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Fermentation and the alcoholic content of wine

The quality of Queensland wines is now recognised as amongst the best in Australia. Overseas exports are increasing, particularly to international markets seeking premium quality boutique wines. The Queensland wine industry has grown significantly over the years to cover a total of 1400 hectares. The majority of this growth has occurred during the past 9 years with significant plantings throughout the southeast corner of the State. However, winemaking is still very much an art rather than science but a interesting EEI can be undertaken in this context. After crushing the grapes the next step in the making of wine is the fermentation of the grape juice and pulp with various yeasts and bacteria. Most books say that the amount of ethanol produced is dependent on the sugar concentration of the starting juice. But how true is this. A good EEI would be to simulate grape juice with glucose (or an equal mix of glucose and fructose), adding a controlled amount of yeast and wine acids and fermenting to stillness at constant temperature. By changing the concentration of sugar there may be a correlated amount of alcohol. But I doubt it! You could repeat it with acidity as the IV and controlling sugar. Another change you could try is the type of yeast. As the alcohol concentration rises the yeast cell membranes become susceptible to rupture by the ethanol. Some yeasts are more susceptible than others. Baker's yeast is very susceptible and will die at just a few % alcohol; brewer's yeasts (for beer) are okay up to 5% but some can get up to 9%; and wine yeast usually go from about 13% (Sav Blanc), Riesling (16%) and a sherry yeast can tolerate about 17%. Or you could look at the susceptibility of yeasts to [SO₂] - winemakers use SO₂ in the form of sodium metabisulfite to kill off wild yeasts as these are less tolerant than wine yeast to the SO₂ . You could hypothesise and test how SO₂ affects the performance of yeast.  Many of the method for determining SO₂ in wine don't seem to work. Have a look at these methods. The photos below were taken during an excursion to Sirromet Winery at Mt Cotton, Brisbane. My old winemaking unit for chemistry teachers is available online.
 

The first little grape buds are seen in August.	A rose bush is planted at the end of each row of vines as an indicator of infection	Fermentation tank at Sirromet

 

Corrosion
Corrosion happens all around us - our cars rust, bridges and other steel structures fail, and we spend billions of dollars each year in replacement and maintenance costs as a result. There are a number of methods used to minimize or prevent corrosion, which include alloying, metallic coating, organic coating, use of inhibitors, and anodic or cathodic protection. Corrosion is one of the more popular topics in Queensland schools for an EEI as we have a warm, humid climate and the bulk of the population lives along the coast. Iron is the most abundant metal on earth and has been a boon to the building industry since the Iron Age. However, as it is susceptible to corrosion or rusting, structures made of iron, such as bridges and ships, need to be regularly monitored for rusting. If not, the damage caused by rusting can be very expensive to fix and, perhaps, hazardous. This is a particular problem in the shipping industry where the moist, salty conditions are ideal for accelerating the rusting process. For shipping and many other uses, iron is converted to one of its alloys, carbon steel, to make it stronger and less susceptible to corrosion. Salinity is only one of many factors that will contribute to the nature and extent of iron and steel corrosion observed at shipwrecks. Others factors, such as the concentration of dissolved oxygen, pH, temperature of the water, among others, may have a significant bearing on the corrosion of a particular wreck. That is why shipwrecks at different ocean depths and latitudes may vary in the nature and the extent of corrosion. Good EEIs often are in the context of shipwrecks. If so, it is not enough to merely put steel nails in different solutions and look at the loss of iron. You should be looking at the environments that ships can be found in and considering how you can simulate corrosion on a speeded up scale. Also important is what you will use for the metal: steel may be okay – but what alloy is it? Is pure iron any use – with no carbon to act as active sites for corrosion? Teachers who have been to Australian Corrosion Association conferences say that their website has useful information.

 

pH and photosynthesis

Oxygen is evolved during photosynthesis but the conditions for maximum reaction rate are intriguing. It can be affected by many things, including: sunlight - its intensity and wavelength, temperature, CO₂ and O₂ availability, water (which closes stomata and restricts CO₂), and any factor that influences the production of chlorophyll, enzymes, or the energy carriers ATP and NADPH, such as pH and Mg²⁺ availability. You could test the effect of pH and temperature. It sure won't be linear but how well your prediction (hypothesis) and results agree will be interesting. There are a lot of variables to control and complex biochemical reactions to examine.

Stability of Vitamin C in

solution
Vitamin C is sensitive to heat, light and oxygen. In food it can be partly or completely destroyed by long storage or overcooking. By refrigeration the loss of Vitamin C in food can be substantially diminished. An interesting EEI would be to see how some of these factors really affect a Vitamin C solution. It may be a good idea to simulate fruit juice by making up an appropriate solution with added citric acid, some citrates, glucose/fructose and so on. Should you measure the concentration of the ascorbic acid with time (and graph) or just measure it after a week or two weeks? What will you control? What will your independent variable be: sugar concentration, [H⁺], light, oxygen, temperature? The possibilities are endless.

Chlorine loss in a swimming pool due to sunlight intensity
Home swimming pools are usually sanitized with chlorine-based compounds such as calcium hypochlorite, Ca(OCl)₂, which produces the hypochlorite ion HClO^- when dissolved in the pool water. Chlorine in a pool can get consumed in many different ways, but the most common is from sunlight and aeration which convert chlorine in an oxidation state of +1 into chloride ion in an oxidation state of -1. Reports suggest that in strong sunlight, up to half of the HOCl is destroyed within 17 min. A good EEI would be to make up some pool water and add a measured amount of either calcium or sodium hypochlorite and measure the rate of consumption of free chlorine in pool water when exposed to sunlight. As a second IV you could look at the rate of loss at different pHs. The standard method for determining free chlorine is to measure the amount of oxidant by its ability to liberate iodine from acidified iodide solution. Titrate a water sample with a standard iodide solution and detect the iodine released by the blue colour formed with a fresh starch indicator. Find the amount of iodine released by back titration with sodium thiosulfate. Click here to see Elaine Bergmann's method. The problem with the iodometric (iodine titration) method is that it takes a long time for students to collect data. Janet Grice suggests Doug De La Matter's Methyl Orange method.  Her Yr 12 Pool Chemistry handout is also available. And I've attached an article from Chem Matters supplied by Janet Grice. As another IV you could look at amounts of aeration by bubbling air through it. Note the warning below!

Chlorine loss in swimming pool water - dependence on colour
Chlorine loss from pool water is known to be due to the action of sunlight (see text above). However, it is possible that the breakdown of chlorine is greater for different wavelengths of light than others. For example, does it breakdown as quickly under red light as under blue light? It would be an interesting EEI to see which colour/s have the greatest effect. You could make up some pool water with a known amount of chlorine (using Ca(OCl)₂ or NaOCl), place in a stoppered test-tube (why stoppered?) and wrap in a single layer of cellophane. You should be able to design the rest of the method yourself but you'd need several colours of cellophane and to measure the free Cl at several intervals of time (see experiment above for titration suggestions). Your problem will be to ensure the same intensity of light gets throught to the solution (yellow may not absorb as much as blue for instance). The image below shows the wavelengths of light most absorbed by each type of cellophane; this is called their l(max), that is, the wavelength most absorbed. I did this on a spectrometer at Moreton Bay College but you could run them again if you can get access to a spectrometer. You would also need to know what % transmission occurs for each colour; I didn't do that. As a second IV you could try thickness: one layer, two layers etc of cellophane to see if the response is linear. Have fun!

Iron filings in fortified cereal

A healthy adult needs about 18 mg of iron each day. Dietary iron is found in large amounts in organ meats such as liver, kidney, and heart. It is also present naturally in egg yolks, some vegetables, and shellfish. In these foods, iron is typically present as Fe (III) ions. Our body absorbs iron in the small intestine in the form of Fe (III), which then is reduced to Fe(II). Under normal conditions, our body absorbs only 5-15% of the iron in the food that we eat. Cereals are fortified with food grade iron filings as a food supplement. This iron is metallic iron (Fe). In the stomach the metallic iron is oxidized and eventually absorbed through the small intestine. You can see the iron if you pass a magnet over a slurry of breakfast cereal. I used Sanitarium's Light 'n' Tasty but any will do (see my centre photo below using a 100mm macro lens). The question is - how to make an EEI out of this? You need to do more than measure and comapre the amount of iron in breakfast cereals. A good EEI would be to investigate methods of extraction of the iron perhaps involving the use of a magnetic stirring bar before analysis. Could you dissolve the metal in acid? Is all the iron in the form of elemental iron (filings) or is there some natural iron compound present?

Polyurethane foam
Polyurethane is a synthetic polymer widely used in flexible foam seating, seals and gaskets, tyres, bearing bushes, adhesives and sealants. The type you may be familiar with from school (if you made a polyurethane foam mushroom) is called a 'rigid foam' and is used for insulation panels and surfboards.  They are made from two monomers - isocyanate and polyol. In 1984 water was accidentally introduced into a reaction mix and the first foam was made. A good EEI could be to look at the conditions required to produce the different densities of rigid foam. You could use equal amounts of the monomers and try them with different temperatures or different amounts of stirring. You could even try adding more water to the polyol monomer. You could even try making a variable density foam by placing the reaction vessel (plastic cup) on a cold surface. The main thing is to explain why you'd want a particular density and hypothesise how it could be achieved. It will be heaps of fun.

Alcohol-water mixture: concentrations and the contraction of volume

When you mix ethanol and water together the final volume is less than the sum of the separate volumes you started with. This shrinkage is known as 'volume contraction' and is due to the strength of the hydrogen bond. Such a bond is strong in water but weaker in alcohols, however, when a mixture is made the dipole-dipole forces tend to make the alcohol-water clusters small. Technically, we could say "departures from Raoult's law are often found in liquid mixtures resulting in volume nonadditivity". In practice, this contraction can have vital consequences. Medical researcher know that alcohol absorption into the bloodstream and the resultant volume contraction can upset the plasma concentration of various biochemicals and lead to all sorts of complications. A good EEI would be to measure the volume contraction of various mixtures of ethanol and water 25:5, 50:50, 75:25 and so on to see how the percentage contraction varies (the point of maximum contraction could be found). And if it is true that the effect is due to H-bonding, should the contraction be different for alcohols exhibiting weaker or stronger dipole-dipole forces (eg the monohydroxy alcohols: methanol, 1- and 2-propanol,  tert-butanol)?  I wish I was doing an EEI - this one would be great.

Alcohol-water mixture: temperature and the contraction of volume
In the suggestion above, the investigation of volume contraction of ethanol water mixtures was suggested. Of equal interest would be the effect of heat which is known to affect the  strength of the H-bond; so you could see how stable the % contraction was over a range of temperatures. Safety warning: alcohol water mixtures can burn even when the amount of alcohol is less than 50% - and especially at higher temperatures. As well, if  the contraction effect is due to H-bonding, shouldn't the contraction be different for alcohols exhibiting weaker or stronger dipole-dipole forces (eg methanol, propan-1-ol, propan-2-ol and methyl propan-2-ol)? As a matter of interest, mix together CS₂ and ethyl acetate and you get volume expansion (but CS₂ is too dangerous for high school experiments).

 

Capillary action
Capillary action is the tendency of a liquid to rise in narrow tubes or to be drawn into small openings such as those between grains of a rock. Capillary action, also known as capillarity, is a result of the intermolecular attraction within the liquid and solid materials. A familiar example of capillary action is the tendency of a dry paper towel to absorb a liquid by drawing it into the narrow openings between the fibers. Some liquids exhibit more capillarity than others; for example, there is a big difference between water, salt water, ethanol and hexane. A good EEI would be to compare capillary action (between two microscope slides; see below) for polar and non-polar liquids, or non-polar ones of different density, or salty water vs distilled water, or as a function of temperature or capillary gap. You could also somehow use capillary tubes (see below). The possibilities are huge, but don't get too carried away.


 

Browning of apples

Apples turn brown when peeled and exposed to air. This discolouration is due to a process called enzymatic oxidation and is catalysed by the enzymes present in the apples. The enzyme polyphenol oxidase (phenolase), in contact with oxygen, catalyzes one step of the biochemical conversion of plant phenolic compounds to brown pigments known as melanins (brown, like a suntan). It occurs at warm temperatures when the pH of the plant material is between 5.0 and 7.0. Browning can be stopped! Vitamin C, being a highly reactive anti-oxidant reacts with the O₂ in the air, preventing/slowing down the enzymatic oxidation of the apples. Another way to reduce browning is to lower the pH in order to inactivate the enzyme. Ascorbic acid is used commercially to prevent enzymatic browning as it acts as both an acidulant and antioxidant. To make an EEI out of this you could test the browning when controlled volumes of acids of various [H+] are used, and then with ascorbic acid of known [H+] to see how much is due to the antioxidant property. Temperature could also be assessed. It is also said that Fe and Cu speed it up but Ca²⁺ slows it down. Question: how will you measure the browning? Remember this is chemistry not MasterChef.

 

Deactivation of pineapple enzymes
If you've ever tried to make a jelly with pineapple or kiwifruit in it you may have been sorely disappointed. It may not set because the enzyme catalyst has played up. All living cells produce enzymes which catalyze metabolic reactions. The enzyme that you could investigate in an EEI is one that is produced in pineapple and hydrolyzes certain kinds of proteins called gelatins. Gelatin used in jelly is derived from skin, bones, and/or connective tissue of animals (vegetarians have to use agar type jellies). Gelatin proteins, when dissolved in hot water and allowed to cool, form a semi-solid or gel state; hence the name gelatin (or gelatine). Hydrolyze, here, refers to breaking up the protein polymer in such a way as to prevent its forming this gel state. The hydrolyzing enzyme from pineapple is denatured (destroyed) by heat; but not freezing - I don't think. Enzymes can also be denatured by changes in pH,  detergents or radiation. You could take some pineapple and subject it to different heat treatments and see its effects on the gelatine. You have to make up a device and method for testing gelatine that allows replicable and meaningful testing.  I recall using the Bloom Strength test at Golden Circle - it was the mass in grams required to press a 12.5 mm diameter plunger 4 mm into the gel. If you did it at home you could even eat the results.

pH of vinegar solutions

If you've completed an acids and bases unit you will be aware that strong acids and bases, like HCl and NaOH respectively, dissociate fully.  However, weak acids and bases only partly dissociate and the equilibrium constant (K_a or K_b) gives a measure of this dissociation. The quantitative behaviour of acids and bases in solution can only be understood if their K_a (or pK_a) values are known. Such knowledge finds applications in many different areas of chemistry, biology, medicine, and geology. For example, many compounds used for medication are weak acids or bases, and a knowledge of the pK_a values can be used for estimating the extent to which a compound enters the blood stream. Acid dissociation constants are also essential in aquatic chemistry and chemical oceanography, where the acidity of water plays a fundamental role. In living organisms, acid-base homeostasis and enzyme kinetics are dependent on the pK_a values of the many acids and bases present in the cell and in the body.  Here's a suggestion for an EEI: if you make up a solution of known concentration of say acetic acid CH₃COOH, and then measure it's pH, you can calculate the K_a using standard formulas. No doubt there will be an error but your EEI could be to investigate the source of this error and try ways to minimize it (is it the formula, the calibration of the pH meter, the dilutions, the temperature?). You could see if the error varies with starting concentration of the acid [HA] and also look at the effects of temperature. A comparison of several weak acids may also be revealing. How accurate is the pH meter for dilutions of strong acids? And then there are the bases. The possibilities are endless.
 

Water retention in disposable nappies
Today's state-of-the-art disposable nappy will absorb 15 times its weight in water. This phenomenal absorption capacity is due to the absorbent pad found in the core of the nappy. This pad is composed of two essential elements, a hydrophilic polymer and a fibrous material such as wood pulp. The polymer is made of fine particles of an acrylic acid derivative, such as sodium acrylate, potassium acrylate, or an alkyl acrylate. These polymeric particles act as tiny sponges that retain many times their weight in water. An interesting EEI would be to measure the water absorption properties of the acrylate polymer mix (rip open a nappy) using 'fake' urine (water, sodium chloride, urea, hydrochloric acid perhaps) in water in appropriate amounts. Does the nappy work equally well on individual solutions of the urine components (or are polar compounds different to non-polar ones)? How does temperature affect its properties?

 

Heat of reaction and E°
All chemical and biochemical reactions involve an energy change; e.g., chemical energy may be transferred as electrical, kinetic, light, sound, or (most often) to heat energy. Chemical to heat energy changes occur, for example, in displacement reactions such as: M(s) + Cu²⁺(aq) → M²⁺(aq) + Cu(s). Chemical to electrical energy changes occur, for example, in simple electrical cells; thus, a potential difference (V) is observed if the metal (M) is more or less reactive than copper. It would seem reasonable that the amount of heat evolved is directly related to the voltage of the cell. How true is this? Does it hold over a wide range of voltages, and is it concentration dependent? The photo (on the left) below may give you a start but how on earth will you measure the temperature change without heat loss? The photo on the right makes you glad you didn't have one of these on your lap.

Strength of plastic

If you’ve ever lifted a full plastic shopping bag you’ll know that some are stronger than others. Manufacturers make plastic objects with different strengths to suit different needs. It is not only thickness that is important, but the type of plastic, its density and amount of crosslinking. For example PE comes in several types: high-density polyethylene (HDPE), low-density polyethylene (LDPE), medium-density polyethylene (MDPE) and so on. You could imagine what UHDPE and VLDPE stand for. High-density polyethylene resin has a greater proportion of crystalline regions than low-density polyethylene. The size and size distribution of crystalline regions are determinants of the tensile strength of the end product. HDPE, with fewer branches than MDPE or LDPE, has a greater proportion of crystals, which results in greater density and greater strength. LDPE has a structure with both long and short molecular branches. With a lesser proportion of crystals than HDPE, it has greater flexibility but less strength. Why not make this an EEI? You could compare tensile strength with density and perhaps use temperature as a second IV. How do PP and PE compare if they have the same density? Hmmm!  I’d have a look at the Australian Standard ASTM D 638 Test method for tensile strength of plastics. You don't need a fancy machine - you can do it at school.
 

Steam distillation of eucalyptus oil
Eucalyptus oil is used as component in pharmaceutical preparations to relieve the symptoms of influenza and colds, in products like cough sweets, lozenges, and inhalants. It has antibacterial effects on pathogenic bacteria in the respiratory tract. It used to be a big industry in Australia but has declined as cheaper imports have taken over. Nevertheless, eucalyptus oil, olive leaf oil and ti-tree oil are of vital importance to Australian industry - and society. One of the most disappointing laboratory experiments you can find is the steam distillation of these oils from leaves. They never work very well and you usually end up with a disappointing emulsion - not clear oil. For a good EEI you would need to do more than just extract some oil; you could have a go at improving the method by trialling different heating and collection methods, different aged leaves and so on; all carefully thought out and justified - not just trial-and-error. If you are stuck you could look at oranges or cloves. A trip to an olive leaf distillery would be a fun day out. The photos would look good in your report.
 

Soapmaking - the saponification of vegetable oil
A soap is the sodium or potassium salt of a long chain fatty acid. Soap making has been around for thousands of years and its manufacture is quite simple. However, there are many pitfalls because the chemistry involved is quite complex. A good EEI would be to make soaps from both sodium hydroxide and potassium hydroxide using a variety of saturated and unsaturated vegetable oils and to compare their properties with commercial soaps and detergents. Instructions for making soap can be found easily but you'd need to work out ways (and reasons) for changing the reactants and their quantities: that is, what problem are you trying to solve, and what is your hypothesis? To keep the investigation manageable, you would be wise to consider just two independent variables (perhaps type of hydroxide and saturation of the oil) and control the rest (salt, temperature, concentrations etc). The tests might involve suds formation in hard and soft water and ability to remove an oil spot. You could add some perfume and give the leftovers to mum for Mother's Day.

Breaking strain and crosslinking in polymers

Clarification of water with alum
Cloudy water for domestic water supplies is commonly treated with alum (a double sulfate of potassium and aluminium: KAl(SO₄)₂·12H₂O). Alum acts as a coagulant, which binds together very fine suspended particles into larger particles that can be removed by settling and filtration. In this way, objectionable color and turbidity (cloudiness), as well as the aluminum itself, can be removed from the drinking water. By the addition of a small amount of alum to water, it can be filtered through ordinary paper without difficulty, and yields a brilliantly clear filtrate, in which there is no trace of suspended matter. If it believed that alum not only clarifies a water, but also removes disease germs and ptomaines, so its use is of incalculable value to society. A good EEI would be to make up a sample of water with suspended clayey matter and then filter it through the best filter paper you have at school. To the (still) cloudy filtrate you could add alum solution (about 0.02 g/L) to see if it settles the clay and enables you to filter the solids out (weighed filter paper). Try different amounts of alum, different acidity/alkalinity, add controlled amounts of albumin (egg white). A great EEI with great social importance.

 

Electrolysis of solutions
Electrolysis is commercially highly important in the separation of elements from naturally-occurring sources such as ores using an electrolytic cell. It involves the passage of an electric current through an ionic substance that is either molten or dissolved in a suitable solvent, resulting in chemical reactions at the electrodes and separation of materials. It is used in the production of metals such as aluminium, lithium, sodium, potassium and magnesium, and of non-metals such as chlorine. The electrolysis of water produces hydrogen and oxygen and that could make an interesting EEI. It is known that for water to be electrolysed, it has to have an ionic substance added such as sodium chloride. You could see how the efficiency of the electrolysis is affected by the voltage across the electrodes, and by the concentration of salt present. You'd need to relate your results to the E° value for the non-spontaneous reaction and what happens at voltages lower than that. You may look at the changing rate of generation of the gases as time passes or at the volume after a set time. It's up to you. Does the car ad below make sense? Is it chemically feasible?

Natural buffers

Our blood cannot tolerate a drastic shift in pH. It's a good thing, then, that human blood contains a buffer of carbonic acid, H₂CO₃, and sodium bicarbonate, NaHCO₃. This buffer regulates drastic shifts in the pH of our blood. If this buffer system was absent from our blood, the eating acidic or basic foods would cause the pH would swing too high (alkalosis) or too low (acidosis) and the result could be deadly. Another buffer system is that of a mixture of 0.1M Na₂HPO₄ and 0.1M NaH₂PO₄. As you add 0.1M NaOH or 0.1M HCl to the buffer solution and record its pH if will be noticeably different to that if you just used water instead of the buffer. Is the buffer any better if you used 0.5M solutions? What if you didn't have equal concentrations? Your EEI could be to locate a buffer system in nature (eg a lake) and test it out using natural environmental chemical changes (eg acid rain, increased greenhouse gases) and find if it has any limits.
 

Electroplating
Electroplating is a common industrial process. It is used to bestow some particular property on an object that it doesn't normally have, for example, abrasion and wear resistance, corrosion protection (galvanising, anodising), or aesthetic qualities (nickel or chrome plating). By applying an electric current, a layer of metal such as copper or nickel can be deposited onto a conductive object. In industry currents of about 500 A are common but in the laboratory a 12V power pack can suffice. A simple experiment that can form the basis of an EEI involves the use of  a copper plate and a graphite rod as the cathode and anode, respectively. Nickel ion solution is used as the electrolyte. Under the influence of the battery, positively charged nickel ion can migrate to the cathode, pickup electrons and deposit on the surface of copper electrode; and there you have nickel plating. You could investigate the role of 'strike': initially, a special plating deposit called a "strike" may be used to form a very thin plating with high quality and good adherence to the substrate. This serves as a foundation for subsequent plating processes. A strike uses a high current density and a bath with a low ion concentration. The process is slow, so more efficient plating processes are used once the desired strike thickness is obtained. The striking method is also used in combination with the plating of different metals. Or you could investigate current density (amperage of the electroplating current divided by the surface area of the part) in this process strongly influences the deposition rate, plating adherence, and plating quality. The higher the current density, the faster the deposition rate will be, although you get poor adhesion. You may even produce some nice jewellery for mum.

Crosslinking in Slime
Slime is merely polyvinyl alcohol (PVA) that has been crosslinked by the addition of borax Na₂B₄O₇.10H₂O (sodium tetraborate). Various types of slime have been manufactured but the polymer polyvinyl alcohol is reasonably cheap and is readily available from suppliers because it is widely used as a thickener, stabiliser and binder in cosmetics, paper cloth, films, cements and mortars. Crosslinked PVA is used in hot or cold packs as they are not dangerous if the fluid leaks out. pH is critical in maintaining the crosslinks in slime. Too much acid will weaken the gel but this can be restored with the addition of alkali. A good EEI would be to test the resultant viscosity (you design the apparatus and procedure) as increasing amounts of borax is added (but you must hypothesise and theorise first); and/or to increase the [H⁺] by the addition of acid and then lowering it by the addition of NaOH. Another great EEI.

Electrorefining metals
Virtually all copper produced from ore receives an electrolytic treatment by electrorefining from impure anodes. In electrorefining, the anodes consist of unrefined impure metal, and as the current passes through the acidic electrolyte the anodes are corroded into the solution so that the electroplating process deposits refined pure metal onto the cathodes. In order to achieve high production rates, high current densities are desirable but an excessive current density causes at least two problems: increased impurity levels in the cathode deposit; and anode passivity occurs at current densities above 25-28 mA/cm². Hence, in industry, the current density is always low. An interesting experiment would be to set up an electrorefining cell for copper and find out the optimum current density and/or acid concentration.

Aspirin hydrolysis using a spectrometer
Aspirin is the common name for acetyl salicylic acid (ASA) and is an important drug on the market today. For example, the treatment of thromboembolism often requires the use of ASA. Aspirin is rapidly absorbed from aqueous solution and hydrolysis occurs during the absorption phase and first pass through the liver. It then is converted to salicylic acid (SA) in the blood, predominantly in the liver but also in blood cells, plasma, and kidneys. The hydrolysis of ASA to SA has been the subject of many investigations and can be studied in a high school laboratory if equipped with a visible spectrometer such as a Spectronic 20. The rate constant “k” for the reaction depends on pH, temperature, buffer concentration, and ionic strength. It can be followed by measuring spectrophotometrically the appearance of the complex of SA with ferric chloride, FeCl₃. The method can be found in The Journal of Chemical Education 2000, Vol 7, p 354 by L. Borer and E. Barry.

 

Conductivity of solutions
Electrical conductance is important in a variety of scientific contexts; e.g., nerve impulses, electroplating, electrical cells, and the extraction of metals by electrolytic reduction. You might expect the conductance of an aqueous ionic compound to be dependent on several independent variables, including the concentration of dissolved compound. A good EEI would be to examine this hypothesis: As the concentration (M) of sodium chloride increases, within the range ?? to ?? mol/L, the conductances (C) of the aqueous solutions increase in direct proportion. However, does the relationship hold for all concentrations, temperatures, electrode area, electrode separation and voltages?

 

Ion exchange resin
Ion-exchange resins are widely used in different separation, purification, and decontamination processes. The most common examples are water softening and water purification. Most recently, they can be used for biodiesel recovery. In many cases ion-exchange resins were introduced in such processes as a more flexible alternative to the use of natural or artificial zeolites. The resins are usually small plastic beads that contain ionic groups attached to a polymer-based resin. These ionic groups can be exchanged for similarly charged ions. There are many possibilities for an EEI here. Start with a cation exchange resin and plan an experiment to find the extent to which Na⁺ ions (from say NaCl solution) exchange with the hydrogen ions on the resin. You could Investigate the rate of exchange of ions by leaving the exchange resin in the sodium chloride solution for different periods of time (and plot graphs). Or you could investigate the effect of using different concentrations of sodium ions on the rate of exchange or the effect using cations such as potassium, calcium, aluminium, copper (II), and iron (II). Do they exchange to the same extent and at a similar rate?

Concrete hydration
 The importance of concrete in modern society cannot be overestimated. Look around you and you will find concrete structures everywhere such as buildings, roads, bridges, and dams. There is no escaping the impact concrete makes on your everyday life. Concrete is prepared by mixing cement, water, and aggregate together to make a workable paste. It is molded or placed as desired, consolidated, and then left to harden.  Adding gypsum, CaSO₄, to Portland cement prolongs the hardening. The most important compounds present in cement are: 3CaO•Al₂O₃, tricalcium aluminate; 3CaO•SiO₃, tricalcium silicate; 2CaO•SiO₃, dicalcium silicate; and CaO, calcium oxide. The 2CaO•SiO₃ reacts slowly with water to yield Ca(OH)₂ and H₂SiO₃. This reaction not only helps in holding the material together, but also makes the concrete less pervious to water. The hardening process is due in part to the hydration of the compounds present and is probably influenced by the crystallization of these hydrates. Concrete with too little water may be dry but is not fully reacted. The properties of such a concrete would be less than that of a wet concrete.  You could make up thin slabs of concrete in a shallow trough with different amounts of water and test their breaking strain. What if you were unable to get fresh water - would seawater be just as good? If you try other additives, you have to say why you think they'd work (otherwise it's not chemistry - it's just backyard trial-and-error). The possibilities are endless.
 

Recycling an aluminium can
Recycling an aluminium can save 95% of the energy required to produce a new can from ore. Aluminum cans are easily recycled into new aluminum cans, but they can also be recycled into other useful aluminum products. A good EEI would be to convert aluminum cans into alum (potassium aluminum sulfate). Large amounts of alum is used by the paper industry as a filler in paper and secondly for drinking water purification. Merely converting can to alum is hardly the basis for an EEI. You’d need to apply some problem-solving and creative thinking. Perhaps you could look at ways of maximizing the yields and minimizing the input energy (heat) and chemical resources (KOH).

The health of our river
The Brisbane River and the waterways of the Moreton Bay catchment play a vital role in the economy, lifestyle and liveability of South-East Queensland. These waterways support the largest population of any catchment in the State and provide a nationally significant drinking supply. They also provide recreational and employment opportunities and are of cultural significance to the people of the region.  But they are under enormous pressure from population growth. Scientific research indicates current levels of human impact on our waterways are unsustainable and our behaviour and practices must change if we are to halt and reverse the current decline in water quality. This context affords some great EEIs but you need to be careful that you don't just end up testing water samples and making some statements about water quality. If you plan to assess the health of the river you would need to state which tests you are using, why, the techniques, the sampling, the appropriateness of the tests if the water is saline, and so on. A good EEI would also be to ask “What is the effect of depth of water and temperature on dissolved oxygen as measured by using the Winkler technique?” or "What is the effect of salinity on chemical tests?" or “What is the more effective way of measuring salinity and what is the effect of tides on salinity?”.Many schools use this context for EEIs and its societal importance is obvious.

 

Strength of fired pottery clay

Pottery is one of the oldest human technologies and art-forms, and remains a major industry today. It is made by forming a clay body into objects of a required shape and heating them to high temperatures in a kiln to induce reactions that lead to permanent changes, including increasing their strength and hardening and setting their shape. Firing produces irreversible chemical changes in the body. As a rough guide, firing temperatures are in the range of about 1000 to 1400 °C. However, the way that ceramics mature in the kiln is influenced not only by the peak temperature achieved, but also by the duration of the period of firing. A good EEI (especially if you do Senior Art) might be to examine the hardness of the fired clay as a function of temperature; or as a function of time. If you were more adventurous you could look at different atmospheres within the kiln. One word of caution. This is a chemistry EEI and chemistry must be at its heart to distinguish it from applied technology or art.  A pyrometric cone (see photo below) is a spike-shaped piece of clay used to measure temperature in a kiln when firing pottery. Cones have carefully calibrated melting points, indicated by their cone number. They are used to visually determine when a kiln has reached a desired temperature, by observing when a given cone in an observation port starts to droop. They are very attractive too.


·     Polarisation of light in acidified sugar solution
Certain materials (sugar in this experiment) are optically active.  When polarized light passes through an optically active material, its direction of polarization is rotated. The angle of rotation depends on the thickness of the material and the wavelength of the light. You could make up a solution of sugar (the disaccharide called sucrose) and hydrolyse it using dilute acid to form the monosaccharides glucose and fructose: C₁₂H₂₂O₁₁(sucrose) + H₂O + H⁺  => C₆H₁₂O₆(fructose) + C₆H₁₂O₆(glucose) + H⁺.  The product is called invert sugar. As the reaction proceeds, the degree of polarisation changes and this can be observed using crossed polarisers either side of the solution placed on an OHP.  Inverted syrups are sweeter than sucrose solutions and because there is glucose present in inverted sugar syrup it is substantially more hygroscopic (water retaining) than sucrose. This means that the syrup tends to keep products made with it moist for longer than when sucrose is used alone. It is likewise less prone to crystallisation and therefore valued especially by bakers. You could look at the effect of angle vs. concentration vs time; depth effects; acidity effects; temperature. If you are after a real challenge you could investigate if the reaction rate constant is dependant on acid concentration.

Carbon dioxide in soft drinks
Design an experiment to measure the solubility of CO₂ in lemonade as a function of temperature (by titration). Results obtained by this procedure are intended to indicate a trend in the solubility of the carbon dioxide as a function of temperature. In aqueous solution, carbon dioxide exists in many forms. First, it simply dissolves: CO₂(g) → CO₂(aq) Then, an equilibrium is established between the dissolved CO₂ and H₂CO₃, carbonic acid: CO₂(aq) + H₂O(l) ↔ H₂CO3(aq) The double-headed arrows mean that the reaction is reversible; that is, the products can react to form the reactants. The “species” are said to be in equilibrium if the rate of the forward reaction equals the rate of the reverse reaction. In this case there will be no change in their concentrations. Only about 1% of the dissolved CO₂ exists as H₂CO₃. Carbonic acid is a weak acid which dissociates in two steps. H₂CO₃ → H⁺ + HCO₃^¯ K_a1 = 4.2 x 10^-7 ; HCO₃^¯ → H⁺ + CO₃^2- K_a2 = 4.8 x 10^-11. When titrated, all the CO₂(aq) is reacted so a titration is a measure of total CO₂ content: H₂CO₃(aq) + 2NaOH(aq) → Na₂CO₃ + 2H₂O.

 

Distillation of alcohol
Distillation is one of the oldest and still most common methods for both the purification and the identification of organic liquids. It is a physical process used to separate chemicals from a mixture by the difference in how easily they vaporize. Distillation relies on the fact that the vapor above a liquid mixture is richer in the more volatile component in the liquid, the composition being controlled by Raoult’s law. Not all mixtures of liquids obey Raoult’s law, such mixtures; called azeotropes, mimic the boiling behavior of pure liquids. These mixtures when present at specific concentrations usually distill at a constant boiling temperature and cannot be separated by distillation. Examples of such mixtures are 95% ethanol-5% water (bp 78.1 °C). I think you could make a successful EEI out of an experiment where you distill various ethanol/water combinations and measure the %ethanol in the distillate as a function of time or temperature of the vapour. You would need to consult vapour pressure diagrams.

 

Annealing
Metals are used for many different purposes. Two hundred years ago, the town blacksmith produced nails, hammers, wheel rims, knives, and horseshoes from the same basic metal.  In some applications, a metal must be able to bend easily without breaking, whereas in other cases the metal must resist bending.  Today metallurgists can produce these results by using different metals, alloying metals, and by heat treating metals.  The substitution of a different metal or using a special alloy is often costly.  Therefore heat treatment of a common metal is often the most cost efficient method of producing a metal that has the properties required in a specific application.  Most metals respond to heat treatment, but the treatment temperatures are unique for different metals.  A great EEI is to examine the effects of annealing, quenching, and tempering on metals. A steel bobby pin would be a useful starting point but you’d need to control the amount of heating and quenching and see how the properties vary with changes. Ask yourself “what type of treatment produces the hardest metal; and the strongest metal”? The male Blood Elf (below) from the World of Warcraft is carrying a quenching bucket. Nothing to do with chemistry however.

 

Anthocyanins in wine
Anthocyanin pigments are responsible for the attractive red to purple to blue colors of many fruits and vegetables including dark wine grapes. Interest in the anthocyanin content of foods has also intensified because of their possible health benefits. They may play a role in reduction of coronary heart disease, increased visual acuity, as well as antioxidant and anticancer properties. Anthocyanins are relatively unstable and often undergo degradative reactions during processing and storage. Measurement of total anthocyanin pigment content along with indices for the degradation of these pigments are very useful in assessing the color quality of these foods. There is a method used for determining anthocyanins in wine. It was developed by Fuleki and Francis and you’ll find it on the web. You'll also need a visible spectrophotometer (520 nm).

 

Corrosion of roofing steel
Corrugated galvanised iron is a building material composed of sheets of hot-dip galvanised mild steel, cold-rolled to produce a linear corrugated pattern in them. Galvanized metals prevent rust not only by protecting the metal from direct oxygen contact, but also by the electrochemistry of zinc. When iron rusts its oxidation state is increased as electrons are transferred away from the metal. Zinc acts as an electron donor in a slightly complex electrochemical reaction, thereby preventing the oxidation of the underlying metal. Nevertheless, rusting will be inevitable, especially if the local rainfall is at all acidic in nature. So for example, corrugated iron sheet roofing will start to degrade within a few years despite the protective action of the zinc coating. An EEI might be is to see how far the zinc protection extends over bare metal. Small scratches don’t rust but if the scratch is 10 mm wide will it? What if kept in a humid atmosphere? Is Lysaght zincalumeÒ better than ordinary galvanising?

 

Heat of combustion
High school experiments on heats of combustion usually involve burning a candle or alcohol and trapping the heat in a beaker of water. The errors are usually massive and chimneys etc are used to try to trap the heat – with little success. How could the accuracy be improved? You could explore ways and provide a theoretical reason for your trials. Alternatively, you could compare the accuracy of DH_C values of methanol, ethanol, propenol; or even of the three C₄H₉OH isomers. Why might the accuracy be different? What does this tell you about intramolecular bonding? Are there any correlations with BPt?

 

Paper chromatography of leaves
Paper chromatography is an analytical chemistry technique for separating and identifying mixtures that are or can be coloured, especially pigments. This can also be used in secondary or primary colours in ink experiments. Most leaves are green due to chlorophyll. This substance is important in photosynthesis (the process by which plants make their food). You have probably done experiments where the different pigments present in a leaf are separated using paper chromatography.  However, to make this a good EEI you need to take it further. Which is the optimum solvent (propanone, ethanol, hexane etc) and why (polar, non-polar, low viscosity, high BPt and so on)?

Diffusion of aqueous ions
Diffusion is the process by which molecules spread from areas of high concentration, to areas of low concentration. Diffusion occurs in liquids but more slowly than in gases because the particles are not as free to move about. When a crystal of Pb(NO₃)₂ and a crystal of KI are placed on opposites sides of a petri dish filled with water a yellow line of PbI₂ forms across the dish closer to one crystal than the other. This gives you an idea of the rate of diffusion of ions. You could repeat this with different combinations so long as they form a precipitate. Is it just the molar mass of the ion, or is it related to the charge, or perhaps something to do with electronegativity. Would anything happen with a non-polar solvent such as hexane, and if not, why not? A great EEI that will keep you entertained for weeks. There will be safety issues with heavy metal ions (eg Pb²⁺) so be warned.

Migration of ions
Ions, being charged, will migrate towards electrodes of opposite charge. For example, the migration of manganate ions (MnO₄^2-) can be observed if you cut a piece of filter paper slightly smaller than a microscope slide and moisten the filter paper with tap water. Then fasten the paper to the slide with crocodile clips and put a small crystal of potassium manganate (K₂MnO₄) in the centre of the paper. When you connect the clips to a power supply set at 12 V DC you should notice the migration of the coloured manganate ion towards the negative electrode. Occasionally permanganate (MnO₄^-) and manganate (MnO₄^2-) salts are confused, but they behave quite differently. How different is the speed of migration for larger ions, for ions of different charge. Is voltage related to migration speed. What a great EEI this is turning out to be.

 

Testing water hardness
Tap water in some parts of the country is very pure and is said to be ‘soft’. It easily makes a lather with soap. Water from other parts may contain various dissolved impurities and is described as ‘hard’ water. Temporary hardness may be removed by boiling, but permanent hardness survives the boiling process. You can measure water hardness by finding out the volume of a soap solution (of known concentration) required to form a permanent lather with a known volume of water. A interesting EEI would be to see if the amount of soap needed is correlated with the concentration of various ions responsible for hardness. You could make up solutions with a range of concentrations of 'hardness' ions and see how much soap is needed to make a permanent lather (one that lasts for 30 seconds) is obtained when shaken. Try 1 mL increments. Analysis of water hardness in major Australian cities by the Australian Water Association shows a range from very soft (Melbourne) to very hard (Adelaide). Total Hardness levels reported in various government reports are listed below:

 

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Other resources:

How to do a Deadly EEI in Physics

300 stimuli and ideas for an EEI in Physics

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