Sunday, January 14, 2018

Bee Killing Chemicals?

This morning I read a story in the Sydney Morning Herald, "Bunnings to pull pesticide allegedly linked to bee deaths".  According to the story, cans of Yates "Confidor" which have been stocked by the homewares and hardware giant Bunnings, contains neonicotinoid, a class of compounds used as an insecticide that some studies have suggested affects bee's navigation and immune systems and ultimately leads to the death of the bee colony. Indeed, a story on this appeared in New Scientist in July 2017 in which Dave Goulson at the University of Sussex, UK, is quoted as saying, "Although the field trial results varied between countries, the overall evidence points to harmful effects for bees. I think you’d have to be pretty unreasonable at this point not to accept that, at least some of the time, these chemicals harm bees when used in normal farming practice.”  The same story quoted Richard Schmuck of Bayer, one of the makers of this class of insecticides, as saying, "We remain confident that neonicotinoids are safe when used and applied responsibly."

As the name neonicotinoids suggests, these are "new" molecules based on the molecular structure of nicotine shown below:
 Nicotine has been used as a pesticide for over 200 years. It is found lots of plants.  Up to 3% of the mass of the tobacco plant is nicotine, and trace amounts of nicotine are found in vegetables like eggplants, potatoes and tomatoes. When used as a pesticide,  it degrades rapidly in the environment and is not very selective so it is not really a good pesticide. For instance, a dose of 1mg per kg of body mas can kill a human.
Development of neonicotinoids began in the 1980s by Shell and1990s by Bayer. Neonicotinoids are generally less toxic to birds and mammals than they are to insects, and, some of the breakdown products are also toxic to insects, this is why they can be used as insecticides.
Consider the structural formula of imidacloprid, an example of a neonicotinoid and one of the most widely used insecticides:
 Imidacloprid was patented by Bayer in 1985 as the first commercial neonicotinoid. Traditionally insecticides were coated onto plants, "crop dusting", but neonicotinoids like  imidacloprid are water soluble and break down slowly in the environment so they are absorbed by plants. Bees are exposed to these compounds in the plant's pollen.
The early 2000s saw the introduction of two other neonicotinoid compounds;  clothianidin and thiamethoxam. 


clothianidin thiamethoxam

Clothianidin can be used as a spray, dust or injectable liquid, depending on which plants it is being to protect.
In 2013 the European Union restricted the use of imidacloprid, clothianidin and thiamethoxam on crops that attract bees.

References:
http://www.smh.com.au/national/bunnings-to-pull-pesticide-allegedly-linked-to-bee-deaths-20180113-h0htzq.html
https://www.newscientist.com/article/2139197-strongest-evidence-yet-that-neonicotinoids-are-killing-bees/

Suggested Further Reading
IUPAC Nomenclature:  http://www.ausetute.com.au/namctut1.html
Introduction to Functional Groups: http://www.ausetute.com.au/fungroup.html
Molecular Formula: http://www.ausetute.com.au/molecularformula.html
2-Dimensional Structural Formula: http://www.ausetute.com.au/structural2D.html
Skeletal Structural Formula: http://www.ausetute.com.au/skeletal.html
 Introduction to Polarity of Molecules: http://www.ausetute.com.au/molpolar.html
Intermolecular Forces and Solubility:  http://www.ausetute.com.au/intermof.html
Aqueous Solutions (water as a solvent): http://www.ausetute.com.au/aqueous.html

Suggested Study Questions:
  1. Use molecular model kits to build models of  the following molecules:
    • nicotine
    • imidacloprid
    • clothianidin
    • thiamethoxam
  2. Draw a 2-dimensional (full display) structural formula for each of the following molecules:
    • nicotine
    • imidacloprid
    • clothianidin
    • thiamethoxam
  3. Write the molecular formula for each of the following molecules:
    • nicotine
    • imidacloprid
    • clothianidin
    • thiamethoxam
  4. Consider the nicotine molecule. Do you expect it to be soluble in water? Explain your answer.
  5. Consider a molecule of imidacloprid. Do you expect it to be soluble in water? Explain your answer.
  6. What property of clothianidin enables it to be used as a spray? Explain this property in chemical terms.
  7.  What alteration to the structure of a nicotine molecule could you make so that it would become more soluble in water?
  8. Carefully compare the structure of clothianidin and thiamethoxam (the molecular models you built could be useful here). In what ways are the molecules:
    • similar
    • different
  9. Considering only the structure of nicotine and the neonicotinoids in this article, explain why nicotine might be more toxic to humans than the neonicotinoids.
  10. Compare the quotes from Dave Goulson and Richard Schmuck in the article. In what ways are the two quotes:
    • similar
    • different
  11. Imagine you have been asked by your government to decide whether or not to ban the use of neonicotinoids in agriculture. What would you advise? Explain why.

Wednesday, January 10, 2018

Gutful of Gas

People can eat interesting things.
In the 1960s in Australia, Leon Samson was eating razor blades to amuse audiences, he even started to eat, slowly, in bits, a car for a bet. A little later, France produced Michel Lotito who was also eating odd things to entertain us, including an airplane between 1978 and 1980.

A razor blade is made out of steel, a particular kind of steel known as razor blade steel. A 2.61 gram razor blade contains between about 13% chromium, 0.6% carbon, and  the rest is iron. Samson would chew up a razor blade and swallow it.

After leaving the mouth, the chewed-up bits of razor blade travel to the stomach. An empty stomach has a volume of about 75 mL but when we eat the volume of the stomach can expand out to about 1 L. Protein-digesting enzymes known as proteases are released into the stomach to help begin the break up of the proteins like you find in meat, fish, eggs and cheese. The optimum pH for these proteases is at about pH 2, so hydrochloric acid is also released into the stomach.

So the small bits of razor blade now find themselves surrounded by hydrochloric acid. Hydrochloric reacts with metals, like the iron in steel, to produce hydrogen gas. Now gases have an interesting property, they expand out to fill the available space. This suggests that eating razor blades might result in a feeling of being bloated. Thankfully, it appears that it takes about 24 hours for the complete reaction between a razor blade and hydrochloric acid in the stomach, plenty of time to remove the gas build-up via burping or, um, farting.

Hydrogen gas is commonly found in our intestines, along with other gases like carbon dioxide, oxygen and nitrogen. Some of these gases get there when we swallow air along with our food and drink, but they also come from chemical reactions inside our bodies. If our bodies are healthy and working well, all the usual gases will be present in the usual concentration, but if there is something wrong, if we are sick, the nature and composition of the gases will change.

Researchers at RMIT University in Melbourne, Australia, have developed and trialed an "ingestible electronic capsule" which is capable of sensing and measuring the gases in the gut like hydrogen, carbon dioxide and oxygen. These capsules offer a new, non-invasive way to monitor the health of our gut. The capsules can be collected after they have been excreted (apparently painlessly).

Reference: 
Kourosh Kalantar-Zadeh, Kyle J. Berean, Nam Ha, Adam F. Chrimes, Kai Xu, Danilla Grando, Jian Zhen Ou, Naresh Pillai, Jos L. Campbell, Robert Brkljańća, Kirstin M. Taylor, Rebecca E. Burgell, Chu K. Yao, Stephanie A. Ward, Chris S. McSweeney, Jane G. Muir, Peter R. Gibson. A human pilot trial of ingestible electronic capsules capable of sensing different gases in the gut. Nature Electronics, 2018; 1 (1): 79 DOI: 10.1038/s41928-017-0004-x

Suggested Further Reading 
Experimental Design: http://www.ausetute.com.au/experimentd.html
Name and Formula of Binary Covalent Compounds: http://www.ausetute.com.au/namcform.html
Percentage Composition:  http://www.ausetute.com.au/percentc.html
Mass-moles Calculations: http://www.ausetute.com.au/massmole.html
Molar Gas Volume Calculations: http://www.ausetute.com.au/molarvol.html
Ideal Gas Law Calculations:  http://www.ausetute.com.au/idealgas.html
Metal + Non-Oxidising Acid Reaction: http://www.ausetute.com.au/metalhcl.html
Hydrogen Ion Concentration of Strong Acids: http://www.ausetute.com.au/hstronga.html 
Reaction Calculations: Mass and Moles http://www.ausetute.com.au/molreact.html 

Suggested Study Questions
  1.   Design an experiment to determine how long it would take for a razor blade to react completely with the hydrochloric acid in the stomach. Investigate ways to speed up, or, to slow down, this reaction.
  2. Give the formula for each of the following:
    • hydrogen gas
    • nitrogen gas
    • oxygen gas
    • carbon dioxide gas
    • hydrochloric acid
  3.   Determine the percentage composition of each of the following compounds
    • hydrogen chloride gas
    • carbon dioxide gas
  4. From the information in the article, calculate the mass of each of the following elements found in a razor blade:
    • iron
    • chromium
    • carbon
  5. Using the information above, calculate the moles of each of the following elements found in a razor blade:
    • iron
    • chromium
    • carbon
  6. Calculate the moles of hydrogen gas that occupy the entire volume of a "full" stomach under the following conditions:
    • 0oC and 100 kPa
    • 25oC and 100 kPa
    • 37oC and 100 kPa
  7. Write a balanced chemical equation for the reaction between the hydrochloric acid in the stomach and the iron in a razor blade.
  8. Calculate the concentration of acid released into the stomach using the information in the article. 
  9. Use the balanced chemical equation to determine the volume of hydrogen gas produced when all the iron in a razor blade has reacted with hydrochloric acid.
  10. Consider all the information in the article, and the calculations you have performed so far. Explain why it takes 24 hours for a razor blade to be completely digested in the stomach.

Sunday, December 31, 2017

Introduction to Entropy

What is entropy?
What is meant by a chemical system having low entropy or high entropy?
What is the relationship between disorder, energy and entropy?

If you are asking these questions, then you will find AUS-e-TUTE's new entropy introductory tutorial, game and test very helpful! AUS-e-TUTE Members should log in to use these new resources (under the topic heading Thermodynamics in the Test Centre).

Not an AUS-e-TUTE Member?
A "free-to-view" tutorial is currently available at http://www.ausetute.com.au/entropy.html

Saturday, December 9, 2017

Chemistry Rockets to Mars

NASA is developing the most powerful rocket in history, the Space Launch System (abbreviated to SLS) to launch the spacecraft known as Orion. Orion is expected to carry humans beyond the Moon and on to Mars in the 2030s.
It is well known that engineers, physicists, mathematicians and computer programmers play a quintessential part in the design, development, launch, trajectory and landing of rockets and spacecraft, but what about chemists?
Chemistry also plays an important role in getting rockets off the ground.
Without an understanding of chemistry there would be no fuel, no thrust, no take-off!

Read more in the December 2017 issue of AUS-e-NEWS.

To subscribe to AUS-e-NEWS got to http://www.ausetute.com.au/ausenews.html

Saturday, November 25, 2017

Ruthenium-106 Cloud

In October 2017 the German Federal Office for Radiation Protection detected a radioactive cloud containing ruthenium-106 wafting over Europe. They identified the Southern Ural Mountains in Russia or Kazakhstan as the most likely source of the cloud. In November 2017 Roshydromet, the authority responsible for monitoring radiation in Russia, finally admitted that it had found extremely high levels of ruthenium-106 at two monitoring stations in this region in late September and early October.

Ruthenium is a transition metal element with the chemical symbol Ru and an atomic number of 44.
 Naturally occurring ruthenium has 7 stable isotopes: 96Ru, 98Ru, 99Ru, 100Ru, 101Ru, 102Ru, and, 104Ru. The abundance of each isotope in naturally occurring ruthenium is given in the table below:

isotopeabundance %
ruthenium-965.54
ruthenium-981.87
ruthenium-9912.76
ruthenium-10012.60
ruthenium-10117.06
ruthenium-10231.55
ruthenium-10418.62

In addition to these naturally occurring stable isotopes, about 30 unstable, or radioactive, isotopes have also been identified. The most stable of these radioisotopes is ruthenium-106 which has a half-life of  359 73.days. It decays by emitting a beta particle to produce rhodium-106:
106Ru0e+ 106Rh
44-145

Ruthenium-106 is produced in a nuclear reactor as a product of the nuclear fission of uranium-235. Ruthenium-106 can be extracted from spent nuclear fuel and then it can be used in medicine to treat eye tumors.

The radioactive cloud wafting across Europe is most likely to be due to a spill of ruthenium-106 rather than a nuclear reactor accident since this would have released other radioisotopes which would have been detected in the cloud. France's nuclear safety agency has estimated the amount of radiation released at the source as between 100 and 300 billion becquerels.
A becquerel (Bq) is the SI unit for measuring radioactivity. It is equivalent to the radioactive decay of 1 nucleus in 1 second.
We can use this to estimate the mass of ruthenium-106 spilled:
ABq =       mass      
atomic weight
x NA x ln(2)
t½

ABq = activity in becquerels = 200 x 109 Bq (averaged)
mass = ? grams
atomic weight = 106 g/mol (from the Periodic Table)
NA = 6 x 1023 mol-1 (Avogadro's number)
t½ =  373.59 days = 373.59 days x 24 hours/day x 60 minutes/hour x 60 seconds/minute = 3.22 x 107 seconds
200 x 109 =       mass      
106
x 6 x 1023 x 0.6931
3.22 x 107
200 x 109 =       mass      
106
x 6 x 1023 x 2.15 x 10-8
200 x 109 =       mass      
106
x 1.29 x 1016
mass = 200 x 109 x 106
1.29 x 1016
mass = 1.64 x 10-3 g

If the source of this ruthenium-106 was an accident involving spent fuel rods, then we can calculate the mass of spent fuel involved since 1.9 kg of ruthenium-106 can be extracted from 1 ton (or 1000 kg) of used fuel.
1.9 kg = 1.9 kg x 1000 g/kg  =  1900 g
1900 g of ruthenium-106 can be extracted from 1000 kg (1 000 000 g) of spent nuclear fuel.
1 g of ruthenium-106 can be extracted from 1 000 000 g/1900 g =  526 g of spent fuel
1.64 x 10-3 g ruthenium-106 would be produced from 1.64 x 10-3 x 526  = 0.86 g of spent fuel

A typical nuclear power plant produces 20 tons (2 x 107 g) of  used nuclear fuel per year, about 0.6 grams per second!

Reference:
http://www.smh.com.au/world/with-a-radiation-cloud-comes-a-mystery-from-russia-20171123-gzrvtf.html 

Further Reading:
Isotopes 
Atomic Number (number of protons) 
Mass Number (number of nucleons) 
Calculating Relative Atomic Mass (atomic weight)
Nuclear Half-life 


Suggested Study Questions
  1.  What does the term "isotope" mean?
  2.  Give the atomic number of each of the following species:
    • ruthenium-96
    • ruthenium-98
    • ruthenium-100
    • ruthenium-102
    • ruthenium-104
    • ruthenium-106
  3. Give the mass number (or nuclear number) of each of the following species:
    • ruthenium-96
    • ruthenium-98
    • ruthenium-100
    • ruthenium-102
    • ruthenium-104
    • ruthenium-106
  4. Determine the number of protons in the nucleus of an atom of each of the following:
    • ruthenium-96
    • ruthenium-98
    • ruthenium-100
    • ruthenium-102
    • ruthenium-104
    • ruthenium-106
  5. Determine the number of neutrons in the nucleus of an atom of each of the following:
    • ruthenium-96
    • ruthenium-98
    • ruthenium-100
    • ruthenium-102
    • ruthenium-104
    • ruthenium-106
  6. Use the information in the article to calculate the relative atomic mass (atomic weight) of ruthenium.
  7. Explain what is meant by the term "unstable isotope".
  8. Explain what is meant by the term "beta decay".
  9. A number of unstable isotopes of ruthenium undergo beta decay. Write balanced nuclear decay equations for the beta decay of the following ruthenium isotopes:
    • ruthenium-103
    • ruthenium-105
    • ruthenium-106
    • ruthenium-107
    • ruthenium-108
    • ruthenium-109
  10. Explain what is meant by nuclear "half-life"?
  11. Ruthenium-106 has a half-life of of  359 73.days. Calculate the percentage of ruthenium-106 remaining after:
    • 359.73 days
    • 719.46 days
    • 1079.19 days
    • 3597.3 days
  12. If the mass of ruthenium-106 in the cloud over Europe is currently 1.64 x 10-3 g, calculate the mass of ruthenium-106 remaining in the cloud after:
    • 1 year
    • 2 years
    • 10 years

Friday, November 17, 2017

Iron from Used Toner Cartridges

Students and teachers all do a lot of printing and photocopying.
If your laser printer or photocopier is like ours, it probably has a sign on it that says you should contact admin when it needs a new toner cartridge.

Have you ever wondered what is inside the "toner cartridge"?
The black "ink", the toner, is  actually a mixture of solid carbon and solid iron oxide. A polymer is included to improve the flow. The particles making up the mixture are very small, around 10 micrometers. In general, the smaller the particle size, the better the resolution of the final print.
These small toner particles carry a positive charge which enables them to be deposited electrostatically on a negatively-charged image. Once deposited on the paper, the paper is electrically discharged then heated so that toner particles melt and bind to the fibers of the paper.

So what happens to all the old, used toner cartridges?
It is estimated that about half of all toner cartridges sold each year end up in landfill.
The rest are collected and recycled.
Your "empty" toner cartridge probably contains about 8% of the original mix of carbon, iron oxide and polymer. Generally this left-over toner will have to be cleaned out before the cartridge can be re-filled.

New research has suggested that this left-over toner could be transformed directly into iron. Iron is the main component of steel, one of the most widely used metals in the world.
The researchers heated toner mixture in a furnace to 1550oC, at which temperature iron oxide is reduced to metallic iron by the carbon:
iron oxide + carbon → iron + carbon dioxide
 The reported yield of iron from toner powder was 98%.

Reference:
Vaibhav Gaikwad, Uttam Kumar, Farshid Pahlevani, Alvin Piadasa, Veena Sahajwalla. Thermal Transformation of Waste Toner Powder into a Value-Added Ferrous Resource. ACS Sustainable Chemistry & Engineering, 2017; DOI: 10.1021/acssuschemeng.7b02875

Suggested Further Reading:
 Percent by Mass (% by mass)
Naming Ionic Compounds
Formula for Ionic Compounds
Name and Formula of Covalent Compounds
Balancing Chemical Equations
Oxidation and Reduction
Oxidation States (oxidation numbers)

Metal Extraction Concepts

Carbon Reduction Method for Extracting Metals from their Ores
Activity Series of Metals

Suggested Study Questions:
  1. Convert 10 micrometers to a diameter in:
    • metres
    • nanometres
    • millimetres
    • centimetres
  2. Write the chemical formula for each of the following substances:
    • iron(II) oxide
    • iron(III) oxide
    • carbon dioxide
    • carbon monoxide
  3. Write a word equation for the reduction of each of the following iron oxides using carbon:
    • iron(II) oxide
    • iron(III) oxide
  4. Write a balanced chemical equation for the reduction of each of the following iron oxides using carbon:
    • iron(II) oxide
    • iron(III) oxide
  5. Give the oxidation state (oxidation number) for iron in each of the following:
    • metallic iron
    • iron(II) oxide
    • iron(III) oxide
  6. Refer to the balanced chemical equations in question 4. In each equation, identify the
    • oxidant (oxidising agent)
    • reductant (reducing agent)
  7. Is the reaction between iron oxide and carbon in the furnace an example of a redox reaction? Justify your answer.
  8. About 40% by mass of the toner cartridge powder is iron oxide. A toner cartridge contains 80 g of toner, what is the mass of iron oxide in the toner cartridge?
  9. At the end of its useful life, a tone cartridge still contains 8% of the original toner. What mass of toner is present in a the toner cartridge at the end of its useful life?
  10. At the end of the toner cartridge's useful life, what mass of iron oxide is present in the cartridge?
  11. Assuming the chemical formula for the iron oxide in the cartridge is Fe3O4, what is the maximum amount of iron in grams that could be obtained from an "empty" toner cartridge?
  12. 350 million "empty" toner cartridges go to landfill each year in the world. If all the available iron could be recovered from each cartridge, what mass of iron would be recovered?

Saturday, November 4, 2017

Energy Content of Food

As I read the"nutritional information" panel on my box of cereal this morning I wondered how you would measure the "energy content" of food.
At AUS-e-TUTE we've come up with a straight-forward experiment that you could do in the school laboratory (or at home if you really wanted too!). We even provided some sample results and calculations so that you can measure the energy content of your favourite foods.

If you are an AUS-e-TUTE Member, you will also find additional resources such as a game, test and drill with worked solutions to help you prepare for your exams.

If you are not an AUS-e-TUTE member, you can access a "free-to-view" tutorial for evaluation purposes at http://www.ausetute.com.au/heatfood.html