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:
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