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Module 4 - Water


Bear Eseentials of Polarity - interesting but not using - good Educator Resource
The Bear/Bare Essentials of Polarity - Various versions based on the cartoon
- The Bare Essentials of Polarity - This is a very clever cartoon (pages 12-15).
- Polarity Essentials Worksheet - This has good questions if you write your own worksheet for the cartoon.  On my "to do" list in Fall 2011.
- The "Bear" Essentials - better quality scan of the original lesson that includes just the cartoon and student worksheets
Hydrogen Bonding
Hydrogen Bonding information from Elmhurst College Virtual ChemBook. Great info!
 Snow Globe Lab - a great practical application of  solutes, solubility, and polarity. Not something I will do as a class, but we may do one together as a review of what dissolves what. 
Surface Tension/Cohesion/Adhesion
Improvement for Surface Tension Experiment - I have always used a single square of toilet paper instead, but I tried this recently and it works.  This is how we will be doing it from now on.
Penny Lab from Science Spot. The classic surface tension/cohesion lab. When class time is short, I use page 5 only since the information page is good and the activity is short. 
General Chemistry Demo Lab: Surface Tension - includes a really nice "hows and whys" of surface tension and how detergents affect it.
Surface Tension, Cohesion and Adhesion information for educators


So, the class is wrapping up Module 3 next class period with a short review and then starting with experiments for Module 4.
Experiment 4.1 - The Chemical Composition of Water - This is a pretty reliable experiment - if you watch the time and not let it run too long.  I found two things helpful: 1. Mix up a separate bowl of salt water to dip the test tubes in so you can put your thumb over the ends and get them into you jar 2. use a rubber band to hold the tubes together.  We have had wonderful results with that. 
Module 4 Practice - I usually include a practice page for each module (when useful). The one attached below is to practice chemical formulas. Homework for the first of the module reading.  
2012 - Week 1 (after reading first half of module)
We started Bonding Basics a while back and stopped intentionally after the chart of ion charges if losing/gaining electrons.  We reviewed this principle while filling in the bottom of the sheet and discussing what an "ion" is.  From there I taught the bonding basics lesson but had them draw the bonds and label on the back of their sheets since we only did 2-3 of them.  Then we did covalent bonds as well, doing 3-4 of them and students drawing these on their sheets (Idid use the cut-out printed element cards with spare beads I had hanging around).  We discussed at length the name of "ionic" and "covalent" bonding  to help instill the difference.  I then divided the covalent bonds by "polar" (H2O) and "non-polar" (H2) and discussed the difference.  We then did Excpeirment 4.2 as a class demo and discuss polarity some more. 

Experiment 4.2 - Water's Polarity. I actually saw an easier way to do this with a liquid detergent bottle (like Dawn or Palmoove or something) and just do that rather than the hole in the cup. We do not use a comb but a balloon because we like to draw the charges on it.  One thought, if you want to be real creative, make a balloon water molecule model and write the charges on them and then do the experiment with that.
We then did: (which I set up a data box eample on the board for their lab books)
Experiment 4. ? - Solutes and Solvents
This is pretty straight forward. We will finish at the beginning of class next week with our review of polar/non polar bonds and then write a conclusion in class.
2012 Week 2
Everyone has finished reading the module and as a review, I wrote "surface tension, polarity, adhesion, cohesion and hygrogen bonding" on the whie board and gave them a few minutes to make a graphic organizer of how they are related.  (This was good because it actually made them think about it).  Many of them got them correct, but it allowed me to review and differentiate between them and clarify things for some.  During the Paper Clip lab (part of the Penny Lab below - page 5 only), and the last two labs in the text, I continually required them to use the correct terms to explain what they saw. "Surrface tension is different than cohesion how? and how is cohension and hydrogen bonding different? cohesion and adhesion?"...etc. 
Experiment 4.5 - Water's Cohesion
Discussion question: would the temperature of the water affect its cohesive properties and surface tension?  Most got this right, but they had to pause and think about it carefully.  
Drops on a Penny Lab/Paper Clip Lab - as simple as this lab is, (the classic surface tension/cohesion lab)...the kids love this for some reason.  A few students will have done it before, but they really enjoy comparing results.  A great short lab to add along with the rest.  A nice lab sheet for this is Penny Lab at Science Spot.  I actually used the paper clip activity and we filled out the worksheet.  Note - each kid needs almost of full box of paper clips!  Be sure to follow the teacher directions for more fun (have them estimate how many clips and then add more water and watch them quickly change their answers).  A student said they had done this with nickels, which when we ran out of paper clips...they were forced to add nickels (which I just happen a few rolls with me for some unknown reason...Saxon math?). 
Experiment 4.6 Forces Between Molecules
They really enjoy this experiment, especially if you expand it a bit.  I use small square flat mirrors (for Module 15) and instead of the wax, I just cut squares of wax paper.  They use eyedroppers to drop water on both surfaces and we review all the terms again above in context of what they are seeing.  This is a good time for them to look at the inside of the dropper and notice the meniscus and discuss why is it shaped that way.  As an extension, I add a drop of food coloring to some alcohol and they drop those on the glass and wax paper to compare cohesion between the fluids (alcohol and water).  Of course, they want to mix up some soap water and drop those  to look at them (and they just finished Experiment 4.5 prior to this so the water and soap are still out). 
Note: be sure to differentiate clearly between polarity (within a molecule), hydrogen bonding (between molecules), cohesion ("sticking" to itself and a result of hydrogen bonding), adhesion ("sticking" to other substances) and surface tension (the affects of cohesion at the surface).  Draw a "concept map" of which comes first and begats the others..... (to do list). Use playdoh or balloon molecules to review and demo.
Debbie Nafzger,
Oct 15, 2012, 7:52 PM
Debbie Nafzger,
Oct 16, 2012, 3:28 PM
Debbie Nafzger,
Sep 7, 2011, 7:00 PM