Student Exploration: Sticky Molecules
Directions: Follow the instructions to go through the simulation. Respond to the questions and
prompts in the orange boxes.
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. James adds some magnetic marbles to a glass jar full of ordinary marbles, and then
shakes up the jar.
What do you think will happen to the magnetic marbles?
2. James then dumps the marbles on a steel cookie sheet and tilts it.
Which type of marble will roll off more easily?
Gizmo Warm-up
Just as some marbles are attracted to one another while others are not, certain
molecules stick together more than others. In the Sticky Molecules Gizmo, you will
discover what causes this “stickiness.” You will investigate a variety of phenomena
that result from the attraction of molecules to one another.
To begin, drag a dropper bottle of Water and a Petri dish (labeled Polarity) to the simulation area. Drag the
dropper over the dish to add water. Examine the molecules.
1. What do you notice about the water molecules?
Different areas of the water molecules are electrically charged. The red portions of the molecules are
negatively charged, while the blue regions are positive. Purple is neutral.
2. Note the yellow lines which show attractions between the molecules. Why do you think these attractions
occur?
, Activity A: Get the Gizmo ready:
Polarity ● Check that the Petri dish contains water.
Introduction: All molecules are neutral overall. However, the charges within molecules are not always
arranged in the same way. In a polar molecule the positive and negative charges are separated into distinct
regions. In a nonpolar molecule the charges are evenly dispersed.
Question: Are polar or nonpolar molecules more “sticky?”
1. Classify: Based on what you observe, are water molecules polar or nonpolar?
Indicate your choice in the data table using the drop-down menu.
The presence of charged regions indicates a polar molecule. However,
these charged regions do not represent full charges as found in
compounds such as sodium chloride. Instead they are partial positive
(δ+) and partial negative (δ–) charges, which are much weaker than full
charges.
2. Hypothesize: Note the yellow lines that form between molecules, which represent hydrogen bonds. A
hydrogen bond (H-bond) is an example of an intermolecular force (IMF). IMFs occur between all
molecules, but hydrogen bonds are the strongest.
A. What causes these H-bonds to form? (Hint: Look at the charged regions.)
B. Why do you think the H-bonds only last a short time before breaking and reforming?
3. Explore: Replace water with hexane (an ingredient in paint thinner). Examine the molecules.
A. Do you see any charged regions? Do any H-bonds form?
B, Is hexane polar or nonpolar? Indicate this in the data table.
C. Observe and classify the other two liquids. Which one is polar?
Which one is nonpolar? Indicate this in the data table.
4. Summarize: Molecules that are attracted to one another can be called “sticky.”
Which types of molecules, polar or nonpolar, are the “stickiest”?
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