South Australia sets a poor example

 I've always admired South Australia for its innovative and interesting chemistry syllabi, and it's great that females are being featured in chemistry labs, but the current image on their website is a big fail in terms of chemistry education.

 

https://www.sace.sa.edu.au/web/chemistry

 

Can you see any problems with this photo?

(revise "Safety in the Lab" at https://www.ausetute.com.au/safety.html)

Dangerous Chemical Spill at Lucas Heights

This is a headline from the Sydney Morning Herald, Friday 1^st March 2019, "Three hospitalised after chemical spill at Lucas Heights nuclear facility" and an excerpt from the newspaper story is below:

"Two men in their 30s, and a woman, 26, were injured when a cap came off a pipe at the Australian Nuclear Science and Technology Organisation facility at Lucas Heights, spilling about 250 millilitres of sodium hydroxide, also known as caustic soda, onto their arms and faces.

 Sodium hydroxide, also known as caustic soda, is corrosive to the skin and eyes and can cause severe burns."

This "sodium hydroxide" or "caustic soda" sounds like really dangerous stuff doesn't it?  I mean to say, it must be if just 250 mL (a quarter of a litre, a bit less than half a pint)  causes 3 people in an up-to-date, modern, nuclear-medicine manufacturing building, to be hospitalized!

 Well, sodium hydroxide is a caustic substance, that is, corrosive to skin, and it is dangerous if handled incorrectly, however, it is also readily available to non-scientists! You will probably find sodium hydroxide in your own home.

Sodium hydroxide is commonly found in household cleaning products that are used to unblock drains. One such product is Mr Muscle Drano  The directions for use including the following:

WEAR EYE PROTECTION AND PROTECTIVE GLOVES WHEN MIXING OR USING. AVOID CONTACT WITH EYES AND SKIN. DO NOT MIX WITH HOT WATER. 

Keep hands and face away from drains and wash hands after use. Ensure adequate ventilation.
• Do NOT mix with other cleaning products or acids as it may give off a dangerous gas
• Open carefully, do not squeeze the bottle, avoid splashing and clean up spills at once.
• Never use a plunger during or after use, as there may be some Mr Muscle® Drano® in the pipe if the blockage did not completely clear.
• Do NOT use in spas, dishwashers, washing machines, rubbish disposals, toilets or any pipes leading to these outlets. Will not remove roots, leaves or non-organic matter. Always refer to product label for full directions.

You will find sodium hydroxide pellets ("crystals") are also readily available, the website of one such product even suggests you use it to make your own soap ...

METHOD 

1. READ THE DANGEROUS GOODS INFORMATION BELOW BEFORE BEGINNING THIS RECIPE. 

2. Pour cold water into the plastic jar. 

3. Measure Glitz Caustic Soda (into a dry plastic cup).

 4. Slowly and carefully add the Glitz Caustic Soda to the cold water, stirring continuously with a plastic rod. (Wear plastic gloves and goggles; test gloves for holes first.) Do not breath the vapor or lean over the container or have children nearby. The mixture will get very hot.  

5. Allow the solution to cool down to a warm temperature (approx 40oC) in a safe place. 

 6. Melt the Coconut Oil (Copha) at a low heat in a stainless steel saucepan. Add the Canola Oil and Olive Oil to the melted Coconut Oil. Mix well 

7. Allow the oil mixture to cool down to a warm temperature (approx 40oC)

 8. Slowly and carefully, pour the Caustic Soda solution into the stainless steel saucepan containing the oil mixture. Mix thoroughly for at least 30 minutes or until it looks like thick pudding. 

9. If desired, select one fragrance from the optional fragrances. Add the fragrance to the soap mixture and mix for a further 30 minutes.  

10. Pour the finished soap into the tupperware container and allow 24hrs of setting. 

11. Cut the set soap into bars and leave it to cure for at least 6 weeks before use

But honestly, making your own soap at home might sound like fun, but unless you fully understand what you are doing then you should NOT use your soap to wash yourself or you might be the one that is rushed to hospital!

Suggested further reading:
Properties of Acids and Bases 
Definitions of Acids and Bases 
Strength of Bases
Heat of Solution
Neutralisation Reactions 
Heat of Neutralisation
Safety in the Lab 
Soaps and Saponification

Suggested Study Questions:

1. Sodium hydroxide is a caustic substance. What GHS (Globally Harmonised System) pictogram would you find on a container of sodium hydroxide.
2. Sodium hydroxide is a caustic substance. What personal protective equipment (PPE) should you use when handling sodium hydroxide?
3. Write a set of instructions, including all required safety precautions, for dissolving 1 g of sodium hydroxide in 1 L of water.
4. Consider the instructions for using Mr Muscle Drano. Why do you think it advises you to NOT use the product in dishwashers, washing machines and toilets?
5. Consider the instructions for using Mr Muscle Drano. Why do you think it advises you to use ONLY in well ventilated areas?
6. Consider the instructions for making soap. Should you use a plastic drinking cup from the kitchen to measure out the caustic soda? Explain your answer.
7. Why do the soap-making instructions tell you to add the caustic acid to the water AND NOT tell you to add the water to the caustic soda? Do you think it matters which you do this step? Explain your answer.
8. The soap-making instructions tell you to use a stainless steel saucepan. Do you think it would matter if you used an aluminium saucepan or a glass saucepan? Explain your answer.
9. Do you think it is advisable to use a saucepan from the kitchen to make soap? Explain your answer.
10. Imagine you were at the Lucas Heights facility when 3 of your co-workers were injured in this chemical spill. What would you do first to help them?

Sulfuric Acid and Sugar

November 28, 2014, The Canberra Times reported that, "Students were looking on as a teacher conducted an experiment involving sugar and sulfuric acid inside a cabinet when the glass container holding the acid exploded."
The experiment referred to is probably similar to the one shown in the YouTube video below in which concentrated sulfuric acid from a container is poured over sugar in a beaker.

Safety Notes

Sulfuric acid will cause permanent damage if it comes into contact with the eyes or skin. Concentrated solutions of sulfuric acid are extremely corrosive. When sulfuric acid is dissolved in water enough heat is released to make water boil! Carbon monoxide and carbon dioxide are both toxic gases. Sulfur dioxide gas is toxic in high concentration and is a severe respiratory irritant at lower concentration.Some people, especially those prone to asthma, may be especially sensitive to sulfur dioxide. In the presence of moisture, sulfur dioxide forms an acidic, corrosive solution, which in contact with the skin or eyes may lead to burns.

You will notice that the reaction seems to proceed slowly at first. The reaction mixture turns yellow as the reaction begins. This reaction releases heat, it is said to be an exothermic reaction. The heat produced by the reaction then speeds up the rate of further reactions, and, in the video, this is also accelerated by stirring the mixture.

Table sugar is made up sucrose, molecular formula C₁₂H₂₂O₁₁ and structural formula as shown below:

The reaction between sucrose and sulfuric acid in which solid carbon, water vapour and heat are produced is known as a dehydration reaction  :
C₁₂H₂₂O₁₁(s) → 12C(s) + 11H₂O(g)     ΔH = -918.9 kJ mol^-1 Since the enthalpy change for this reaction is negative, the reaction is exothermic, the reaction gives off heat.
Sulfuric acid molecules have a great affinity for water, that is, sulfuric acid will readily and spontaneously dissolve in water. The water produced by the dehydration of sucrose will then be used to dilute the sulfuric acid that is present. This reaction is also exothermic.
H₂SO₄(l) → H₂SO₄(aq)     ΔH = - kJ mol^-1 The heat produced by this reaction also speeds up the rate of the dehydration reaction and subsequent dilution reactions.
Solid carbon is black, so the "black snake" is just carbon.
But what causes the carbon to "rise up" out of the beaker? This must be the result of evolving gases forcing their way through the mixture as the reaction proceeds. The gases that have been identified as products of this reaction  are:

• carbon monoxide (CO) 66% of the dry gas volume (ie, water has been condensed out)
• carbon dioxide (CO₂) 17% of the dry gas volume
• sulfur dioxide (SO₂) 17% of the dry gas volume

Since sulfuric acid does not oxidize carbon, it is most unlikely that the carbon monoxide and carbon dioxide gases are the result of a reaction between the black snake carbon and sulfuric acid. It is much more reasonable to assume that some of the sucrose undergoes dehydration by the sulfuric acid while some this sucrose (and/or some of the resulting intermediate organic products) is oxidized by the sulfuric acid to produce carbon monoxide gas and carbon dioxide gas. During this process, the sulfuric acid will itself be reduced, resulting in the formation of sulfur dioxide gas.

Reference:
http://www.canberratimes.com.au/act-news/students-treated-after-spill-in-burgmann-anglican-school-sciencbe-laboratory-20141128-11vzad.html

Further Reading:
http://ausetute.com.au/safety.html
http://www.ausetute.com.au/mmcalcul.html  
http://www.ausetute.com.au/moledefs.html
http://www.ausetute.com.au/massmole.html
http://www.ausetute.com.au/concsols.html 
http://www.ausetute.com.au/molarvol.html
http://www.ausetute.com.au/molreact.html

Suggested Study Questions:

1.  Describe two hazards in the YouTube Video.
2.  Describe the safety precautions you would take to minimize the risk of the hazards identified in question 1 above.  
3.  Why do you think the concentrated sulfuric acid is added to the sugar rather than adding the sugar to the container of sulfuric acid?
4.  In a typical experiment, 25 mL of 18 mol L^-1 sulfuric acid is added to 50 g of granulated sugar (sucrose). Calculate the amount in moles of :
   • sucrose used
   • sulfuric acid used
5. Calculate the mass of carbon that could be produced in the typical experiment given in question 4.
6. What assumptions have you made in order to calculate the mass of carbon in question 5?
7. Assume that all 50 g of the sucrose is now oxidized at 25^oC to produce carbon dioxide gas and liquid water. What is the maximum volume of carbon dioxide gas, in litres, that could be produced?
8.  Predict what you think might happen if a 50 g of granulated sugar were quickly added to 25 mL of concentrated sulfuric acid in a 100 mL conical flask that was being swirled continuously.
9. Sucrose is a disaccharide, made up of the monosaccharide glucose and the monosaccharide fructose. Starch and cellulose are both polysaccharides, that is, they are made of repeating glucose monomer units. Predict what would happen if you spilled concentrated sulfuric acid on:
   • a paper cup (cellulose)
   • a piece of raw potato (starch)
   • a cotton shirt (cellulose)
10. Design an experiment that could safely be performed in the laboratory to test your predictions in question 9.
11. Do you think that concentrated sulfuric acid will react with the monosaccharide glucose? Explain your answer using a chemical equation.
12.  Design an experiment that could safely be performed in the laboratory to test your prediction in question 11.

Student Safety Contract

The new Student Safety Agreement (or Student Safety Contract) is now available  as a pdf to download from

http://www.ausetute.com.au

you will find it on the downloads page.

The online version of the Student Safety Quiz is available in the Class/School Group Members area, while the printable version of the same quiz is available in the Teachers Only area of the AUS-e-TUTE website.

Safety in the Laboratory

Do you need teaching and learning resources to educate students about safety in the laboratory?
AUS-e-TUTE's Safety in the Laboratory topic now has a new tutorial, game, test and exam!

Visit http://www.ausetute.com.au and click on the "Safety in the Laboratory" links.

AUS-e-TUTE Members should log-in to the Members Only area to get the full range of resources on this topic.

Light Bulb Elements

The traditional incandescent light bulb, currently being phased out in many countries because it is considered to be energy inefficient, is really nothing but a glass ball containing a thin filament of tungsten, a metal with a high melting point, in an inert gas such as argon. As electricity passes through the tungsten, the metal heats up and glows bright white. The argon gas prevents the tungsten coming into contact with oxygen and burning.

The compact fluorescent lamp, also known as CFL's or energy saving lights, are commonly being used to replace incandescent light bulbs because they are more energy efficient. Any fluorescent lamp is just a gas discharge tube that uses electricity to excite mercury vapour. CFL's contain between 1mg and 5mg mercury per bulb. Now, while this may not sound like much, it has been estimated that if all of the 270 million CFLs sold in the USA on 2007 were sent to landfills, this would represent about 0.13tonnes, or 0.1%, of all US mercury emissions. Mercury is a toxic metal, and, when disposed of in landfills and waste incinerators, can contribute to air and water pollution.

Light-Emitting Diodes (LEDs) are also considered strong candidates to replace energy inefficient incandescent light bulbs. LEDs consist of a semiconductor chip doped with impurities so that current flows easily in one direction but not in the reverse direction. Light is emitted when an electron falls to a lower energy level while traveling along the semiconductor. The colour of light emitted by an LED is determined by the compound the semiconductor is made of, eg, red though to yellow light is achieved using gallium arsenide phosphide, aluminium gallium indium phosphide, or, gallium (III) phosphide. However, LEDs also contain potentially hazardous substances such as lead and arsenic which are linked to several diseases such as cancers, kidney disease, skin rashes and hypertension.
University of California Irvine's Department of Population Health & Disease Prevention scientists have discovered that low-intensity red LEDs contain up to 8 times the legal amount of lead allowed in California as well as significant levels of arsenic, and that white LEDs, while containing the least amount of lead, contain high levels of nickel.

Reference
Seong-Rin Lim, Daniel Kang, Oladele A. Ogunseitan, Julie M. Schoenung. Potential Environmental Impacts of Light-Emitting Diodes (LEDs): Metallic Resources, Toxicity, and Hazardous Waste Classification. Environmental Science & Technology, 2011; 45 (1): 320 DOI: 10.1021/es101052q

Further Reading
Elements and Compounds
Metals and Non-metals
Definitions of a Mole
Ideal Gas Law
Parts per Million Concentration
Greenhouse Effect

Study Questions

1. Locate each of the elements listed below in the Periodic Table. Provide the symbol for each element.
• tungsten
• argon
• oxygen
• mercury
• lead
• arsenic
• nickel
• gallium
• phosphorus
• aluminium
• indium


2. Draw up a table using the headings metal, non-metal, and semi-metal, and place each of the elements above in the relevant column.
3. What does a Chemist mean when they refer to an inert gas?
4. Estimate the volume of an incandescent light bulb.
   • If the light bulb contains argon gas at 0.1kPa pressure, how many moles of argon are present?
   • Convert the moles of argon gas to a mass of argon gas.
5. Assume a compact fluorescent lamp contains 5mg mercury vapour at 0.3% atmospheric pressure and 25^oC.
   • How many moles of mercury does the compact fluorescent lamp contain?
   • Calculate the volume of the compact fluorescent lamp.
   • What is the concentration of mercury vapour in the CFL in parts per million?
6. There are many different ways to produce electricity; coal-fired power stations, power from uranium fission or from hydroelectricity schemes. For each of these types, discuss the impact on greenhouse gas emissions of replacing incandescent light bulbs with CFLs or LEDs.
7. If a person were to drop and break a compact fluorescent lamp at home, describe the steps that should be taken to safely clean up, and dispose of, the mess.