The mass number was 46
The following proton numbers were registered on the scanner...
Es - 45
S - 36
Am - 36
Mg - 41
O - 42
Si - 43
Xe - 12
Cf - 42
Lr - 42
Th - 41
235U - 42
Hg - 42
Ne - 40
Li - 34
Be - 43
Pt - 44
Md - 43
Ag - 35
Mn - 41
Kr - 41
Ag - 43
Au - 44
Ra - 27
Pu - 37
Any problems or clashes mail me or see me on Saturday. We will go over problems in the test next time we meet and go over covalent bonds.
Have a great weekend!
Thursday, October 28, 2004
Chemical testing in progress - Isotopes needed
I have been through the tests, but haven't come up with any conclusive results yet. The results should be posted up here with Mass number and proton/positive charge number tonight by about 8pm after which point I'm going out to play at the Mall.
However initial tests reveal the presence of some double-bonded elements which are in need of isotopes. The elements listed below are the elements that have been taken but if your element is has a * by it then your element is being used by more than one person. If this is the case please email me with another element or an isotope of that element that you would like to use instead. Remember that some isotopes have their own names like Tritium and Deuterium
Es - Einsteinium
S - Sulphur
Am - Americium
Mg - Magnesium
Si - Silicon
Ca - Calcium
Ra - Radon
O - Oxygen
Xe - Xenon *
Cf - Californium
Ir - Iridium
Th - Thorium
235U - 235 Uranium
Hg - Mercury
Li - Lithium
Be - Berylium
Pt - Platinum
Md - Mendelevium
Ag - Silver *
Mn - Manganese
Kr - Krypton
Au - Gold *
Pu - Plutonium
Watch this space
However initial tests reveal the presence of some double-bonded elements which are in need of isotopes. The elements listed below are the elements that have been taken but if your element is has a * by it then your element is being used by more than one person. If this is the case please email me with another element or an isotope of that element that you would like to use instead. Remember that some isotopes have their own names like Tritium and Deuterium
Es - Einsteinium
S - Sulphur
Am - Americium
Mg - Magnesium
Si - Silicon
Ca - Calcium
Ra - Radon
O - Oxygen
Xe - Xenon *
Cf - Californium
Ir - Iridium
Th - Thorium
235U - 235 Uranium
Hg - Mercury
Li - Lithium
Be - Berylium
Pt - Platinum
Md - Mendelevium
Ag - Silver *
Mn - Manganese
Kr - Krypton
Au - Gold *
Pu - Plutonium
Watch this space
Week 9 Homework - Calling all poets!!!
A simple one this week so you guys can think of something other than chemistry for a change. This weeks homework is for online submission right here in the comments box below under your chemical pseudonym please. This must be done by Wednesday.
Very simple homework this week. All you have to do is come up with a 5 line limerick explaining something we have covered this year in chemistry. Look over your sylabus and you will see that we have covered
The nature of matter
Elements, mixtures and compounds
Particulate state of matter
Absolute zero
Gases under pressure
Diffusion
Atoms and elements
Ions, ionic bonding, ionic compounds
Covalent bonds
The periodic table, periods, groups
Properties of groups
Atomic structure
You can also write on experimental techniques, which we should cover later on in the term and on any subject that you feel you can enlighten the rest of us on.
You will get marks for wit, intelleigence and factual content. The homework is only the 5-line Limerick but if you want to go overboard and write a full ode to chemistry then feel free to submit these by email to the usual address and I will post the best ones right here as the main body and you will get a credit the day after it appears online.
Original stories involving chemicals in bizarre adventures will also be considered, original computer artwork can be posted too.
In case you are unsure of what a limerick is, they are a kind of poem. Limericks have a special form. There are five lines, with lines 1, 2 and 5 rhyming, and lines 3 and 4 are rhyming. Good limericks use different words at the end of each line. They also need the right rhythm, or metre:
Very simple homework this week. All you have to do is come up with a 5 line limerick explaining something we have covered this year in chemistry. Look over your sylabus and you will see that we have covered
The nature of matter
Elements, mixtures and compounds
Particulate state of matter
Absolute zero
Gases under pressure
Diffusion
Atoms and elements
Ions, ionic bonding, ionic compounds
Covalent bonds
The periodic table, periods, groups
Properties of groups
Atomic structure
You can also write on experimental techniques, which we should cover later on in the term and on any subject that you feel you can enlighten the rest of us on.
You will get marks for wit, intelleigence and factual content. The homework is only the 5-line Limerick but if you want to go overboard and write a full ode to chemistry then feel free to submit these by email to the usual address and I will post the best ones right here as the main body and you will get a credit the day after it appears online.
Original stories involving chemicals in bizarre adventures will also be considered, original computer artwork can be posted too.
In case you are unsure of what a limerick is, they are a kind of poem. Limericks have a special form. There are five lines, with lines 1, 2 and 5 rhyming, and lines 3 and 4 are rhyming. Good limericks use different words at the end of each line. They also need the right rhythm, or metre:
| d'DAH-dah d'DAH-dah d'DAH (dah)
d'DAH-dah d'DAH-dah d'DAH (dah) d'DAH-dah d'DAH d'DAH-dah d'DAH d'DAH-dah d'DAH-dah d'DAH |
|
There WAS an old MAN from DarJEEling
Who TRAVelled from LONdon to EALing It SAID on the DOOR Please don't SPIT on the FLOOR So he CAREfully SPAT on the CEILing |
Notice how we can sneak in the odd syllable here and there.
Post all limericks in the comments box, anything larger send to me first.
Good luck!
Formulae of Ionic Compound - Questions 8-12
To do these questions you are missing a vital piece of information at the moment, which will be extremely useful, not just in this exercise but in your study of chemistry as a whole.
So far we have learnt about ions as single atoms that have lost or gained an electron, causing imbalance of charge. We also know that on a larger scale, when lots of atoms get together and have more electrons than protons, we also get charge imbalance for example the electrodes in our experiment and the charged plate in the test.
And in all the cases, on the small scale and the large scale, opposite charges attract and like charges repel.
But we have not yet considered the case in between. What about a case of compounds being charged?
When ionic compounds get together, they do so to balance their charges, but there are some groups of elements that get together regularly and are still not balanced in charge. So even though they are combined into a new molecule they are still ions.
Lets take as an example one compound that we have come across already, Sodium Hydroxide.
Sodium hydroxide has the chemical formula NaOH.
What charge does the ion of sodium have? It's in group I so the ion of sodium is created by losing an electron and is hence positive and has a valency of +1. Now we have this other part of the equation, the OH bit. What you have to imagine is that their is a molecule of OH that goes around as a group on it's own. The OH behaves as if it was one ion on it's own. So it's compound and an ion, or a so called compound ion.
The OH molecule is called a HYDROXIDE.
When this combines with Na, it creates NaOH. What charge then does this compound ion have? It has to be the exact opposite of Na to balance out the charge on the Na. So OH as a compound ion has the charge -1.
The compound ion can be written in brackets and treated as if it were just one ion
e.g. Hydroxide = (OH)-1
The charge on a compound ion you just need to remember, unlike with the other ions where you can work it out. Now that we know this piece of info about hydroxide ions, we can do question 9 very easily. Aluminium Hydroxide would be the combination of Al with hydroxide
Al is in Group 3 so its ion has a valency of +3
(OH) has a valency of -1
So you write these (metal first remember) as
Al3+(OH)-1
Flip the numbers down
Al(OH)3
et Voila! That was easy huh? Just ignore the numbers in the bracket and treat the whole thing as if it’s just one ion, paying attention only to the charge outside the bracket.
Now here's some more info on some compound ions that you may want to use to help you answer questions 8-12
Remembering these compound ions and being able to spot them in an equation will help a lot later on in chemistry IGCSE with balancing equations and with identifying and naming compounds, so it’s worth remembering them early.
So far we have learnt about ions as single atoms that have lost or gained an electron, causing imbalance of charge. We also know that on a larger scale, when lots of atoms get together and have more electrons than protons, we also get charge imbalance for example the electrodes in our experiment and the charged plate in the test.
And in all the cases, on the small scale and the large scale, opposite charges attract and like charges repel.
But we have not yet considered the case in between. What about a case of compounds being charged?
When ionic compounds get together, they do so to balance their charges, but there are some groups of elements that get together regularly and are still not balanced in charge. So even though they are combined into a new molecule they are still ions.
Lets take as an example one compound that we have come across already, Sodium Hydroxide.
Sodium hydroxide has the chemical formula NaOH.
What charge does the ion of sodium have? It's in group I so the ion of sodium is created by losing an electron and is hence positive and has a valency of +1. Now we have this other part of the equation, the OH bit. What you have to imagine is that their is a molecule of OH that goes around as a group on it's own. The OH behaves as if it was one ion on it's own. So it's compound and an ion, or a so called compound ion.
The OH molecule is called a HYDROXIDE.
When this combines with Na, it creates NaOH. What charge then does this compound ion have? It has to be the exact opposite of Na to balance out the charge on the Na. So OH as a compound ion has the charge -1.
The compound ion can be written in brackets and treated as if it were just one ion
e.g. Hydroxide = (OH)-1
The charge on a compound ion you just need to remember, unlike with the other ions where you can work it out. Now that we know this piece of info about hydroxide ions, we can do question 9 very easily. Aluminium Hydroxide would be the combination of Al with hydroxide
Al is in Group 3 so its ion has a valency of +3
(OH) has a valency of -1
So you write these (metal first remember) as
Al3+(OH)-1
Flip the numbers down
Al(OH)3
et Voila! That was easy huh? Just ignore the numbers in the bracket and treat the whole thing as if it’s just one ion, paying attention only to the charge outside the bracket.
Now here's some more info on some compound ions that you may want to use to help you answer questions 8-12
| Compound ion | Charge |
| Hydroxide | (OH)- |
| Carbonate | (CO3)2- |
| Sulphate | (SO4)2- |
| Nitrate | (NO3)- |
| Ammonium | (NH4)+ |
Remembering these compound ions and being able to spot them in an equation will help a lot later on in chemistry IGCSE with balancing equations and with identifying and naming compounds, so it’s worth remembering them early.
Portrait of a molecule part 1 - Oxygen
Every other week, if I get the time, there will be a portrait of a molecule, adapted from John Emsleys "Molecules at an Exhibition" just for your reading pleasure.
This weeks molecule is the most important gas in the atmosphere, making up 21% of the volume of dry air. In it's absence or where it gets depleted we would die, as it is essential for respiration.
This weeks molecule is Oxygen.
Early mountain explorers thought that there was less oxygen as we get higher up, but there is still 21%, but the pressure is too low to extract it from the air. If we remember back to our lesson on pressure, where you lot got very confused and picture the particles of air up a mountain and at the bottom of a mountain the ones at the bottom will be "squashed" closer together by the weight of all the air particles above it so would be closer together. As we get higher up there is less pressure from above and hence the particles move further apart. When we breathe air at low pressure there is therefore less particles per breath and so up a mountain we take in less oxygen (and other molecules) with every breath so it becomes harder to breathe. (Can you explain why mountaineers have to take tea that brews at a lower boiling point when they climb mountains using the particle theory and the universal gas law?)
ON May 29, 1953 Tenzig Norgay and Edmund Hilary became the first men to climb Mount Everest, which they did with the help of oxygen cylinders. 40 years later Harry Taylor, a 33 year old ex-SAS officer climbed to the summit alone, without extra oxygen. In 1975 the first woman to scale the peak, Junko Takei of Japan took an oxygen sylinder and in May 1996 the late Alison Hargreaves became the first woman to achieve this feat without the aid of oxygen.
Oxygen is vital for our body but equally it can be lethal. There is a lower and upper limit to the amount of oxygen in the air if it is to be considered safe. If we are not to suffocate, the amount must be above 17%. If we are not to burst into flames the oxygen level must be below 25%. When we consider that the amount on Earth is 21% it is really quite a fortunate coincidence that we are here.
This upper limit of oxygen was used as the plotline by the most amazing comics writer of modern times, the British writer Alan Moore. In his now-classic epic "Swamp Thing", which I highly recommend as one of the most groundbreaking novels across any media, the villain of the piece takes control of the the worlds flora and fauna and holds the world to ransom by pushing the oxygen level of the world up through photosynthesis, while the worlds superheroes look on powerless. The world suddenly becomes a very flammable place and it is up to the hero of the piece to save the day.
We can breathe in oxygen-enriched air, as many sick people do but it does come with associated risk. Hospital patients inside oxygen tents have suffered horrific burns when they have tried to light a cigarette (duuuuuuuuuuh! I have no sympathy for smokers...) The three astronauts destined for the first manned Apollo flight in Earth orbit were burned alive in minutes in their spacecraft on January 27, 1967, when fire started in the oxygen-enriched air of the cabin.
But generally it is too little oxygen that poses the biggest threat to life. The Biosphere project in Arizona came to a premature end in January 1993 when 8 people sealed in a glass-walled ecosystem were left gasping for breath. The project was to investigate if it was possible to sustain human life in a space station or on the moon. Somehow, over a few weeks 30 tons of oxygen had disappeared and the oxygen level fell below the critical level of 17%. It is thought that it had probably reacted with iron in the soil.
This property of iron, that it will readily react with oxygen, is utilised by our bodies. You will learn all about this in Biology. Oxygen is attracted to Haemoglobin in our blood, which contains iron, and is thus efficiently transported to where it is needed. Most, but not all, species use iron as the oxygen carrier. Spiders and lobsters use copper, which is why their blood is blue. Because of iron, a litre of blood can dissolve 200ccs of oxygen, fifty times more than will dissolve in the same volume of water.
Molcules of oxygen gas consist of 2 oxygen atoms, but the bond still puzzles chemists. It appears to be a double bond, and yet the molecule still has 2 rogue electrons which means that it is a so-called 'free radical'
Oxygen gas will liquefy at -183 Celsius and the liquid is magnetic, as Michael Faraday discovered in 1848 when he spilled some and watched it run towards the poles of a magnet; it behaves like this because of the 2 free electrons. (it's observations like these that make good chemists and this should be a lesson to everyone - make a note of everything you observe as it may be useful)
In theory it should react instantly with anything it touches, and yet we know that oxygen is a fairly unreactive molecule, otherwise it would not have built up over millions of years to comprise a fifth of the Earth's atmosphere. Even when it enters our bodies it does not react chemically with its target molecules, but needs an enzyme to catalyse the reaction.
There are a million billion tons of oxygen gas circling the globe, and all of it is produced as a byproduct of photosynthesis in plants. The seven billion tons of fossil fuel we burn each year consumes around 24 billion tons of oxygen, which is only 0.00024% of the total, and plants replace most of it. Even if plants did not replenish the oxygen in the atmosphere, it would take over 2000 years at the present rate of depletion for the oxygen level to fall from 21% to 20%
Our brain must have oxygen to function, and without it this vital organ will begin to die within minutes. There is a critical time after someone stops breathing that you become brain dead, where doctors know that resucitation will probably do more harm than good.
Less well known is that too much oxygen will poison the brain. This threat is not appreciated by many sports divers, according to Kenneth Donald of Edinburgh University, Scotland, who has made a lifelong study of the subject. In his book "Oxygen and the Diver" Donald warns against breathing pure oxygen below 25 feet, since this can lead to convulsions and several divers have drowned. Instead of using compressed air, amateur divers such as undersea photographers, bounty hunters and archaeologists have takent o using so-called nitrox mixtures, which is air with a boosted oxygen content - but this too can be dangerous. Nitrox is a mixture of nitrogen and oxygen, and was developed by the British Navy in World War II for divers disposing of mines, because it allowed more time underwater while avoiding oxygen poisoning and decrompression sickness (the 'bends') Today professional divers use a costly mixture of oxygen and helium (remember your work from elements, compounds and mixtures?) which allows them to work safely at 500 metres and below.
Oxygen is produced industrially by distilling liquefied air, and is either made on site, or delivered via a pipeline, or transported in specially insulated tankers. In the USA production is 25 million tons a year, and in the UK it exceeds 4 million tons. Over a half goes to making steel, about a quarter to making ethylene oxide, which is turned into antifreeze or polyester for fabrics and bottles, and the rest is used as the gas itself, either in medical care, or to purify sewage and so prevent environmental disasters like the one in Paris in 1992. A violent storm caused raw sewage to flood the river Seine, and this rapidly used up the oxygen in the water and killed all the fish. There are now giant pumps to bubble 15 tons of oxygen gas a day into the Seine.
Who first discovered oxygen? The credit usually goes to Joseph Priestly, who was born in Leeds, England. He was a nonconformist preacher and left-wing intellectual who supported the aims of the French Revolution, and an amateur chemist who specialised in studying gases. He discovered oxygen in 1774 after he moved to Lord Shelbourne's estate at Calne in Wiltshire, and it was there that he heated mercury oxide and collected the gas which it gave off. He breathed his new gas (all in the name of science! What a hero! I don't suggest any of you do this in class....) and reported how light-headed it made him feel. He also noted taht a mouse could survive much longer in this new gas than in ordinary air. Priestly moved to Birmingham but there his house was ransacked by a right-wing mob. (That doesn't surprise me at all, as I lived in Birmingham for 3 years and that's the sort of place it is. Horrible. Avoid it like a plague, though just up the road, Stratford upon Avon is very beautiful and was the birthplace of Shakespeare.) Perhaps not surprisingly he eventually moved to the USA. Heck after living in Birmingham for 3 years I moved out here! See the effect that place has!
Little did Priestly know, that Carl Scheele at Uppsala, Sweden, had made oxygen a few months earlier, but had failed to gain the credit that was due because the publisher to whom he sent his manuscript did nothing to publish it. Neither Priestly nor Scheele was responsible for naming the new gas. 'Oxygen' was chosen by the great French chemist Antoine Lavoisier (look this guy up on the web people - he is a chemist of great importance). The name oxygen is actually wrong as it means 'acid-forming', because Lavoisier thought, wrongly, that this element was an essential component of acids. In fact the essential component of acids is Hydrogen.
But could there have been a previous discoverer of oxygen? There is evidence that oxygen was produced 150 years earlier. How else do we explain a remarkable event that happened in London in 1624, when King James and his subjects turned out in their thousands to watch a new wonder of the age: a submarine. This remarkable craft consisted of a wooden framework covered by a watertight, greased leather skin. It was manned by 12 rowers whose oars protruded through sealed ports. With its Dutch inventor, Cornelius Drebel, on board with a few other passengers, it sailed for two hours underwater from Westminster to Greenwich (near my house back home). The Admiralty was not impressed and advised against its adoption.
This mysterious journey was still being talked about 40 years later by no less a scientist than Robert Boyle (of Boyles Law fame) He wrote that one of the passengers, then still alive, had said that when the air in the submarine had been consumed, Drebbel was able to refresh it with pure air from a container. It has been suggested that this purer air must have been oxygen.
One explanation is given by Zbigniew Szydlo in his book "Water which does not wet hands", in which he says that Drebbel was conversant with the work of the Polish alchemist Michael Sendivogius, who lived from 1566-1636, and who knew of a gas which he referred to as 'the aerial food of life'. 'Water which does not wet hands' was Sendivogius' code name for nitre. Sendivogius had observed that when nitre (the old name for potassium nitrate) was heated, gases were evolved. Gentle heating of this salt produces oxygen. In those days nitre was collected from the walls of cellars and latrines (that's toilets to you and me. mmmmm...nice), where it grew as white crystals, or from the leachings of manure and soil. mmmmmmmm...niiiiiiiiiiiiice.... Nitre was gathered on a commerical scale because it was needed to make gunpowder.
Nitres curious ability to produce oxygen might have been known to John Mayow (1641-1679), an Oxford chemist and early fellow of the Roayl Society of London. This is the premier body for scientists and any of you who really want to be scientists should aspire to join these guys when you grow up! He wrote about 'nitro-aerial particles' which came from nitre when it was heated, and this phrase too is thought to refer to oxygen. It has even been suggested that the alchemists' Elixir of Life was not a liquid as popularly supposed, but might have been this secret gas, oxygen.
This weeks molecule is the most important gas in the atmosphere, making up 21% of the volume of dry air. In it's absence or where it gets depleted we would die, as it is essential for respiration.
This weeks molecule is Oxygen.
Early mountain explorers thought that there was less oxygen as we get higher up, but there is still 21%, but the pressure is too low to extract it from the air. If we remember back to our lesson on pressure, where you lot got very confused and picture the particles of air up a mountain and at the bottom of a mountain the ones at the bottom will be "squashed" closer together by the weight of all the air particles above it so would be closer together. As we get higher up there is less pressure from above and hence the particles move further apart. When we breathe air at low pressure there is therefore less particles per breath and so up a mountain we take in less oxygen (and other molecules) with every breath so it becomes harder to breathe. (Can you explain why mountaineers have to take tea that brews at a lower boiling point when they climb mountains using the particle theory and the universal gas law?)
ON May 29, 1953 Tenzig Norgay and Edmund Hilary became the first men to climb Mount Everest, which they did with the help of oxygen cylinders. 40 years later Harry Taylor, a 33 year old ex-SAS officer climbed to the summit alone, without extra oxygen. In 1975 the first woman to scale the peak, Junko Takei of Japan took an oxygen sylinder and in May 1996 the late Alison Hargreaves became the first woman to achieve this feat without the aid of oxygen.
Oxygen is vital for our body but equally it can be lethal. There is a lower and upper limit to the amount of oxygen in the air if it is to be considered safe. If we are not to suffocate, the amount must be above 17%. If we are not to burst into flames the oxygen level must be below 25%. When we consider that the amount on Earth is 21% it is really quite a fortunate coincidence that we are here.
This upper limit of oxygen was used as the plotline by the most amazing comics writer of modern times, the British writer Alan Moore. In his now-classic epic "Swamp Thing", which I highly recommend as one of the most groundbreaking novels across any media, the villain of the piece takes control of the the worlds flora and fauna and holds the world to ransom by pushing the oxygen level of the world up through photosynthesis, while the worlds superheroes look on powerless. The world suddenly becomes a very flammable place and it is up to the hero of the piece to save the day.
We can breathe in oxygen-enriched air, as many sick people do but it does come with associated risk. Hospital patients inside oxygen tents have suffered horrific burns when they have tried to light a cigarette (duuuuuuuuuuh! I have no sympathy for smokers...) The three astronauts destined for the first manned Apollo flight in Earth orbit were burned alive in minutes in their spacecraft on January 27, 1967, when fire started in the oxygen-enriched air of the cabin.
But generally it is too little oxygen that poses the biggest threat to life. The Biosphere project in Arizona came to a premature end in January 1993 when 8 people sealed in a glass-walled ecosystem were left gasping for breath. The project was to investigate if it was possible to sustain human life in a space station or on the moon. Somehow, over a few weeks 30 tons of oxygen had disappeared and the oxygen level fell below the critical level of 17%. It is thought that it had probably reacted with iron in the soil.
This property of iron, that it will readily react with oxygen, is utilised by our bodies. You will learn all about this in Biology. Oxygen is attracted to Haemoglobin in our blood, which contains iron, and is thus efficiently transported to where it is needed. Most, but not all, species use iron as the oxygen carrier. Spiders and lobsters use copper, which is why their blood is blue. Because of iron, a litre of blood can dissolve 200ccs of oxygen, fifty times more than will dissolve in the same volume of water.
Molcules of oxygen gas consist of 2 oxygen atoms, but the bond still puzzles chemists. It appears to be a double bond, and yet the molecule still has 2 rogue electrons which means that it is a so-called 'free radical'
Oxygen gas will liquefy at -183 Celsius and the liquid is magnetic, as Michael Faraday discovered in 1848 when he spilled some and watched it run towards the poles of a magnet; it behaves like this because of the 2 free electrons. (it's observations like these that make good chemists and this should be a lesson to everyone - make a note of everything you observe as it may be useful)
In theory it should react instantly with anything it touches, and yet we know that oxygen is a fairly unreactive molecule, otherwise it would not have built up over millions of years to comprise a fifth of the Earth's atmosphere. Even when it enters our bodies it does not react chemically with its target molecules, but needs an enzyme to catalyse the reaction.
There are a million billion tons of oxygen gas circling the globe, and all of it is produced as a byproduct of photosynthesis in plants. The seven billion tons of fossil fuel we burn each year consumes around 24 billion tons of oxygen, which is only 0.00024% of the total, and plants replace most of it. Even if plants did not replenish the oxygen in the atmosphere, it would take over 2000 years at the present rate of depletion for the oxygen level to fall from 21% to 20%
Our brain must have oxygen to function, and without it this vital organ will begin to die within minutes. There is a critical time after someone stops breathing that you become brain dead, where doctors know that resucitation will probably do more harm than good.
Less well known is that too much oxygen will poison the brain. This threat is not appreciated by many sports divers, according to Kenneth Donald of Edinburgh University, Scotland, who has made a lifelong study of the subject. In his book "Oxygen and the Diver" Donald warns against breathing pure oxygen below 25 feet, since this can lead to convulsions and several divers have drowned. Instead of using compressed air, amateur divers such as undersea photographers, bounty hunters and archaeologists have takent o using so-called nitrox mixtures, which is air with a boosted oxygen content - but this too can be dangerous. Nitrox is a mixture of nitrogen and oxygen, and was developed by the British Navy in World War II for divers disposing of mines, because it allowed more time underwater while avoiding oxygen poisoning and decrompression sickness (the 'bends') Today professional divers use a costly mixture of oxygen and helium (remember your work from elements, compounds and mixtures?) which allows them to work safely at 500 metres and below.
Oxygen is produced industrially by distilling liquefied air, and is either made on site, or delivered via a pipeline, or transported in specially insulated tankers. In the USA production is 25 million tons a year, and in the UK it exceeds 4 million tons. Over a half goes to making steel, about a quarter to making ethylene oxide, which is turned into antifreeze or polyester for fabrics and bottles, and the rest is used as the gas itself, either in medical care, or to purify sewage and so prevent environmental disasters like the one in Paris in 1992. A violent storm caused raw sewage to flood the river Seine, and this rapidly used up the oxygen in the water and killed all the fish. There are now giant pumps to bubble 15 tons of oxygen gas a day into the Seine.
Who first discovered oxygen? The credit usually goes to Joseph Priestly, who was born in Leeds, England. He was a nonconformist preacher and left-wing intellectual who supported the aims of the French Revolution, and an amateur chemist who specialised in studying gases. He discovered oxygen in 1774 after he moved to Lord Shelbourne's estate at Calne in Wiltshire, and it was there that he heated mercury oxide and collected the gas which it gave off. He breathed his new gas (all in the name of science! What a hero! I don't suggest any of you do this in class....) and reported how light-headed it made him feel. He also noted taht a mouse could survive much longer in this new gas than in ordinary air. Priestly moved to Birmingham but there his house was ransacked by a right-wing mob. (That doesn't surprise me at all, as I lived in Birmingham for 3 years and that's the sort of place it is. Horrible. Avoid it like a plague, though just up the road, Stratford upon Avon is very beautiful and was the birthplace of Shakespeare.) Perhaps not surprisingly he eventually moved to the USA. Heck after living in Birmingham for 3 years I moved out here! See the effect that place has!
Little did Priestly know, that Carl Scheele at Uppsala, Sweden, had made oxygen a few months earlier, but had failed to gain the credit that was due because the publisher to whom he sent his manuscript did nothing to publish it. Neither Priestly nor Scheele was responsible for naming the new gas. 'Oxygen' was chosen by the great French chemist Antoine Lavoisier (look this guy up on the web people - he is a chemist of great importance). The name oxygen is actually wrong as it means 'acid-forming', because Lavoisier thought, wrongly, that this element was an essential component of acids. In fact the essential component of acids is Hydrogen.
But could there have been a previous discoverer of oxygen? There is evidence that oxygen was produced 150 years earlier. How else do we explain a remarkable event that happened in London in 1624, when King James and his subjects turned out in their thousands to watch a new wonder of the age: a submarine. This remarkable craft consisted of a wooden framework covered by a watertight, greased leather skin. It was manned by 12 rowers whose oars protruded through sealed ports. With its Dutch inventor, Cornelius Drebel, on board with a few other passengers, it sailed for two hours underwater from Westminster to Greenwich (near my house back home). The Admiralty was not impressed and advised against its adoption.
This mysterious journey was still being talked about 40 years later by no less a scientist than Robert Boyle (of Boyles Law fame) He wrote that one of the passengers, then still alive, had said that when the air in the submarine had been consumed, Drebbel was able to refresh it with pure air from a container. It has been suggested that this purer air must have been oxygen.
One explanation is given by Zbigniew Szydlo in his book "Water which does not wet hands", in which he says that Drebbel was conversant with the work of the Polish alchemist Michael Sendivogius, who lived from 1566-1636, and who knew of a gas which he referred to as 'the aerial food of life'. 'Water which does not wet hands' was Sendivogius' code name for nitre. Sendivogius had observed that when nitre (the old name for potassium nitrate) was heated, gases were evolved. Gentle heating of this salt produces oxygen. In those days nitre was collected from the walls of cellars and latrines (that's toilets to you and me. mmmmm...nice), where it grew as white crystals, or from the leachings of manure and soil. mmmmmmmm...niiiiiiiiiiiiice.... Nitre was gathered on a commerical scale because it was needed to make gunpowder.
Nitres curious ability to produce oxygen might have been known to John Mayow (1641-1679), an Oxford chemist and early fellow of the Roayl Society of London. This is the premier body for scientists and any of you who really want to be scientists should aspire to join these guys when you grow up! He wrote about 'nitro-aerial particles' which came from nitre when it was heated, and this phrase too is thought to refer to oxygen. It has even been suggested that the alchemists' Elixir of Life was not a liquid as popularly supposed, but might have been this secret gas, oxygen.
Monday, October 25, 2004
Practical write up - Something to think about
The 2 ions that make up the ionic compound are disociated in water. This means that they are free to move about on their own. So each one goes to the oppositely charged electrode, splitting the ionic compound into it's 2 ions.
This means that at one electrode there is a gas formed and at the other electrode there is a group 1 metal formed. In your write up can you write a word equation that describes what has just happened? Then write a balanced symbol equation to describe the breakdown of salt including the charges on each ion.
Now look at the safety points.
Ýou have been told that you may smell a gas produced that smells like swimming pools. What is this gas? Which electrode does it form at the anode or the cathode? Remember that it goes to the opposite pole.
At the other electrode there is group I metal formed. Now think about the properties of group I metals. You were warned that the solution produced would be dangerous and you needed to wear goggles. Why do you think this is?
The group I metal is created in water. What happens when group I reacts with water? What happens to the water? What other gas is produced? Write a word and balanced symbol equation in your write up to explain the second reaction in the experiment. Full marks will only go to those who have related all the theory to the practical.
This means that at one electrode there is a gas formed and at the other electrode there is a group 1 metal formed. In your write up can you write a word equation that describes what has just happened? Then write a balanced symbol equation to describe the breakdown of salt including the charges on each ion.
Now look at the safety points.
Ýou have been told that you may smell a gas produced that smells like swimming pools. What is this gas? Which electrode does it form at the anode or the cathode? Remember that it goes to the opposite pole.
At the other electrode there is group I metal formed. Now think about the properties of group I metals. You were warned that the solution produced would be dangerous and you needed to wear goggles. Why do you think this is?
The group I metal is created in water. What happens when group I reacts with water? What happens to the water? What other gas is produced? Write a word and balanced symbol equation in your write up to explain the second reaction in the experiment. Full marks will only go to those who have related all the theory to the practical.
Saturday, October 23, 2004
Homework Week 8 part 2 - to be collected in Wednesday
Now that we all know what an ion is and how we make one and we know what an isotope is, so for our second homework of the week, to be handed in on Wednesday, you will need to research the medical uses of radioactive isotopes and ionising radiation.
Radiation is used in medicine for both seeing and treating illness, and ionisation is a side effect of using it. Find out what you can about the ionisation process and write at least a page on the dangers of using xrays or gamma rays in the hospital, as well as why it is used.
As usual downloads straight from the internet will be given 1/10 so put in the time to learn about ionisation it could be very useful.
Then you need to look up medical and industrial uses of radioactive isotopes. What is an isotope? What does radioactive mean? Where are they used? Take a look at the use of Uranium and Technetium in medical and industrial settings. Then you need to write a page about radioactive isotopes, saying what they are, where they are used and arguing either for or against their use.
In summary
2 Tasks
Radiation is used in medicine for both seeing and treating illness, and ionisation is a side effect of using it. Find out what you can about the ionisation process and write at least a page on the dangers of using xrays or gamma rays in the hospital, as well as why it is used.
As usual downloads straight from the internet will be given 1/10 so put in the time to learn about ionisation it could be very useful.
Then you need to look up medical and industrial uses of radioactive isotopes. What is an isotope? What does radioactive mean? Where are they used? Take a look at the use of Uranium and Technetium in medical and industrial settings. Then you need to write a page about radioactive isotopes, saying what they are, where they are used and arguing either for or against their use.
In summary
2 Tasks
- Write about the ionisation process of ionising radiation. Why and where is radiation used in hospitals and what are the benefits and dangers? Does the benefit outweigh the danger? What effect does ionising radiation have on the body? Where else does ionising radiation come from. At least one page on the medical uses, benefits and dangers of ionising radiation.
- Look at the industrial and medical uses of radioactive isotopes. You may want to look up Uranium and Technetium isotopes. Write a one page argument (or more) for or against the use of radioactive isotopes either backing their use and saying they are safe or that they are a danger and argue your case using available evidence.
Due Wednesday so I can mark over the weekend. I know there is a lot of homework this week but next week I will go easy on you. Remember you have a test and this is all good preparation for it.
Good luck!
Still need a bit of help with ionic compounds in solution?
Try the bbc bitesize website. This is not the best website but if anyone can find any better explanations on the web please post them in the comments box at the end of this post.
Homework for this week part 1
Now that we have done the experiment to investigate ionic compound concentration on electrical conductivity, it's up to you to write up the method, the diagram, the apparatus and the conclusion.
Remember to include in your conclusion any improvements you could make to make a repeat of your experiment more accurate. What other factors could you investigate to look at the electrical properties of ionic compounds? What went wrong if anything and how would you ensure that it doesn't go wrong next time?
In your conclusion, you must look at your results and interpret them. Can you see any trends? What do they tell us? In what way do your results relate to the theory of ionic compounds in solution that you researched for homework? Try to relate yourknowledge of ions to conductivity.
Remember, your method must be in past tense, without the words "I" or "we" - write in the third person passive voice. e.g. "1 Spatula of salt was added" not "I then added 1 spatula of salt" and must be written in such a way that anyone reading it may be able to repeat your experiment exactly as you done it.
Remember to include in your conclusion any improvements you could make to make a repeat of your experiment more accurate. What other factors could you investigate to look at the electrical properties of ionic compounds? What went wrong if anything and how would you ensure that it doesn't go wrong next time?
In your conclusion, you must look at your results and interpret them. Can you see any trends? What do they tell us? In what way do your results relate to the theory of ionic compounds in solution that you researched for homework? Try to relate yourknowledge of ions to conductivity.
Remember, your method must be in past tense, without the words "I" or "we" - write in the third person passive voice. e.g. "1 Spatula of salt was added" not "I then added 1 spatula of salt" and must be written in such a way that anyone reading it may be able to repeat your experiment exactly as you done it.
Ever wondered where chemistry fits in to your life?
Chemistry not feel relevant to you? Why bother learning about molecules, atoms and compounds you may wonder.
Chemicals are present in your food, they are in the air around you, they are IN you. Why not find out something about the world around you and how chemicals fit in to yourlife. There's a great book out there called "Molecules at an Exhibition" by John Emsley in which you can read about some of the assorted gallery of chemicals that we encounter every day, presented as portraits with all their properties and some interesting facts.
The chemicals in Coca Cola and Chocolate are laid bare, vital life chemicals are in there, smelly chemicals, weird chemicals all presented in a readable, well presented, easily digested volume.
Chemicals are present in your food, they are in the air around you, they are IN you. Why not find out something about the world around you and how chemicals fit in to yourlife. There's a great book out there called "Molecules at an Exhibition" by John Emsley in which you can read about some of the assorted gallery of chemicals that we encounter every day, presented as portraits with all their properties and some interesting facts.
The chemicals in Coca Cola and Chocolate are laid bare, vital life chemicals are in there, smelly chemicals, weird chemicals all presented in a readable, well presented, easily digested volume.
Wednesday, October 20, 2004
Covalent bonding - share and share alike
Also next week we will cover another type of bonding called covalent (co = joint/sharing, valent as in valency) bonding. If you are interested in getting ahead why not read about covalent bonding and think of an analogy to explain to the class what covalent bonding is all about? If you're good enough (and you talk to me before the lesson about it) I'll let you take the lesson and write the explanation, which everyone else has to have in their books...
No I mean it
No I mean it
Also in preparation for the practical
make sure you know what a voltmeter and ammeter is and how to measure current and voltage. Study and find out how to draw graphs PROPERLY! What is the dependent and independent variable?
Also practice writing methods PROPERLY in a SCIENTIFIC way.
Drop the words "we", "I" etc. and write in a detached past tense. No "person" needs to be involved and write as if you want someone else to follow your instructions. don't use bullet points.
Also practice writing methods PROPERLY in a SCIENTIFIC way.
Drop the words "we", "I" etc. and write in a detached past tense. No "person" needs to be involved and write as if you want someone else to follow your instructions. don't use bullet points.
Tip for tests - cgp guide
I really should be a salesman. These are really good. http://www.cgpbooks.co.uk/
Reminder - Atomic Structure test on Wednesday
Revise or die. All results to be written into your homework diary after the test and signed by your parents and me.
Recommended reading - CGP Chemistry - higher tier (obviously!) there is a brilliant chapter in there that sums up all you need to know. If you ask me early I may be able to get you copies of the page before the test but i can't promise anything there. It's up to YOU! Go to Marina Mall and buy it yourself, you're most probably going to be there anyway....
Recommended reading - CGP Chemistry - higher tier (obviously!) there is a brilliant chapter in there that sums up all you need to know. If you ask me early I may be able to get you copies of the page before the test but i can't promise anything there. It's up to YOU! Go to Marina Mall and buy it yourself, you're most probably going to be there anyway....
Week 8 - Forthcoming attractions
Have marked most of your books (you never thought you'd hear me say that did you) and we are doing exceptionally well as a class. I feel that you guys have done enough to deserve a bit of a change from writing so I'm going to test what your experimental skills are like and give you a practical.
Week 2 of Ramadan and, though I am finding atomic structure fascinating I think that you deserve a break and a chance to show me how good you really are. There will be a test on atomic structure at the end of the week but I think we can cover all the material and get in a practical on the electrical properties of ionic compounds. We are the extended set after all.
What you need to do this weekend is research over at least one page what happens to the electrical properties of ionic compounds when they are molten or in solution and explain why in your own words. Find out some common examples of Ionic compounds. Remember, they are metals combined with non-metals. This will provide the background for our practical and give you an idea of what we should be searching for.
Then on Sundays double lesson I will give you the equipment, the bare minimum of hints and tips and will expect you to be able to set up an experiment to test if what you have read is actually true. Think you're good enough?
I'll be the judge of that...
Week 2 of Ramadan and, though I am finding atomic structure fascinating I think that you deserve a break and a chance to show me how good you really are. There will be a test on atomic structure at the end of the week but I think we can cover all the material and get in a practical on the electrical properties of ionic compounds. We are the extended set after all.
What you need to do this weekend is research over at least one page what happens to the electrical properties of ionic compounds when they are molten or in solution and explain why in your own words. Find out some common examples of Ionic compounds. Remember, they are metals combined with non-metals. This will provide the background for our practical and give you an idea of what we should be searching for.
Then on Sundays double lesson I will give you the equipment, the bare minimum of hints and tips and will expect you to be able to set up an experiment to test if what you have read is actually true. Think you're good enough?
I'll be the judge of that...
Welcome to The Phoenix Science Year 9 IGCSE chemistry site
Welcome year 9. On this site you will find the forthcoming schedules of lessons (subject to change), homework reminders, suggested reading for preparation for lessons and for extension and anything else I think will help our team learn chemistry. If you have any suggestions for the site please feel free to mail me on phoenixscience2000@hotmail.com and i will try to add anything reasonable. Please leave comments and discuss work on this site, but remember to use the site responsibly or lose it.
I will hopefully be adding a noticeboard soon keep your eyes on the site.
Good luck to everyone
I will hopefully be adding a noticeboard soon keep your eyes on the site.
Good luck to everyone
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