11/22/2010

Announcements- Lab Test tomorrow.

Homework- Do the analysis questions from today's lab. Look over your labs to study for the test.

In class today we did the Polarity Olympics lab.

-Part one- Solubility.

In this part of the lab, we want to see if hexane, ethanol, pentanol, methanol, butanol, and acetone mix with water.

~This is what it looks like if it does not mix with water. There is a split between the different solutions.

After we do this, We see if it mixes immediately. If it does not mix we have to put a stopper on the test tube, shake it, and then see if it mixes then.

-Hexane- Does not mix immediately, Does not mix after shaking.

-Ethanol- mixes immediately, It stays mixed after shaking.

-Pentanol- Does not mix immediately, Does mix after shaking.

-Methanol- Does not mix immediately, Does mix after shaking.

-Butanol- Does not mix immediately, Does mix after shaking.

-Acetone- mixes immediately, Stays mixed after shaking.

-Part two- Volatility and Surface Tension

In this part of the lab we want to see which solution spreads faster and which solution evaporates the fastest. What we do is we put a drop of each liquid on the lab table and see which one spreads more and which one evaporates faster. 7th being spreads out the least and evaporates the slowest.

Liquid Spreading rank Evaporating rank

-water 7 7

-hexane 1 2

-ethanol 5 4

-pentanol 6 3

-methanol 4 5

-butanol 3 6

-acetone 2 1

The liquids that spread out more are non polar and the liquids that spread out the least are polar because the atrraction is has on the solution gets the solution closer together and holds it together more. Also if something is more polar, then it will evaporate the slowest because sticks more together to the table. That is why hexane evaporates faster, it is because it is non polar and there is no attraction to it that holds it down and together.

The next scriber will be Mahak =]

11/18/10

Announcements: Chem day tomorrow 11/19/10 in the lyceum

Quiz on Monday

Lab test on Tuesday

Homework: None

In the beginning of class we learned about polar and non-polar molecules. Polar molecules can not be split while non-polar can. If the molecule is bent it will always be polar. Just because it has polar bond does not mean it is a polar molecule.

The Lab: In the lab we put drops of water and hexane on a penny. The penny was able to hold more drops of water than hexane because it is a polar molecule. Polar molecules like to clump together because of the opposite charges within itself attract each other.

We also put drops of water and hexane in a watch glass and then put a thin glass tube (called a capillary tube) upright and covered the top of the tube so the liquids would go up the tube. The water went up further and stayed in the same spot when we tipped the tube back and forth. While the hexane didn't go up as far and would move around when tilted. Since the water molecule stayed in the same spot, the glass molecules are polar. This is because it attracted the water which is polar and did not attract the hexane because it it non-polar and likes attract likes.

In the last part of the lab we drew two lines on a watch glass. One of the lines was with a transparency marker and the other with a permanent marker. When we use the cotton swab with water on it the transparency line came off and the color leaked onto the swab. It also cleaned up all of the permanent line. Then we drew two more lines on a watch glass and put hexane on a different cotton swab. When we wiped the transparency line it did not come off and the line stayed on the watch glass. When we wiped the swab on the permanent line it came off. The ink in transparency marker is polar because the water(polar) was able to be wipe up while the hexane(non-polar) was not able to pick up the transparency line.

The next scriber will be Elizabeth.

11.16.10

ANNOUNCEMENTS: We took a quiz today, pick up pages 21-24 if you were not here, and I think that is it.

HOMEWORK: Page 24

Today we learned about different types of bonds that are related to electronegativity. Electronegativity as you may remember, describes an element's tendency to "hog" electrons (pull them closer to themselves than the other atom). We got a periodic table that has each element's electronegativity.

The three different bonds we learned were:

Purely covalent/non-polar: In this bond, neither atom has that much of a stronger pull than the other. The difference between the electronegativites of the two atoms will be 0.0-0.4

(*To find the electronegativity difference just subtract the smaller electronegativity from the larger one. EX: Carbon has an electroneg. of 2.5, Hydgrogen has an electroneg. of 2.1 so the difference is .4 This would be a non-polar covalent bond.)

Polar covalent: One atom has a slightly larger electroneg. causing it to have a stronger attraction to more electrons. Difference of electroneg. is 0.5-1.6

(EX: Hydrogen is 2.1, Oxygen is 3.5. The difference is 1.4 so it is polar covalent.)

In both of these, electrons are shared.

Ionic: In an ionic bond, one atom has a significantly larger attraction to the electrons than the other. In this case electrons are transferred. The range for this is 1.7 or greater.

(EX: Sodium is .9 and Flourine is 4.0 The difference is 3.1 so it is ionic)

We also learned how to identify atoms with a partial positive and a partial negative charge.

The atom with the greater electronegativity will have a partial negative charge because there are more electrons going towards it. And the partial positive atom has the smaller electronegativity because there are less electrons attracted to it.

Mr. Paek taught us the symbol that is used for this.

Disregard the second picture, he did not teach us that. The S looking thing is the symbol. If it's partial negative then a - sign will follow the symbol. And if its partial positive then it will be a + sign. In this image, hydrogen has an electronegativity of 2.1 and flourine has one of 4.0 Because flourine's electroneg. is greater, more electrons are attracted to it so it has a partial negative charge.

That's all folks!

Oh and the next scriber shall be Jillian (:

Monday, November15, 2010

11/15/2010

Announcements:

-Test will be on Wednesday after thanksgiving break.

-Web assigns are due Tuesday after thanksgiving break.

-Mr. Paek said he will not return our quizzes, but we get to retake one and drop the lowest.

-Mr. Paek also said that if there is anyone who doesn't get the lewis structure, they should go see him ASAP because it's important. The lewis structure is a key concept and you have to completely get it in order to understand upcoming lessons.

Homework:

-Finish up to page 19.

- Make sure you finish the 2 practice sheets we got on Thursday that go along with the chem think.(they might be collected tomorrow.)

In Class:

Well first Mr. Paek introduced to us the concept of VSEPR. He said that he will use this term a lot and he wants us to understand it. here is what each letter stand for:

-V= Valence

-S= Shell

-E= Electron

-P= Pair

-R= Repulsion

-This theory is used to prove that electron want to repel as far away from each other as possible.

-there are 5 types of molecular shapes: linear, bent, trigonal planar, trigonal pyramid, tetrahedral.

*Linear and bent are usually associated with 2 electrons and are are usually 2 dimensioned . (example by Mr. paek: If Mac and Kevin were to have a fight where would they go in the room to be as far away from each other as possible? the answer was in the corners of the room.)

*Trigonal planar, trigonal pyramid, and tetrahedral are associated with 3 electrons and are usually 3 dimensioned.(example by Mr. paek: if Max, Kevin, and Jimmy were to fight over kinga, where would they want to be in the room in order to be as far away from each other as possible? the answer was 2 would be in each corner and one would be in the middle)

- those were examples to help us visualize and help us understand what molecular shapes look like.

-Other key things to remember is that the lone pairs are key because they push everything down and change shape. And for shape you don't need dots unlike lewis structure.

- The picture at the right is page 16: I am going to go over the first one, so you guys get an idea on what we did today.

CS2

Needs: 24; Has:16;Shares:8; Bonds:4 .

I am sure we all know how to draw the lewis structure for this one ( see Mr. Paek if you don't), well the molecular shape is the same as the lewis structure but without the dots. and the name of the shape is linear.

The next scriber will be Andrea.

11-10-10 11-14-10

THURSDAY

Announcements: total review. don't forget you can drop your lowest quiz that we take.

Homework: none!!

Class: On Thursday we had a total review day. we reviewed all lewis structures, also went over homework pages 11,12,13. Then we took a quiz. after the quiz, we finished all the pages in our notebook.(up to 15) we worked on the pages all through class. most people had 10 minutes to spare at the end.

FRIDAY

Announcements:You can drop one quiz.

Homework: Finish chem think(if not finished in class) and finish the 2 practice pages.

Class: In class on Friday we went to the computer lab to work on chem thinks. The name of the chem think is "Molecular Shapes". This can be found under Covalent Bonding. It started of by explaining what VSEPR stands for. VSEPR stands for Valence Shell Electron Pair Repulsion. When you get atoms in a molecule, the bonds in the electrons repel each other. when more are added the atoms repel so they can get the furthest away from the other atoms.

While working on this chem think we had to answer a work sheet. A covalent bond is electrons being shared by two atoms. Electrons are found in the middle of the two atoms when in a covalent bond. When two atoms are bonded to a central atom the angle between them is a 180 degrees. when there are 3 is is 120 degrees. for four atoms bonded to a central atom it is 109.5 degrees.

While working with molecular shapes there are (as you can tell in the title) many different shapes. when there is just two to a bond the shape is linear. when it is in two dimensional with three atoms it is called trigonal planar. If their is a lone pair of electrons, it doesn't affect the atom but it does make the atom bent. the shape is called bent. when their is three atoms and it is three dimensional the shape is called a tetrahedral. again with lone electrons and three atoms the shape is called a trigonal pyramid.

after we finished the tutorial we moved on to the question set where you have to answer ten correct with getting 2 or less wrong. if you get three wrong you have to start over again.

Next scriber will be...... YASSINE!! (you know why)

11.9.2010

Announcements:

-During Unit 5, we will take 6 quizzes and be able to drop the lowest score.

-We took quiz #1 today.

-We will take quiz #2 tomorrow.

-We received pages 9-15 today.

Homework: Finish pages 9-15

Class: Today, we started off by doing a quick question and answer about what material was going to be on the quiz. After this, we then took our first quiz of unit 5. Once everyone had finished the quiz, Mr. Paek showed us what the answers were and went over them with us. The quiz was out of 8 total points with each question being worth half of a point.

We then started going over pages 9-15.

Page 9: This first page was Guidelines for Drawing Lewis Structures. What you first must do when you are drawing the Lewis Structures is to count the total number of valence electrons in the compound. If you are finding the structure of an ion, remember to add electrons for a negative charge and subtract electrons for a positive charge. Secondly, you should predict the arrangement of the atoms in the molecule, drawing a line to represent a single bond between each pair of bonded electrons. Thirdly, you should find the number of valence electrons left over after forming single bonds. The fourth step is to place electrons around the outside atoms until each is surrounded by eight electrons (the octet rule). H is the only element which does not follow the octet rule. The final step is to place any left over electrons around the central atom.

Page 10: Lewis Structures 1

-Ex: What is the Lewis Structure for CH4

Ans: What you would do would be to find out the needed electrons, how many electrons the compound has, how many electrons are shared, and how many bonds there are. In this instance there are 8 electrons needed for C. There are also 8 electrons needed for H4 because H needs 2 electrons and since there are 4 of the H electrons that makes 8. If you add 8+8 you will get 16. Therefore this compound needs 16 atoms. Next, is the amount of electrons they have. H4 has 4 electrons combined, and C has 4 electrons. That gives you 8 more electrons for 16. Therefore, they have 8 electrons shared. Then, you divided the shared electrons by 2 and you get the amount of chemical bonds. Then you need the formula. For this atom the formula would be H

/

H-C -H

/

H

Page 11: This is just a page of practice problems

Ex: H2O

Ans: There are 12 electrons needed, there are 8 electrons between H2 and O. There are 4 electrons shared. There are 2 bonds. Based upon this information, the formula would look like this ..

H-O-H

..

Page 12: Lewis Structures 2

Ex: Which elements are allowed to break the octet rule?

Ans: Elements allowed to break the octet rule if they do not have a full shell of valence electrons.

Ex #2: Does element A violate the octet rule?

/ / /

A

/ / /

Ans: Yes because each of those lines has two electrons in it and A would have more than eight electrons with those connected to it.

Page 13: More practice formula pages

Ex: What is the Lewis Structure for HCN?

Ans: There are 18 electrons needed, they have 10 electrons combined, therefore there are 8 electrons shared which means that there are 4 bonds. The formula would look like this:

H=C=N

Page 14: Lewis Structure 3

Ex: Draw the Lewis structures for carbon tetra-fluoride.

Ans: First you have to realize that that is CF4. Once you have done this, you can solve. Together they need 40 electrons. They have 20 electrons, this means that they share 20 electrons which comes out to 10 bonds. The formula would look like this:

.. ..

F F

/ /

C

/ /

F F

.. ..

Page 15: This is the final page of the journal and it is half of a page of practice problems.

Ex: Name the group of elements that X would belong to.

X .

Ans: X would belong to the Alkali metals group because it only has one valence electron and alkali metals only have one valence electron.

NEXT SCRIBER: JIMMY

11.8.10

Announcements:

-We picked up and taped in our calender for Unit 5

-As well as sheets 2-8

-This unit we will have 6 quizzes (and drop the lowest score if desired)

-Our first quiz will be tomorrow (Tuesday October 9, 2010)

Homework: Finish pages 2-8 (excluding page 3)

We started off by reviewing a little bit of covalent bonding (talking about where there is the least potential energy (when they are sharing electrons at a comfortable distance) and the most potential energy (when the atoms become too close so the protons of each nuclei repel each other)).

We took the rest of class to finish pages 2-8

Page 2: Questions about potential energy

-Ex: Does the potential energy increase/decrease as the atoms move closer?

Ans: Decrease as the atoms are sharing the electrons thus making their pull on them less.

Page 4: Naming Covalent Bonds Practice 1

-Ex: What is the name for the bond of CO?

Ans: Carbon Monoxide. Because there is only one carbon atom and it is the first atom named, the mono- is dropped leaving just carbon but because the second atom is oxygen and there is only one it uses the prefix mono and because the second atom should end in -ide, it becomes oxide creating Carbon Monoxide.

Page 5: Naming Covalent Bonds (2)

-Ex: CO. Ionic or Covalent?

Ans: Covalent (because it is between two non-metals) Carbon Monoxide

Page 6: Naming Covalent Bonds (3)

-Ex: Nitrogen Dioxide. Ionic or Covalent?

Ans: . NO2 (Because there is only one nitrogen it is simply nitrogen, and because there are two oxygens the prefix di- (indicating two) is placed in front of oxygen and the suffix -ide is placed at the end) and it is covalent (two non-metals)

Page 7: Naming Covalent Practice (3)

-Ex: PCl3

Ans: Phosphorous Trichloride (one phosphorous is simply phosphorous and because there are three Chlorines the prefix tri- (indicating three) is added as well as the suffix -ide)

Page 8: Naming Covalent Compounds (4)

-Ex: SiO2

Ans: Silicon Dioxide (again, one silicon is just silicon and because there are two oxygens a di- is placed in front and you get Silicon Dioxide)

8.1 - 8.2 Molecular Compounds/ Covalent Bonding

Covalent bonds are formed when electrons have a "tug of war" with each other attracting them to each other. The atom is held by sharing electrons forming a Covalent bond. The Octet Rule applies for all Covalent bonding. In the bond, electrons are trying to get the electron configuration of noble gases like Ionic bonding. For a hydrogen pair, they share the two electrons to form a hydrogen molecule. Combinations in the non-metalic elements tend to form covalent bonds. Single Covalent bonds are held by the sharing of a pair of electrons. Such as H (hydrogen atom) + another H = the single covalent bond of H:H. In "H:H", the ":" represents the shaired pair of electrons. A structural formula represents the bond using "-". For example, Fluorine has 7 valence electrons. If F+F, they still need to fill in the noble gas. so either they form together making a 14 valence electron bond, or split 7 valence electrons each. In a bond, the elements need to share valence electrons evenly with each other, thus making a covalent bond.

Chapter 8 Summary

In the last chapter, we learned about how ionic compounds connected with other molecules, and by doing this, there was a complete transfer or electrons. Each atom had its own electron, while in a covalent bond, there is a sharing of electrons which are held together. To make a covalent bond, electron sharing happens so that atoms get the electron configuration of noble gases. When a covalent bond forms and atoms get closer to each other, they attract. A single covalent bond is when two atoms are held together by a sharing a pair of electrons. Example H-H is equal to H:H the colon represents the shared pair of electrons since Hydrogen has only 1 electron, it forms a single covalent bond. A structural formula represents the covalent bonds by dashes - and shows the arrangement of covalently bonded atoms. Its basically the same thing as the colon, H:H or H-H. Covalent Bonds ONLY forms through Non Metals.You can draw electrons dot structures for molecules of compounds in much as the same way you draw diatomic elements. By taking the name of the element with the lowest number of electrons, and then surrounding it with the name of the element with the highest number of electrons.

Chapter 8 Summary

Section 8.1 describes what molecules and molecular compounds are. Molecules that are monatomic are consisted of only single atoms. Molecular compounds are only between non-metals. Another topic is that it tells us what a covalent bond is. It is formed by a pair of electrons by two atoms.

Section 8.2, it shows and teaches us about how covelant bonds are formed, and what type of bonds it can form. It shares that covalent bonds' electrons usually occur so that atoms attain the electron confliguration of the noble gases. An example of this would be a pair of hydrogen atoms to form a hydrogen molecule, which will attain the electron confliguration of helium, which is a noble gas and has 2 electrons. A single covelant bond joins 2 atoms which are held together by a pair of electrons. An example of how this could be written is H:H where the colon is represented by the shared electrons. Another way of writing the same formula is H-H. When there is a dash, you are writing a structural formula. It may be confusing when writing this because a similar symbol is H2. The difference is that H2 means that there are two molecules in the atom Hydrogen. H-H or H:H means that there is a covalent bond connecting two different atoms which are sharing electrons. They are drawn for molecules of compounds The opposite of this is called an unshared pair, when a pair of valece (outer) electrons that are not shared between atoms. This is also known as a lone pair or a nonbonding pair. Using dot structure can be used between 2 different atoms. Let's say we are trying to figure out dot structure for ammonia (NH3). All that would happen would have N in the middle and have the 3 H's around it. These sections have done very well explaining what it had to teach.

10.4.10

Handouts:

·         Practice Conversions – due next Monday (only if asked by Mr. Pak but should be done anyway)

·         Periodic Table

Homework:

·         Two ChemThinks – due Wednesday

    

   - Atomic Structure

   - Isotope (take notes)

In Class:

·         We were given two pages to tape into our notebooks

-Electron Configuration 1 pg.6

-Electron Configuration 1 pg.7

·         We were given practice conversion sheets which if told that you needed to do them, they are due Monday.

·         Took notes from power point on Quantum Theory (see below for notes)

·         Went to the computer lab to work on the ChemThink’s.

Power Point Notes:

        Page 1-

              Quantum Theory

o   Where are the electrons?

o   Orbitals are predictions of electron location

Page 2-

       First Quantum # -n energy levels

o   1-7

o   Describes the energy

o   The larger, then more energy and usually further from the nucleus

Picture below is of electrons placed in definite orbitals (called shells) around the nucleus.

TESTS:

·        Test - October 8^th

·         Lab Test - October 11th

Oct 29, 2010

Polyatomic Ions
In class today we learned about naming and writing formulas for ionic compounds. The chart below shows some Polyatomic Ions.

• You have to treat these as One Thing.
  Ex) write the formula for elements:

Follow steps for naming and writing formulas for ionic compounds.

1)Find the name of each element

2)Write metal first

• If the first elements are in the transition column; Sn, Pb and D-block elements; then, you use roman numerals in the name of an ionic compound.
  Ex)
  

3) Write non-metal next

• For step 3, the non-metal ends with – ide.
  Ex) carbon→carbide



• When you have a polyatomic ion you write the given names of them.
  Ex) CaCO → calcium carbonate

Upcoming event!

We have Quizzes on Monday through Wednesday! Prepare for these quizzes!.