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Electricity

What’s the charge?

Develop effective scientific explanations to learn more about static electricity.

  • Grade 8
  • Group work
  • 30 mins
  • New

Overview

While developing effective scientific explanations of a common classroom experiment designed to demonstrate static electricity, students learn how materials change their state of charge and how materials with similar charges repel each other.

What you'll need

  • "Creating an effective scientific explanation" worksheet, one per student
  • "What’s the charge?" slideshow
  • Digital projector and screen
  • Balloon (optional)

Instructions

  1. Organize your students into pairs and provide each student with a copy of the "Creating an effective scientific explanation" worksheet. Guide your students’ attention to the two statements at the top of the worksheet, and prompt groups to decide which statement is the most effective. Encourage groups to note at least one reason to support their decision. 
  2. Invite groups to share their decision and thinking with the class. As groups share, use their ideas to co-develop or present the criteria for an effective scientific explanation. An effective scientific explanation:
    • Uses observations, measurements, and facts
    • Suggests possible conclusions and outcomes 

Draw your students’ attention to the criteria on the worksheet, and invite groups to reconsider their initial decision, this time using the criteria to guide their thinking.  

  1. Guide your students’ attention to their worksheet and the question “What happens to the electrons when the objects are rubbed together?” Briefly explain to your students that their challenge is to create an effective scientific explanation of what happens to the electrons in an experiment featured in a short video. 
  2. Show the video Static Flyer.
  3. Ask groups to note their initial explanation of why the balloon and plastic bag seem to repel each other.  
  4. Display slides 2-4 of the "What’s the charge?" slide show, inviting students to describe what they notice about the charges before objects are rubbed together, after rubbing, and when the balloon and plastic are brought together. 
  5. Guide your students’ attention back to their worksheet. Prompt groups to develop a revised scientific explanation of why the balloon and plastic bag seem to repel each other. 
  6. To conclude the activity, consider asking students to predict what will happen when a balloon is rubbed against someone’s head, and then placed against a wall: will the balloon be attracted or repelled? 
    • Invite a student volunteer to rub a balloon on their head, and then “stick” the balloon to the wall. Invite students to develop a scientific explanation to explain the result.

Additional information

Assess your students’ abilities to:

  • develop effective scientific explanations
  • effectively describe why some objects attract each other, while others repel 

Extension

Consider providing groups with a selection of materials that vary on how strongly they hold on to electrons (see Teaching Notes about the triboelectric series). Ask groups to hypothesize which materials will create the strongest charge, and then develop experiments to test their predictions. Invite groups to develop effective scientific experiments to explain their findings.

To understand what is happening when a static charge develops, it is important to think about the atoms that make up everything around us. All matter is made up of atoms, which are themselves made up of charged particles. Atoms have a nucleus consisting of neutrons and protons. They also have a surrounding "shell" that is made up of electrons. Typically, matter is neutrally charged, meaning that the number of electrons and protons are the same. If an atom has more electrons than protons, it is negatively charged. If it has more protons than electrons, it is positively charged.

Some atoms hold on to their electrons more tightly than others do. How strongly matter holds on to its electrons determines its place in the triboelectric series. If a material is more likely to give up electrons when it contacts another material, it is considered to be more positive in the triboelectric series. If a material is more likely to "capture" electrons when it contacts another material, it is considered to be more negative. The farther the separation in the table, the greater the effect. Positive items in the series are at the top, and negative items are at the bottom:

  • Human hands Very positive
  • Rabbit fur
  • Glass
  • Human hair
  • Nylon
  • Wool
  • Fur
  • Lead
  • Silk
  • Aluminum
  • Paper
  • Cotton
  • Steel Neutral
  • Wood
  • Amber
  • Hard rubber
  • Nickel, Copper
  • Brass, Silver
  • Gold, Platinum
  • Polyester
  • Styrofoam
  • Saran Wrap
  • Polyurethane
  • Polyethylene (like Scotch Tape)
  • Polypropylene
  • Vinyl 
  • Silicon
  • Teflon Very negative                                               

(The above list is adapted from Nature's Electricity by Charles K. Adams.)

Grade 8 Science

Big idea

The behaviour of matter can be explained by the kinetic molecular theory and atomic theory.

Content

  • models can be used to represent:
    • the arrangement and motion of particles in different phases
    • the arrangement of and forces that bind protons, neutrons, and electrons in an atom
    • the quarks and leptons in protons, neutrons, and electrons
  • protons and neutrons (made of quarks) are held together in the nucleus by a strong nuclear force
Curricular Competencies
Questioning and Predicting
  • Demonstrate a sustained intellectual curiosity about a scientific topic or problem of personal interest
  • Make observations aimed at identifying their own questions about the natural world
  • Identify a question to answer or a problem to solve through scientific inquiry
Processing and Analyzing Scientific Information
  • Use scientific understandings to identify relationships and draw conclusions
  • Construct and use a range of methods to represent patterns or relationships in data, including tables, graphs, keys, models, and digital technologies as appropriate
Evaluating
  • Demonstrate an understanding and appreciation of evidence (qualitative and quantitative)
Applying and innovating
  • Contribute to care for self, others, community, and world through personal or collaborative approaches
  • Transfer and apply learning to new situations
Communicating
  • Communicate ideas, findings, and solutions to problems, using scientific language, representations, and digital technologies as appropriate

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