Building Height and Earthquakes

• High-frequency, low amplitude waves affect short buildings
  
• Low-frequency, high-amplitude seismic waves affect tall buildings
  
• Middle height buildings are affected by 2-3 second-long seismic waves
• (Mexican earthquake damage 1985)

Energy from Hydrogen

Hydrogen releases a lot of energy when it combusts, so much energy that it is hoped we will be able to use it to power our future.

Where does all that energy come from?

Read the June 2021 edition of AUS-e-NEWS to find out more.

Subscribe for free at https://www.ausetute.com.au/ausenews.html

Chemical Equations for Equilibrium Reactions

 

When do you use single arrow → in a chemical equation and when do you use a double-headed arrow ⇌ in a chemical equation?

Go to https://www.ausetute.com.au/equilibriumeqtn.html to find out!

 

AUS-e-TUTE Members should log-in to use the new Writing Chemical Equations for Equilibrium Reactions tutorial, game, test and exam with worked solutions.

Coming to terms with chemical equilibrium

In order to understand chemical reactions, you are going to have to come to terms with an important concept, that is, chemical equilibrium.

In AUS-e-TUTE's new set of resources (tutorial, game, test and exam questions with worked solutions) we look at how the type of system (open or closed) and the type of reaction (reversible or irreversible) determines whether a system can achieve a state of balance otherwise known as chemical equilibrium.

AUS-e-TUTE members should log-in to use these new resources.

If you are not an AUS-e-TUTE members you can view the tutorial for free at 

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

Reversible and Irreversible Changes

 Physical changes are, in general, reversible, but only some chemical changes are reversible while others are irreversible.

AUS-e-TUTE has just added new resources to help you classify changes as reversible or irreversible.

AUS-e-TUTE members should log-in to use the new resources.

If you are not an AUS-e-TUTE Member you can access a "free-to-view" tutorial at https://www.ausetute.com.au/reversible.html

Chemistry of Tooth Decay and Prevention

Tooth decay is a major health concern.

For more than 50 years we have been adding fluoride to our water supplies and toothpaste to help prevent tooth decay.

It is estimated that this fluoridation of drinking water alone has resulted in a 25% decrease of tooth decay in children and adults.

What causes tooth decay and how does fluoride prevent tooth decay and cavities?

 Learn about the chemistry of tooth decay and how to prevent it in the March 2021 issue of AUS-e-NEWS. Subscribe to AUS-e-NEWS for free at https://www.ausetute.com.au/ausenews.html

pH After Mixing Weak Acids

 Acetic acid is a weak acid (K_a = 1.8×10^-5).  The pH of 100 mL of 0.10 mol L^-1 acetic acid is 2.9.

Hydrocyanic acid is a weak acid (K_a=6.3×10^-10). The pH of 100 mL of 0.10 mol L^-1 hydrocyanic acid is 5.1.

But what is the pH of the resultant solution if you mixed these two weak acids together?

AUS-e-TUTE has just added new resources to help you understand how to calculate the pH of solutions after mixing weak acids together. AUS-e-TUTE Members should log-in to access the new tutorial, game and test with worked solutions.

If you are not yet an AUS-e-TUTE member, you can access the "free-to-view" tutorial at https://www.ausetute.com.au/phmixwa.html