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Let me give some work that I intend to give for GCSE students. I am helping with two or three different GCSE Syllabuses and one of them is Edexcel AND OTHERS such as AQA and OCR. I have looked into the current GCSE Edexcel syllabus and past exam papers before I prepared this work. The reason is, I have to make sure the work is within their syllabus. This section is about 8 pages long. It is better to print this Q&A then read. If you have any questions please contact me by email.
The students must know exactly how the notes are used in questions, which are called application of notes. It is very important to apply the knowledge within a given time. Updated [05/09/2009]
I have seen in GCSE examination halls, some students are looking through the windows and gazing at the sky. I also looked to see what can they see, I saw some pigeons flying in and out of roof tops, a plane passed by every now and again and beautiful cloudy sky. I was wondering, were they counting pigeons or planes or both? Some students chew some sweets, non-stop. Some kept on drinking fizzy drinks, then chewing again, looking lost and looking at the watch or the clock. Some students kept on asking for a sharpener, a rubber, a ruler and so many little things, how many times they scratched their heads, bit the nails then again started to counting pigeons and planes. Are they all signs of some kind of nervousness? As teachers we have to understand these and tolerate these things as they can happen in that examination environment. I can describe a few more scenes from a real examination hall. Is anybody is going to deny these? One must remember the exams are timed, a time to start and finish. If they have done the revision in the proper way, there is no time to count pigeons and planes, just go on.
I have to give the work according to a syllabus so that we know how much is required for this GCSE syllabus.
Below are some Revision questions and answers. I have given some parts of answers only and if you think you need the rest or similar work please come back, send me an email on chemistry4u@tiscali.co.uk or gcsechemistry4u@tiscali.co.uk . My web site address is www.chemistry4u.co.uk . You can type in chemistry4u in your browser and press in to search, [your browser may yahoo, MSN or internet explorer] then you would find my name as Dr Hector Perera in several places and in several search engines.
Let me give some work, if you need similar or the rest of the work please contact by email. I made private tuition affordable for every student that is why I want to give some work for FREE then you decide whether you need that kind of work. If you say “YES”, then I will give this tuition written in a CD at an affordable price, just £2/00 per lesson or 4 lessons £6/00 or for GCSE only on a special offer. I know in some tuition classes, they charge £20 to £25 per lesson but I give the lessons at an affordable price. Again in the tuition class there are few students, may be 4 or 5 students. At the tuition class, all what the students do is to listen to the tutor and make notes. They hardly ask questions from the tutor because they are too shy to; look FOOLISH in front of the others. How do I know because I used to have these tuition classes? I thought it is not right, too expensive but it brings results to students, not every one or an average mum or dad can afford that kind of tuition fees, am I correct? I have to see who is paying for this tuition, it is your parents so I have to be very reasonable about this fees. That is why I have this INTERNET TUITION class and the work sends on a CD for a small fee and still there are FREE lessons in my web site. If you didn’t understand any of this work on the CD, you are FREE to send me an email so that I will answer them FREE of charge. If you need the work to be printed and posted that be done as well. This is the time of new technology, with faster and faster broadband so why not make the best use of it, not just playing computer games. Students know exactly how to download games and music but if there were some GCSE chemistry help for FREE, would they visit the web site that provides this FREE work? I am sure you would. Remember this is for your own good; you get some work for FREE on my web site, www.chemistry4u.co.uk
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Edexcel GCSE suitable work. Revision Q&A about water.
Q1. (a) Equal volumes of different samples of water were shaken with equal volumes of soap solution in three separate test tubes.
The height of the lather in each test tube was measured.
Sample of water height of lather (cm)
A 0
B 6
C 6
Answer: A scum.
Additional notes : When soap does not dissolve in water it breaks into small pieces to from a substance called scum. This is a test for hard water.
Hard and soft water
Soap lathers easily in distilled water. With some types of tap water, it is hard to get lather, and such water is described as hard. In Sri Lanka water in some parts of the country is hard water. Water in which soap lathers easily is called soft water. Hard water contains substances, which combine with soap ions to prevent them from doing their job. The above experiment shows that it is the calcium and magnesium ions in water that make it hard. They combine with soap ions to form insoluble calcium and magnesium compounds. These compounds are the scum that you see floating on your bath water and we call it is a waste of soap. The soap ions are no longer free, and the soap has little effect.
soap ions + calcium ions ------- à scum
2 soap - + Ca 2+ (aq) ---------- à Ca(soap) 2 (s)
There are some soap-less detergents that will still work in hard water because their calcium and magnesium salts are soluble. Soapless detergents have taken over from soaps to a large extent. Now of the cleaning products market, nearly 80% is soapless detergents.
Answer: Hard water.
Answer: Shake the solution with some washing soda so that it will remove the hardness. Na 2 CO 3 10H 2 O is washing soda.
Answer: A and B.
Q.1 (b) Describe and explain what you would see when the following solutions are shaken with soap solution.
Answer: There will be no lather [bubbles] but a scum [a layer] will be formed because Calcium nitrate solution has calcium ions that cause the hardness.
(ii) What about with Lithium nitrate solution?
Answer: Please contact for the answer .
Q2. Silver chloride (AgCl ) can be prepared by reacting silver nitrate (AgNO 3 ) solution with sodium chloride solution. Silver chloride is insoluble.
Complete the balanced equation, including state symbols, for this reaction. [I have completed it with state symbols]
AgNO 3 (aq) + NaCl(aq) -------- à AgCl(s) + NaNO 3 (aq)
Answer: Please contact for the answer.
Q2. (C) Three test tubes contain solutions of potassium chloride, potassium bromide and potassium iodide.
Dilute nitric acid and silver nitrate solutions are added to each solution.
A precipitate is formed in each test tube.
Draw a line to join each solution to the result of the test.
Solution test result
Potassium chloride cream precipitate
Potassium bromide red precipitate
Potassium iodide white precipitate
Yellow precipitate
Answer: Potassium chloride gives a white precipitate.
Potassium bromide gives a cream precipitate.
Potassium iodide gives a yellow precipitate.
Notes: How did you find the tests for chlorides, bromides and iodides, let me write them down in a more detailed but in a simple form?
Test for chloride: Please contact for the answer .
Q2 (d) Describe a test to show the presence of potassium in solid potassium chloride.
Answer : Please contact for the answer.
Additional notes for the above answer: Have you seen the fire works colours ? In the fire works, yellow colour is due to sodium, red due to calcium, blue due to copper, brilliant white due to magnesium. You might see lilac flame and that is due to potassium. Next time when you see fire works, try and see how many different colours are there. Sodium light is found in all streetlights, in all motorways and also in all other street lamps. Here I have explained chemistry in simple sense from everyday life. Chemistry is not limited to classroom only.
Additional notes on hard and soft water.
Methods of softening hard water: Please contact for the answer .
Temporary hardness: Please contact for the answer .
Additional notes for the above answer: A simple experiment:
Boil about two cups of tap water in a milk pan until it goes down to about one third. When it cools down, examine the milk pan; you should see a white powder like substance, which is calcium carbonate. This calcium hydrogen carbonate is in the tap water we drink but this chemical breaks down or decomposes on boiling. How did you get this white powder? When water boils calcium hydrogen carbonate decomposes into calcium carbonate and carbon dioxide. This is the same thing happening in the kettle when you boil some water. Have a look inside an electric kettle, what would you see? Did you see a white scale at the bottom then around the heating element? That is kettle fur and it is the same substance found I mentioned before, calcium carbonate. If someone asked you is calcium carbonate water soluble, what would you say, soluble or insoluble?
Calcium carbonate is water insoluble, that means it does not dissolve in water. How do I convince you? Well, have you heard about the coral barrier reef in Australia, I think it is over 1500 miles long? If calcium carbonate dissolves in water that coral barrier reef would have long gone. So remember calcium carbonate water insoluble. This is application of chemistry knowledge for your day today life.
Let me ask you a question, this is about water-soluble oxides, name some water-soluble oxides. As a help let me give some oxides, sodium oxide, calcium oxide, copper oxide, iron oxide and magnesium oxide. Now you have to go through books and find out which oxides are water-soluble. If you know the answer, why not email to me. One thing please let me know how long it took to find out this information. How many hours? Here I am giving the answers all prepared because this how you get in private tuition. I send the work HOME, distance no matter. How would I do that without INTERNET TUITION?
Remember the hardness which can be removed by boiling is called temporary hardness. This is an examiner favourite.
Permanent hardness is due to: Please contact for the answer . Temporary hardness is due to; Please contact for the answer .
Permanent hardness cannot be removed by boiling.
Temporary hardness is removed by boiling.
Home Activity: Put half a teaspoonful of table salt into a plastic basin or bowl full of tap water then try and dissolve some soap in it. What did you notice?