Answer

Experiment: Demonstrating Polar Properties

Follow these directions and answer these questions.

1. Rub the acetate strip with the tissue paper.
2. Bring the strip near a slow stream of running water.
   What happened when the strip was brought near the stream?

My Response

The slow stream of running water bends towards the acetate strip.
From your ideas about charges on acetate and vinyl strips, predict what will happen if a charged vinyl strip is brought near the slow stream of water. (Review Unit 4.)

My Response

When a charged vinyl strip is brought near a slow stream of water, the water will be attracted to the charged strip.

1. Test your hypothesis. Rub a vinyl strip with a woolen cloth.

Bring the charged strip near a slow stream of water.

Now analyze your prediction.

1. Was your prediction correct?

My Response

No, my prediction was incorrect.

1. If not, propose a reason for the difference.

My Response

Water stream bend away from the vinyl strip since it may have acquired similar charges with the water molecules.
Analyze the shape of H2O.
a. What is the shape of the H2O molecule?

My Response

Water molecule comprise of two lone pairs and two bonding pairs. The molecular geometry for the water molecule is bent with the H-O-H bond at an angle of 104.5° (Lumen, 2020).
b. Is it symmetrical?

My Response

Yes, water molecule is symmetrical with two-fold rotation axis and two mirror planes of symmetry (University of Illinois, 2020).
c. Does this mean that the H2O molecule is polar or nonpolar?
My Response

Yes, water molecule is polar since it has two lone pairs of electrons (Lumen, 2020).
Analyze the bonds of CCl4.
a. What is the shape of the CCl4 molecule?

My Response

CCl₄ has tetrahedral geometry with no lone pairs on the central carbon. The Cl atoms repel each other equall with Cl-C-Cl bond angle being 109.5° (MyTutor, 2019).
b. Is it symmetrical?

            My Response

Yes, CCl₄ symmetrical since all Cl-C-Cl bond angles are 109.5° (MyTutor, 2019).
c. Does this mean that the CCl4 molecule is polar or nonpolar?
My Reponse

CCl₄ is a nonpolar substance since it does not have lone pair of electrons in the central C (MyTutor, 2019).
Assume that the water stream is replaced by a stream of CCl4. Predict what would happen in each case.
a. charged acetate strip:

My Response

The stream of CCl₄ will continue bending without bending towards the charged acetate strip since CCl₄ lacks lone pair of electrons (MyTutor, 2019).
b. charged vinyl strip:

My Response

The stream of CCl₄ will continue bending without bending towards the charged acetate strip since CCl₄ lacks lone pair of electrons (MyTutor, 2019).
c. Explain your predictions.

My Response

CCl₄ lacks lone pair of electrons hence will not be attracted to charged vinyl or acetate strip (MyTutor, 2019).

Chemists have found that charged acetate and vinyl strips have no effect on a stream of CCl4. Does this fact match your prediction?
My Response

Yes.
Develop a model or picture of water, H2O, and carbon tetrachloride, CCl4 that would account for observations with the charged strips for the two compounds.

My Response

Figure 1: Water molecule (Lumen, 2020).

Figure 2: CCl₄ Structure (Socratic Q&A, 2020).