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
Sunday, December 31, 2017
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
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:
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:
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 = 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
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
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:
| isotope | abundance % |
|---|---|
| ruthenium-96 | 5.54 |
| ruthenium-98 | 1.87 |
| ruthenium-99 | 12.76 |
| ruthenium-100 | 12.60 |
| ruthenium-101 | 17.06 |
| ruthenium-102 | 31.55 |
| ruthenium-104 | 18.62 |
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:
| 106 | Ru | → | 0 | e | + | 106 | Rh |
| 44 | -1 | 45 |
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
- What does the term "isotope" mean?
- Give the atomic number of each of the following species:
- ruthenium-96
- ruthenium-98
- ruthenium-100
- ruthenium-102
- ruthenium-104
- ruthenium-106
- 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
- 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
- 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
- Use the information in the article to calculate the relative atomic mass (atomic weight) of ruthenium.
- Explain what is meant by the term "unstable isotope".
- Explain what is meant by the term "beta decay".
- 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
- Explain what is meant by nuclear "half-life"?
- 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
- 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:
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:
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:
- Convert 10 micrometers to a diameter in:
- metres
- nanometres
- millimetres
- centimetres
- Write the chemical formula for each of the following substances:
- iron(II) oxide
- iron(III) oxide
- carbon dioxide
- carbon monoxide
- Write a word equation for the reduction of each of the following iron oxides using carbon:
- iron(II) oxide
- iron(III) oxide
- Write a balanced chemical equation for the reduction of each of the following iron oxides using carbon:
- iron(II) oxide
- iron(III) oxide
- Give the oxidation state (oxidation number) for iron in each of the following:
- metallic iron
- iron(II) oxide
- iron(III) oxide
- Refer to the balanced chemical equations in question 4. In each equation, identify the
- oxidant (oxidising agent)
- reductant (reducing agent)
- Is the reaction between iron oxide and carbon in the furnace an example of a redox reaction? Justify your answer.
- 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?
- 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?
- At the end of the toner cartridge's useful life, what mass of iron oxide is present in the cartridge?
- 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?
- 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
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
Thursday, November 2, 2017
Spud Lite?
"Spud Lite", the advertising poster said, "25% less carbs", followed in fine print by "than other potatoes".
"How strange", I thought, "I thought you ate potatoes for their carbohydrate (carbs) content so why would you want a potato with less carbohydrate?"
But then I started thinking about what this meant in terms of the chemical composition of the potato. If it contains 25% less carbohydrate, then surely that means something else must have been increased or added? Or are you just getting less potato for your money?
Typically, a traditional potato has the following approximate composition:
That is, 100 g of traditional potato contains about 79 g of water, 17.5 g of carbohydrate, 2 g of protein and 0.1 g of fat.
One way to reduce the percentage of carbohydrate in a potato would be to reduce the density of the potato.
If 100 g of a traditional potato had a volume of 92 mL, then the density of the potato would be 1.09 g/mL. 1 mL of traditional potato has a mass of 1.09 g and contains 17.5% by mass (0.19 g) of carbohydrate.
If "spud lite" has a lower density of potato "flesh", say 0.8 g/mL, then 1 mL of "spud lite" has a mass of 0.8 g and contains 17.5% by mass (0.14 g) of carbohydrate.
If we then compare equal volumes (sizes) of potatoes, say 1 mL of traditional potato and 1 mL of "spud lite" we find that "spud lite" contains 100 x (0.19 - 0.14)/0.19 = 26% less carbohydrate (by volume!).
But, if the density of "spud lite" is less, the % by mass composition remains the same, that is, for every 100 g of potato (traditional or "spud lite") there will be 17.5 g of carbohydrate (but the "spud lite" potato will be a bigger potato for your 100 g).
The nutrition label on a packet of "spud lite" potatoes gives the following masses per 100 g of potato:
(assuming the dietary fibre is cellulose which is also a carbohydrate).
This means that the actual mass of carbohydrate per 100 g of potato has been decreased. That is, "spud lites" are not just less dense than traditional potatoes.
Another way to decrease the proportion of carbohydrate in your potatoes would be to increase their water content.
Imagine you have 100 g of traditional potato. This potato is made up of 79 g of water and 17.5 g of carbohydrate.
"Spud lite" contains 11.4 g of carbohydrate.
Further Reading
Experimental Design
Carbohydrates
Proteins
Lipids (fats and oils)
Percentage Composition
Density
Suggested Study Questions:
"How strange", I thought, "I thought you ate potatoes for their carbohydrate (carbs) content so why would you want a potato with less carbohydrate?"
But then I started thinking about what this meant in terms of the chemical composition of the potato. If it contains 25% less carbohydrate, then surely that means something else must have been increased or added? Or are you just getting less potato for your money?
Typically, a traditional potato has the following approximate composition:
| nutrient | % by mass |
|---|---|
| water | 79 |
| carbohydrate | 17.5 |
| protein | 2 |
| fat | 0.1 |
That is, 100 g of traditional potato contains about 79 g of water, 17.5 g of carbohydrate, 2 g of protein and 0.1 g of fat.
One way to reduce the percentage of carbohydrate in a potato would be to reduce the density of the potato.
If 100 g of a traditional potato had a volume of 92 mL, then the density of the potato would be 1.09 g/mL. 1 mL of traditional potato has a mass of 1.09 g and contains 17.5% by mass (0.19 g) of carbohydrate.
If "spud lite" has a lower density of potato "flesh", say 0.8 g/mL, then 1 mL of "spud lite" has a mass of 0.8 g and contains 17.5% by mass (0.14 g) of carbohydrate.
If we then compare equal volumes (sizes) of potatoes, say 1 mL of traditional potato and 1 mL of "spud lite" we find that "spud lite" contains 100 x (0.19 - 0.14)/0.19 = 26% less carbohydrate (by volume!).
But, if the density of "spud lite" is less, the % by mass composition remains the same, that is, for every 100 g of potato (traditional or "spud lite") there will be 17.5 g of carbohydrate (but the "spud lite" potato will be a bigger potato for your 100 g).
The nutrition label on a packet of "spud lite" potatoes gives the following masses per 100 g of potato:
- fat < 0.1 g
- protein 1.4 g
- carbohydrate: 8.9 g
- sugars: 1.1 g
- dietary fibre: 1.4 g
(assuming the dietary fibre is cellulose which is also a carbohydrate).
This means that the actual mass of carbohydrate per 100 g of potato has been decreased. That is, "spud lites" are not just less dense than traditional potatoes.
Another way to decrease the proportion of carbohydrate in your potatoes would be to increase their water content.
Imagine you have 100 g of traditional potato. This potato is made up of 79 g of water and 17.5 g of carbohydrate.
"Spud lite" contains 11.4 g of carbohydrate.
If all the lost mass of carbohydrate in the "spud lite" (17.5 - 11.4 = 6.1 g) was present as water, then the mass of water in "spud lite" = 6.1 + 79 = 85.1 g
And you, the consumer, is just paying for additional water in your potato!Further Reading
Experimental Design
Carbohydrates
Proteins
Lipids (fats and oils)
Percentage Composition
Density
Suggested Study Questions:
- Design an experiment to test the hypothesis that "spud lite" potatoes have a lower density than traditional potatoes.
- Design an experiment to test the hypothesis that "spud lite" potatoes have a greater percentage by mass of water than traditional potatoes.
- For each serving of traditional potato given below, calculate the mass of carbohydrate consumed:
- 25 g of potato
- 75 g of potato
- 135 g of potato
- Calculate the mass of "spud lite" you would have to consume in order to obtain
- 1 g of carbohydrate
- 7 g of carbohydrate
- 21 g of carbohydrate
- The density of potato changes as the potato ages on the shelf. The table below shows the results of an experiment in which the mass and volume of the same potato is measured and recorded every 3 days. Calculate the density of the potato on each day.
Day Mass (g) volume (mL) 1 142 130 4 140 129 7 138 128 - Consider the results of the experiment above. Describe any trends that you see in the data and suggest reasons for these trends.
- Explain what chemists mean when they refer to "carbohydrates".
- The nutrition label on "spud lites" lists the mass of carbohydrate, sugars and dietary fibre separately. What do you think the "carbohydrate" is on this label?
- Add together the percent by mass of all the components listed for a traditional potato.Suggest reasons for why the total percentage is less than 100%.
- Potatoes are usually classified as high on the glycemic index (GI). What does this mean?
Thursday, September 14, 2017
Food From Toxic Cycads
The Chamorro people of Guam were suffering from a terrible
disease that resulted in paralysis, dementia and death.
As the Chamorro became more “Americanised”, fewer people
were dying from this disease. Researchers started to look closely at
traditional Chamorro food to find the compounds causing the disease. They
thought they had found the answer, flour made from the seeds of toxic cycads.
But, there was a problem. Cycad seeds are used by many
traditional communities all over the world as food. Why didn’t these other
people get sick and die?
Read more in the September 2017 edition of AUS-e-NEWS:
Sunday, September 10, 2017
I Hate STEM Education!
You might think it strange that I hate STEM education since I spend my life encouraging people to study chemistry. It's not the education part I hate, it's the acronym "STEM" and what it stands for.
I recently read an article by Bryan Scaf, "STEM - We know what it stands for, but what does it mean?" (https://au.educationhq.com/news/40140/stem-we-know-what-it-stands-for-but-what-does-it-mean/).
Which started me wondering if we really do have a shared understanding of the meaning of STEM.
What STEM means depends on who you are talking to.
If you ask a scientist, they will probably tell you that STEM stands for a Scanning Transition Electron Microscope and the first STEM was built in 1938.
If you try asking people in the street, they are most likely to think it has something to do with biology, plant stems or stem cells for example.
Towards the end of the twentieth century, STEM started being used as an acronym for Science, Technology, Engineering and Mathematics (STEM), superseding the previous (and possibly slightly less ambiguous) SMET acronym. STEM education has come to mean an integrated approach to the teaching of science, technology, engineering and mathematics using an inquiry-based learning model.
So the question arises of whether we do indeed know what STEM stands for.
In case you are not convinced that "STEM" is ambiguous, head on over to http://www.acronymfinder.com/STEM.html and read through their list of 19 uses of the acronym STEM.
The first reason why I hate STEM is that the term is ambiguous.
STEM (as science, technology, engineering and maths) is a huge area. It encompasses observable, concrete entities as big as the entire cosmos and as small as elementary particles, and, that's just the STE part! The "M" part is quite nebulous (yes, groan, groan, another bad pun). Maths is based on numbers, shapes and other abstract entities. So when we lump abstract maths and concrete science (including the applied fields of engineering and technology) together we've pretty much covered everything, making STEM so large and all-encompassing that is a useless concept. You can't teach "STEM", but you can attempt to teach a few scientific concepts which can be applied to problems in engineering and/or technology. You can try the same with mathematics, except that you land yourself in the middle of another problem ....
And this next HUGE problem is the way most (non-mathematical) people think about mathematics, the big "M" in "STEM". Science (including engineering and technology) uses maths (small "m") like a tool, an aid to defining and solving problems and to build models. But this isn't really Maths (big "M"). Maths is based on logical reasoning, but there are differences between scientific reasoning and mathematical reasoning.
The scientific method is, broadly speaking, a form of deductive reasoning. A mathematical proof, the essence of maths, is largely based on inductive reasoning. The way "science" views the world is different to the way "maths" views the world. So why on earth do we lump "M" in with the "STE" ?
If I were a Maths teacher, I would be very concerned that lumping maths in with science, engineering and technology makes it look like maths is just a tool to be used rather than an elegant, logical, reasoning process.
I would make a similar argument for Science (S). Lumping science in with engineering and technology makes it look like science is just a tool to be used to solve engineering and technology problems. Science can be used this way, just like mathematics can be used as a tool, but this is not the most important aspect of science. Science is the systematic study of the structure and behaviour of "the world". Scientific study may lead to a theory or a model which can be used to make predictions, which can be tested, lending support to the theory or suggesting modifications to the theory, etc. It is the results of "science", the theory or model, that can be applied to problems (engineering and technology), but teaching/learning science should not be primarily about the application of results, it should be about understanding scientific concepts.
Let me just add that even within the science (S) part of STEM there are huge differences and difficulties. Chemists are primarily interested in understanding and making patterns with "atoms". Physicists are more interested in the interaction of energy and forces. A Chemist might analyse a rubbery material, then think about how atoms could be pushed around in the lab to make a similar material, or a different material with enhanced stretchiness compared to the original, or with less stretchiness, or the same stretchiness but a different colour, or different melting point, etc. A Physicist might look at the same material and be fascinated by the forces required to stretch the material, how far it can be stretched before it deforms or breaks, or whether its stretchiness depends on how fast or slow it is stretched or on how hot or cold it is, etc. Now you might be thinking that this would form a great basis for a STEM education (inquiry-based learning) activity, but I beg to differ. Indeed, students could probably competently and safely investigate stretchiness of a suitable material and think about how the material might be used (engineering/technology) but what have they learnt by doing this? They will have investigated one example (or maybe a few), and drawn a few conclusions about a specific material(s). But what is the point? Will they actually have any understanding of the chemistry and physics principles underlying their observations, because it is the scientific principles that are really useful, not the results of an isolated experiment or two.
In order to have an understanding of the material they need to understand how Chemists might analyse it, and they need to understand how structure and bonding effect properties. If they want to make a new material based on the structure of the original, then they are going to have to come to an understanding of reaction mechanisms. This in itself constitutes a lot of concepts before we even begin on the physics concepts they would need to understand stretchiness.
The problem with STEM education is that it over-emphasizes concrete application and under-emphasizes abstract reasoning. Mathematics and science are so much more than just "tools" to be applied to solve engineering and technology problems.
Mathematics (M) is based on logical reasoning.
Science (S) is based on logical reasoning.
What is engineering (E) based on? Engineering is the application of science and maths.
So what is technology (T) ? Technology is also the application of science.
So, STEM stands for Science (S), Mathematics (M) and their application (TE or should that be TA?).
I think a better acronym would therefore be S&M. I think students might find that more entertaining than STEM.
I recently read an article by Bryan Scaf, "STEM - We know what it stands for, but what does it mean?" (https://au.educationhq.com/news/40140/stem-we-know-what-it-stands-for-but-what-does-it-mean/).
Which started me wondering if we really do have a shared understanding of the meaning of STEM.
What STEM means depends on who you are talking to.
If you ask a scientist, they will probably tell you that STEM stands for a Scanning Transition Electron Microscope and the first STEM was built in 1938.
If you try asking people in the street, they are most likely to think it has something to do with biology, plant stems or stem cells for example.
Towards the end of the twentieth century, STEM started being used as an acronym for Science, Technology, Engineering and Mathematics (STEM), superseding the previous (and possibly slightly less ambiguous) SMET acronym. STEM education has come to mean an integrated approach to the teaching of science, technology, engineering and mathematics using an inquiry-based learning model.
So the question arises of whether we do indeed know what STEM stands for.
In case you are not convinced that "STEM" is ambiguous, head on over to http://www.acronymfinder.com/STEM.html and read through their list of 19 uses of the acronym STEM.
The first reason why I hate STEM is that the term is ambiguous.
STEM (as science, technology, engineering and maths) is a huge area. It encompasses observable, concrete entities as big as the entire cosmos and as small as elementary particles, and, that's just the STE part! The "M" part is quite nebulous (yes, groan, groan, another bad pun). Maths is based on numbers, shapes and other abstract entities. So when we lump abstract maths and concrete science (including the applied fields of engineering and technology) together we've pretty much covered everything, making STEM so large and all-encompassing that is a useless concept. You can't teach "STEM", but you can attempt to teach a few scientific concepts which can be applied to problems in engineering and/or technology. You can try the same with mathematics, except that you land yourself in the middle of another problem ....
And this next HUGE problem is the way most (non-mathematical) people think about mathematics, the big "M" in "STEM". Science (including engineering and technology) uses maths (small "m") like a tool, an aid to defining and solving problems and to build models. But this isn't really Maths (big "M"). Maths is based on logical reasoning, but there are differences between scientific reasoning and mathematical reasoning.
The scientific method is, broadly speaking, a form of deductive reasoning. A mathematical proof, the essence of maths, is largely based on inductive reasoning. The way "science" views the world is different to the way "maths" views the world. So why on earth do we lump "M" in with the "STE" ?
If I were a Maths teacher, I would be very concerned that lumping maths in with science, engineering and technology makes it look like maths is just a tool to be used rather than an elegant, logical, reasoning process.
I would make a similar argument for Science (S). Lumping science in with engineering and technology makes it look like science is just a tool to be used to solve engineering and technology problems. Science can be used this way, just like mathematics can be used as a tool, but this is not the most important aspect of science. Science is the systematic study of the structure and behaviour of "the world". Scientific study may lead to a theory or a model which can be used to make predictions, which can be tested, lending support to the theory or suggesting modifications to the theory, etc. It is the results of "science", the theory or model, that can be applied to problems (engineering and technology), but teaching/learning science should not be primarily about the application of results, it should be about understanding scientific concepts.
Let me just add that even within the science (S) part of STEM there are huge differences and difficulties. Chemists are primarily interested in understanding and making patterns with "atoms". Physicists are more interested in the interaction of energy and forces. A Chemist might analyse a rubbery material, then think about how atoms could be pushed around in the lab to make a similar material, or a different material with enhanced stretchiness compared to the original, or with less stretchiness, or the same stretchiness but a different colour, or different melting point, etc. A Physicist might look at the same material and be fascinated by the forces required to stretch the material, how far it can be stretched before it deforms or breaks, or whether its stretchiness depends on how fast or slow it is stretched or on how hot or cold it is, etc. Now you might be thinking that this would form a great basis for a STEM education (inquiry-based learning) activity, but I beg to differ. Indeed, students could probably competently and safely investigate stretchiness of a suitable material and think about how the material might be used (engineering/technology) but what have they learnt by doing this? They will have investigated one example (or maybe a few), and drawn a few conclusions about a specific material(s). But what is the point? Will they actually have any understanding of the chemistry and physics principles underlying their observations, because it is the scientific principles that are really useful, not the results of an isolated experiment or two.
In order to have an understanding of the material they need to understand how Chemists might analyse it, and they need to understand how structure and bonding effect properties. If they want to make a new material based on the structure of the original, then they are going to have to come to an understanding of reaction mechanisms. This in itself constitutes a lot of concepts before we even begin on the physics concepts they would need to understand stretchiness.
The problem with STEM education is that it over-emphasizes concrete application and under-emphasizes abstract reasoning. Mathematics and science are so much more than just "tools" to be applied to solve engineering and technology problems.
Mathematics (M) is based on logical reasoning.
Science (S) is based on logical reasoning.
What is engineering (E) based on? Engineering is the application of science and maths.
So what is technology (T) ? Technology is also the application of science.
So, STEM stands for Science (S), Mathematics (M) and their application (TE or should that be TA?).
I think a better acronym would therefore be S&M. I think students might find that more entertaining than STEM.
Thursday, September 7, 2017
Graphene from Graphite
In 2004, University of Manchester researchers isolated graphene by applying sticky tape to a piece of graphite and peeling off a layer, then repeating the sticking and peeling process on this and subsequent layers until they had a layer that was just one carbon atom thick. The final 2-dimensional layer of carbon atoms is graphene. The structure of graphene is shown below:
The researchers, Professors Andre Geim and Kostya Novoselov were awarded the 2010 Nobel Prize in Physics.
Graphene is a highly sought after material. It is stronger than steel, yet it is a million times thinner a strand of hair. It is also a better conductor than the copper commonly used for electrical wiring. In order to use graphene in consumer products it needs to be produced on a large scale and in commercial quantities. It is not commercially viable to spend large amounts of time peeling off layers from graphite using sticky tape to produce small quantities of graphene. So the race has been on to find a process that could be used commercially.
One method is to oxidize graphite using hazardous oxidizing agents like anhydrous sulfuric acid and potassium peroxide. A representation of a layer of this oxidized graphene from the stacked layers making up graphite is shown below:
Layers of oxidized graphene can then be separated chemically from the bulk graphite, but these processes take a long time, and, the product is not graphene but oxidized graphene which is not as conductive as pure graphene.
University of Connecticut (UConn) Professor Doug Adamson has found a new way to produce graphene based on its solubility. Graphene is insoluble in liquids like oil, hexane and water.
Imagine you have a jug containing some oil and some water. If you wait, the two liquids will separate out, forming two distinct layers as represented below:
The less dense oil will float on top of the more dense water. If you add graphite to the area where these two liquids meet (the interface), then the stacked layers of graphene sheets in the graphite spontaneously "unstack" and spread out to cover this interface. These trapped graphene sheets can be locked into place using a cross-linked polymer.
The researchers are now investigating how this graphene composite material could be used to desalinate brackish water.
Reference
The researchers, Professors Andre Geim and Kostya Novoselov were awarded the 2010 Nobel Prize in Physics.
Graphene is a highly sought after material. It is stronger than steel, yet it is a million times thinner a strand of hair. It is also a better conductor than the copper commonly used for electrical wiring. In order to use graphene in consumer products it needs to be produced on a large scale and in commercial quantities. It is not commercially viable to spend large amounts of time peeling off layers from graphite using sticky tape to produce small quantities of graphene. So the race has been on to find a process that could be used commercially.
One method is to oxidize graphite using hazardous oxidizing agents like anhydrous sulfuric acid and potassium peroxide. A representation of a layer of this oxidized graphene from the stacked layers making up graphite is shown below:
Layers of oxidized graphene can then be separated chemically from the bulk graphite, but these processes take a long time, and, the product is not graphene but oxidized graphene which is not as conductive as pure graphene.
University of Connecticut (UConn) Professor Doug Adamson has found a new way to produce graphene based on its solubility. Graphene is insoluble in liquids like oil, hexane and water.
Imagine you have a jug containing some oil and some water. If you wait, the two liquids will separate out, forming two distinct layers as represented below:
The less dense oil will float on top of the more dense water. If you add graphite to the area where these two liquids meet (the interface), then the stacked layers of graphene sheets in the graphite spontaneously "unstack" and spread out to cover this interface. These trapped graphene sheets can be locked into place using a cross-linked polymer.
The researchers are now investigating how this graphene composite material could be used to desalinate brackish water.
Reference
- Steven J. Woltornist, Andrew J. Oyer, Jan-Michael Y. Carrillo, Andrey V. Dobrynin, Douglas H. Adamson. Conductive Thin Films of Pristine Graphene by Solvent Interface Trapping. ACS Nano, 2013; 7 (8): 7062 DOI: 10.1021/nn402371c
Further Reading:
Suggested Study Questions
- Explain why graphite is a good conductor of electricity.
- Explain how the structure of graphene and graphite are:
- similar
- different
- Explain why graphene is considered to be a 2-dimensional material but graphite is considered to be a 3-dimensional material.
- Explain why graphene is a much better conductor of electricity than graphite.
- What characteristics of graphene allow it to be peeled off in layers from bulk graphite. Explain your answer.
- Explain why a mixture of oil and water will separate out into 2 distinct layers rather than forming a homogeneous mixture.
- Consider the structure of graphene to explain the insolubility of graphene in:
- water
- oil
- Explain why copper is a good conductor of electricity.
- Discuss how the structures of copper and graphene are:
- similar
- different
- Explain why graphene is a much better conductor of electricity than copper.
Monday, September 4, 2017
Formula for Hydrogen?
I admit it. I love TV game shows. Last Friday I watched one of my favourite shows while eating my (late) lunch. I was even moderately successful at answering some of the questions, until the Host asked The Chaser what the chemical formula for hydrogen was. This led to the following exchange:
Chaser: H
Host: Incorrect
Contestants: H one (we will assume they meant H1)
Host: Incorrect. The correct answer is H two (we will assume he meant H2)
So, who was right?
Let's take the Host's "correct" answer first.
The Earth's atmosphere contains small amounts of diatomic molecules of hydrogen gas. "Di" means two and "atomic" refers to atoms so hydrogen gas in the atmosphere is made up of molecules in which 2 atoms of hydrogen are bonded together. When we make hydrogen gas in the laboratory we are making these H2 molecules. So it seems that the Host got it right ..... except ..... the question didn't ask for the formula of hydrogen gas found in the atmosphere!
So let's turn our attention to the Contestants' response.
Is H1 a plausible chemical formula for hydrogen?
Not really. If there is only 1 atom of an element in the chemical formula, the "1" is trivial and not included in the formula, so H1 is the same as H which was the Chaser's response!
So, was the Chaser right?
Is H a valid chemical formula for hydrogen?
Hydrogen is a strange atom. It has 1 proton in its nucleus, and 1 electron "orbiting" that nucleus. In fact, this 1 so-called "valence electron" is a feature common to all Group 1 metals (alkali metals), but other properties of hydrogen suggest it is more like a non-metal than a metal. This similarity to the Group 1 metals led to the prediction that it should be possible to create metallic hydrogen. This would be a solid in which the hydrogen atoms (protons in effect) would be held in a 3-dimensional array with delocalised electrons acting as the metallic bonds holding the array together. This metallic hydrogen would, in theory, be an excellent conductor, indeed it would be a "superconductor", which is why the race has been on to create it!
A chemical formula of a covalent molecule tells us how many atoms of each element are covalently bonded together, H2 has 2 atoms of hydrogen with a covalent bond between them.
But the chemical formula for a 3-dimensional metallic array refers to the ratio of atoms of each element, if only 1 element is present in a metallic array, like that of sodium metal, then the chemical formula is just the symbol for the element, Na, in this case, or H if you are referring to metallic hydrogen.
So, H is a valid chemical formula for metallic hydrogen, if it exists.
But does metallic hydrogen exist?
In January 2017, researchers at Harvard University announced that they had produced metallic hydrogen in the laboratory using immense pressure. So metallic hydrogen, H, can exist.
Back to the game show.
The Host was right, H2 is the chemical formula for gaseous hydrogen in the atmosphere.
The Chaser was right, H is the chemical formula for metallic hydrogen.
The Contestants were almost right: Chemists don't write H1 they just write H.
There is a moral to this story.
Be careful when writing questions. The question should not be ambiguous unless you are prepared to accept multiple different answers that are correct.
Be even more careful when answering test and exam questions. If you need to make assumptions to answer the question you MUST state what those assumptions are when you write your answer.
Reference:
Chaser: H
Host: Incorrect
Contestants: H one (we will assume they meant H1)
Host: Incorrect. The correct answer is H two (we will assume he meant H2)
So, who was right?
Let's take the Host's "correct" answer first.
The Earth's atmosphere contains small amounts of diatomic molecules of hydrogen gas. "Di" means two and "atomic" refers to atoms so hydrogen gas in the atmosphere is made up of molecules in which 2 atoms of hydrogen are bonded together. When we make hydrogen gas in the laboratory we are making these H2 molecules. So it seems that the Host got it right ..... except ..... the question didn't ask for the formula of hydrogen gas found in the atmosphere!
So let's turn our attention to the Contestants' response.
Is H1 a plausible chemical formula for hydrogen?
Not really. If there is only 1 atom of an element in the chemical formula, the "1" is trivial and not included in the formula, so H1 is the same as H which was the Chaser's response!
So, was the Chaser right?
Is H a valid chemical formula for hydrogen?
Hydrogen is a strange atom. It has 1 proton in its nucleus, and 1 electron "orbiting" that nucleus. In fact, this 1 so-called "valence electron" is a feature common to all Group 1 metals (alkali metals), but other properties of hydrogen suggest it is more like a non-metal than a metal. This similarity to the Group 1 metals led to the prediction that it should be possible to create metallic hydrogen. This would be a solid in which the hydrogen atoms (protons in effect) would be held in a 3-dimensional array with delocalised electrons acting as the metallic bonds holding the array together. This metallic hydrogen would, in theory, be an excellent conductor, indeed it would be a "superconductor", which is why the race has been on to create it!
A chemical formula of a covalent molecule tells us how many atoms of each element are covalently bonded together, H2 has 2 atoms of hydrogen with a covalent bond between them.
But the chemical formula for a 3-dimensional metallic array refers to the ratio of atoms of each element, if only 1 element is present in a metallic array, like that of sodium metal, then the chemical formula is just the symbol for the element, Na, in this case, or H if you are referring to metallic hydrogen.
So, H is a valid chemical formula for metallic hydrogen, if it exists.
But does metallic hydrogen exist?
In January 2017, researchers at Harvard University announced that they had produced metallic hydrogen in the laboratory using immense pressure. So metallic hydrogen, H, can exist.
Back to the game show.
The Host was right, H2 is the chemical formula for gaseous hydrogen in the atmosphere.
The Chaser was right, H is the chemical formula for metallic hydrogen.
The Contestants were almost right: Chemists don't write H1 they just write H.
There is a moral to this story.
Be careful when writing questions. The question should not be ambiguous unless you are prepared to accept multiple different answers that are correct.
Be even more careful when answering test and exam questions. If you need to make assumptions to answer the question you MUST state what those assumptions are when you write your answer.
Reference:
- Ranga P. Dias, Isaac F. Silvera. Observation of the Wigner-Huntington Transition to Metallic Hydrogen. Science, 2017 DOI: 10.1126/science.aal1579
Tutorials Relevant to this Post
Periodic Table of the Elements
Elements and Compounds
Metals and Nonmetals
Molecular Formula
Periodic Table of the Elements
Elements and Compounds
Metals and Nonmetals
Molecular Formula
Naming Covalent Compounds
Empirical Formula and Molecular Formula
Trends in Group 1 Elements
Metallic Bonding
Suggested Study Questions
Empirical Formula and Molecular Formula
Trends in Group 1 Elements
Metallic Bonding
Suggested Study Questions
- Use the Periodic Table of the Elements to find the chemical symbol for each of the following atoms:
- hydrogen
- helium
- carbon
- nitrogen
- oxygen
- chlorine
- Write a molecular formula for each of the following diatomic gas molecules:
- hydrogen
- nitrogen
- oxygen
- chlorine
- Give the number of atoms of each element present in the molecular formulae below:
- H2O
- H2O2
- CO
- CO2
- NH3
- NO
- NO2
- N2O2
- Let M represent an atom of an element. Circle the elements below for which the molecular formula of the element at room temperature and pressure could be represented by M
- helium
- sodium
- oxygen
- iron
- gold
- neon
- chlorine
- nitrogen
- hydrogen
- For the description of each molecule below, write the molecular formula
- one carbon atom and four hydrogen atoms
- one nitrogen atom and three chlorine atoms
- two nitrogen atoms and one oxygen atom
- one nitrogen atom and five oxygen atoms
- two chlorine atoms and two oxygen atoms
- one carbon atom, one hydrogen atom and three chlorine atoms
- Given the name of each molecule below, write the molecular formula:
- hydrogen chloride
- carbon monoxide
- carbon dioxide
- sulfur dioxide
- sulfur trioxide
- sulfur dichloride
- Consider the list of compounds with a possible molecular formulae below. Circle the incorrect formulae and justify your answer:
- water, 2HO
- carbon monoxide, C1O1
- hydrogen peroxide, H2O2
- sulfur trioxide: SO2
- ammonia, NH3
- hydrogen sulfide, H2S
- carbon dioxide, C2O
- sulfur dichloride, S1Cl2
- From the list below, circle the elements that belong to Group 1 of the Periodic Table of the Elements:
- sodium
- helium
- oxygen
- lithium
- chlorine
- nitrogen
- carbon
- potassium
- calcium
- Draw a table with the headings "metal" and "nonmetal". Place each of the following elements in the correct column:
- hydrogen
- helium
- calcium
- carbon
- nitrogen
- potassium
- oxygen
- chlorine
- sodium
- From the list below, circle the elements that would exist at room temperature and pressure as an array of "atoms" help together by delocalised electrons:
- hydrogen
- carbon
- sodium
- lithium
- nitrogen
- chlorine
- iron
- gold
- oxygen
Thursday, August 31, 2017
Betaines
Betaines are found in plants, animals and microorganisms. Rich sources of betaines in the human diet are seafood, spinach and wheat germ or bran. Research is beginning to indicate that betaines are important nutrients for the prevention of chronic disease. Researchers are also interested in incorporating betaines into polymer brushes used for antifouling and lubrication.
Betaines are compounds with a positively charged functional group linked to a negatively charged functional group with an alkyl chain in between. The alkyl chain is often referred to as an alkyl chain spacer. The general structure of an N-alkyl betaine is shown below:
The first betaine discovered was found in sugar beets in the nineteenth century. This betaine is (trimethylammonio)a
Another example of a betaine is 2-(trimethylammonio
2-(Trimethylammonio
Betaines are strongly attracted to water molecules because of these two charged functional groups.
The solubility of betaines in water is dependent on the length of the carbon chain, as well as on temperature and pH.
In acidic solution, betaines acquire a net positive charge and act like a cationic surfactant. In anionic solutions, betaines acquire a net negative charge and act like an anionic surfactant.
Betaines can also be used in polymer brushes which are polymers bound to a surface. Polymer brushes can be used for antifouling and lubrication because the hydration of the ionic groups reduces the ability of other materials to adhere to the surface.
Researchers at Kyushu University recently investigated a series of alkly chain spacers of different lengths bound to a silicon surface. They found that the polymer brushes swelled in humid air and water. It is believed that this is due to electrostatic repulsion between charged groups, and not dependent on the length of the alkyl chain.
In deionised water, net positive cations and net negative anions are repelled because of the electrostatic force which causes the chain dimension to expand, whereas they shrink under high ionic strength by a charge screening effect of the bound ions.
Reference:
https://www.sciencedaily.com/releases/2017/08/170821094302.htm
Further Reading
Introduction to Functional Groups
2-Dimensional Structural Formula
Condensed Structural Formula
Molecular Formula
Amino Acids
Surfactants ( as found in synthetic detergents)
Intermolecular Forces and Solubility
Suggested Study Questions
Betaines are compounds with a positively charged functional group linked to a negatively charged functional group with an alkyl chain in between. The alkyl chain is often referred to as an alkyl chain spacer. The general structure of an N-alkyl betaine is shown below:
The first betaine discovered was found in sugar beets in the nineteenth century. This betaine is (trimethylammonio)a
2-(Trimethylammonio
Betaines are strongly attracted to water molecules because of these two charged functional groups.
The solubility of betaines in water is dependent on the length of the carbon chain, as well as on temperature and pH.
In acidic solution, betaines acquire a net positive charge and act like a cationic surfactant. In anionic solutions, betaines acquire a net negative charge and act like an anionic surfactant.
Betaines can also be used in polymer brushes which are polymers bound to a surface. Polymer brushes can be used for antifouling and lubrication because the hydration of the ionic groups reduces the ability of other materials to adhere to the surface.
Researchers at Kyushu University recently investigated a series of alkly chain spacers of different lengths bound to a silicon surface. They found that the polymer brushes swelled in humid air and water. It is believed that this is due to electrostatic repulsion between charged groups, and not dependent on the length of the alkyl chain.
In deionised water, net positive cations and net negative anions are repelled because of the electrostatic force which causes the chain dimension to expand, whereas they shrink under high ionic strength by a charge screening effect of the bound ions.
Reference:
https://www.sciencedaily.com/releases/2017/08/170821094302.htm
Further Reading
Introduction to Functional Groups
2-Dimensional Structural Formula
Condensed Structural Formula
Molecular Formula
Amino Acids
Surfactants ( as found in synthetic detergents)
Intermolecular Forces and Solubility
Suggested Study Questions
- Locate and identify each functional group on the skeletal structural formula of
- general formula N-alkyl betaine
- (trimethylammonio)a
cetate - 2-(trimethylammonio
)octadecanoate - 2-(trimethylammonio
)tetradecanoate - Draw a 2-dimensional structural formula for each of the following molecules:
- (trimethylammonio)a
cetate - 2-(trimethylammonio
)octadecanoate - 2-(trimethylammonio
)tetradecanoate - Write the condensed structural formula for each of the following molecules:
- (trimethylammonio)a
cetate - 2-(trimethylammonio
)octadecanoate - 2-(trimethylammonio
)tetradecanoate - Write the molecular formula for each of the following molecules:
- (trimethylammonio)a
cetate - 2-(trimethylammonio
)octadecanoate - 2-(trimethylammonio
)tetradecanoate - Compare the structure of betaines to that of 2-amino acids. Can N-alkyl betaines be classified as alpha amino acids (2-amino acids) ? Justify your answer.
- Write chemical equations to describe what happens to an N-alkyl betaine in:
- acidic aqueous solution
- basic aqueous solution
- Compare the structure of N-alkyl betaines to the surfactants found in synthetic detergents. In what ways are surfactant molecules
- similar to N-alkyl betaines
- different from N-alkyl betaines
- Explain how N-alkyl betaines act like
- a cationic surfactant in acidic aqueous solution
- an anionic surfactant in basic aqueous solution
- Consider the structure of (trimethylammonio)a
cetate and 2-(trimethylammonio )octadecanoate. Which molecule do you expect to be more soluble in water? Justify your answer. - Consider the structure of (trimethylammonio)a
cetate and 2-(trimethylammonio )octadecanoate. Which molecule do you expect to be more soluble in paraffin oil? Justify your answer.
Thursday, August 24, 2017
Nanoparticles to Remove Coral Bleaching Oxybenzone
Sunblocks contain a number of different compounds including oxybenzone which acts as a UV filter. The skeletal structural formula of oxybenzone is shown below:
Oxybenzone is soluble in water.
Before you go snorkeling in the Great Barrier Reef to be amazed by the beautiful corals, fascinating fish and other exciting wonders, you smother yourself in sunblock. When you step into the water, the oxybenzone starts to dissolve. Unfortunately, oxybenzone contributes to coral bleaching, the killing off of the tiny, colourful zooxanthellae marine algae that live inside corals. The result is that the coral loses its colour and appears white, as if it has been bleached.
Researchers have found a way to soak up the oxybenzone from the seawater using magnetite nanoparticles.
Magnetite, Fe3O4 , is a mineral made up of iron(II) and iron(III) oxides and is one of the main iron ores, that is, magnetite is mined in order to produce iron. Magnetite is ferromagnetic, that is, it is attracted to a magnet. It is the most magnetic naturally occurring mineral on Earth. If you could get the oxybenzone in the seawater to attach to magnetite nanoparticles then you could pull the oxybenzone out of the water using a magnet.
First, the researchers coated the magnetite nanoparticles with sodium oleate. The skeletal structural formula of sodium oleate is shown below:
Next, they oxidised the oleate coating to increase the number of hydroxyl (OH) functional groups:
Since oxybenzone can interact with other molecules via hydrogen bonds, magnetite nanoparticles covered in a coating rich with hydroxyl functional groups increases the interactions between oxybenzone and the nanoparticles. Once the oxybenzone has hydrogen bonded to the nanoparticle coating, a magnet can be used to extract the particles from water.
Does it work?
One brave researcher applied sunblock, stepped into the ocean, waited 10 minutes, then collected a sample of the surrounding seawater. Back at the lab, chromatography was used to determine the concentration of oxybenzone in the water, 1.3 ppm. This is a disturbing result since it is known that the concentration needed to bleach coral is measured in parts per billion.
Next, the researchers prepared seawater samples. Some had no magnetite nanoparticles added, others had the nanoparticles added. Then they added 30 ppm oxybenzone to all the samples. The concentration of oxybenzone in the samples with no nanoparticles did not change in an hour. In the samples that contained the nanoparticles, 95% of the oxybenzone was removed within the hour.
Reference
American Chemical Society. "Sopping up sunblock from oceans to save coral reefs." ScienceDaily. ScienceDaily, 21 August 2017.
Further Reading
Solutions Concepts
Water as a Solvent
Transition Metals (magnetism)
Fatty Acids
Carboxylic Acids
Nanoparticles and Nanotechnology
Parts per Million (ppm)
Chromatography
Experimental Design
Variables
2-Dimensional Structural Formula
Skeletal Structural Formula
Molecular Formula
Suggested Study Questions
Before you go snorkeling in the Great Barrier Reef to be amazed by the beautiful corals, fascinating fish and other exciting wonders, you smother yourself in sunblock. When you step into the water, the oxybenzone starts to dissolve. Unfortunately, oxybenzone contributes to coral bleaching, the killing off of the tiny, colourful zooxanthellae marine algae that live inside corals. The result is that the coral loses its colour and appears white, as if it has been bleached.
Researchers have found a way to soak up the oxybenzone from the seawater using magnetite nanoparticles.
Magnetite, Fe3O4 , is a mineral made up of iron(II) and iron(III) oxides and is one of the main iron ores, that is, magnetite is mined in order to produce iron. Magnetite is ferromagnetic, that is, it is attracted to a magnet. It is the most magnetic naturally occurring mineral on Earth. If you could get the oxybenzone in the seawater to attach to magnetite nanoparticles then you could pull the oxybenzone out of the water using a magnet.
First, the researchers coated the magnetite nanoparticles with sodium oleate. The skeletal structural formula of sodium oleate is shown below:
Since oxybenzone can interact with other molecules via hydrogen bonds, magnetite nanoparticles covered in a coating rich with hydroxyl functional groups increases the interactions between oxybenzone and the nanoparticles. Once the oxybenzone has hydrogen bonded to the nanoparticle coating, a magnet can be used to extract the particles from water.
Does it work?
One brave researcher applied sunblock, stepped into the ocean, waited 10 minutes, then collected a sample of the surrounding seawater. Back at the lab, chromatography was used to determine the concentration of oxybenzone in the water, 1.3 ppm. This is a disturbing result since it is known that the concentration needed to bleach coral is measured in parts per billion.
Next, the researchers prepared seawater samples. Some had no magnetite nanoparticles added, others had the nanoparticles added. Then they added 30 ppm oxybenzone to all the samples. The concentration of oxybenzone in the samples with no nanoparticles did not change in an hour. In the samples that contained the nanoparticles, 95% of the oxybenzone was removed within the hour.
Reference
American Chemical Society. "Sopping up sunblock from oceans to save coral reefs." ScienceDaily. ScienceDaily, 21 August 2017.
Further Reading
Solutions Concepts
Water as a Solvent
Transition Metals (magnetism)
Fatty Acids
Carboxylic Acids
Nanoparticles and Nanotechnology
Parts per Million (ppm)
Chromatography
Experimental Design
Variables
2-Dimensional Structural Formula
Skeletal Structural Formula
Molecular Formula
Suggested Study Questions
- For a molecule of oxybenzone:
- draw the 2-dimensional structural formula
- give the molecular formula
- On the 2-dimensional structural formula of oxybenzone identify and name each functional group present.
- Use diagrams to explain why oxybenzone is soluble in water.
- Draw the 2-dimensional structural formula for oleic acid.
- On your structural formula of oleic acid, identify and name the functional group(s).
- Suggest a method by which you could change oleic acid into sodium oleate in the laboratory.
- Suggest a method by which you could oxidise sodium oleate in the laboratory.
- Explain the term "nanoparticle".
- Why do you think the researchers chose nanoparticles of magnetite rather than bulk magnetite for this research?
- Consider the description of the experiment used to determine the effectiveness of the magnetite nanoparticles in removing oxybenzone from seawater:
- What was the hypothesis being tested?
- What was the aim of the experiment?
- What variables need to be considered in this experiment?
- What is the independent variable in the experiment?
- What is the dependent variable in the experiment?
- Which variables are constant variables in the experiment?
- Why did the experimenters add nanoparticles to some samples but not to others?
- Write out a suitable method for this experiment.
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