Although scientists do not fully understand the mechanism behind lightning, they think it is created when particles collide with other particles, causing them to generate and build up large amounts of static charges. The same basic process that creates lightning also occurs on a much smaller scale when you get a shock after shuffling across a carpet and touching a door knob. What is giving you a shock is static electricity.
In this set of activities, students will generate static electricity by rubbing or “charging” a balloon. Using the balloon, students will observe the effects of static electricity on different types of matter. Based on these observations, students will understand that materials with opposite charges will be attracted to one another while materials with similar charges will repel.
2-3 (45 minute) periods
Bringing Down the Bolt Video
- Pieces of wool cloth
- Dry cereal (preferably Cheerios)
- Access to a working water faucet
Before The Lesson
Atom: the smallest portion into which an element can be divided and still retain its properties. Atoms are composed of a nucleus, containing protons and neutrons, surrounded by electrons.
Proton: a positively charged particle found inside the nucleus of an atom.
Neutron: a neutral particle found in the nucleus of an atom. Neutral particles contain no charge.
Electron: a negatively charged particle that orbits the nucleus of an atom.
Static Electricity: a build up of an electric charge on an object.
Part I: What To Do
1. Have students watch the Science Friday video Bringing Down the Bolt. Lead a discussion with the students on what we know about how lightning is formed as seen in the video. What is a spark and how are sparks created? Tell students that lightning is an enormous spark, or electric discharge, and is one of the effects of static electricity. Tell students that they are going to conduct three experiments to observe other effects of static electricity.
2. Create a chart with a numbered column for each experiment. After each experiment, discuss and record their observations in the appropriate column.
Part II: Experiment 1
1. Have students crush the dry cereal into small crumbs. Make sure students do not crush the cereal into powder.
2. Have students inflate a balloon with air and tie it off. Ask students what do they think they should do to the balloon to create static electricity. What action was demonstrated in the video to create a spark?
3. Have students vigorously rub the inflated balloon on the wool. Ask students what they think is happening on a molecular level to the balloon as they are rubbing it.
4. Have students place the part of the balloon being rubbed close to the crushed cereal without actually touching it. Have students observe and discuss what happened. Why did the cereal jump onto the balloon?
Part III: Experiment 2
1. Have students tie a piece of the dry cereal to a string and tape the other end of the string onto the edge of a table so that the cereal will hang freely.
2. Have students rub the balloon on the wool again and then bring the balloon near the hanging piece of cereal. Ask students to describe what happened when the balloon came close to the cereal. What happened after the balloon and cereal touched?
Part IV: Experiment 3
1. Tell students that they are going to try the same experiment with water. Ask students to predict what will happen if they place the balloon near a running stream of water after rubbing it against the wool.
2. Have students rub the balloon against the wool and then hold the balloon near a thin stream of running water (about 1/8th of an inch thick) from a nearby faucet. Ask students to describe what happened. Why did the stream of water bend towards the balloon?
Part V: What's Happening?
All matter is made of atoms. The core, or nucleus, of an atom consists of positively charged protons, surrounded by an outer “shell” of negatively charged electrons. Materials that have an equal amount of protons and electrons are considered to be balanced or neutral. However, when certain materials rub up against another, the negatively charged electrons from one material can be picked up by the other material. This causes the material that loses electrons to be positively charged and the material that gains the electrons to be negatively charged. The build up of electrical charges on the surface of the material is called static electricity.
Static electricity can cause materials to attract or repel one another. Opposite charges attract, similar charges will repel and both types of charges will be attracted to a neutral material. In each of these activities, the balloon picked up electrons from the surface of the wool, causing the balloon to become negatively charged. The negatively charged balloon will now be attracted to materials that have an opposite charge, or to a neutral or balanced material (with no charge). This caused the cereal and the charged balloon to come towards each other. When the charged balloon touches the cereal, electrons will flow into the cereal, giving it a negative charge. This then causes them to repel each other.
A high accumulation of positive charges on the surface of one material and a high accumulation of negative charges on the surface of another material can cause an attraction between the charges so great that the electrons will jump the air gap between the objects. Once the electrons start to move across the gap, they heat up the dry air, causing a visible spark or on a larger scale, lightning.
Part VI: Topics for Science Class Discussion
- How can static electricity cause your hair to stand up?
- What would happen if you brought a positively charged object next to the stream of water, instead of the negatively charged balloon?
- What are some beneficial uses of static electricity? What are some harmful effects of static electricity?
- Explain the relationship between static electricity and lightning.
- Why do tall skyscrapers have lightning rods on top of them?
Part VII: Extended Activities and Links
- Experiment with other materials (such as confetti, Styrofoam, salt or pepper) to see what the charged balloon will attract. Have students compare and contrast their observations for each material.
- Have students list examples of static electricity in their everyday lives. What are the processes that cause each ofthese examples to happen?
- Draw a diagram to illustrate what happens to the electrons in the clouds and on the ground during a lightning storm.
- Use magnets to demonstrate how opposite charges attract and similar charges repel.
- Learn more about lightning through this interactive online activity.
- Try this Exploratorium experiment to produce a spark that you can see, hear and feel.