HW #9 for 12/8

1) HW #9 for 12/8--pg. 615 exer 17.4, pg. 618-9, exer. 17.5 & 17.6 (yellow boxes)
2) Late HW due this Friday
3) Composition books due this week--Per 1 on Wednesday, Per 2 on Thursday, Per 3, 5 & 6 on Friday
4) Test on Chapter 17 on Friday

Practice Test for Final

Here is the link for the website that contains the practice test for the final. 

http://quizstar.4teachers.org/indexs.jsp

After you click on the link, click on register and make an account.  Make sure to put your correct name so I can monitor the tests.  After you register, search for a new class.  Search for West Adams Chemistry Final Review as an exact match.  That will allow you to register for the test, so click and register to take the test. Then go to your classes to take the practice test, you can take it a maximum of 10 times.

HW #8 for 12/7

1) HW #8 pg. 629-632 #20-22, 63-64
2) Take Home Lab #4, 6 & Bonus labs due Monday

Take Home Bonus Lab

Take Home Lab BONUS: Mechanoluminescence:

Making Things Light Up

Question: Why does a Life Saver light up when crushed?

Safety: Be sure to look around before turning the lights off to notice any hazards. Be very careful biting down hard on candy, especially if you have had dental work done.

Materials: several Wint-O-Green Life Savers, transparent tape, sugar cube, plastic knife

Procedure: Mechanoluminescence basically means making something light up with the use of force to create a chemical reaction. There are many substances around you that are mechanoluminescent (also called triboluminescent or fractoluminescent). You will experience three substances to see how they light up.

            Wintergreen (methyl salicylate) cannot luminesce (give off light) through a force, but it can luminesce when ultraviolet light shines on it. The combination of the sugar and the wintergreen creates this effect. The sugar gives off some ultraviolet light when it is crushed, and the wintergreen absorbs the light and gives it off again in a color that our eyes can see. The energy the sugar gives off is mostly at about 350 nanometers (nm). Our eyes cannot see that light the same way our ears cannot hear a dog whistle. The wintergreen absorbs that energy and re-emits it at about 450 nm, which we can see.

1. Have the two Wint-O-Green Life Savers with you and the transparent tape roll ready so that you can find the end in the dark.

2. Go to a room with no windows. A bathroom works best. It must get very dark in this room and there must be a mirror. Let your eyes adjust to the darkness for 3-5 minutes.          

3. Put the Life Saver standing up between your upper and lower teeth. Look into the mirror and bite down hard with your lips open. Keep chewing and record what you see. Repeat with the second candy.

4. Grab the end of a transparent tape and quickly pull about 12 inches (30 cm) off the roll. Record your observations.

5. Take your sugar cube and scrape it quickly with a plastic knife and observe. Record your observations.

Data:

Substance:	Color observed:	Wavelength (in nm):
Life Saver
Sugar cube
Transparent tape

Post-Lab Questions:

1  Copy the data table for all three trials.

2. What color did you see the candy luminesce?

3. What color did you see the transparent tape luminesce?

4. What color did the sugar cube luminesce?

5. Find a picture of the electromagnetic spectrum online (search Wikipedia for visible spectrum article) and answer the following questions:

   a. What color should 450 nm be? Did that match your answer to #1?

   b. What do you think is the wavelength of the light given off by the transparent tape? Do you think that sugar or wintergreen had anything to do with this?

    c. What do you think is the wavelength of the light from the sugar cube?

Take Home Lab #6

Take Home Lab #6:  Mean Free Path Activity

Question: What is the average distance between atoms (also known as mean free path)?

Materials: Ruler, target diagram

Procedure: Mean free path is the average distance an atom has to move before colliding with another atom. This is approximately the distance between molecules or atoms. It is usually used when dealing with gases and plasmas. Mean free path is important for understanding temperature and pressure in nuclear chemistry, optics and sound propagation. Mean free path is important when analyzing chemical reactions that involve gases, calculating the conductivity or density of a gas, and working with plasmas such as in fluorescent lightbulb or in a fusion reactor. (See the Wikipedia entry for more details about the applications of mean free path.) Remember that the word mean used in this context means the same thing as average.

                Consider the diagram on the next page in which there are many circles representing atoms or molecules of a gas or plasma in a container.  Measure the distances between 10 of the atoms and their closest neighbors. Take the average of those 10 distances to find the mean free path. Be sure to use centimeters when measuring. One distance has already been marked for you.

Data:

Copy the data table on a separate sheet of paper.

Number	1st Atom	2nd Atom	Distance (cm)
1	A	D
2
3
4
5
6
7
8
9
10
Mean	All	all

Post-Lab Questions:

1. If two of these atoms were very close together, would it have changed your answer very much? Explain.

2. If you were to increase the number of atoms or molecules in this container, how would it change the mean free path? Explain.

3. If you were to increase the size of the container, how would it change the mean free path? Explain.

HW #7 for 12/3

1) HW #7 pg. 629 #24-26
2) Take Home Lab #6 and bonus lab due Monday

HW #6 for 12/1

1) HW #6 pg. 628 #18-19
2) Take Home Lab #5 due Wed. 12/2