LAB – Polar, Non-Polar, Water Lab

Chemistry 20 – Molecules & Compounds 3-6
LAB – Polar, Non-Polar, Water Lab
Introduction:
Solutions are homogeneous mixtures made up of a solute (the dissolved substance) mixed in a solvent
(what it is dissolved in). Homogeneous solutions are evenly distributed, meaning that when observing the
mixture, it all “looks” the same. A glass of tea is an example of a homogeneous solution.
In living systems, water is considered the universal solvent. Solutions are physical combinations, not
chemical combinations. As we discussed in class, there are two types of covalent bonds – polar and
nonpolar. Molecules joined by polar covalent bonds are not “sharing” the electrons evenly and will have
resulting areas of partial charge around different areas of the molecule. Molecules joined by nonpolar
covalent bonds are “sharing” the electrons evenly and will not have areas of partial charge around the
molecule. Ions are single atoms or groups of atoms that have gained or lost electrons and now have a
resulting charge. This information is important in understanding how solutes and solvents will combine.
This lab explores the interaction of various solvents and solutes related to the types of bonds they have.
An important phrase to remember is that “like dissolves like”… solutes will only dissolve in solvents that
have the same type of bonds (polar or nonpolar).
We only need to determine what solvents to use. Water is the first choice… but is it polar or
nonpolar? The Lewis structure is
> Use the ‘electronegativity arrows’ to explain why water is a
polar covalent molecule:
For a suitable non-polar solvent, we have the following to choose from in the chemistry lab:
Acetic Acid Methanol Acetone
®Which is the best choice? (Show your answer on the structural formulas above,
using the ‘electronegativity arrows’)
Follow the directions of the lab and write your observations in the spaces provided. Be
very specific and detailed with your observations. They will help you answer the
analysis questions that follow.

Part A: What type of bonds are in each solute?
Materials:
5 test tubes – labeled #1 through #5
Copper(II) chloride
Iodine (poisonous and can cause burns)
Water
Substance X (the nonpolar solvent)
Spatula
Stoppers
Graduated cylinder
Marker-and-masking-tape
Procedure:
1. In test tube #1 – Using a spatula, add a FEW crystals of copper(II) chloride to 3 mL of water in a
test tube. Stopper the tube and shake vigorously. Does the copper(II) chloride dissolve in water?
Explain what you see.
2. In test tube #2 – Add a few crystals of iodine with a spatula to 3 mL of water in a second test
tube. Be careful with the iodine! Stopper the test tube and shake it up. Does the iodine readily
dissolve in the water? Explain what you see.
3. In test tube #3 – Add a few crystals of copper(II) chloride to 3 mL of “Substance X”. Stopper and
shake well. Does the copper(II) chloride dissolve in substance X? Explain what you see.
4. In test tube #4 – Add a few crystals of iodine to 3 mL of substance X. Stopper and shake well.
Does the iodine dissolve well in the substance? Explain what you see.
5. In test tube #5 – Add 3 mL of substance X. Then add the iodine water solution you prepared in
test tube #2. Pour the contents of test tube #2 into test tube #5. Stopper and shake well.
Describe the results.
6. Pour the contents of test tube #1 into test tube #4. Stopper and shake well. Describe your
results.
7. Now add 10 drops of detergent to test tube #4 which contains the combination of test tubes #1
and #4. Stopper and shake well. Do the two liquids separate as before? Describe what you see.

Analysis Questions
Study your data that you have recorded concerning the solvents and solutes that you combined
above. Think about the nature of the bonds as you answer the following questions.
1. Define the bolded terms from the introduction.
2. Which solute, [copper(II) chloride or iodine] can dissolve in water, and why?
3. Which solute, [copper(II) chloride or iodine] can dissolve in substance X, and why?
4. Which of the solutes used in this lab is nonpolar, and WHY?
5. Which of the solvents used in this lab is nonpolar, and WHY?
6. What did you do in step #5, and why did you get the results that you observed
in step #5?
7. What did you do in step #6, and why did you get the results that you observed in
step #6?
8. What did you do in step #7, and why did you get the results that you observed
in step #7?
9. [On a separate paper] What is one application where ‘molecular geometry’
(or shapes-of-molecules) is important to real-life? MAKE SURE each group member
chooses a different topic AND explain in a well-described paragraph of 45 words,
minimum. (links provided)

Part B: Pennies
Using the pennies and dropper provided – each team member should perform and
complete this activity. Compete with each other for “who can place the most drops of
water on the penny WITHOUT spilling off the penny” and “who can place the most
drops of alcohol on the penny WITHOUT spilling off the penny.” Record your results in the table below.
Name of Team Member
# of Water Drops
on the penny
# of Alcohol Drops
on the penny
Analysis Questions:
1. Explain how ‘hydrogen bonding’ relates to the surface tension of water. (link provided)
2. From your group’s findings, does an alcohol have more or less ‘hydrogen bonding’ than water?
How can you tell?
Part C: Pepper
Shake some pepper on top of water in a small petri dish. Add a drop of detergent to the petri dish. What
happens to the water and pepper when you added the drop of detergent?
Analysis Questions:
1. Based on your observations, hypothesize (with reasons) whether the pepper is polar or
nonpolar.
2. Using ‘hydrogen bonds’ in your answer, explain why the pepper did-whatit-did
when the detergent was added. (link provided)