Sticky Tape Lab

A Discussion

Charge

Which items in the Sticky Tape Lab exhibited a charge?

What behavior was displayed that makes you believe those objects were charged?

No Charge?

Were there items that were not charged (neutral)?

What behavior was displayed that makes you believe those objects were not charged?

Neutral

If the paper and foil were neutral, how can you explain their attraction to both the positive and negative tapes?

What does neutral really mean?No charge?Equal amounts of positive and negative

charges?

Timing

When did the tapes become charged?

If they didn’t become charged until after we pulled them apart, what conclusion can we make?

TransferWhat is the smallest “subatomic particle”

we are aware of that can be transferred?

Atoms?

Does moving an atom or a group of atoms from one place to another change the charge of something?

There must be something smaller than an atom that can be transferred.

Something Smaller

Based on our observations so far, what characteristics can we assign to the object that was transferred?

• It’s smaller than an atom

• It’s mobile (it moved from one tape to another)

• It has a charge (moving it changed the charge of both tapes)

Which Charge?

If the object is charged, does it have a positive or negative charge?

With the aid of research presented at the end of our lab, we determined the top tape (T tape) was positive and the bottom tape (B tape) was negative.

Two Possibilities

If the mobile charged object is positive, it moved from the B tape to the T tape, increasing the positive charge of the T tape while increasing the negative charge of the B tape.

If the mobile charged object is negative, it moved from the T tape to the B tape, increasing the positive charge of the T tape while increasing the negative charge of the B tape.

SummaryThe object is smaller than an atomThe object is mobileThe object has a chargeResearch tells us the charge is

negativeWe call this charged mobile object an

electron.

J.J. Thomson’s Experiment

http://www.kentchemistry.com/links/AtomicStructure/JJThompson.htm

J. J. Thomson’s Atomic Model

J.J. Thomson came up with a new model of an atom to incorporate this tiny negative particle that we call electrons.

The red dots represent the electrons, which he called plums. They are negative. The rest of the atom was like a bowl of pudding. The bowl of pudding is positive.

. .. . .

The Plum Pudding Model

The plums (electrons) transferred from the pudding (atom) of the T tape to the B tape.

The bottom tape is “plum rich” and the top tape is “plum poor”

Neutral Objects

Can this model explain how a neutral object can be attracted to both positive and negative?

Last Question!

Why was the foil more attracted to the charged objects than the paper was?

What do you know about metals and electricity?