would need classical and quantum physics to collaborate more smoothly. In 1976 Levitt and Warshel successfully simulated an enzymatic reaction, and this program would work for any kind of molecule.

The use of computers to simulate chemical reactions is increasingly important as a tool for understanding how reactions occur and the paths the reactants take. Computer programs can be used to optimize chemical process in order to produce better solar cells, improve catalysts in motor vehicles, develop more effective drugs, and so much more.

Reference:
http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2013/popular-chemistryprize2013.pdf

Further Reading:
Enzymes: http://ausetute.com.au/members/enzymes.html 
Proteins: http://ausetute.com.au/members/proteins.html
 

Nobel Prize Facts 2013

Alfred Nobel was a Swedish Chemist and the inventor of dynamite. The fortune that he made from this during his lifetime, about SEK 31 million (today about SEK 1,702 million or about $265 million), was left in his will to institute the Nobel Prizes. One of these prizes is awarded to "the person who shall have made the most important chemical discovery or improvement". The announcement regarding the award of Nobel Prizes is made in October each year.
While we wait for this years announcement, here are a few facts about the Nobel Prize in Chemistry:

• 104 Nobel Prizes in Chemistry have been awarded since 1901.
• A Nobel Prize in Chemistry was not awarded in 1916, 1917, 1919, 1924, 1933, 1940, 1941 and 1942
• 63 Chemistry Prizes have been given to one Laureate only
• 23 Chemistry Prizes have been shared between 3 Laureates. 
• A Nobel Prize in Chemistry can not be awarded to more than 3 people in each year.
• 162 individuals have been awarded the Nobel Prize in Chemistry (these people are called Laureates).
• 1 person, Frederick Sanger, has been awarded the Nobel Prize in Chemistry twice.
• 4 women have been awarded the Nobel Prize in Chemistry:
  • Marie Curie 1911
  • Irene Joliot-Curie 1935
  • Dorothy Crowfoot Hodgkin 1964
  • Ada Yonath 2009
• 2 Chemistry Laureates have been awarded Nobel Prizes in other areas as well:
  • Marie Curie (Physics 1903, Chemistry 1911)
  • Linus Pauling (Chemistry 1954, Peace 1962)
•  1 person, Linus Pauling, is the only person who has been awarded 2 unshared Nobel Prizes.
• 4  Nobel Prize Families:
  • Marie and Pierre Curie - husband and wife (Physics 1903)
  • Irene Joilot-Curie and Frederic Joliot - husband and wife (Chemistry 1935)
  • Hans von Euler-Cheplin (father, Chemistry 1929) and Ulf von Euler (son, Medicine 1970)
  • Arthur Kornberg (father, Medicine 1959) and Roger D. Konberg (son, Chemistry 2006)
• Average age of all Chemistry Laureates is 57
• Youngest Chemistry Laureate was Frederic Joliot who was 35 years old when awarded his Nobel Prize in 1935 (together with his wife Irene Joliot-Curie)
• Oldest Chemistry Laureate was John B. Fenn who was 85 years old when he was awarded the Nobel Prize in Chemistry in 2002.
• 0 posthumous Nobel Prizes in Chemistry. A Nobel Prize cannot be awarded posthumously unless death occurred after the announcement of the Nobel Prize.
• 2 Nobel Laureates in Chemistry have been forced by authorities to decline the Nobel Prize. Adolf Hitler forbade Richard Kuhn (Chemistry 1938) and  Adolf Butenandt (Chemistry 1939) from receiving their Nobel Prizes.

Reference:
http://www.nobelprize.org/nobel_prizes/facts/chemistry/

6 Random Questions Answered

If you are an AUS-e-TUTE member you can just ask us a question and we'll do our best to answer it in a meaningful way, but, if you are not an AUS-e-TUTE member you'll have to resort to asking a search engine, and if you are lucky, we might answer your question here (if you have encrypted your search, for example if you are logged into a gmail account when you search google, we can't answer your question here).

Question from USA, "a substance that cannot be separated into simpler substances by physical or chemical mean is an it a mixture"
Answer from ausetute.com.au Yes, a substance that cannot be separated into simpler substances by physical means is a pure substance and not a mixture. If the pure substance can be separated by chemical means, then it is a compound and not an element.
Reference: http://ausetute.com.au/puresubs.html
http://ausetute.com.au/elements.html

Question from USA, "what is the density of a substance with a mass of 47.2 g and a volumn of 36 mL ?"
Answer from ausetute.com.au density = mass(g)/volume(mL) = 47.2/36 = 1.31g/mL
Reference: http://ausetute.com.au/density.html

Search from Canada, "what are some princeples of pure substance and mixturs"
Reply from ausetute.com.au "Mixtures can be separated by physical means. Pure substances cannnot be separated into their component parts using physical means"
Reference: http://ausetute.com.au/puresubs.html

Search from Malaysia, "why stable compound release less energy"
Reply from ausetute.com.au "Breaking bonds requires energy, making bonds releases energy. The more energy that is required to break the bonds, the more stable the compound will be."
Reference: http://ausetute.com.au/members/heatbond.html

Search from USA, "density of elements between 3.0g/ml and 6.0g/ml"
You can look these up for yourself here http://www.ausetute.com.au/members/ptablei.html

Search from USA, " electron neon orbitals"
Response from ausetute.com.au Do you want the set of orbitals (s and p orbitals) or the electron configuration of neon (1s² 2s² 2p⁶)?
Reference: http://www.ausetute.com.au/econfig.html

Propene on Titan

 Titan, one of Saturn's moons, is very special. It is the only satellite in our solar system that has a fully developed atmosphere.
Hydrocarbons were first detected in the atmosphere of Titan by NASA's Voyager 1 spacecraft way back in 1980. Titan's atmosphere is made up of 98.4% nitrogen gas and 1.4% methane. Sunlight breaks this methane apart and the fragments then link up to form chains with 2, 3 or more carbon atoms in the chain. Voyager found the presence of propane and propyne, but not propene.

More recently, NASA's Cassini spacecraft's mass spectrometer data suggested that propene might be present in Titan's upper atmosphere, and in 2013, using a form of infrared spectroscopy, propene was indeed found in Titan's atmosphere.

On planet Earth, propene is second only to ethene as a starting product in the petrochemical industry. About two thirds of all the propene produced is used to make the plastic known as polypropene, or polypropylene, which is used widely in packaging materials.

Reference:
C. A. Nixon, D. E. Jennings, B. Bézard, S. Vinatier, N. A. Teanby, K. Sung, T. M. Ansty, P. G. J. Irwin, N. Gorius, V. Cottini, A. Coustenis, F. M. Flasar. DETECTION OF PROPENE IN TITAN'S STRATOSPHERE. The Astrophysical Journal, 2013; 776 (1): L14 DOI: 10.1088/2041-8205/776/1/L14

Further Reading
http://ausetute.com.au/namctut1.html
http://ausetute.com.au/namsanes.html
http://ausetute.com.au/namsenes.html
http://ausetute.com.au/namsynes.html
http://ausetute.com.au/members/polymers.html
http://ausetute.com.au/members/polythen.html

Suggested Study Questions:

1. What is meant by the term "hydrocarbon"?
2. Give the molecular formula for each of the following hydrocarbons:
   • methane
   • ethane
   • ethene
   • ethyne
   • propane
   • propene
   • propyne
3. Give the structural formula for each of the following hydrocarbons:
   • methane
   • ethane
   • ethene
   • ethyne
   • propane
   • propene
   • propyne 
4. Propene is used to produce polypropene (polypropylene). Draw a representative section of polypropene.
5. Would you describe the polymerisation of propene as an addition polymerisation or as a condensation polymerisation? Explain your answer.
6. Ethene is used to produce polythene or polyethylene. Draw a representative section of polythene.
7. Would you describe the polymerisation of ethene as an addition polymerisation of as a condensation polymerisation? Explain your answer.
8. Both ethene and propene have been found in Titan's atmosphere. Do you think it is likely that polythene and polypropylene will be found in Titan's atmosphere? Explain your answer.