Thursday, March 10

(MY COMPUTER IS ACTING WEIRD AND IS DELETING HALF THE STUFF I WRITE, SO IT WILL SEEM STRANGE READING THIS). Today we began the class by reviewing and doing packet pages 16 and 17. We then proceeded on completing the lab. Here is the information for station 5 and 6.

Station 5: Surface Tension:

After completing station 5 my group and I found that if you placed a paper clip on the surface of water, oil, and acetone, the paper clip may sink or float. This depends on the intermolecular forces holding bonds together.

After testing each substance we concluded that a paper clip placed on water will float; a paper clip placed on oil will sink quickly; and a paper clip placed on acetone will sink very slowly.

This is due to the type of bonds holding molecules together. Liquids with the strongest bonds between molecules will hold together very strongly, creating a strong surface tension. Therefore because water was the only liquid to hold the paper clip above the surface, it is safe to say it has the strongest surface tension. Because it has the strongest surface tension, it therefore has the strongest intermolecular forces. Next is acetone. When a pa0per clip was placed on acetone it sunk much slower than when it was placed on oil. Because of this characteristic, acetone has a greater surface tension then oil. This also means acetone has a greater intermolecular force because the strength of intermolecular forces are directly related to surface tension. However, we know that acetone does not have a stronger surface tension than water because acetone was not able to hold the paper clip above the surface.

Surface Tension:

oil

Intermolecular Force Strength:

oil

After completing this assignment, it is clear that the greater the intermolecular force, the greater the surface tension. This is because the stronger the molecules are being pulled together, the less likely an object will pass through them.

Station 6: Beading:

Observing substances bead together is also very closely linked to intermolecular forces. This is due to the fact that if there is a strong intermolecular force between 2 molecules, they will pull towards each other with greater force. The greater the beading the stronger the intermolecular forces.

After completing this assignment, we observed that if water was placed on wax paper it would bead together. Hexane placed on wax paper would not bead together, and oil placed on wax paper would bead only a little. Likewise, if you placed the same substances on the same lab bench, you would get the similar results. Water would have the most beading, followed by oil, and last you would have hexane. The only difference is there would be slightly more beading (for substances that did bead) on the lab bench. This is observed when looking at the beading differences between water on wax paper and water on a lab bench. Because water is attracted to the wax paper there is less interaction between nearby molecules. This is because the attraction to the wax paper is preventing some molecules to attract. Therefore, when water is placed on a lab bench, it does not attract to a lab bench, but instead the molecules pull toward each other with greater force.

This assignment has demonstrated that the stronger the intermolecular force, the more likely that the molecules will bead together. Furthermore, if a molecule repels the surface on which it is rested on, it will bond together with greater strength.

HW:

Test is tomorrow.

Thursday, February 24

Today we began the class by looking at Wednesday's blog. From there we proceeded to review ionic compounds, which was discussed on Wednesdays. We recapped on the difference between ionic, Polar, and Non-Polar bonds. We were also given the answers from the previous days homework, Pg. 3 of the packet.

1.a.- 1 b.-2

c.-6 d.-7 f.-3

2.a- [Ne] 3s1 & it loses 1 electron

b.-[Ne] 3s2 3p4 & it gains 2 electrons

c.-[Ar]4s2 & it loses 2 electrons

d.-[Ar] 4s2 3d10 4p5 & it gains 1 electron

We then began to discuss covalent bonds and the Lewis dot structure. From last nights homework we all know that every element wants to gain or lose electrons so that it has 8 valence electrons (2 in the case of H and He). That is why noble gases are so stable. In an ionic bond, one atom will gain electron wh

ile another atom loses an electron. (ex: in NaCl, sodium gives up 1 electron to chlorine, so that both elements have 8 valence electrons). However sometimes, 2 atoms will form covalent bonds and each element will share atom. To begin diagramming a covalent bond, you have to be able to Lewis Dot structure any given

element given the number of electrons.

For example, if you have Cl, you know it has 7 valence electrons.

Step 1: write Cl

Step 2: place 1 dot around Cl for every electron

-it should look like

Now if you wish to write a covalent, you:

1. begin by drawing the Lewis Dot Structure for each element

2. remove 1 electron and draw an electron to represent a pair

3. it should look like this

Each pair of dots can be represented by a dash. As you can see, the H and Cl are each sharing a dot so that H has 2 valence electrons and Cl has 8. They are both stable.

HW:

Webassign