Written by Suzanne Boniface
Stories about NZ Scientists The MacDiarmid Institute has just launched the first two stories in a series, about New Zealand scientists. Aimed at Year 10 and above, these articles are intended to illustrate aspects of the Nature of Science in the New Zealand Curriculum. The stories include information about the science, the scientist and their inspiration. The first story is about Alan MacDiarmid, who received a Nobel Prize in 2001 for his discovery of conducting polymers. The second story is about Professor Sir Paul Callaghan, a recipient of this year’s Prime Minister’s Science Award for his work with nuclear magnetic resonance. The stories are available in PDF format at: http:// www.macdiarmid.ac.nz/opportunities/nature.php.
Useful chemistry experiments The following experiments have been developed by the Royal Society of Chemistry to help inspire and engage students. They are reproduced here by permission of The Royal Society of Chemistry. These and others can be found at: www.practicalchemistry.org. Rates and Rhubarb This is great for a novel introduction to rates of reaction. There is sufficient oxalic acid in rhubarb stalks (leaves contain higher levels and are poisonous and not to be used) to decolourise a dilute solution of potassium permanganate. And it’s great to use as students might be more familiar with rhubarb than some laboratory reagents (such as magnesium ribbon) and it is possible to measure the surface area of the rhubarb – thus quantifying the change in surface area. This experiment works well on a simple level, although the reaction itself is quite complex; the Mn2+ ions produced actually catalyse the reaction so it is difficult to relate the rate back to the reaction. 1. Surface area: The reaction is carried out using 30mL of potassium permanganate solution in a 100mL beaker. Students will need 5cm lengths of rhubarb. One piece should be left whole and other pieces sliced into similar sized strips to give varying surface areas. For example, one piece halved and one quartered etc. The total combined surface area of each piece could be measured using squared/graph paper. The potassium permanganate solution should be pale pink and can be made by dissolving 4 or 5 crystals into 500mL of distilled water and then adding 500mL of 2 mol L-1 sulfuric acid. Since the oxalic acid concentration of the rhubarb varies, the reaction should be checked beforehand to ensure that a colour change will occur in an appropriate time with the rhubarb that is being used. 2. Effect of concentration: The rhubarb should be boiled for about 5 minutes (5cm rhubarb to 250mL water) until it falls to pieces. Cool and strain the mixture and keep the filtrate. Measure 30mL of potassium permanganate into a 100mL beaker and the same amount of water into a second 100mL beaker. Add 5 drops of the rhubarb filtrate to the potassium permanganate and start the timer. Stop the timer when the colour disappears. Repeat for varying numbers of drops of rhubarb filtrate. Use results to discuss with students ways for improving the experiment to make it a fair test.
Neutralisation Circles. The following experiment gives a permanent record of the colours of Universal indicator in acidic and basic solutions. Use a 12.5cm diameter piece of filter paper (Whatman no. 1 works well). On the paper, draw two circles in pencil about 1cm in diameter and about 2–3cm apart. Label one ‘acid’ and the other ‘base’. Place the paper on a white tile and add a few drops of the acid and base supplied to the appropriate circle (0.1 mol L-1 NaOH and 0.1 mol L-1 HCl). Wait for a few minutes for the solutions to soak through the filter paper and meet. Place drops of universal indicator on the area of the filter paper where the acid and base have met and reacted. A ‘rainbow’ will be produced showing the range of colours produced by universal indicator. The filter paper can be dried and will retain the colour. Flame tests without Nichrome wire. Cheaper more convenient flame tests can be carried out using wooden splints soaked in salt solutions. The splints should initially be soaked in water at least 24 hours before they are needed for the experiment. The water soaked splints should be then be placed into boiling tubes half filled with the salt solutions at least 4 hours before the lesson. Students to place a soaked splint in a blue Bunsen flame and record the flame colour. Note: It is important not to let the splint burn too vigorously. A beaker half filled with water can be used for the disposal of the used splints.
International Year of Chemistry 2011 - tense issues Plans are still coming together for IYC 2011 in New Zealand and was launched in Wellington on 9th February. The following Friday secondary school students were invited to a Chemistry Variety Show which included an address by a visiting Nobel Prize winner. Each branch of the NZ Institute of Chemistry will be running their own local programme and a number of national and international events are being planned. 1. Global Chemistry Experiment. Schools are invited to take part in an international study of water quality and water purification in their local environment. Data collected will be logged on a website to build up a picture of global water quality. The project can be tailored to different levels, from Years 7/8 to Years 12/13. Information about this project can be obtained from: www.chemistry2011.org. 2. Senior secondary school quiz. Regional branches of the NZIC will be running local competitions to select a team of four students to represent the region in the final of the national quiz, which is being held on 5th July at Victoria University in Wellington. 3. Other activities. During the year there will be other competitions and activities including patchwork and knitted Periodic Tables. For further information check out: www.yearofchemistry.org.nz. For further information contact: Suzanne.Boniface@vuw.ac.nz New Zealand Association of Science Educators