The Polar Nature of Water
Contributors
Colleen Conway, Ph.D.
Margaret Franzen, Ph.D.
Based on the Water Cup from 3D Molecular Designs.
Last revised 2/2021

This Jmol Exploration was created using the Jmol Exploration Webpage Creator from the MSOE Center for BioMolecular Modeling.

version 2.0
Exploration Content

Introduction

This activity explores the polar nature of water using molecular models from the Water Cup from 3D Molecular Designs. At this large scale, you will explore the interactions between individual atoms of different molecules (intermolecular interactions). If you do not have access to the models, videos and images in the activity will help guide you.

The models in this activity use magnets to simulate interactions between polar atoms. Two atoms that have a similar partial charge (either δd+ or δ-) will repel each other, and atoms with opposite charge will attract each other. If an atom is non-polar, it has no magnet. Note that when two polar atoms interact, you'll also hear the 'click' of the magnets. The models The models in this activity use the standard CPK color scheme, with gray carbon atoms, red oxygen atoms and white hydrogen atoms.

Throughout the activity, this icon indicates you are to provide a response. You may enter your response in the activity, then download a file with your answers at the end of the tutorial. Alternately, you may download and print a paper copy of the worksheet. Question numbers are included to allow you to easily transition from the tutorial to the worksheet.

Learning Objective


  • Students use models to differentiate between polar and nonpolar bonds

Exploring the Structure of Water

Click the button below to see a water molecule in the Jmol window at the right. You may click and drag your mouse over the image to rotate it, and you can hover the cursor over an individual atom to identify it.

water

1. Draw the chemical structure of a molecule of water. Be sure to label each atom as oxygen (O) and as hydrogen (H) and to use δ+ and δ– symbols to show which atom (or atoms) has a partially positive charge and which atom (or atoms) has a partially negative charge.

Interactions Between Water Molecules

If you have access to the water molecule models, explore the interactions between two water molecules. If you don't have the models available, observe the interactions in the videos below.

oxygen-oxygen interactions
hydrogen-hydrogen interactions
oxygen-hydrogen interactions

2. Briefly describe (or draw, with O and H atoms labeled) what happens when two oxygen atoms from two different water molecules collide.

3. Briefly describe (or draw, with O and H atoms labeled) what happens when two hydrogen atoms from two different water molecules collide.

4. Briefly describe (or draw, with O and H atoms labeled) what happens when an oxygen atom on one water molecule collides with a hydrogen atom on another water molecule.

5. What type of Intermolecular force (NOT a chemical bond) holds two water molecules together? Describe (or draw) what atoms are involved in this interaction.

6. What type of chemical bond(s) are keeping a single water molecule together? (What type of chemical bond is connecting the two hydrogen atoms (white) to the oxygen atom (red)?)

7. Your answers to Q5 and Q6 should be different answers. According to your models, which chemical bond is stronger?

Interactions with Sodium Chloride

The cpk color for sodium (Na) is blue, and chlorine (Cl) is green. Observe the interactions between sodium chloride (NaCl) and water.

interaction with sodium chloride

8. Will water interact with sodium chloride (NaCl)? Why?

Interactions Between Water and Ethane

Ethane (C2H6) is a short hydrocarbon. Hydrocarbons are combinations of carbon and hydrogen atoms. Ethane is an odorless, colorless gas that can be used as a fuel, a freezing agent, and in making other chemicals. Explore how ethane interacts with water.

ethane
water interactions with ethane

9. Draw the chemical structure of a molecule of ethane. Be sure to label which atoms are carbon (C) and with atoms are hydrogen (H).

10. Will ethane interact with water? Why or why not?

Interactions Between Water and Ethanol

Ethanol (C2H5OH) is a volatile flammable colorless liquid. Also known as ethyl alcohol or as grain alcohol, it is best known as the alcohol in alcoholic beverages, but it is also used in thermometers, as a solvent, and as fuel. Explore how water interacts with ethanol.

ethanol
water interactions with ethanol

11. Draw the chemical structure of a molecule of ethanol. Be sure to label which atoms are carbon (C), which atoms are oxygen (O), which atoms are hydrogen (H).

12. Will ethanol (C2H5OH) interact with water? Why or why not?

13. Describe the differences you see between the way ethane interacts with water and the way ethanol interacts with water.

14. Explain why you observe differences between the ways ethane and ethanol interact with water.

Reflections

Models, like the models we used in Parts 1 and 2 of today's lab are useful, but they are not perfect. A model cannot perfectly replicate a biological molecule or a biological process.

15. Explain one way in which you found one model of your choice useful.

15. Explain one way in which you found one model of your choice useful.

Save/Export Your Answers to the Questions in This Jmol Exploration
Jmol