More answers uploaded

The only remaining answers to upload were the ones your first test was on e.g. atomic structure. As most of you done particularly well at that I have left those til last and may not even get round to doing them, as I feel you are confident enough with these questions.

Periodic trends answers can be found here http://www.geocities.com/sally500uk/PracticeExamQuestionsPart3.doc

Your chance to ruin Phoenix holiday!

Want your books marked? Hand them in after your chemistry exam to the table outside the science staff room and, as I will endeavour to mark them. I won't mark the exam style questions as you should be looking over those answers yourself in preparation for the exams but I will mark all work set for you that hasn't been marked this term.

Good luck Year 9

December checklist uploaded in case you need it

December checklist can be found at http://uk.geocities.com/sally500uk/DecemberChemyr9Revisionchecklist.doc

This is the one that you got in class in case you need to use it

Practice exam questions sample answers part 2

The second set of sample answers have been uploaded. They can be found on http://uk.geocities.com/sally500uk/PracticeExamQuestionsPart2.doc

Still more to come.

Practice exam questions - sample answers part 1 uploaded

Year 9

Seeing as you will probably find it hard to get in to see the sample exam answers I have uploaded the sample answers onto the web for a limited time to help you to revise.

The first set of sample answers can be found by right clicking and saving the following link http://www.geocities.com/sally500uk/PracticeExamQuestionsPart1.doc

The next set of answers will be uploaded shortly. Good luck

Good luck year 9!

Just a quick post to wish you all good luck in this set of exams. I am sure you will all do really well and I am looking forward to seeing you on the other side.

Final Week before exams - Alloys and revision

We meet twice this week. We will be finishing metals by talking about alloys and the hows and whys of their properties, then it's revision with exam practice for the next lesson.

Any questions please ask! I will also be in school every day while the exams are on.

End first term exam checklist

Thus far we have taken 2 tests and done commendably on the whole and I am confident that we will all do brilliantly.

As we were all given a copy of the syllabus at the beginning of the year we know what the IGCSE syllabus contains so there’s no point in replicating that information here, though that will provide you with good guidance of the information that you will need to know. If you have lost your copy o want another copy of that syllabus it can be downloaded and printed from the Cambridge website at http://www.cie.org.uk/

In addition to the information contained there what follows is a checklist of the skills you should have picked up in Chemistry so far.

By the time we have broken up for exams you will be able to:

• describe the states of matter and explain their interconversion in terms of the kinetic particle theory
  
• describe and explain diffusion
  
• describe evidence for the movement of particles in gases and liquids
  
• describe dependence of rate of diffusion on molecular mass (treated qualitatively)
  
• state the relative charges and approximate relative masses of protons, neutrons and electrons
  
• define proton number and nucleon number
  
• use proton number and the simple structure of atoms to explain the basis of the Periodic table (see section 9), with special reference to the elements of proton number 1 to 20
  
• define isotopes
  
• state the two types of isotopes as being radioactive and non-radioactive
  
• state one medical and one industrial use of radioactive isotopes
  
• describe the build-up of electrons in ‘shells’ and understand the significance of the noble gas electronic structures and of valency electrons.
  
• (Note that a copy of the Periodic Table will be available in the examination)
  
• describe the Periodic Table as a method of classifying elements and its use to predict properties of elements
  
• describe the change from metallic to non-metallic character across a Period
  
• describe the relationship between Group number, number of valency electrons and metallic/non-metallic character
  
• describe lithium, sodium and potassium in Group I as a collection of relatively soft metals showing a trend in melting point, density, in reaction with water.
  
• predict the properties of other elements in the Group, given data, where appropriate
  
• describe chlorine, bromine and iodine in Group VII as a collection of diatomic non-metals showing a trend in colour, state and their reaction with other halide ions
  
• predict the properties of other elements in the Group given data, where appropriate
  
• identify trends in other Groups given information about the elements concerned
  
• describe the transition elements as a collection of metals having high densities, high melting points, and forming coloured compounds, and which, as elements and compounds, often act as catalysts.
  
• describe the noble gases as being unreactive
  
• describe the uses of the noble gases in providing an inert atmosphere, i.e. argon in lamps; helium for filling balloons
  
• describe the general physical and chemical properties of metals
  
• explain why metals are often used in the form of alloys
  
• Identify representations of alloys from diagrams of structures
  
• describe metallic bonding as a lattice of positive ions in a ‘sea of electrons’ and use this to describe the electrical conductivity and malleability of metals
  
• place in order of reactivity; calcium; copper, (hydrogen), iron, magnesium potassium, sodium and zinc by reference to the reactions, if any, of the metals with water or steam dilute hydrochloric acid and the reduction of their oxides with carbon
  
• deduce an order of reactivity from a given set of experimental results
  
• describe the differences between elements, mixtures and compounds, and between metals and non-metals.
  
• describe alloys, such as brass, as a mixture of a metal with other elements.
  
• describe the formation of ions by electron loss or gain
  
• describe the formation of ionic bonds between elements from Groups I and VII
  
• describe the formation of ionic bonds between metallic and non-metallic elements
  
• describe the lattice structure of ionic compounds as a regular arrangement of alternating positive and negative ions
  
• Describe the reactivity series as related to the tendency of a metal to form its positive ion, illustrated by its reaction, if any, with the aqueous ions, the oxides, of the other listed metals
  
• describe the action of heat on the hydroxides and nitrates of the listed metals
  
• account for the apparent unreactivity of aluminium in terms of the oxide layer which adheres to the metal
  
• describe the ease in obtaining metals from their ores by relating the elements to the reactivity series
  
• describe the essential reactions in the extraction of iron from hematite
  
• describe the conversion of iron into steel
  
• describe in outline, the extraction of zinc from zinc blende
  
• name the main ore of aluminium
  
• name the uses of aluminium: in the manufacture of aircraft because of its strength and low density; in food containers because of its resistance to corrosion
  
• describe the idea of changing the properties of iron by the controlled use of additives to form steel alloys
  
• name the uses of mild steel (car bodies and machinery) and stainless steel (chemical plant and cutlery)
  
• name the uses of zinc for galvanising and for making brass
  
• name the uses of copper related to its properties; electrical wiring and in cooking utensils

and by the end of this week we should be able to tick every single thing in that list and begin revision and exam practice next week.

RedOx reactions

In our lesson on Sunday we covered 2 definitions of Oxidation and Reduction reactions

One view of oxidation is the gain of oxygen another view is that it's the loss of electrons

One chemicals loss of electrons is another chemicals gain so oxidation and reduction happen at the same time. Hence the Reduction - oxidation name cos it's a two way thing. The electrons thing is quite confusing because it doesn't involve oxygen and the name of the process is oxidation.

Oxidation is easy to remember when oxygen is involved as it's obvious that a gain of oxygen is an oxidation and a loss is a reduction. That much is obvious. With electrons the process is the opposite hence the OILRIG acronym to help you remember the process for electrons

Now a little insight into what's going on here. You need to know a little about ions and the convention for writing them. As you know if an ion has a positive charge it's written with a little "+" sign up top after the number. We know that if it loses one electron it becomes + and if 2 electrons are lost it becomes 2+, 3 electrons 3+ etc, e.g Li goes to Li+, Mg to Mg2+ etc
That number up top is related to it's combining power and it's got a number of names...
Valency
oxidation number
ionic charge
...and there are more names on the redox sheet you got on wednesday

But notice that it's also called oxidation number

So anything that changes the oxidation number positively is an oxidation. rememebr that Losing a negative (electron) is like gaining a +. It's a messy state of affairs but losing an electron (single negative) has the same effect ON THE CHARGE as gaining an oxygen ION (single positive) so from an ionic point of view it is exactly the same. Yeah that used to do my head in as well!

So if there is a change in the valency of the reacting chemicals it's technically, by our definition of redox reactions, a redox reaction.

Take a look at http://www.chemistry.co.nz/redox_new.htm (it would be helfpul just to look at the bits in the boxes - copy them out into your book if you need to - I don't mind you writing abything into your book if it helps you learn) - Also click on the links at the top of that page for more info on how to get the valencys and a bit more info on ionic equations and a few examples.

New feature - Message board

A messageboard has been created for you lot to discuss any issues you have on chemistry or physics with each other. There's also a general section to discuss Avril as that's obviously on your mind.

I will be moderating but want this to be used responsibly to discuss issues - remember that you have exams soon and should be using every resource available to you to make sure that you perform to the best of your ability. If this board helps use it, if it doesn't then don't. It's there if you need it.

I will try and answer questions that arise but it should be an opportunity for you to ask questions and answer each others questions. Sometimes the best learning and teaching is done at the same level not from above. Remember that each one of you can do well, it's not a race against each other but a test of your own abilities, so every one of you is a resource.

The board can be found at http://phoenixscience.proboards38.com/index.cgi

I hope this is useful for your learning. And Avril is overrated

Typical...

After you lot left the class I spent the next lesson preparing the mixture and blew it up after I had given my reports out. I went out into the playground and *BANG!* Lumps of lovely iron were made. And only I saw it. Anyway if you're lucky we'll get to do it properly after the holidays.

More work 4 U! Revision tips

Any of you who want to get ahead should pay a visit to the website of the Royal Society of Chemistry http://www.chemsoc.org/networks/learnnet/miscon2.htm

This website contains a load of worksheets that I STRONGLY recommend that you download and print out. The worksheets are in the form of question and answer sheets for discussion or thinking about, and they go into good depth.

The way to do them is to print them out and read the question paper, answer them on the answer paper then check your answers on the answer paper. Sounds simple and it is. If you follow these simple instructions you are gonna learn a LOAD of stuff about chemistry and it will reinforce what you've learnt in class.

Firstly I strongly suggest you download and study the following files from that site

Iron - this is exactly what we are doing in class about metals

and for your revision i would suggest
Periodic Table
Elements Compounds, Mixtures

HEADS DOWN! We're going in!

Everyone has worked really hard this term and I'm really pleased with the work you have all produced. As you know we have exams after the break and for many of you this will be your major concern before learning the chemistry of murder, so next term we will be putting that part of the sylabus on the back burner for a while, getting our heads down and making sure that every single part of the sylabus we need to know is covered in great detail with the necessary exam practice.

Murder week will still go ahead start of next term but will be taken a little out of context. We won't be doing the chemistry of murder until after the exams but will instead concentrate on getting all the work on metals done ready for the exam.

It's been a long term, you've worked really hard and produced some excellent work but there's still work to be done, so I've planned that for next term all lessons will take a really simple structure. Every lesson will start with recap questions, followed by a demo then discussion of the principles proved in the demo and some questions. Homework will be exam practice style questions.

Normal service (i.e. chaos) will be resumed after we've proven to every other chemistry set that we really ARE the best!

All this chemistry is killing me....

Week 1 of the next half term is going to be...

MURDER WEEK

The job of forensic scientists depends on a number of scientific techniques which we will look at at the start of next term in the context of

MURDER

so just to get you in the mood we will be playing a game that week, a bit like Cluedo in which all of us will be involved in a spot of

MURDER

On the first lesson back we will finish off the work on the reactivity series that we should have started at the end of term. This will include looking up the mechanism of the Thermit reaction, which we will see on the last day of term and explaining how it works. Once we are all ok with the steps in the reactivity series then the game commences...

MURDER

The game is very simple. Think Cluedo and you're on the right track. In Cluedo you have to work out who was killed where and by whom.

All the names of all the pupils in the class will be in a hat. A list of "props" will be in another hat. Fially a list of locations around the school will be in a third hat. Each person will come to the front, pick a victim from the victim hat, a prop from the props hat and a location from the locatios hat. If they find they have picked themselves then put your name back in the hat and pick another one.

MURDER

The game then commences. Now every person in the room except for the judges and the police are potential murderers and victims. You don't know who is coming for you.

MURDER

The aim of the game is not to ACTUALLY kill anyone let me make that clear to you now! Kills are registered when you set up a situation whereby your victim unwittingly takes the item you are assigned to kill him/her with. The item must be taken willingly with room to deny.

MURDER

What does it all mean?! I hear you cry. Well let's take an example. Strontium has picked out of the hats the following...

Victim: Arsenic
Prop: Balloon
Location: Outside the art room

Stronitum would have to try to maneuver a situation whereby Arsenic would not suspect that being handed a balloon outside the art room is an ususual occurence. So Strontium thinks about it and designs a project to decorate the art room for a party. He calls Arsenic over and asks him to hold the chair while he paints "Happy Birthday" on the walls. Then turns to Arsenic and says

"Can you just hold this balloon while I dip my paintbrush in the green paint?"

Arsenic unwittingly obliges (but of course he has the opportunity to say no)

MURDER

By taking the balloon Arsenic has become a victim. Stronitum laughs heartily at him and shows him the 3 pieces of paper with hi name on. At this point Arsenic falls out of the game without telling anyone else that he is dead just to keep it interesting. Arsenic goes to the police (That's the volunteer who is helping set the game up) and reports the crime for the records.

MURDER

But in his death throes, Arsenic has one more task. In order for the game to continue smoothly, Arsenic needs to give his three pieces of paper to his killer. Strontium now has a new target, new prop and new location and a death score of 1.

But all the while someone has Strontium in their sights.

MURDER

No-one is safe...

A word of warning

This is YOUR site to keep YOU up to date and help YOUR learning. If you choose to use the comments to mouth off then you'll lose them. Believe me this takes time and effort on my part and there are some pupils who have decided to abuse the freedom they have been given. You have been warned.

Week 10 Highlights - End of term mayhem to look forward to

As we've now know how metals bond with non-metals and how non-metals bond with other non-metals it looks like we only have one more type of bond to look at which is obviously the bond between metals and metals, called metallic bonding strangely enough.

This week we'll finish off looking at covalent bonds and look at some different covalent structures and compare these with ionic structures. The properties of ionic and covalent molecules will be related to their structure then the properties of metals will be explained by looking at metallic bonding.

Before we begin next week it may be a good idea for you to all get familiar with the various properties of metals, so that nothing comes as a surprise to you next week.

As we finish week 9, we'll investigate how the structure of molecules defines their properties by looking at allotropes of sulphur and carbon, and seeing how diamond and graphite compare.

In next weeks lessons, we'll look at Metals in great detail then we'll cover one of the most important topics you have covered so far - the reactivity series.

Now here's the good bit - the reactivity series includes one of the most exciting demos in the whole sylabus - the thermite reaction. This is so dangerous it will involve us taking a lesson outside because it is too dangerous to do inside.

So if we manage to get through all the required work the last lesson of term will be absolutely BRILLIANT!

Atomic test results

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!

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

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:

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

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.

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.

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

1. 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.
2. 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.

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.

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

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.

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....

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...

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