Stinky Socks and Shmelly Shirts?

Northumbria University researchers have identified six volatile organic compounds on dirty socks and t-shirts which are responsible for the stench of your dirty laundry. Surprisingly, some of these compounds can survive washing in a machine with detergent at 20°C, that is, washing in cold water will not remove all the compounds responsible for the smell.

The researchers wanted to identify the volatile organic compounds from dirty clothes before washing, after washing while still wet, and after drying, to see which compounds are responsible for bad smells and to see if they were eliminated during the washing process.

6 men and 2 women were each given a new pair of socks. Each person was asked to wash their feet and dry them before wearing the socks for at least 10 hours in a specified type of shoe. Each sock was then placed in a separate bag and stored in the dark overnight. 9 men were each given a t-shirt to wear for 2-3 hours while taking part in a soccer match. After the match the t-shirts were bagged separately and refrigerated.

The researchers smelled each item and graded it on a scale of 0 (no bad smell) to 10 (very bad smell).
Then the items were washed in a Tergotometer, a lab machine made up of several miniature washing machines, at 20°C using non-perfumed detergent. Each item was graded for odour after washing while still wet and then again after drying.

Using analytical techniques like gas chromatography, the team identified 6 main volatile organic compounds that contribute to the smell of dirty laundry:

• butanoic acid (butyric acid); rancid butter odour
• dimethyl disulfide; onion-like odour
• dimethyl trisulfide; powerful, unpleasant odour
• heptan-2-one (2-heptanone); fruity odour like bananas
• nonan-2-one (2-nonanone); herbaceous odour
• octan-2-one (2-octanone); apple-like odour

As the concentration of these volatile organic compounds decreased after each washing, the items became less smelly.


Reference:
Chamila J. Denawaka, Ian A. Fowlis, John R. Dean. Source, impact and removal of malodour from soiled clothing. Journal of Chromatography A, 2016; 1438: 216 DOI:10.1016/j.chroma.2016.02.037

Further Reading:
Scientific Method: http://www.ausetute.com.au/scientificm.html
Experimental Design: http://www.ausetute.com.au/experimentd.html
Writing Lab Reports: http://www.ausetute.com.au/labreport.html
Introduction to Functional Groups: http://www.ausetute.com.au/fungroup.html
Naming Alkanoic Acids: http://www.ausetute.com.au/namalkacid.html
Naming Alkanones: http://www.ausetute.com.au/namalkanone.html
2-Dimensional Structural Formula: http://www.ausetute.com.au/structural2D.html
Condensed Structural Formula: http://www.ausetute.com.au/condensedsf.html
Molecular Formula: http://www.ausetute.com.au/molecularformula.html
Molar Mass Calculations: http://www.ausetute.com.au/moledefs.html
Gas Chromatography (GC) : http://www.ausetute.com.au/gc.html

Suggested Study Questions:

1. What hypothesis was being tested by the researchers in this experiment?
2. Write an aim for the experiment conducted by the researchers.
3. Write a method for this experiment as a series of steps.
4. Tabulate the results of this experiment.
5. Write a suitable conclusion for this experiment.
6. Discuss how you could improve this experiment.
7. Give the 2-dimensional structural formula for each of the following compounds:
• butanoic acid
• heptan-2-one (2-heptanone)
• nonan-2-one (2-nonanone)
• octan-2-one (2-octanone)
8. On each structural formula above, circle the functional group and name it.
9. Classify each of the compounds listed in question 1 on the basis of their functional groups.
10. Give the molecular formula for each of the following compounds:
    • butanoic acid
    • heptan-2-one (2-heptanone)
    • nonan-2-one (2-nonanone)
    • octan-2-one (2-octanone)
11. Give the condensed structural formula for each of the following compounds:
    • butanoic acid
    • heptan-2-one (2-heptanone)
    • nonan-2-one (2-nonanone)
    • octan-2-one (2-octanone)
12. Calculate the molar mass for each of the following compounds:
• butanoic acid
• heptan-2-one (2-heptanone)
• nonan-2-one (2-nonanone)
• octan-2-one (2-octanone)
13. Which of the following do you think would have the longest gas chromatography retention time ? Explain your answer.
    • heptan-2-one (2-heptanone)
    • nonan-2-one (2-nonanone)
    • octan-2-one (2-octanone)
14. Why is gas chromatography (GC) a good choice of analytical technique for this experiment compared to other chromatographic techniques?

Why Study Science?

Listen to four of the world’s most eminent physicists discuss and deliberate on the biggest challenges facing the science community today.

• Professor Steven Chu was the co-recipient of the 1997 Nobel Prize for Physics. He has devoted his recent scientific career to the search for new solutions to our energy and climate challenges. 
• Professor Schmidt was jointly awarded the 2011 Nobel Prize in Physics for the discovery of the accelerating Universe.
• Professor Lawrence Krauss is theoretical physicist and the author of several bestselling books, including The Physics of Star Trek and A Universe from Nothing. He is an advocate of scientific scepticism, science education and the science of morality.
• Professor Lisa Randall studies theoretical particle physics and cosmology at Harvard University. Her research connects theoretical insights to puzzles in our current understanding of the properties and interactions of matter.

The podcast is about 1.5 hours, but you can select parts of it to listen to.

There is a very nice discussion of what is meant by "good science", there is also some very interesting discussion on "accidental discovery", "experiment to "prove" or "disprove" theory, and the importance of acknowledging that science is not an "absolute" but rather about belief in the "truth" of a scientific theory based on statistical probabilities.

https://soundcloud.com/experience_anu/when_does_science_matter

Scientific Method and Designing an Experiment

AUS-e-TUTE has just added two new resources sets:

• Scientific Method
• Experimental Design

All the Chemistry Syllabus Study Guides in the Test Centre have been updated to include these new resources.

Why Use a Volumetric Flask?

In order to prepare an aqueous standard solution, you transfer the solute to a volumetric flask and then you add water "up to the mark", that is, until the bottom of the meniscus lies on the "mark" when viewed at eye-level. You can quickly convince yourself of the need to view the "mark" at eye-level just be preparing your standard solution as above and then changing the angle you view it from.
But what about this need to add water to the solute in this oddly-shaped vessel called a volumetric flask?
Why couldn't you just weigh out the solute into a beaker then add the required volume of water from a pipette?
Or, if the solute is a liquid or a solution, why not just pipette the required volume into a beaker then pipette the required volume of solvent into the same beaker?

So, why not try it?

Experiment (a) For solid solutes such as sodium chloride (table salt) or sucrose ("sugar") just pour the solid into a small DRY measuring cylinder until you have 5 mL for example. Pour this solid into a 100 mL measuring cylinder. Add 50 mL of water from a pipette (you will need to keep swirling the flask while you add the water). Record the volume of the final solution. Repeat the experiment using different volumes of solute and solvent.
Repeat this experiment using sand as the "solute" and water as the solvent.

Experiment (b)  For liquid solutes such as ethanol (ethyl alcohol) or acetone (propanone) use a pipette to place 50 mL of the solute into a 100 mL measuing cylinder then add 50 mL of water from a pipette and record the volume of the final solution. Repeat the experiment using different volumes of solute and solvent.
Repeat this experiment using vegetable oil as the "solute" and water as the solvent.

If a solute dissolves in a solvent, the volume of the final solution is not equal to the volume of the solute plus the volume of the solvent. Sometimes adding a solute to a solvent results in a solution with a volume less than that of the solvent + solute, and sometimes adding a solute to a solvent results in a solution with a volume greater than that of the solvent + solute. Right now, there are no good, general theories to explain this behaviour! But it is because of this that we use that oddly shaped piece of glassware called a volumetric flask when we make up a standard solution.

Restricting Chemical Sales

Police in Western Australia want to restrict stores selling some chemicals in a bid to "smash" clandestine drug laboratories according to a story in the Courier Mail today.
The list of chemicals being targeted includes drain cleaners, battery acid, and common lawn fertilizers.

Drain cleaners often contain sodium hydroxide, also known as caustic soda or lye. Sodium hydroxide, a white solid at room temperature, is a strong base that can cause chemical burns.
When sodium hydroxide is added to a blocked drain it dissolves in the water in the pipe and releases heat. This heat can melt the grease blocking the pipe. The sodium hydroxide also reacts with some of the fat in the pipe to form soap. This soap helps remove the grease blocking the drain.

Lead-acid batteries that are typically found in cars contain sulfuric acid, also known as vitriol. It is a strong acid that used in concentrations of around 30% w/w in battery acid. When sulfuric acid dissolves in water, heat is given off. Sulfuric acid can be neutralized by sodium hydroxide with the products of the reaction being water and sodium sulfate.

High-nitrogen content fertilizers can contain ammonium nitrate which is itself a white solid at room temperature and pressure. When ammonium nitrate dissolves in water it absorbs energy from the surroundings. Ammonium nitrate reacts with sodium hydroxide to produce ammonia gas, water and sodium nitrate.
Ammonia is a colourless gas with a pungent odour at room temperature and pressure. "Household ammonia", sold as a cleaning product for ovens, glass, porcelain and stainless steel, is a solution of ammonia in water. The concentration of this basic solution varies from 5% w/w to 10% w/w.
Ammonia is used to make many pharmaceuticals.

Reference
http://www.couriermail.com.au/news/national/police-bid-to-restrict-chemical-sales/story-e6freooo-1226077611068

Further Reading
Naming Ionic Compounds
Writing Ionic Formula
Definitions and Properties of Acids and Bases
Enthalpy Change
Concentration: Percent by Mass
Concentration: Molarity


Study Questions

1. Give the chemical formula for the following compounds:
   
   • sodium hydroxide
   • sulfuric acid
   • sodium sulfate
   • ammonia
   • ammonium nitrate
   • sodium nitrate
   • water
2. Draw up a table with the headings, acidic, basic, neutral. Place the compounds listed above in the appropriate places in the table.
3. Draw up a table with the headings ionic and covalent. Place the compounds listed in question 1 in the appropriate places in the table.
4. Define the terms exothermic and endothermic.
5. Write an equation to show sodium hydroxide dissolving in water. Include the energy term. Is this reaction exothermic or endothermic?
6. Write an equation to show sulfuric acid dissolving in water. Include the energy term. Is this reaction endothermic or exothermic?
7. Write an equation to show ammonium nitrate dissolving in water. Include the energy term. Is this reaction endothermic or exothermic?
8. Convert the following percent by mass concentrations to concentrations in mol/L
   
   • 30% w/w aqueous sulfuric acid solution
     
   • 5% w/w aqueous ammonia solution
   • 10% w/w aqueous ammonia solution
9. Write balanced chemical equations for each of the following:
   
   • the neutralization of sulfuric acid by sodium hydroxide in aqueous solution
   • ammonium nitrate reacts with sodium hydroxide in solution
10. Write an equation to show how sodium hydroxide can react with a fat to produce soap.
11. Explain how soap can clean up built up grease in your drain.
12. A student found a container of solution in the family's garage. it is believed to be either household cleaner or battery acid. Describe tests that you could conduct in order to determine what solution is in the container. What safety precautions would you take when conducting these tests?
    

Fingerprint Powders

University of Queensland scientists have just completed a study revealing that the human factor involved in the process of identifying a set of fingerprints could lead to errors and false convictions of innocent people.
In the study 37 qualified fingerprint experts and 37 novices were given pairs of fingerprints to examine and decide whether a simulated crime scene matched a potential suspect or not. Some of the print pairs belonged to the "criminal" while others were highly similar but actually belonged to an "innocent" person.
The experts correctly matched just over 92 percent of the prints to the criminal. But, they mistakenly matched 0.68 percent of the prints to the innocent person.

Fingerprint powders are fine powders used in dusting for fingerprints by crime scene investigators. Fingerprint powders are often white or black in colour. White powders would be used on dark surfaces while black powders would be used on light coloured surfaces.

Examples of powders that have been used to dust for fingerprints:

White Powders Black Powders Calcium oxide Chalk Titanium dioxide White tempera (starch + titanium dioxide) Haddonite white (titanium dioxide + kaolin + chalk) Lanconide (zinc sulfide + zinc oxide + barium sulfate + titanium dioxide + bismuth oxychloride + calcium carbonate) Charcoal Graphite Lampblack Dragon's blood (Daemonorops draco plant resin) Haddonite black (lampblack + graphite + powdered acacia) Dactyl black (graphite + lampblack + gum acacia)

The fingerprint powder must be fine enough to show fingerprint details. The finer the powder is the better it should be.
To be a good fingerprint powder the powder must adhere to, or stick to, the fingerprint but not to the surface the fingerprint is on.


Reference:
Association for Psychological Science (2011, May 11). Dusting for fingerprints -- It ain't CSI. ScienceDaily. Retrieved May 15, 2011, from http://www.sciencedaily.com­ /releases/2011/05/110511162536.htm

Further Reading:
Pure Substances and Mixtures
Elements and Compounds
Allotropes
Writing Ionic Formula
Calculating Percentage Composition

Study Questions

1. What are the main chemical constituents of:
   
   • chalk
   • lampblack
   • charcoal
   • graphite
2. Draw up a table dividing the fingerprint powders into pure substances and mixtures.
3. For the pure substances listed in question 2, draw up another table dividing these up into elements and compounds.
   
4. Write the chemical formula for each of the following:
   
   • calcium oxide
   • titanium dioxide
   • zinc sulfide
   • zinc oxide
   • barium sulfate
   • calcium carbonate
5. Calculate the percentage composition of each of the following compounds:
   • calcium oxide
   • titanium dioxide
   • zinc sulfide
   • zinc oxide
   • barium sulfate
   • calcium carbonate
6. Titanium dioxide features in many of the recipes for making white fingerprint powders. What properties of titanium dioxide make it useful for this purpose?
7. Graphite is a common constituent in many black fingerprint powders. What properties of graphite might make it particularly useful as a fingerprint powder?
8. For the University of Queensland study, give examples of the following types of variables:
   
   • independent variable
   • dependent variable
   • controlled variables
9. Based on the information provided in the article, do you think the University of Queensland study was a fair test? Explain your answer.
10. Design an experiment to test the statement that graphite is a better powder than charcoal to use for detecting fingerprints on the surface of tiles.
    
    

Beads of Saliva

You can stretch a glob of saliva between your thumb and forefinger. Before the strand of spittle breaks, a string of beads is formed.

Saliva, and other complex viscoelastic fluids like shaving cream and shampoo, contain long chains of molecules called polymers. In the case of saliva, the polymers are proteins known as mucopolysaccharides.

Key factors involved in the beading mechanism are :

• fluid inertia, or the tendency for a fluid to keep moving unless acted upon by an external force
• viscosity, or the time it takes a stretched polymer to 'relax' or snap back to its original shape when the stretching ceases
• capillary time, or how long it would take for the surface of the fluid strand to vibrate if plucked

In order to form beads the fluid inertia has to be large enough and the relaxation time has to be small enough. Bead formation depends on two ratios:

• the viscous force compared to the inertial force
• the relaxation time compared to the capillary time

Learning how to control bead formation could be used to improve printing because smearing 'satellite' beads form around droplets produced by an inkjet printer. Understanding bead formation could also help improve industrial processes such as electrospinning which is used to make a variety of products, and spray coating used in painting.

Reference:
Pradeep P. Bhat, Santosh Appathurai, Michael T. Harris, Matteo Pasquali, Gareth H. McKinley, Osman A. Basaran. Formation of beads-on-a-string structures during break-up of viscoelastic filaments. Nature Physics, 2010; DOI: 10.1038/nphys1682

Activities

1. Design an experiment to measure the viscosity of shampoo.
2. Suggest ways that the viscosity of shampoo could be changed.
3. Design an experiment to test one of the hypotheses above.
4. Design an experiment to measure the fluid of inertia of a range of different fluids.