Sunday, October 24, 2004

 

Chem Lab Fall

Click to view Chem 1 Lab
 

Chem Lab Spring

Click to view Chem 2 Lab

Friday, October 22, 2004

 

Chemistry Take Home (Make-up) Lab

Chemistry Lab: #1 To Do Paper Chromatography With Leaves
Name: _______________________
Date: ________ Time: ___ minutes
Introduction:
Chromatography is a way to separate different molecules in a mixture.
Most plants contain several pigment molecules, so experiment with different leaves to see the wide range of pigments.
Time Required: 2 hours
Materials:
Leaves
Baby Food Jars with Lids
Rubbing Alcohol
Coffee Filters
Hot Water
Shallow Pan
Kitchen Utensils
Tips:
1. Try using frozen chopped spinach leaves.
2. Experiment with other types of paper.
3. You can substitute other alcohols for the rubbing alcohol, such as ethyl alcohol or methyl alcohol.
4. If your chromatogram is pale, next time use more leaves and/or smaller pieces to yield more pigment.
Procedures:
1. Take 2-3 large leaves (or the equivalent with smaller leaves), tear them into tiny pieces, and place them into small jars with lids.
2. Add enough alcohol to just cover the leaves.
3. Loosely cover the jars and set them into a shallow pan containing an inch or so of hot tap water.
4. Let the jars sit in the hot water for at least a half hour. Replace the hot water as it cools and swirl the jars from time to time.
5. The jars are 'done' when the alcohol has picked up color from the leaves. The darker the color, the brighter the chromatogram will be.
6. Cut or tear a long strip of coffee filter paper for each jar.
7. Place one strip of paper into each jar, with one end in the alcohol and the other outside of the jar.
8. As the alcohol evaporates, it will pull the pigment up the paper, separating pigments according to size (largest will move the shortest distance).
9. After 30-90 minutes (or until the desired separation is obtained), remove the strips of paper and allow them to dry.
10. Can you identify which pigments are present? Does the season in which the leaves are picked affect their colors?
Questions:
1. What is chromatography?
2. Name 4 methods used to separate mixtures.

http://chemistry.about.com/cs/howtos/ht/endothermic.htm

_________________________________________________________

Chemistry Lab #2 Copper Caper
Name: ______________
Date: ________ Time: _____ minutes
Introduction:
Copper atoms can combine with oxygen atoms from the air to make a molecule called copper oxide. The pennies looked dull and dirty because they were covered with copper oxide. When the vinegar and salt dissolve the copper-oxide layer, they make it easier for the copper atoms to join oxygen from the air and chlorine from the salt to make a blue-green compound called malachite. A mixture of salt and vinegar is really good at dissolving metals and metal oxides. When steel nail is put in the mixture, some of the iron dissolves. In an acid (like vinegar or lemon juice), lots of hydrogen ions (hydrogen atoms that are missing an electron) are floating around. In the chemical reactions at the surface of the screw, some of these hydrogen ions join and form hydrogen gas.
Time required: 40 minutes
Materials:
20 dull, dirty pennies
1/4 cup white vinegar
1 teaspoon salt
A clear, shallow bowl (not metal)
2 clean steel nails
A clean steel screw or bolt
Paper towels
Procedures:
1. Put the salt and vinegar in the bowl. Stir until the salt dissolves.
2. Dip one penny halfway into the liquid. Hold it there for about 10 seconds, then pull it out. What do you see?
3. Dump all the pennies into the liquid. You can watch them change for the first few seconds. After that you won't see anything happen.
4. After 5 minutes, take half of the pennies out of the liquid. Put them on a paper towel to dry.
5. Take the rest of the pennies out of the liquid. Rinse them really well under running water, and put them on a paper towel to dry. Write "rinsed" on the second paper towel.

6. Put a nail and a screw into the liquid. Lean another nail against the side of the bowl so that only part of it is in the liquid
7. After 10 minutes, take a look at the nails. Are they a different color than they were before? Is the leaning nail 2 different colors? If not, leave the nails in the bowl and check on them again in an hour or so.
8. What's happening to the screw? You may see lots and lots of fizzing bubbles coming from the threads. Is the screw changing color? Leave it in the liquid for a while and see what happens.

9. After about an hour, look at the pennies on the paper towels. What's happened to the ones you rinsed? What's happened to the others? What color is the paper towel under the unrinsed pennies?

Questions:
1. Why did the pennies look dirty before I put them in the vinegar?

2. Why did the vinegar and salt clean the pennies?

3. Why did the unrinsed pennies turn blue-green?

4. How did the nail and the screw get coated with copper?

5. Why did bubbles come off the steel screw?

http://www.glencoe.com/sec/science/web_resources/index.html

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