1/24/11

Announcements- There will be 6-7 quizzes this unit. If you get 5-6 perfect scores then you will get some extra points added to your quiz category. Also, in order to take the final test, you must have a perfect score on at least 1 quiz you take. If you fail to do so, Mr. Paek will not let you take it with the class until you do.

Today In Class- Today in class, after rejoining us to the class again and welcoming any new students, we were introduced to the mol. A mol is 6.02 x 10 to the 23rd power. We were also told that a pair=2 and a dozen=12. Then we did a lab that worked on using Unit Analysis for finding the number of atoms in a certain number of grams, the number of grams in a certain number of mols, and the number of mols in a certain number of grams. An example of a question for finding the number of grams would be: How many grams would 3.01 x 1023 atoms of Al (26.98 grams) be? 3.o1 x 1023 atoms x 26.98 g
6.02 x 1023 atoms
Then you would cancel out atoms and do the math.

Homework- Finish the lab. We're going over it in class if you have any questions.

THE NEXT SCRIBER WILL BE....... paul mcmahon

12/8/10

Announcements

• Quiz tomorrow on balancing
• Possibly a quiz on Friday so be ready
• Test on the last Thursday before break

What We Did In Class

Today in class we first went over the homework we had the night before, which was pages 8 and 9. If you didn't do it, you probably should. It's good practice. We asked questions about it in class and got many questions cleared up. We then basically reviewed of what we learned yesterday, and elaborated more on each subject. We went over single replacement (p. 13), double replacement (p. 14), Decompostion (p. 15), synthesis (p. 16 &17), and Combustion (p. 17).

Before I describe anything we did today for you, I want you to know 1 trick that is needed every time this happens. Whenever the elements Hydrogen, Oxygen, Nitrogen, Chlorine, Bromine, Iodine, and Florine appears alone in an equation, always put a 2 after it. This is how it is used in nature so it is needed in the writing part too. A way to remember this is HONClBrIF and sound it out.

When going over single replacement, you need to find out which elements are positive or negative ions. If there are 2 positives and 1 negative, then you switch the negative from the one positive to the other. And then of course, balance it out. For example, if you had the formula: ZnS+ O2--->_____. Zn is positive, S is negative, and O is negative. So therefore, on the other side, it would be ZnO2 +S. But then you would have to balance it. So on the right side it would be 2ZnO because on the left it says there are 2 atoms of O (O2). And since I had to change that on the right, on the left it would be 2ZnS, which means on the right I would change it to 2S.

For double replacement, you do the exact same thing as single, except there will be 2 positive ions and 2 negative ions. So you would just swap them and balance them out again.

When doing decomposition, one compound splits up into 2 different ones. For example AB---> A + B. When using elements, an example would be HgO---> Hg + O2. or MgCl2---> Mg + Cl2. Make sure to balance them at the end.

Synthesis is the exact opposite of decomposition. Just put them back together. A + B---> AB. An example using elements would be K + Cl2---> KCl. Mg + O2---> MgO. Make sure that they're balanced at the end.

Finally, we have combustion. This is when there is a carbon atom, hydrogen atom, and oxygen atom all in the same equation. The answer for every single one would be CO2 + H2O no matter what. But the hard part about this is balancing them out. The easiest and smartest way to do this is by using the CHO rules. This is the order of balancing out the equation. Carbon, Hydrogen, and Oxygen. CHO. You won't forget.

Homework:

Page 10 in your journal

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THE NEXT SCRIBER WILL BE........... VIT

Wednesday September 8, 2010

Today in class, we finished our labs working on density that we started yesterday. Next, Mr. Paek showed us a demo by using gas, a special type of soap, and a long stick with fire on the end. He had a volunteer shake and pinch on the tube from where the gas was coming from in order to make the soap from inside the beaker rise into the air as a bubble. Once it did, he poked the stick on fire at the rising bubble and a big burst of flames came from the air.

After the demo, Mr. Paek reviewed with us about finding the density of certain objects, and the ntaught us about using Unit Analysis. This means that the units in the numerator and the denominator cancel out so then another unit used will replace its spot. For example, if we are trying to figure out the number of seconds in 1 day, then we would write out the equation like this: 1 day/1 x 24 hrs/1 day x 60 min/ 1 hr x 60 sec/ 1 min = 24 x 60 x 60= 86,400 sec in 1 day. This works because the units day, hrs, and min cancel out which leave sec as the remaining unit for the final answer.

Since we didn't do so well on the last section of the quiz we took last week, we have a quiz on friday covering the same material. So our only homework for tonight is to study measuring the volume of water in graduated cylinders and note cards, and make sure you make 1 guess.