polytetrafluoroethene

Polytetrafluoroethene is a very useful polymer. You can can find it encasing electrical wires, being sprayed out of a can of lubricant, and as the non-stick covering on your baking tray. So what is this remarkable polymer? How is it made? What are its properties and uses?
Find out the answers to these and other questions at AUS-e-TUTE.
AUS-e-TUTE members should log-in to view the polytetrafluoroethene tutorial, play the game and take the test and exam.
If you are not a member, you can access a "free-to-view" tutorial at https://www.ausetute.com.au/ptfe.html

Science Week 2019

Did you know it's Science Week in Australia (10^th to 18^th August 2019)
This year's theme is "Destination Moon: more missions, more science"
You can find events near you at https://www.scienceweek.net.au/
There is a downloadable pdf of classroom ideas available (https://www.scienceweek.net.au/wp-content/uploads/2019/02/2019ASTA-DestinationMoon_ResourceBook.pdf)

How to Maximise Marks in Your Chemistry Exam

Are you ready for your chemistry exam?
The Sydney Morning Herald provided 8 dot points to help you answer Chemistry exam questions, which we have expanded out below:

• Write correctly balanced equations.(Include state, or phase, of matter)
• Structure your answers to ensure they are logical. Written calculations should be neatly organised and sequential.
  • If you dilute an acid with water at 25°C, the pH of the solution will not rise above 7
  • If you dilute a base with water at 25°C, the pH of the solution will not fall below 7
• Clearly label your graphs (plots, scale, axis, line of best fit).
• Use relevant scientific terminology.
  • Check your spelling! Ethane is NOT the same as ethene! Molarity is NOT the same as morality! Calorimetry is NOT the same as colorimetry!
  • If the question is about physical properties, think about intermolecular forces.
  • If the question is about chemical properties, think about intramolecular forces, and think about types of chemical reactions for inorganic chemicals and for organic chemicals (combustion, addition, substitution, elimination, condensation, polymerisation)
• Explain the underlying chemistry and provide relevant chemical equations.
  • Is it a gas question? Ideal Gas Law? Molar Volume? 
  • Precipitation question? Solubility Rules? Solubility Product? Gravimetric Analysis? Conductometric Analysis?  Argentimetric Analysis?
  • Equilibrium question? Equilibrium concepts? Le Chatelier's Principle? Equilibrium law?
  • Acid/base question? Definitions? Properties? Acid strength? Acid-dissociation constant? Neutralisation reaction? Titration techniques? Titration calculations?
  • Chemical kinetics question? Reaction rate? Maxwell-Boltzmann distribution?
  • Determination of organic structure? C-13 NMR, Mass Spectroscopy? IR Sopectroscopy?
• Use subscripts and superscripts where appropriate.
  • Formula of ions, superscript to right of symbol (number first followed by sign)
  • Formula of isotopes, mass number superscript to left of symbol, atomic number subscript to left of symbol 
  • Molecular formula or empirical formula, number of atoms of each element shown as a subscript to the right of the element's symbol
  • "States" or "phases" of matter are sometimes written as a subscript to the right of a molecular formula, eg, CO_2(g), but are usually written in line with with formula, eg, CO₂(g)
• Use stimulus materials to answer the question.
• Use clear labels when continuing responses in a different booklet.

ALWAYS check that you have answered the question that was asked, and not provided an answer to a question that you wish had been on the paper!

Gold Nuggets in 2019

Between 1850 and 1900, the city of Bendigo in Victoria, Australia, was the centre of a Gold Rush. Central Deborah Gold Mine, the last commercial gold mine to operate in Bendigo, re-opened as a tourist attraction in 1986.
Gold can still be found in the Bendigo area.
On Mothers' Day 2019, a family out walking Lucky their dog on the outskirts of Bendigo walked onto a gold nugget. They took it along to the local IGA supermarket to weigh it. The gold nugget weighed 624 grams (about 20 ounces).
Today, the price of gold in Australia is listed as $65.76 per gram. So, if pure, the gold in this nugget would be worth 624 × $65.76 ≈ $41,000.
How big would this gold nugget be?
We know the mass of the nugget is 624 grams.
We can look up the density of gold in tables, ρ = 19.3 g cm^-3
Since density = mass (g) ÷ volume (cm³)
19.3 = 624 ÷ volume (cm³)
volume (cm³) = 624 g ÷ 19.3 g cm^-3 = 32.3 cm³
Which could be represented by a cube approximately 3.2 cm × 3.2 cm × 3.2 cm
Not very big at all is it!

Ballarat, another Victorian Gold Rush town and site of the historic "Eureka Stockade", was also the place where another spectacular gold nugget was found in June 2019 (and reported nationally in July 2019). This gold nugget weighed about 2 kilograms, or 2,000 grams.
At today's prices, it would have a value of about 2,000 × $65.76 ≈ $130,000
And how big would this nugget be?
density = mass (g) ÷ volume (cm³) volume (cm³)
density = mass (g) ÷ density (g cm^-3) = 2,000 g ÷ 19.3 g cm^-3 = 103.6 cm³
The dimensions of a cube with this volume would be about 4.7 cm × 4.7 cm × 4.7 cm
Which would fit nicely into the palm of your hand as shown in the photograph below

Further Reading:
Density Calculations

Suggested Study Questions:

1.  The density of gold is 19.3 g cm^-3. Calculate the mass of
   • 1 cm³ of gold 
   • 10 cm³ of gold 
   • 1 m³ of gold
2.  The density of gold is 19.3 g cm^-3. Calculate the volume of
   • 1 g of gold
   • 10 g of gold
   • 1 kg of gold 
3.  The density of gold is 19.3 g cm^-3. Calculate the dimensions of a cube of gold which has a mass of
   • 5 g
   • 500 g
   • 5 kg
4. The density of gold is 19.3 g cm^-3. Calculate the diameter of a sphere of gold which has a mass of
   • 2 g
   • 200 g
   • 2 kg
5. A credit card has the approximate dimensions 65 mm × 55 mm × 1 mm. Calculate:
   • volume of the credit card in cm³
   • mass of a gold credit card
   • value of a gold credit card if the cost of gold is $65 per gram
   • Why aren't "gold" credit cards really made out of gold?
6. Gold is one of the few metals that is found in nature as the "native" element (that is, it is found as the element and not in compounds). Explain why gold can be found in nuggets.
7. Name some other metals that can also be found in their native state (that is, found as the element and not as compounds). Explain why these metals can be found in their native state. 
8. Name a metal that is not found on Earth in its native state, and explain why it is not found in nature as the uncombined element.

Word Equations for Chemical Reactions

A word equation is Chemistry short-hand for describing how new substances can be made using an initial substance (or substances).
The initial substances are called reactants.
The new substances formed are called products.
The most general form of a word equation is:

reactants  →   products

AUS-e-TUTE has just added a new tutorial, game and test to help our members understand and use word equations. Members should log-in to the Test Centre to use these resources.

A "free-to-view" tutorial on word equations is currently available for non-members to access at

https://www.ausetute.com.au/wordeqtn.html

Join AUS-e-TUTE today to start solving chemistry problems, and getting feedback, to help you understand and apply chemistry concepts.

Glycaemic Index

Low GI food or high GI food?
What is GI?
How is it measured?
What does it mean?
These are many other questions are addressed in AUS-e-TUTE's new glycaemic index (GI) resources.
AUS-e-TUTE Members should log-in to access the new tutorial, game, test and exam.
If you are not an AUS-e-TUTE Member you can access a "free-to-view" tutorial for evaluation purposes at https://www.ausetute.com.au/glycaemic.html

Hydrolysis of Proteins

Lots of foods contain protein. When you eat them the proteins undergo hydrolysis reactions to break them down into their constituent amino acids.
AUS-e-TUTE has just added a new tutorial, game, test and exam to help you understand this.
AUS-e-TUTE Members should log-in to use these new resources (listed under Biochemical Reactions).
Non-members can currently access a "free-to-view" tutorial at
https://www.ausetute.com.au/hydrolysisprot.html