Suggested Practicals
From the Edexcel IGCSE Chemistry Teacher's Guide.
Principles of Chemistry
- Diffusion of gases and in solutions •
- Diffusion of NH3(g) and HCl(g) •
- Physical properties of substances compared to structure and bonding •
- Determination the formula of copper oxide by reduction •
- Determination of the volume of one mole of hydrogen •
- Acid/alkali titrations •
- Electrolysis of molten lead bromide •
- Electrolysis of aqueous solutions
Chemistry of the Elements
- Determination of the oxygen content of the air •
- Laboratory preparation of oxygen •
- Burning elements in oxygen •
- Laboratory preparation of carbon dioxide •
- The thermal decomposition of copper(II) carbonate •
- Group 1 metals with water . You can sometimes buy small quantities of Group 1 metals on eBay.
- Displacement reactions of metals (solutions and thermite type) - Copper Sulphate displacement reactions are easy and fun.
- Reduction of metal oxides using carbon •
- Cause and prevention of rusting • Anion and cation analysis •
- Reaction of halogens with iron wo
- ol/‘Dutch metal’ •
- Dissolving hydrogen chloride in water and methylbenzene •
- Endothermic reactions – sodium carbonate decahydrate with citric acid crystals •
- Measurement of enthalpy change (displacement reactions; combustion)
Organic Chemistry
- Fractional distillation of ‘artificial crude oil’ •
- Reaction of hexane with bromine in uv light •
- Reaction of alkenes with bromine water •
- Dehydration of ethanol Physical Chemistry •
- The effect of acids and alkalis on a selection of indicators •
- Reactions of acids with metals, metal carbonate and metal oxides •
- Making crystals of a soluble salt using an insoluble metal oxide or metal carbonate •
- Making crystals of a soluble salt by titration •
- Precipitation reactions •
- Making dry samples of insoluble salts •
- The effect of heat on ammonium chloride •
- The effect of surface area on rate using marble chips and hydrochloric acid •
- The effect of concentration on rate (metals/marble chips with acid; thiosulfate with acid; clock reactions) •
- The effect of temperature on rate (metals/marble chips with acid; sodium thiosulfate with acid; clock reactions) •
- Catalytic decomposition of hydrogen peroxide
Chemistry in Society
- Making polystyrene •
- Cracking long chain alkanes •
- Nylon rope trick.
Heating curve for water: definitely do-able at home! Tips from practicalphysics may help: http://www.practicalphysics.org/go/Experiment_207.html
and here:
http://www.kentchemistry.com/links/Matter/HeatingCurve.htm
Nylon Rope Trick- synthesising nylon. Can be done at home with care, using this Nylon Rope Trick kit from Edulab
From Futurelearn Kitchen Chemistry Course.
Experiment - Catalysis in biology
For this experiment you will need:
A potato
Yeast (dried or fresh)
Hydrogen peroxide (available at different concentrations - max 40% - at pharmacies)
A small amount of water
A few drops of washing-up liquid
A glass, jar, yoghurt pot or other container
Safety spectacles
Please be aware that hydrogen peroxide is a bleach and will discolour any material it comes into contact with (even your hands). While it is always a good idea to wear safety spectacles when doing chemistry this is one experiment, depending on how it is carried out, where it is highly advisable.
Mix the yeast and water and leave it to stand for 5 - 10 min. There should be enough water that the mixture pours easily. While you are waiting cut a fresh piece of potato. Put some hydrogen peroxide solution in a container and add the freshly cut piece of potato. What do you observe?
Put some more hydrogen peroxide into another container and add a few drops of washing-up liquid. The enzymes in the yeast should turn the hydrogen peroxide into water and oxygen. As oxygen is a gas the washing up liquid will make a foam that captures the bubbles of the gas, making it easier to see what is happening. Add the yeast to the mixture of hydrogen peroxide and washing up liquid and observe what happens.
Testing for Oxygen
Oxygen re-ignites a glowing splint. A “glowing splint” is just a stick like a wooden kebab skewer that you have set alight and then blown out.
When you are decomposing your hydrogen peroxide, you want to catch some oxygen and then test it.
If you have made “elephant toothpaste” by putting washing-up liquid in your hydrogen peroxide before adding the catalyst, as above, then the bubbles will contain a lot of oxygen. However, the skin of the bubbles is made of water and detergent, and as we all know, poking a glowing stick into bubbles will extinguish the glow. But not necessarily with these -play around poking the glowing splint gently into the **upper part** of the foam, and see if the glow increases.
Next, repeat the experiment without adding washing-up liquid, and try putting the glowing splint down into the container, just above the liquid. Don’t put the splint into the liquid. If all goes well and oxygen is being produced, you’ll see the splint re-ignite.
Generating and testing Hydrogen
We generated hydrogen at home by adding hydrochloric acid to powdered zinc. However, it is easy to do using more readily available materials if you don’t want to buy in chemistry stock. You can make it by adding aluminium foil to caustic soda solution (sodium hydroxide). Sodium hydroxide is caustic so you need gloves, goggles, covered skin etc.. When you make up the solution, put the water in first and then add the sodium hydroxide. This is because you get an exothermic reaction between sodium hydroxide and water; if you put the sodium hydroxide in first and then add water, the heat of the initial reaction could cause steam and bubbling and splashing. Putting the water in first and then adding the sodium hydroxide reduces the splash risk. Add aluminium foil when the caustic soda is all dissolved. After a little while, the reaction will get going and hydrogen will be produced. The container will still get hot, so you may wish to stand it in a bowl of cold water. See this YouTube video on generating hydrogen with caustic soda and aluminium foil.
Using Hydrochloric acid and zinc: We found that just a large pinch of zinc powder in a test tube with 2mls of 4M Hydrochloric Acid produced enough hydrogen for us to do several tests. You are using acid so obviously, goggles and gloves on, feet and arms covered. Put the zinc in the test tube, then drop the acid onto it.
Testing for hydrogen
When you see bubbles rising, that is hydrogen. To test for the presence of hydrogen, it helps to have a partner. Put your thumb over the test tube and keep a firm seal until you feel pressure building up. Meanwhile, your partner lights the splint (wooden kebab skewer) and holds it up. We found it worked best to test as follows. The lighted splint is held still and the person with the test tube brings the tube up underneath it. Hydrogen is lighter than air so as soon as you remove your thumb, it floats up out of the tube. If the tube is directly under the flame, as close as possible, you have more chance of success. When the hydrogen meets the flame it makes a distinctive “Pop” sound which has a squeak to it.
Here’s a lower-risk way of generating hydrogen, making bubbles with the gas - requires a side-arm test-tube,, still using caustic soda.
Or you could combine it with some electrochemistry and use simply a battery and salt water; you won’t get much this way, but if you’re careful it will still be enough to test.
Hydrogen Balloon
I generated more hydrogen in a conical flask, but you could use a bottle as per the YouTube video on generating hydrogen with caustic soda and aluminium foil. I held a balloon over the neck of the flask until it was inflated a bit, then tied off the balloon and taped it to a long stick. Then I put a candle outside and took the balloon to the flame. A gratifying bang was heard and nice flames were seen.
Where to get chemicals and equipment
You can buy small quantities of most of the chemicals you need on eBay or Amazon.
Kitchen-Chemistry is an eBay store which works with many home educations, and the Echo Education distance learning tutors, to supply small quantities of chemicals and equipment used in IGCSE-level practicals.
For larger quantities see www.reagent.co.uk Many chemicals can be supplied without restrictions, but if you need something which they say is ‘restricted’ then you can contact them and provide evidence that you’re working towards and exam. This company asked me to send some evidence that we were working towards a specification.
Some things can be found easily in hardware stores, eg Sodium Hydroxide is Caustic Soda - NaOH.
An easy source of hydrochloric acid is ‘Spirits of Salts’ which is sold in hardware/cleaning shops - it’s approx 30% HCl solution in water.
Balance
A good, laboratory-style balance opens up the possibilities of experiments you can do.
A 'balance' is just laboratory-speak for scales, but ordinary kitchen scales are not accurate enough to do many of the activities on the chemistry syllabus
If you're going to buy a new balance, preferably get one which will weigh in increments of 0.01g for IGCSE-level chemistry.
A 'jeweller's scale' can be bought for under £10 and, according to this RSC Chemistry teachers' forum discussion, is robust enough for classroom use.
A larger option is the My Weigh iBalance 201 which costs around £70 - eg http://www.ourweigh.co.uk/table-top-scales/ibalance-201.html .
Rapidonline are brilliant for cheap equipment and have various robust-looking balances aimed at schools which weigh in intervals of 0.1g for around £35 + VAT.
The full range is at http://www.rapidonline.com/pocket-portable-balances , then click 'parametric search' to make sense of it all. Rapidonline are brilliant for value and speed and service, but their website isn't the most user-friendly.
Resources
Jim Clark, author of the Edexcel textbook, has a chapter-by-chapter list of additional resources here. http://www.chemguide.co.uk/igcse/index.html
Practical Chemistry - http://www.practicalchemistry.org - thorough notes on safety issues etc.. so may help you to decide whether it’s practical to do this experiment at home. Also has good explanations and teaching tips.
RSC Classic Chemistry Experiments - Royal Society of Chemistry. Source for any activities referred to as ‘CCE’ or ‘RSC CCE’ below.
NOTE: Always worth checking the Practical Chemistry page on the CCE; often there are additional tips or updates.
RSC Classic Chemistry Demonstrations - activities listed below as ‘RSC CC Demo’ are for the teacher to demonstrate, not for the class to do. These too are detailed on the RSC site; just go to RSC Learn Chemistry site and search for the demonstration you need, with title as listed in the Scheme of Work.
RSC Education Playlist on Youtube
RSC Demonstration Videos - for teachers, with demo tips:
RSC/Teachers TV Video Clips: http://www.rsc.org/Education/Teachers/Resources/Practical-Chemistry/video-clips/index.asp
Doc Brown’s free support page for IGCSE Edexcel Chemistry:
Khan Academy - lots of chemistry videos.
Basic chem lab techniques from About.com
MIT Chemistry Lab Techniques - YouTube collection
‘Illustrated Guide to Home Chemistry Experiments’ by Robert Bruce Thompson. Book aimed at home-educators and those interested in doing serious home chemistry. I have referred to it below as ‘Home Chem Expt:... ‘ Useful on safety and practical considerations when carrying out experiments at home, plus which pieces of equipment you can substitute or improvise. Author’s website, with some amendments and additions to the text. Support forums have lots of discussion from home-edders.
How to write a lab report: http://chemistry.about.com/od/chemistrylabexperiments/a/labreports.htm (I think this goes way beyond GCSE level though)
How to make Limewater - to test for CO2. Easy home-make solution of calcium hydroxide. And here is a video showing how to test for CO2 in exhaled air compared to room air, using the limewater.
Acid-Base titration step by step from titrations.info
Chemistry lab technique tutorials: http://www.sciencebuddies.org/science-fair-projects/project_ideas/Chem_Lab_Techniques.shtml
Safety issues: http://www.sciencebuddies.org/science-fair-projects/project_ideas/Chem_Safety.shtml
Chemistry Diagrams: http://www.btinternet.com/~chemistry.diagrams/index.htm
Home-ed High School Chemistry - a US-based list of resources and their chemistry curriculum, with good links.