Chemistry – Unit 6 Sticky Tape Post-Lab
Thomson Model and Sticky Tape
Thompson’s “Plum Pudding” model of atoms.
Atoms have negatively charged electrons evenly distributed (floating) throughout the atom’s positive interior. Apply Thomson’s model to explain the following:
| A representation of the plum pudding model |
How did tapes get charge? The diagram represents atoms in the top tape and bottom tape before they stuck together. Black dots are the negatively charged particles in Thompson’s model: | Complete a similar particle drawings of the sticky tape when it is stuck together, and another particle drawing immediately after it is pulled apart. |
Describe how and when and why did the the top tape and the bottom tape get charged? | |
Why are foil and paper attracted to charged objects? Review the Phet balloon simulation at the class website to help answer this. | |
Conductor vs Insulator For a substance to conduct electricity, it must have charged particles that can move. | Question: What does the difference in conductivity between metals and nonmetals tell us about the attraction between the (+) core electrons in metal atoms vs nonmetal atoms? |
Polarization: Uneven distribution of charges in a substance or an atom or molecule is called polarization. | |
Positive charged tape near a conductor | Positive charged tape near an insulator |
Consider the particle drawings given above. In which example is the entire material polarized? In which example are the individual atoms polarized, but not the bulk material? | |
Rub a balloon against your hair. What types of materials does it stick to well? What kinds of materials does it stick to poorly? | Explain the observation that a balloon, after rubbed against the hair, sticks to the wall? |
Chemistry – Unit 6 Sticky Tape Post-Lab
Thomson Model and Sticky Tape
Let’s see how we can use Thomson’s model to explain the behavior of the sticky tape when we made our tape stacks.
A few atoms from the top tape and the bottom tape are represented in the diagram below. Add electrons to each atom to show what happens to the electrons when we make a tape stack out of neutral pieces of tape and then pull them apart.
Describe the macroscopic changes in the tapes and then provide a microscopic explanation based on Thomson’s model of the atom and your drawings.
Behavior of Foil and Paper with Charged Tapes
We observed that neither foil (metal atoms) nor paper (non-metal atoms) would attract each other. But foil and paper are both attracted to both the charged tapes (top and bottom).
How can we use the pudding model of atoms to explain the differences we observed?
Several atoms from the paper and foil are drawn on the next page. The ones on the left have no charged object near them. The ones on the right are next to a top tape
(+ charge).
Add force vectors to the non-metal (paper) atoms and the top tape in the first row to show the attraction between the paper and the tape. Then do the same for the foil and the tape in the second row. Be sure the size of the vectors shows the relative strengths of the attractions.
Now draw the electrons in each atom “bowl” to show their arrangements when no charged object is near present and then when a charged object is brought near.
Explain why these arrangements of electrons would produce the observed attractions.
©Modeling Instruction – AMTA 2013 U6 Sticky Tape v1.0