Friday September 10, 2010

Today's class started off by getting our lab notebooks back. Mr. H graded Labs 1-4, but didn't tell us our grades in our lab notebooks. He told us that he wrote comments and suggestions in most lab books.

Mr. H then had everyone take out their chemistry packets and he went over the question on the bottom of page 6, which was about listing significant numbers when adding, subracting, multiplying, and dividing. He went over significant numbers again and how many to include when adding, subtracting, multiplying, and dividing. The rules are as followed when adding/subrtracting or multiplying/dividing:

Addition/Subraction: The number of decimal places in the result is equal to the number of decimal places in the quantity with the least certainty (i.e., least number of decimal places).

Multiplication/Division: The number of significant figures in the result is the same as that of the quantity with the least number of significant figures.

Mr. H then worked with the class on the first two practice problems to clarify what the rules were saying. He then had us work on the rest of the practice problems by ourselves. After a few minutes of working Mr. H revealed the answers to the class, so everyone was able to check their answers. He answered a few questions from students and then he went to our class's chem blog.

Mr. H went over Hannah's and Neil's blog posts and then gave a few tips on how to make both blogs a bit better for next time.

Mr. H then had the class open up their chemistry packets to the last page to look over today's lab, which was MM6 Conservation of Mass Lab. As the class wrote down the purpose, he explained what we were going to do in today's lab and what to expect. He told the class that since we were going to be dealing with liquids and chemical reactions, that we should wear our safety glasses. He explained to us that we were to find the mass of a flask before the chemical reaction and after, and then compare the differences.

As everone went to their lab stations, they first began by pouring a blue liquid into a flask and then put a testing tube filled with a white substance. Groups then went and measured the flask with all its components as shown below. 

Click to view video.

Groups then returned the their stations, recorded the mass, and then put a cap over the flask, flipped over the flask, and saw the chemical reaction between the white substance and the blue liquid. The result of the chemical reaction was a white solid that formed. Groups then went on to find the mass of the flask with all its components and record their results.

When students finished, they went back to their desks and Mr. H began to pass out scan-trons for our pop quiz. The quiz was only 14 questions, and consisted of the material learned in chapters 1:1-2. The quiz lasted untill the end of class.

Wednesday, September 8, 2010

Today's class started off as usual while discussing the blog from the previous day even though we weren't able to view Hannah's blog post because she wasn't able to post it online. Mr. H gave us a general overview on what we need to successfully post a blog online. Mr. H told us that we also have to make sure to join the blog, so that we have the ability to post on it.

We then looked at lab MM5 titled the Chemical Properties Lab. Mr. H put up the page in the Unit
1 packet, which had the guidelines for the lab on the page. While the whole class begins writing the purpose of the lab, Mr. H stresses the safety precautions associated with the lab. Sodium hydroxide and hydrochloric acid can cause damage to the eyes and the skin, Ammonium hydroxide vapors can be hazardous to the lungs. Cupic chloride is toxic, but only when ingested. Magnesium and Zinc dust are flammable. We had to keep these mind, while doing the lab. Mr. H also told us the procedure of this lab where we were going to be determining the chemical properties of hydrochloric acid and copper chloride.


Before we began the lab, Mr. H reviewed with us how to precisely write down the measurements when reading a graduated cylinders. We have to make sure to measure to greatest degree of certainty. Basically that means one should record all digits that are certain and one additional estimated digit. What is important to remember is that the degree of certainty depends on the precision of the measuring device.
Mr. H then has us continue on to the next page where we learned about counting the number of significant zeros in a measurement. The number of significant zeros in a measurement reveals the degree of certainty of the measurement. Mr. H taught us the following four rules

A. All non-zeros digits are considered significant
B. For zeros:
1. Leading zeros(those which precede non-zero digits) are never significant
2. Captive zeros(those surrounded by non-zero digits) are always significant
3. Trailing zeros(those which come at the end of the number) are significant only if there is a decimal point listed in the number.
After explaining the rules with a brief explanation, Mr. H lead us in an significant number excercise where we had to determine the number of significant numbers.
Once we completed working on the worksheet we began the lab. The lab required us to have a set up where we placed hydrochloric acid and copper chloride in a tray with 4 rows of 6 containers. We were to determine the chemical properties of hydrochloric acid and copper chloride when mixed with other substances. The pH level of the hydrochloric acid was tested. Also, another substance mixed with the hydrochloric acid was an Aluminum shot, Zn mossy, and Magnesium. Same goes for the copper chloride. We recorded the reactions to each test that was performed in our lab notebook.


This video was the set-up to the lab where hydrochloric acid and copper chloride where each put into separate rows.







In this video Mr. H placed Ammonium hydroxide in the hydrochloric acid and copper chloride.

In the closing moments before class, Mr. H assigned the homework. We were to begin on the web assign, prepare for our 'pop quiz' and finish the measurements lab.