Today we took a look at a worksheet about writing chemical equations from words.

The answers are available but please do as much as you can before looking at them.

Here’s an interesting video called Dangerous Science about chemistry sets in the present and past.

Over the past three classes many demos have been performed. Most of these are on youtube. Here are some links:

Purple Iodine Vapor

Fire Ice

The following link is to a video that was done for an AP chemistry class two years ago or so the young videographer says. I do NOT recommend trying this because it is becoming increasingly illegal to explode anything in public places and, well, you would never do this indoors except under controlled laboratory conditions. Having said this – this video is being watched by young people – note the misspelled words (thier) and the young hands in the video – and it is important to understand this kind of chemistry that is easily available to the public – as failure to understand it has resulted in injuries. As we learned in class, Drano contains caustic lye and solutions of Drano can easily damage any exposed skin they contact.

Drano

Pay particular attention to the use of aluminum, a very active metal but only when the outer coating of aluminum oxide is removed.

We’ve been studying gases, especially gas stoichiometry. The exam is tomorrow and covers material in Chapters 1-5. I’ve noticed that folks are getting much better with the polyatomic ions. I will be holding a problem solving session tonight in Room 3162 at 7:40 pm. The class I am teaching tonight finishes at 7:30 pm.

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.

Online flash cards may help.

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.

Today the class met in the laboratory room (3175), reviewed some problems, took a quiz, and carried out the experiment: Single and Double Displacement Reactions.

Please complete the exercise “How to Describe” and submit, by email or on paper, descriptive paragraphs of two household items. This exercise should be completed by next Wednesday.

Check List:

• Have you turned in your Interview yet?
• Have you completed homework assignments 1 to 6?
• Have you kept up with the Table of Contents in your Laboratory Notebook?
• Have your read the first two chapters of your text book?

And one more “heads up” – the laboratory for Monday is from the laboratory textbook. A single copy costs $2.99 from Centage.

Tonight at 7:30 in room 3162 I will provide an opportunity for folks to make up the first laboratory: Mystery White Powder.

Today we continued to study chemical reactions – and looked at two classification schemes. The classification scheme used for Basic Chemistry sorts reactions into Synthesis, Decomposition, Single Replacement, Metathesis (Double Replacement) and Combustion. Our textbook takes a different approach and recognizes Acid-Base reactions, Precipitation reactions and Redox reactions. We will study redox reactions in more detail later in the course.

Helpful facts:

1. Not all reactions are redox reactions – atoms (at least two) have to undergo changes in oxidation state for a reaction to be classified this way. Having said this – all single replacement reactions are redox reactions. Metals are oxidized to ions, and in the case of chlorine reacting with hydrogen bromide – the chlorine is reduced to chlorine ion (1-).
2. Metathesis (Double displacement) reactions are NOT redox reactions. Sometimes they are precipitation reactions – if a precipitate is formed. Sometimes they are acid/base reactions and water if formed.
3. Most decomposition reactions and synthesis reactions will be redox reactions.

We learned about total molecular reactions, total ionic reactions and net ionic reactions. These terms related to the analysis of a precipitation reaction. To correctly predict precipitates you must know the solubility rules (Table 4.1).

A variety of demonstration reactions were carried out today.

1. 95% denatured ethyl alcohol is combusted in a Blaster Ball Canon
2. 3M H₂SO₄ is added dropwise to pieces of mossy zinc
3. Barium nitrate is combined with sulfuric acid to produce barium sulfate, an insoluble white precipitate used to coat tissues for diagnostic purposes.
4. Milk of Magnesia is diluted with water, universal indicator is added to the mixture, 6M HCl is added in small portions and the solid is dissolved as it neutralizes the acid.
5. Yellow chromate and orange dichromate can be interconverted by adjusting the pH using HCl and NaOH.

Reminder:Quiz tomorrow covers reactions and stoichiometry. There are practice quizzes posted.

>Reminder: Lab tomorrow – please don’t wear sandals. Come prepared.

Did I forget any?

Chemistry 201 students took their first quiz, covered material in Chapter Five: the mole, grams to moles and moles to grams conversions, percent by mass, empirical formula, balancing equations, and carried out a laboratory on qualitative analysis. It was a very busy day.

Some folks still didn’t have laboratory notebooks. Monday was the last time that any stamps will be given outside the notebook. Notebooks are required everyday – not just for laboratories but also for demonstrations.

Some folks came to laboratory with no evidence of any preparation – i.e. the notebook was blank. This leads to poor laboratory work. Please come prepared. Read laboratory instructions ahead of time – write title, date and materials into the lab notebook and write a brief outline of the procedure.

One white precipitate made in laboratory was barium sulfate. Read about its use in the medical field.

The grading policy has been updated to include more details about grading for the laboratory portion of the course.

The first worksheets have been posted for the one book extra credit project for this summer. Extra credit is used to resolve borderline grades like 89% – and is worth about 1% of the final grade.

City Colleges of Chicago produces a summer newsletter that explains how to access your email and retrieve your username.

Today we focused on a review of Basic Chemistry – we covered the material in Chapter One and Chapter Two. Topics included states of matter (3 common on Earth and one more universally common), physical change vs. chemical change, units conversions: milli, micro, nano, kilo, quantities: mass, volume and length, density (mass/volume), Rutherford’s gold foil experiment, classification of matter: pure substances vs. mixtures, arrangement of the periodic table: alkali metals, alkaline earth metals, halogens, noble gases, metals vs. non-metals, and nomenclature.

Take a look at problems 1.6, 1.78, 2.3, 2.21, 2.153 from the text book.

We completed an activity to improve our skills giving instructions to each other.

If you haven’t done so already, please send me the Interview document.

Have a nice weekend!

Students took the placement assessment – a 50 question math and chemistry test used to determine readiness for this course. Students who score less than 20/50 on this test are strongly recommended to take Basic Chemistry 121. In cases where the student just finished Basic Chemistry – a low score indicates lack of retention of important concepts. The student should consider spending the summer reviewing Basic Chemistry and taking Chemistry 201 in the Fall where the pace of the course is not so fast.

We went over all the first day documents; syllabus, grading policy, course objectives (student learning outcomes) and spent some time looking over the website.

To do tonight: Continue to explore the website and follow the various links to learn what is available to you.

We briefly discussed atomic structure. Remember that Rutherford’s famous gold foil experiment showed that an atom is mostly empty space.

We went over some expectations for the laboratory notebook. Sample notebooks were passed around. This checklist is a good summary what should be included in a laboratory notebook. We performed the laboratory “Mystery White Powder” where students use a variety of tests to match an unknow substance to one of five know white powders: salt, sugar, baking powder, baking soda and potato starch.

The textbook is highly recommended for this course. We will be covering the first two chapters tomorrow so you might want to read them tonight. If you don’t have the textbook you may want to look over Mark Bishop’s website.

Vocabulary words: Qualitative Analysis, Empirical