Today I explained that the foundation for learning chemistry is understanding the lexicon – and that means knowing the names and formulas of common chemical compounds. Knowing that zinc forms a 2+ ion and that lead forms a 2+ and a 4+ ion is essential to writing products for chemical reactions. Knowing a sulfate from a phosphate gives you fluency to easily write formulas like lead(II) sulfate and copper (I) phosphate. Memorization takes time – but once it is accomplished you will be free to think about other aspects of chemistry.
We will be retaking the stoichiometry quiz after class on Monday. The stoichiometry map is another essential tool for successful problem solving. Whatever information you are given to begin a problem you must be able to plot a route to the desired information about an unknown. This process involves many small steps that are taught independently such as how to convert some volume of a pure liquid to mass, or how to differentiate a pure liquid from a solution (where molarity is used). To help develop skills in solving stoichiometry problems you must practice, practice, practice…
If you do a search for “stoichiometry problems” on the Internet you will find there are many, many worksheets available – such as this one.
We started talking about gases and gas laws. The combined gas law P1V1/T1=P2V2/T2 and the ideal gas law PV=nRT are used to solve basic gas law problems. We reviewed these equations and learned how to calculate the density of any gas. We talked about sulfur hexafluoride, a potent green house gas.
Jay Leno is playing with sulfur hexafluoride in this video – notice how long the effect lasts. It takes time to get sulfur hexafluoride out of the lungs once it enters. Even though sulfur hexafluoride is non-toxic I don’t recommend this experiment.
Sulfur hexafluoride became a problem for Nike when its potent greenhouse properties were realized.
Sulfur hexafluoride is just one gas with interesting stories. You should learn the properties of these common gases: carbon dioxide, carbon monoxide, sulfur dioxide, nitrous oxide, nitrogen dioxide, hydrogen, helium, nitrogen. Fill out the Gases: Descriptive worksheet before Tuesday as we will discuss this in class. You can easily find information about all of these gases on the Internet. There are usually some interesting videos showing gas behavior and other demos.
On the day of the exam – Wednesday – you should turn in your homework notebook and it should be completed through assignment 11.
And please come prepared for laboratory on Monday – it is a great lab but you must know what you are doing or it could be dangerous. Read the lab ahead of time – it is in the laboratory textbook but you can buy it as a single lab from Centage Brain. Check the syllabus to see which experiments we are going to do this summer.