A-level Applied Science/Planning and Carrying out a Scientific Investigation
About this UnitEdit
From the AQA Specification:
You need to produce a portfolio of evidence which shows that you can plan and conduct an investigation and present your findings in a suitable way for a chosen client.
Your portfolio of evidence should... demonstrate knowledge of the following: • how to plan an investigation; • how to carry out the investigation; • recording and processing the data obtained; • evaluating and drawing conclusions from the investigation; • presenting the outcomes of the investigation.
How you will be assessedEdit
This unit is assessed through the work you complete for your portfolio.
The marking criteria are found in the AQA specification.
Most suggestions below have suggestions for a client's problem which needs to be addressed. This is an important aspect of the Unit 7 task - the investigation must meet a realistic requirement. Changes to the suggestions below, or additional suggestions, are welcome - this is a wiki after all!
Here is a list of suggestions for Science Investigations. Please add/amend/extend the list as you see fit. This is essentially a brainstorm...
Client: Some industries will mix liquids by cascading one liquid into another, assuming mixing will be complete. These drops may prevent complete mixing and need to be investigated.
Recent research has shed light on this phenomenon: The fast-moving shiny drops that skid across the surface of soapy water. Detergents play a crucial role – but how does the concentration of detergent affect the drops? What about ‘non-ionic’ detergents? What about a surface of anionic detergents and drops of cationic ones?
Challenges: Making drop-producing apparatus, Researching the chemistry of detergents, Assessing the numbers of drops
Client: Chemical producers who rely on reactions in solution will need to know how viscosity might affect rates of the reaction.
Many chemical reactions depend on molecules colliding, so slowing the rate of collisions will slow the rate of the reaction. In solution, the viscosity of the solvent can affect the reaction by slowing the collision rate, but it does not work for every reaction. The reaction between calcium carbonate and acids is highly dependent on viscosity, but when acids react with thiosulphate the viscosity seems not to be a factor.
Challenges: Assessing the viscosity of solutions, Researching and investigating the kinetics of reactions.
Marble chip reaction with acidEdit
Client: Chemical industries using heterogeneous reactions will need to know how the rate of reaction can be altered.
How is the rate affected by various factors (e.g. surface area, temperature, concentration, stirring, viscosity, ionic strength). Estimation of surface area of marble chips.
Sodium Thiosulphate and Hydrochloric acid reaction (‘disappearing cross’)Edit
Client: Chemical engineers wishing to check if turbidity is a useful surrogate measurement for whether a reaction has reached completion.
How does the reaction respond to changes in acid concentration (it is first order for thiosulphate concentration but varies from first to zero order with acid).
How can we assess the amount of oil contamination on beaches?Edit
Client: Various groups will want to assess oil contamination, and a simple quick method would be appreciated.
The method used solvent extraction. Sand samples were laced with oil and the efficiency of recovery was measured. The sensitivity of the method was also estimated.
Synthesis and isolation of propanoic acid from propan-1-ol.Edit
Client: Chemical suppliers who want to investigate production of this chemical.
Trialling different methods.
Making biodiesel from waste vegetable oil.Edit
Client: Motoring enthusiasts who want to make their own environmentally-friendly and cheap fuel.
Using methanol and sodium hydroxide it is possible to make diesel fuel from old chip fat.
Analysing the gases remaining after burning a candle in a gas jar.Edit
Client: Motor vehicle engineers who want to check the composition of exhaust gases.
CO2 is easy; it is readily absorbed with NaOH.
O2 is harder; an oxygen probe is very useful but otherwise oxygen could be absorbed by, for example, the slow reaction of steel wool.
CO is challenging; it will be absorbed by CuCl solution but it is in very low concentrations.
Extraction of caffeine from tea.Edit
Client: Suppliers or independent analysts who want to assess the caffeine content of tea products. Chemical suppliers who want to provide pure caffeine to clients.
 This method usually involves solvent extraction with a chlorinated alkane (e.g. dichloromethane or 1,1,1,-trichloroethane). With care it is possible to recycle the solvent and avoid health and environmental damage.
- Investigation of weak acid strengths/synthesis of new acids
- Rate expression for tin/iodine reaction – kinetics of a reaction
- Nobili’s rings – strange colours seen during electrolysis.
- A transient red colour – the chemistry of iron/sulphate complexes.
- Liesegang rings – stripey effects in gels.
- Polarimetry to investigate concentrations of sugars. Client: Suppliers of sugar syrups who want to assess their products.
- Flame photometry to determine concentrations of aqueous ions. Client: Analysis of mineral water samples to check manufacturers' claims.
- Is there a connection between aluminium and Alzheimer's disease?
- Is the level of chloramines found in swimming pool water affected by temperature? Client: Swimming pool operators concerned about eye irritation amongst their customers.
- Effectiveness of two major washing powders on five common household stains. Client: Consumer testing organisation who wants to test commercial claims.
- Factors affecting the decomposition of biodegradable plastics. Client: Environmental agencies testing claims of environmental-friendliness from plastics manufacturers.
- Studies of infrared spectroscopy: nature and applications. Client: Applications include breath-testing for alcohol and testing vehicle exhaust emissions.
- NaCl and potential alternatives to NaCl as a roadway de-icer. Client: Highways agency investigating de-icers which cause less environmental damage - but at what cost?
- Synthesis and analysis of hexane-3,4-diol.
- Calcium carbonate content of seashells.
- Characterisation of New Polyethylenes Prepared by Single-Site Catalysis.
- An Investigation Into The Uses Of Environmentally Friendly Additives/Alternatives To Petrol.
- Protein Purification.
- Water Pollution in Hong Kong.
- A study into the colour of ketchup.
- An investigation into the effects of heat, pH and long term UV radiation on sunscreens.
- Comparison By Spectral Characterisation Of Myoglobin In Beef, Pork and Turkey.
- Spectrophotometric Determination of Trace Amounts of Iron in Plant Samples.
- The effect of disulphide reduction on the structure, and activity of Yeast Alcohol Dehydrogenase.
- Investigation into the effect of pH on the mechanism of glycation of phenylalanine as a model of the glycation of the B chain of insulin.
- Analysis of Vitamin C in Orange Juice through a Chemiluminescent Clock Reaction.
- Investigating the Effect of Different Halide Ions on the Stem Volmer Constant.
- Developing and Validating an Assay for Tissue Thiols and the Analysis of the Effects of Aging and Taurine on Tissue Thiols.
- Relation between the Slow Relaxation Time and Foaming of Selected ICI Surfactants.
- Purification of ibuprofen from commercial tablets.
- Building a breathalyser.
- Titration of various commercial vinegar samples.
- Titration of vitamin C content of commercial fruit juices.
- Investigation in the synthesis of acetylsalicylic acid (aspirin).
Client: Manufacturers of military flak jackets are investigating if jackets can be made flexible at low strain but rigid at high strain by incorporating shear-thickening fluids.
Corn starch mixed with water has bizarre properties - under low strain it behaves as a liquid but if hit with a hammer it solidifies and shatters. What composition achieves the best transition from fluid to solid? What force is required to achieve the transition?
Client: Ice-cream manufacturers who want to reduce time by freezing their product from warm samples instead of cooling to room temperature before freezing.
Strangely, under the right conditions, warm water will freeze faster than cooler water. Various reasons for this have been proposed, but it is still a prime example of an experiment that defies intuition.
Challenges: Research the literature on the phenomenon. Establish conditions under which the effect is observed. Monitor the experiment closely to discover what causes the effect. Use the information discovered to design a change the conditions so that the effect is no longer observed.
Studying the impact of air rifle pellets in gelatin.Edit
Client: Forensic laboratories investigating wounding incidents. Air rifle manufacturers concerned about safety.
The student made ballistic-concentration gelatin and assessed the velocity of the air rifle pellet and its subsequent penetration into the gelatin target.
Making a vee-notch flowmeter from a plastic milk bottle and calibrating it.Edit
Client: People who might require a cheap method to assess flow rates of running water e.g. environmental surveyors, central heating engineers.
This is a very simple experiment, but challenging to do well. The student will need to measure the water level exactly as well as measuring the flow rate by collecting water over a measured period of time.
Thermal death point of cell membranes.Edit
Client: Farmers who would like to predict which crops would fare better in conditions of increased summer temperatures.
Using a colorimeter, it is easy to assess damage to the cell membranes of beetroot samples by the amount of pigment they release to the medium. This correlates to the temperature at which the beetroot is incubated. Red cabbage seems to require a higher temperature which may reflect the mediterranean origins of brassicas. Non-pigments plants could be assessed by measuring the amount of protein/salts/carbohydrate/etc they release.
Client: Health food suppliers who wish to promote the anti-oxidant properties of various foods.
The peroxidase activity of various organisms can be assessed by measuring the rate of oxygen production (either collecting the gas and measuring its volume, timing how long an enzyme-impregnated circle of paper takes to rise to the surface, or datalogging the decrease in mass of the sample as gas is released). Organisms compared could be: animal/fungus/plant or different varieties of pepper. The effect of temperature or other conditions on the enzyme could also be studied. Lead cations and nitrate anions are both inhibitors, although the latter is not well known as an inhibitor.
Investigating the colour perception of a range of subjects.Edit
Client: Paint and dye manufacturers who would like to identify if different client groups would use different names for the same colour.
There are interesting gender differences in identifying greens and pink.
- Teachers or candidates reading this article of suggested investigations need to be aware that the specification is clearly based around the needs of a client who needs to know something for a purpose. All the investigations appear to be about a particular scientific observation, feature, phenomenon or principle. None appear to be linked to client with a problem that needs solving. When undertaking this Unit 7 investigation the list of ideas suggested here need to be translated into a problem that needs solving - the specification is APPLIED science and should not simply be based on an investigation out of context. (Principal Moderator)
- Suggested IB Extended Essay projects
- In search of more solutions - Royal Society of Chemistry resource book