Tuesday, September 7

Today in Chemistry, we mainly focused on measurements. We began the class by reviewing the assignments. Mr. Henderson reiterated that Labs 1-4 and packet pages 3 and 4 are due tomorrow, Wednesday September 9; and the Intro to Measurement Lab is due on Wednesday. He then proceeded to discuss the lab from yesterday, the MM4 Separating Mixtures Lab. He used a similar (example) lab about coins to demonstrate how to find the percent composition of each element in a mixture. First it is needed to find the total mass of the mixture, and then the mass of the element whose composition you wish to find. Then, you divide the mass of the element by the total mass, and you have the percent composition of that element. Mr. Henderson multiplied the number present of each coin by the mass of that type of coin, then divided the total mass of the coin mixture to find the percent of coins which make up the mixture. He then gave us time to This link describes how to find the percent composition:
http://www.chem.tamu.edu/class/majors/tutorialnotefiles/percentcomp.htm


Next, we began the Intro to Mixtures lab, which taught us about the precision of different instrument (with some divisions), and a graduate (with many divisions). Then we had to measure the length of a blue pen with multiple rulers that had various degrees of divisions. Through these two experiments, we found out that the instruments with less divisions force you to estimate more, and therefore be less precise. After that, we weighed the mass of a penny using three different mass balances, which gave slightly varying numbers. We then discussed significant digits, which are important when communicating the precision of our measurements. Mr. Henderson stated that in regards to significant figures, one figure is one that is always estimated. In other words, it can be assumed that all of the digits are exact up until the last one (and it is important to do this when measuring something yourself in order to communicate it to others).
This link is very helpful in understanding the concept of the degree of uncertainty:
http://www.tutorvista.com/content/chemistry/chemistry-iii/chemistry-concepts/uncertainty-measurement.php

^^These are the different instruments we used to measure the volume of water.

Mr. Henderson today emphasized the importance of the difference between mass and weight. He clarified that mass is the amount of matter one object has, and gravity is the force which acts on that amount of matter. He gave the example that if a person were to go to outer space, they would have a different weight (because different planets have different amounts of gravity), but his/her mass would remain the same. He also pointed out that our scales in Chemistry calculate mass, whereas typical scales calculate weight.
This is a really good link that describes the difference between mass and weight:
http://www.colorado.edu/physics/2000/periodic_table/mass.html

Overall, today was a very informative day in Chemistry; and we learned much about measurements. Don't foget about the pop quiz on Friday!

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.

Friday, September 3, 2010

Todays class period was a rather unique one, but it started off the same as usual before it got interesting. We viewed Emma's blog in which she did an excellent job. Mr. Henderson then explained to us the photo situation. The photos that we would take on his camera for the blog would be on a website called dropshots.com.

We then looked at lab MM4. Separating Mixtures Lab and wrote down the purpose. Mr. Henderson then had us turn to page 18 in our Chemistry Basics packet to learn how we could separate sand, salt, and iron. It said that each method relies on the fact that the components have different physical properties which can be used in separation method.

To show us how this all worked, Mr. Henderson showed us a very fun and original demo. He talked about how sand had many variables in itself and could be split up into rocks, little pebbles, fine sand, and super fine sand. He used different sized screens to split these variables up going from the biggest openings to the smallest. As he started to 'shake it up,' he danced to one of his favorite songs by KC and the Sunshine Band. http://www.youtube.com/watch?v=8GtGY6tuDaA&feature=fvst

After that attention-grabbing demo, our class began the lab by weighing or finding the mass of the mixture by using the zero, or tare button. The mixture consisted of salt, sand, and iron and was a heterogeneous mixture because we could visibly see the differences in the substances. We then had to figure out how to separate them. First, we used a magnet to separate the iron because iron is magnetic. Next, we poured the rest of the mixture into water because we knew that salt was soluble, and we could filter out the sand. This is exactly what we did. We poured the mixture of sand, salt, and water through filter paper and a funnel which left behind the sand.

After that, we put the filter paper with the sand on a hot plate to dry it off. We did this because when we would weigh the sand to figure out its mass, we would not want to have water be part of that mass too.

We then weighed the iron and the sand to find out the mass in grams. To find the mass of the salt we subtracted the weight of iron and sand from the weight of the total mixture. We did this because salt was the only substance remaining so it would have to have the remaining weight of the mixture. For example, if the mixture weighed 2 grams, the iron weighed 0.24 grams, and the sand weighed 0.46 grams, then the salt would have to weigh 1.30 grams because 2 - (0.24+0.46) = 1.30. Furthermore, we calculated the percent of the salt, sand, and iron in the mixture by dividing its weight by the total weight of the mixture and multiplying it by 100. After doing that math, we wrote down our conclusion.

Class time was running out, and the Web Assign homework was assigned. We all left class 'shaking our booties' as Mr. Henderson put the song back on for the last couple minutes of class.

Thursday, September 2, 2010

Today was a rather average day in Chemistry Class. Mr. Henderson began by taking attendance and then going over the blog post done by Dmitriy from the previous day. Mr. Henderson then explained our homework due Tuesday more thoroughly. The homework was a 1.1 WebAssign on the Classifications of Matter. Mr. Henderson explained how the questions worked and how for some questions you received multiple chances to get them correct.

We then moved on to pages 1 and 2 in our Unit 1 packets. Page 1 and the first half of page 2 were about the symbolic language of mixtures. For the first group we were given a drawing of a substance and asked how many types of atoms were in it and how many types of compounds were in it. Then in part 2 we were given a diagram of the substance, and the symbol for it. We were then asked to describe the substance using words like atom, compound, molecule, element, etc...

The bottom half of page 2 was about the interpretation of mixtures. We were given long symbols for a substance and were asked how maybe elements and compounds there were, as well as the total number of atoms and the total number of molecules. This part was the most difficult for the class to understand.

We finished class up with Lab MM3 or the Salt, Sand, and Iron Lab. The purpose of the lab was to distinguish between salt, sand, and iron on the basis of their physical characteristics. We began by just observing the three substances and recording their color, granular size, and texture. Next we tested each of the item's magnetic properties by moving a magnet over each and seeing how it reacted. My lab group discovered that only iron had magnetic properties and that they were very strong. Next we tested the solubility in water of each substance by adding a little bit of each to a test tube of water and mixing it around. My group found that only salt dissolved in the water and the other two just sunk to the bottom.

Class today was very fun and very educational. The lab was a great way to test properties and it was great to have more practice on the types of matter.

Wednesday, September 1, 2010

Today's chemistry class was educational, yet different from day to day events. The large, red thing I have above this text is an illustration of a water molecule. H2O - the large hydrogen atom in the center, and the two oxygen atoms on the outside. But this isn't just any ordinary chem "mumbo jumbo"; we performed an exercise in class today based on molecules such as this one.

At the beginning of class, we completed the preliminaries. We discussed Shidan's blog entry, and Mr. Henderson stated we are to be doing a computer activity that day. Entering Room 339, we started immediately.

To begin our work, we proceeded to log on to our computers. Next, we all created ChemThink accounts like Mr. Henderson has shown us in the class. After this, we proceeded through an "atom tutorial". In this tutorial, we learned about certain terms. Included were: pure substance, solution, mixture, atom, molecule, element, and compound. These will be discussed in later paragraphs.

For example, a solution would be much like the water molecule above. It is a compound that fits together nice and smoothly. All the atoms blend into a common molecule. A mixture is different. A mixture contains many different particles, but they do not fuse together in one convenient molecule. Our own drinking water is filtered through the process of distillation; as many non-water particles get taken out as possible.

In the tutorial, we also learned the definition of atoms and molecules. An atom is the basic building block of matter. Everything in existence is composed of atoms. Every element on the periodic table is composed of a single type of atom. A molecule is a series of atoms bonded together. A molecule may be a compound, different elements together, or you could even have a molecule of the same element (a pure substance).

After passing the tutorial, the class took a small quiz on the content. It was necessary to pass the quiz by answering ten questions correctly without getting three wrong in a row. The students could have taken this quiz an unlimited amount of times.

The homework besides that was to complete pages 3-4 in our packet. It was basically a review of what we had studied earlier that day. We had to illustrate atoms and molecules based on their chemical formulas. The pages tested us on whether or not we could distinguish between a solution, a mixture, or a pure substance.

To summarize, our period 3 chemistry class had a productive day today. I personally found the activity very interactive and fun. I may now say I have learned at least something about atoms and their chemical properties.

Blog written by Dmitriy Kalin

Picture taken from Wikimedia Commons