Name: ______
Chemistree Lab: Absorption & Evaporation
Background
In this activity, you will prepare a mixture with four different substances. After the solid salt is dissolved in the liquids, the blotter paper will absorb all parts of the solution. This allows the salt to travel up and through the paper. Overnight, the liquids, which are the solvents, will evaporate. The salt is the compound sodium chloride, which has ionic bonds and is normally a cube-shaped crystal. The tiny particles of the bluing act as “seed” particles around which the salt crystals form. Thus, the resulting crystals look very different than the original sodium chloride. Sodium chloride, which is the solute, will remain as fine crystals on the edges of the tree. Because evaporation occurs fastest on the edges, this is where many of the crystals will form on the chemistree. This process is an example of a physical change because the salt dissolves and recrystallizes.
Materials
blotter paper petri dish plastic spoon
cup of table salt laundry bluing (will stain) tray
ammonia food coloring scissors
hot water stirring rod large plastic cup
Procedure
DAY 1
1. Cut two pieces of blotter paper in the shape of a tree. Cut a slit from the bottom to the middle of one tree. Cut a slit from the top to the middle of the other tree. Insert the two papers to from a tree that stands on its own.
2. With another group, prepare a special solution. In the large plastic cup, add the following chemicals in the order in which they are listed below:
table salt (6 spoons)
hot water (6 spoons)
ammonia (1 spoon)
laundry bluing (6 spoons)
3. Gently, stir the solution in the cup.
4. Place a petri dish on a tray. Label your tray by writing your name on masking tape and sticking the tape to the tray.
5. Pour the solution into the petri dishes. Use the spoon to transfer any remaining solid in the plastic cup into the petri dish.
6. Place your tree in the petri dish so it stands.
7. Place only 1 drop of food coloring at the tip of one “tree branch.”
8. Make observations of your tree. Store it somewhere safe so you can make observations the next time you have class.
DAY 2
9. Obtain your tree. Make observations. Draw what your tree looks like now.
10. Throw out the tree. Clean and dry the petri dish
Observations
Day 1:
Day 2:
Analysis
Answer these questions in complete sentences.
1. How did the salt get on the chemistree?
2. Explain how the salt crystals formed on the edges of the tree.
3. Why did it take so long to occur?
4. Use your textbook: Define the word crystal.
5. Name two edible crystals.
Bonus. What is the purpose of the bluing?
Conclusion
Explain what occurred in this experiment using ALL of these vocabulary words and underline each word in your explanation.
crystal, solid, solute, solution, evaporation, liquid, solvent
American Association of Chemistry Teachers
American Association of Chemistry Teachers
American Association of Chemistry Teachers