Physical Science 9 #4A

Unit 2: Get a Charge Out of Matter

Activity #4A: The Solution To Solutions

Exploration of Electrostatic Forces with Sticky Tape

To Begin

There is a large overlap of the world of static electricity and the everyday world that you experience. Clothes tumble in the dryer and cling together. You walk across the carpeting to exit a room and receive a shock from the door knob. You pull a wool sweater off at the end of the day and see sparks of electricity. Sparks of electricity are seen as you pull a wool blanket off the sheets of your bed. You stroke your cat's fur and observe the fur standing up on its end. Bolts of lightning dash across the evening sky during a thunderstorm. And worst of all, you have a bad hair day. These are all static electricity events - events that can only be explained by an understanding of the science of electrostatics.

Not only do electrostatic occurrences permeate the events of everyday life, without the forces associated with static electricity, life as we know it would be impossible. Electrostatic forces - both attractive and repulsive in nature - hold the world of atoms and molecules together in perfect balance. Without this electric force, material things would not exist. Atoms as the building blocks of matter depend upon these forces. And material objects, including us Earthlings, are made of atoms and the acts of standing and walking, touching and feeling, smelling and tasting, and even thinking are the result of electrical phenomenon. Electrostatic forces are foundational to our existence.

One of the primary questions to be asked in this unit is: How can an object (or a particle) be charged and what affect does that charge have upon other objects (or particles) in its vicinity? We will attempt to answer this question through a series of activities intended to give you macroscopic evidence of what is happening at the microscopic level. This understanding will help us understand why some solutions conduct electricity and eventually help us plan ways to clean up oil-coated seabirds.

Answer the following:

1.  What has been your personal experience with electrostatic forces (static electricity)?

2.  What do you know (or guess) about the cause of electrostatic forces?

Learning Objectives:

·  Make a conclusion about how distance affects the strength of the electrostatic force.

·  Use reasoning skills to infer of how electrostactic charges interact with each other.

Process and Procedures

Materials: Scotch (Magic) tape

Part I. Follow the directions exactly!

1.  Tear approx 20 cm (8 inches) of tape and fold over one end to make a small non-sticky handle. Stick this strip of tape (smooth and flat) to your desk top or lab bench. This is your base tape.

2.  Stick another 20 cm piece of tape (make a handle for this one as well) on top of the base tape. Smooth it down very thoroughly with your thumb and fingers. Label the handle of this tape T, for top tape.

3.  With a quick motion, peel off the T tape from the base tape. Test whether this T tape (non-sticky side) is attracted to your finger- if it is not, remake the T tape.

4.  Once you are successful, make two T tapes. Each partner should hold one of the T tapes by the handle. Bring the non-sticky sides of the tapes towards each other. What happens?

Respond to these Questions:

1.  Are the T tapes showing an attractive force or a repulsing force with each other?

2.  How does the behavior of the tapes change when the distance between the tapes increases? Be very specific in explaining how the behavior changes with distance.

Part II. Follow the directions exactly!

1.  Place another base tape on the desk or lab bench as before. This time label the handle of the base tape, B, for bottom tape.

2.  Press another strip of tape on top of the B tape, sticky side down and label its handle, T. Make sure the two tapes are stuck smoothly to each other.

Very slowly, remove the pair of tapes (together!) from the table.

3.  Check whether the pair of tapes is attracted to your finger. If you do see an attraction, have your lab partner rub the slick side of the tape with their thumb. The goal is to have this pair of tapes neither be attracted or repulsed by your finger.

4.  Now quickly, peel the B and T tapes apart from each other. Make a second pair of B and T tapes. Observe all interactions/behavior between all combinations: a pair of B tapes, a pair of T tapes, and a T and a B tape pair. Complete this table, and then copy this table into your notebook.

B – B pair / T –T pair / B – T pair
Behavior

Respond to these Questions

1.  Based on your results how many kinds of electrostatic forces are there?

2.  If you assume that the charge on the B tapes is always the same (because you made the B tapes in the same way) and that the charge on the T tapes is the same (electrostatically the same), then the B tapes have “like charges” and the T tapes have “like charges”. Using the same logic we can say that the T tape charge is “unlike” the B tape charge.

Make a general statement about like and unlike charges and the kinds of electrostatic behavior (attraction or repulsion) you observed:

Part III: Follow the directions exactly!

1.  Make another pair of B and T tapes and hang them from your bench top or desk top.

2.  Bring a plastic spoon close to each tape (but don’t touch it) and observe the behavior.

3.  Charge the plastic spoon by rubbing it on your hair or your clothing (it can be tricky to make it hold the charge). Once again, observe the behavior of each tape as you bring the rod close to each one.

Respond to this Question:

Does the plastic spoon have the same charge as the B tape or the T tape? Explain your reasoning!