Standards-based assessment and Instruction

# Science 3-5

### What Is Static Electricity?

During this investigation, you will use a balloon and some other common objects to explore and observe what static electricity is and how it behaves. Choose a number of small items to test and then rub a balloon with a piece of wool to prepare it for your investigation. Write your “testable question” at the top of your page and make some predictions about the materials you selected: What do you think will happen when they come in contact with the balloon? Will they stick (be attracted to) or do something else (be repelled)? Make sure to record your predictions before starting your observations.

Now, conduct your tests observing the materials you selected to see which ones stick to the balloon. As you test the materials, think about why this is happening. What is causing the objects to stick or not stick to your balloon? Record your results on your sheets and try to make some conclusions based on what you observed.

### Big Ideas and Unifying Concepts

• Cause and effect

### Physical Science Concepts

• Transfer and transformation of energy
• Motion and forces

### Inquiry Process Skills

• Communicate investigations and explanations
• Employ simple equipment and tools to gather data
• Make observations
• Plan and conduct a simple investigation
• Use data to construct a reasonable explanation

### Mathematics Concepts

• Data collection, organization and analysis
• Diagrams
• Measurement

### Suggested Materials

Start with balloons, pieces of wool and items to test such as small pieces of tinfoil, paper, string, cotton, fabric, plastic, salt, puffed rice, flour, paper clips and packing peanuts. Then, you can let students select other items in the classroom to test. (A little water is handy to decharge objects.)

## Context

This is one of several investigations with which I begin a unit on electricity. We first look at static electricity, something students know a little about from prior knowledge and experience (they know they get a shock when walking on carpet and then touching something or that clothes out of the dryer stick to each other) but are not sure exactly what is happening or why. This is a good introductory, guided investigation that focuses students on the idea that the balloon “attracts” the objects and that the wool rubbed on the balloon gives it this attraction. This information will help them through later investigations on current electricity and magnetism. It also provides the opportunity for students to practice writing hypotheses or testable questions, making predictions, recording data/observations, conducting tests and drawing conclusions.

## Instructional Stages

Engagement: Students access prior knowledge and engage with phenomena.

Exploration: Students explore ideas and phenomena using inquiry to clarify their understanding of concepts.

Explanation: Students construct explanations of concepts and phenomena.

This investigation will help students begin to have some ideas about what static electricity is and how it behaves. They will practice making predictions based on what they already know and then test to see if their predictions were correct. They will have the opportunity to communicate and compare with others what their conclusions are, and this will allow the teacher to assess their understanding of the concept of static electricity as well as their science process skills. It is also possible that students will extend their thinking to make observations about the characteristics of the materials tested and/or characteristics of the wool or other objects that might be rubbed against the balloon. They might also notice that two charged balloons repel each other due to like charges.

## How the Students Will Investigate

Students will first examine the materials they have chosen and think about which ones might and might not stick to the balloon. They will then write their question, record their objects to be tested and make their predictions. Once they have recorded these predictions, they will rub their balloon with the piece of wool and then test each of the materials to see what happens. In drawing their conclusions, they should consider how the materials behaved when they came in contact with the balloon and then consider why. Students testing similar materials might want to check their findings with those of their classmates, to verify their data (as a scientist would do).

Science: Other possible investigations might be comparing other materials (fabrics) by rubbing them on the balloon to see if they “charge” the balloon as strongly as the wool does. This could be set up as a “fair test,” where the control would be to test the same objects on similarly-sized balloons rubbed with different fabrics. Students could try other materials besides the ones included in this investigation to see what happens, or use a comb instead of a balloon. Some interesting ideas might include the following: two (negatively) charged balloons will repel each other; the energy field of a well-charged resin rod or comb held close, but not touching, a very slow stream of water (running out of a tap) pushes the stream of water (water does not have a charge but is a balance of positive and negative) or bends it (negative comb repels negative charges in water and attracts positive charges in water); some, but not other, materials can de-charge the balloon. These can also be great science-fair demonstrations.

Mathematics — Estimating and Predicting: Students can time how long each object sticks to (is attracted to) the balloon. Which ones hold their attractions the longest? Propose an explanation for why an object will stick to the balloon for the longest amount of time. Students can also count how many objects will stick to the balloon at one time. What is the most of an item they can make stick?

History of Science: Research who discovered static electricity and how it affected scientific thought. Share what was learned with the class.

## Teaching Tips and Guiding Questions

Try to teach about static electricity during a time of year when the weather is dry so that static can be generated. Electrons need dry air in which to build up and jump. (That is why there is more static cling in dryer clothes on a dry day than a humid day.) Combing hair and pulling off sweaters can also produce a spark and snap! The balloon picks up electrons (negative charges) when rubbed and becomes negatively charged. The negative charge on the balloon attracts the positive charges on objects, which are neutral (having both negative and positive charges on them).

Once the students are busily testing their predictions, some guiding questions to ask might
be:

• How does rubbing charge the balloon? Does more, or faster rubbing make more charge? Can you make a super attractor?
• Can you make the objects dance?
• Are the objects easy to pull off the balloon once they are on there? Which materials stick well to the balloon? Which materials do not? Can you see a pattern as to why?
• What happens if you hold the balloon farther away from the object?
• Compare the materials that work and do not work. How are they different? How are they alike?
• Why do you think these objects stick?
• How is the charged balloon like a magnet?

## Concepts to Be Assessed

(Unifying concepts (big ideas) and science concepts to be assessed using the Science Exemplars Rubric under the criterion: Science Concepts and Related Content.)

• Physical Science — Transfer and Transformation of Energy: Students understand that all bodies are capable of producing electrical charges; that conductors allow electrons to move, but insulators do not allow electrons to move easily; and that static electricity is the result of build up or deficiency of electrons. Students observe that like charges repel and unlike charges attract (cause and effect) and that there are positive and negative charges.
• Physical Science — Motion and Forces: Students observe that material that has been
electrically charged pulls on all other materials and may either push or pull other charged materials.
• Mathematics: Students make precise measurements and diagrams. Students collect, organize and analyze data appropriately.

### Possible Solutions

There are a variety of solutions to the testable question/hypothesis used. Many different objects will stick to the balloon after it has been “charged” by the wool. Most metal-like objects will not stick, however, and it is hoped that the students will discover this while testing and begin to wonder why. Conclusions that the students draw should include their ideas about what static electricity is. It is not necessary for them to have a textbook definition of what it is, but some key words and ideas like attraction and charge should be a part of their explanation. They might also speak of “jumping” electrons.

Click on a level for student example.
Novice This student did not complete the investigation according to the directions given. There is no testable question stated to be investigated and only one prediction and test were completed. Without relevant data, this student was unable to make an informed conclusion. The student did use the word “repel” as it related to what was investigated, but there is no connection to static electricity or the question originally posed. This student does not yet demonstrate understanding of the inquiry or data-gathering processes.
Apprentice This student framed the testable question (using an attempt at “if ... then ...”) and investigated a number of objects. The predictions given were based on some understanding of the concept. This student also has some understanding of the inquiry process and uses the relevant skills but is unable to make an informed conclusion based on the results recorded. The conclusion given relates more to a comparison made about conductors of static electricity (“hair is better than wool”) than to what they observed during this particular investigation (testing tinfoil, cotton, etc.). However, this comparison is somewhat valid and interesting and could be further explored to help the student make some connections.
Practitioner This student framed the testable question (using an attempt at “if ... then ...”) and investigated a number of objects. There is a good basic understanding of the physical science concepts. An interesting comparison of static electricity to magnetism and correct use of the term “attracted” are included. The graphic representation is well labeled and demonstrates scientific reasoning and thinking skills in that the student extended the investigation from wool to hair and collected appropriate data.
Expert This student’s investigation was clear and well conducted to answer the question posed. All parts were included and results recorded accurately, evidence of the scientific method applied well. The conclusion includes some of the important ideas about static electricity. Again, a comparison was made to magnetism. This student also made an important, more specific observation about the objects only sticking to the part of the balloon that was charged. The graphic representation is very clear; all columns are labeled.

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