Moles and Molar Mass

Today in chemistry, we picked up additional worksheets that went along with Unit 8. We then worked on pages 7 and 8 to refresh our minds on ionic and covalent formulas. Remember that an ionic compound consists of a metal and a non-metal. Covalent compounds consists of only non-metals. Writing the name of the formula depends on what compound it is. On page 8 of the review, we started to determine the molecular mass of compounds. When given a compound, you must write out the formula first. Then, count how many atoms are in the first element and multiply that number by the element's atomic mass. The atomic mass can be found on the periodic table. Do the same thing with the second element in the formula. Then, add these two products together and the sum you get is the molar mass. An example would be like this:

Compound given: carbon dioxide
Formula: CO2
There is one C so you multiply 1 by the atomic mass. Carbon's atomic mass is 12.01 grams. 1 x 12.01 g. Looking at oxygen, it has two atoms. The atomic mass of Oxygen is 16.00 grams. 2 x 16.00 g. Then you add these two products. The answer is 44.01. The equation should look like this: (1 x 12.01 g) + (2 x 16.00 g) = 44.01 grams.


The next thing we did was how to calculate the number of moles. You had to apply your knowledge of molar mass to figure out how to do this. It is like unit conversion. An example would be like this: 50 g of carbon dioxide.
You should write down the number that is given to you so you should write out 50 g of CO2. You need to multiply this by something. Since we want to figure out the number of moles in a compound, we would write 1 mole of CO2 at the top of the dividing line. At the bottom would be the molar mass of CO2 and the unit should be g of CO2 since we want to cancel this out. You then calculate all this and the answer should come out to be 1.14 moles of CO2. The equation should look like this:
50 g of CO2 x 1 mole of CO2/44.01 g of CO2 = 1.14 moles of CO2.

After completing pages 7 and 8, we started on page 1. It pretty much had the same concept on what we did on page 8. Near the end of class, Mrs. Mandarino stamped the labs.
Homework is to complete worksheets pg 1 and 2!

January 7, 2011

In Mrs. M class, Friday we did the usual getting the homework stamped and looked over it. Following it we got off track talking about other things. In doing so we made it impossible to go over all of the neccessary information on the test. But we did go over half lives a bit more along with chain reactions and nucleor reactors. If you forgot, half-lives are the length of time it takes for a substance to decay over a period of time. Every set of years half of the substance dissapears until stable or gone. Chain reactions occur during Fission not fusion. Fission is the splitting of atoms and fusion is the combining of them. Fission occurs when a neutron hits a bigger nucleus causing large amounts of energy to be released in different elements and more nuetrons. More can be found on page 15 of the worksheets. Nuclear Reactors are divided into three parts. A.) Control rods absorb neutrons to slow down chain reactions B)Fuel Rods contain 3 percent of U-235 C.) Moderator slows down neutrons so they can be absorbed by the control rods. Again since we talked during class we ran out of time and did not cover Ionizing Radiation or Radon and we do not have to learn it for the test. Remember the test is MONDAY!
Happy Studies.
M.J.

January 4, 2011

Today in chemistry, Mrs. M asked for us to bring our journals to get them stamped for the homework of the previous night which was page 3. After stamping we went over page 3 and checked all of our answers. Then we moved onto page 6 and learned about isotopes. Isotopes are atoms that have the same number of protons but have a different number of neutrons. Then we started pages 5 and 7 for practice to get familiar with how to identify: the isotope symbol, the name of the isotope, the atomic number, the mass number, number of electrons (in a neutral atom), the number of protons, and the number of neutrons.

• To find the isotope symbol you have to put the mass number on top of number of protons the element has, then put the element's symbol after that.

After finishing with page 7 we moved onto page 10 and learned about "half-lives." A half-life is the period of time it takes for a substance undergoing decay to decrease by half. We then practiced using half-lives to figure out a problem. Then class ended and Mrs. M assigned us page 9 and page 10 #3 for homework.

P.S. HAPPY NEW YEAR ;)

- Taso K.

Single and Double Replacement Labs

Alright, so today in class we went over the double and single replacement labs that we did with Mr. Tucker Monday. If you missed it you should have the papers in your journal but if not, there are copies on the back counter of the classroom. Tonight our homework is to review the quiz that we took on Friday, and correct any mistakes that we might have made. Above I've posted pictures from the board and those are the answers from the chemical reactions lab that we went over in class today.For a review, single reactions replace a single uncombined element replaces another in a compound. Two reactants yield two products.
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In a double replacement reaction, parts of two compounds switch places to form two new compounds.
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Also, don't forget to balance!

By Corey L.

scribe post December 9

Today in Chemistry Mrs. M told us to not talk and be obnoxious when she is talking. Then she told us she got the presents for the little kids, after that we went over page 18 in our journal which was our homework, and the class seemed to understand it very well. After page 18 we went onto page 19, and learned about predicting products, using the reactions, synthesis, decomposition, single replacement, double replacement, and combustion. To predict the product you first have to find what type of reaction it is, then you have to create the product by the different reaction rules, and finally when you have your product you simply balance the equation. We did numerous problems to practice our new topic. After that Mrs. M assigned page 20 for homework, and she gave us time to start it. All in all it was a blast!

By Simone K

Scride Post Nov 22 Per. 5

Monday November 22, 2010

We started chemistry class today by picking up Polarity Olympics: The Games sheets and getting Polarity of Molecules 2 (pg 26) stamped. Before starting the lab we learned that polar molecules are molecules that have both a positive and negative side like water. Also, intermolecular forces are when the attraction is weaker than the bonds that hold it together, but is strong enough to affect the properties of water. We then started the Polarity Olympics lab which had two parts, The Trials and The Games.

The Trials:

Trial 1- The Penny Pile-on: In this trial each liquid will try to create as large a pile on a penny as possible.

Trial 2- The Capillary Tube Climb: In this trial each liquid will try to climb as high as possible in a vertical glass tube.

Trial 3- The Marker Clean Up: In this trial each liquid will try to clean two types of marker from glass.

The Games:

Part 1- Solubility: In this part we each liquid was added to water to see if they would mix.

Part 2- Volatility and Surface Tension: In this part each liquid was ranked in its ability to spread on a table and evaporate.

Homework

Finish Polarity Olympics Lab

Webassigns

Study for Lab Test

Thursday November 18

Yesterday we started the class by picking up pages 21-25 plus another sheet. After picking up the pages, we all sat down for class. Some of the people did not finish building their molecules from two days ago so we then took the time to do that. Mrs. M went around stamping like crazy. After we finished the lab, we did page 20. When we completed 20 we started polar and nonpolar covalent bonding. One of the sheets we got was a periodic tables with a bunch of numbers with the different elements. We got half way through page 21. The rest of it was for homework

Today we started class by picking up 4 pages. After we all settled down we started on the different types of bonds. There are three kinds of bonds; Polar covalent, non-polar covalent and ionic. A polar bond is when one electron has a stronger electronegativity than the other in the bond and holds the electron closer to it's nucleus. Non-polar covalent bonding is when the electron being shared is evenly distributed between the two atoms. An ionic bond is when the pull from one atom is so strong that it rips the electron from an other atom. To find out what kind of bond the molecule has you take the electronegativity of the two atoms and subtract the bigger one from the smaller one. If the difference is less than or equal to 0.4 the bond is non-polar covalent. If the difference is 1.7 or higher the bond is ionic. Anything inbetween those is polar covalent. After learning this we went through and did pages 22-25.

Homework: Page 26 and webassigns & chemthink if you have not finished them