Electrical Conductors

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Objective

SWBAT classify items as electrical conductors or nonconductors

Big Idea

Students build circuits and then replace the switch with various items to test if they are good conductors of electricity.

Rationale and Preparation

The Why Behind Teaching This: 

Unit 2 addresses standards related to matter and it's interactions.  The unit begins with identifying types of matter and the particles that make it up.  This is covered in standard 5-PS1-1: Developing a model to describe that matter is made of particles too small to be seen.  We will be changing matter by melting, evaporating, and dissolving to prove that although the physical appearance has changed, the same amount of matter  still exists.  This is covered in standard 5-PS1-2: Measure and graph quantities to provide evidence that regardless of the type of change that occurs when heating, cooling, or mixing substances, the total weight of matter is conserved.  We will also be using a variety of properties to identify matter through standard 5-PS1-3: Make observations and measurements to identify materials based on their properties.  The investigations and experiments during this unit will focus on physical and chemical changes that occur when mixing matter which is addressed in standard 5-PS1-4: Conduct an investigation to determine whether the mixing of two or more substances results in a new substance.   

This specific lesson targets standard 5-PS1-3: Make observations and measurements to identify materials based on their properties.  Students will be using a circuit to test various items to determine if they are good electrical conductors or not.  They will then compare properties of all items in the good conductor list for similarities, such as, they are all metals.  The clarification statement following standard 5-PS1-3 in the K-12 Science Framework gives examples of matter that may need to be identified using properties and one of those examples is metal.  Properties that may be used to identify matter are listed as well, and one of the properties is electrical conductivity.  Completing this lesson ensures that these areas are covered in case this is what students are assessed on.   

Lesson Goal: 

The goal of this lesson is for students to identify similar properties between items that are good conductors.   

Success Criteria:

Students will demonstrate success by correctly classifying items provided as either good conductors or nonconductors and creating a list of properties all conductors have in common.  

Preparing for Lesson:

Warm Up:

Guided Practice: 

  • 1 battery in holder for each group 
  • 1 light in holder for each group 
  • 3 alligator clips for each group 

Explore: 

  •  1 bag of items to test conductivity.  I used a pencil with both ends sharpened, a nickel, a penny, a plastic straw, a plastic game token, a piece of aluminum foil, a craft stick, a paperclip, and a piece of basal wood.  

Wrap Up: 

Warm Up

10 minutes

Finding the Right Circuit:

I begin today's lesson by providing each group with four examples of circuits from the which circuit is complete resource. They have not learned about circuits or electric energy yet.  I chose to do this activity prior to teaching so that I can see how much background information students already have on the topic. I will know by the end of the warm up activity what vocabulary the students already know, as well as what they know about electricity and circuits.  

I ask groups to choose which circuit they believe will light the bulb when the switch is flipped and be prepared to explain why they believe it will light.  I also give them the direction to discuss what is wrong with the other 3 that will prevent the light from coming on when the switch is flipped.  I give them about 3 minutes to discuss this in their small groups while I circulate to listen to conversations.  I tell groups that each student in the group needs to explain one of the circuit diagrams, explaining if they believe it will work or not, and why.  Each group consists of ESE, ELL and regular education students.  By allowing them to talk with their groups and have a conversation about the circuits together, I am promoting science talk and providing an opportunity for the ELL and ESE students to practice vocabulary and explanations after hearing it from another student.  Hopefully this will help them feel confident in sharing.

I choose a group to begin and everyone else listens to their explanations.  You can see in the first video of student explanations on circuits that this group did not identify the correct circuit, but I do not let them know that.  I choose a second group to explain their choices as everyone else listens.  This group identified the correct circuit but I do not tell the class that.  Here, you can see the video of student explanations on circuits that was the correct response.  

I take the pictures of the two circuits that were chosen by the first two groups and use the overhead to point out the difference.  The first group believed that the one with a wire on each end of the switch would work, while the second group believed it would be the one with both wires attached to the same end (but on opposite sides) of the switch.  I ask the class which they agree with and the three other groups all tell me the second group.  I tell them that is correct, and then I trace the flow of energy from the battery through the circuit pointing out how the wires would need to be on the same side, the side that the switch will be flipped to, in order to work.  


Guided Practice

15 minutes

Building a Circuit: 

I provide each group with 1 battery already in a battery holder for circuits, 1 switch, 1 light bulb in a light bulb holder, and 3 alligator clip wires.  I prefer to use alligator clips because students tend to have a difficult time securing regular wires to the battery case and light bulb holder. I model, using the overhead, how to construct the circuit as I ask guiding questions:

What is our energy source for the circuit? Students answer the battery. We set the battery out. 

How is the energy going to get from the battery, to the light bulb? Students respond with wires.  We connect a wire to each end of the battery. 

What needs to be connected to this wire (pointing to one on the overhead)? They say the light bulb.  We connect the light bulb. 

What needs to be connected to the other wire? They say the switch.  We connect the switch. 

Are we done? They say, no, we need to connect the switch to the light bulb.  We do that. 

I ask all groups to close their switch to complete the circuit and make sure their light bulb comes on.  If any do not light, we have to trouble shoot by checking everything is hooked up correctly, and then switch out the light bulb and/or battery to see if one of them is bad.

                                         

The photo above is of a completed circuit.  There is a nickel where the switch was.  

Draw a Model of the Circuit

I ask students to draw a model of their circuit in their science notebooks.  While they do this, I pass out a bag of items to each group and ask them not to take anything out until I give them further directions.  You can put any items in the bag you would like as long as some conduct electricity and some do not.  I put a paperclip, a penny, a nickel, a piece of aluminum foil, a pencil sharpened at both ends, a plastic straw, a plastic game token, a craft stick, and a piece of basal wood in each bag for today's lesson.  

                                         

The photo above shows everything that the students have at their seats.  Their circuit is already assembled following the above activity.  

Explore

25 minutes

Setting Up the Science Notebook Chart: 

Once all students have completed their model drawing, I ask them to draw a 3-column chart in their science notebook under the model they drew.  I draw this in my notebook which is projected on the overhead as well.  This allows ESE and ELL students to have an example to copy from.  I label one column of my chart conductors, the second column nonconductors, and the third column predictions.  I explain to students that they will be testing each of the items in their bag to see if they are electrical conductors or nonconductors.  Conductor is a vocabulary word that students are not yet familiar with so we discuss that a conductor is matter that allows energy to travel through it.  I ask them if we replace the switch with an item that is a good conductor, what should happen.  Students tell me the light will still be on.  I ask them if the item is not a good conductor what will happen and they tell me the light will go off.  

Before they begin testing, I write each item from the bag in the column labeled as predictions, and they copy them down.  By doing this, I am ensuring that they know the name of each item, as well as how to spell it.  Before they begin testing, I ask them to get the items out of their bag, observe them, and make two groups, items they believe will conduct electricity and those that they predict will not.  I circulate as students discuss with their groups, and place items into groups.  After they have their groups formed, I ask them to place a check mark next to each item they believe will be a good conductor in the prediction column.  

Testing for Conductivity:

I explain to students that they will be replacing the switch with the items from the bag to see if they allow the light to come on.  Each group removes the switch and I come to collect them.  As students test each item from the bag, they record the item under the correct section of the T-chart based on whether the light comes on or not. I circulate to listen to conversations and to ensure that they are testing accurately.  One common mistake I usually see at least once, is that the alligator clips are touching each other when attached to an item which causes the light to come on.  Instead of the energy having to travel through the item, it just goes from one alligator clip to the other making it look like the item is conducting electricity when in reality it is not.  I want to be sure to catch any mistakes like this before groups get too far into testing.  

The video of students testing conductors shows one group testing the aluminum foil, then getting ready to move on to test the plastic straw.  I have to stop them to ask them where they are recording their information because they almost forget to record the results from the foil in their chart.  After recording the foil as a good conductor, they move on to test the straw.  

After students test all items, they put them back into the bag and I collect them.  We go over the lists they have created in their notebooks together.  I begin by asking if any of their predictions were wrong.  I like to start with that to see how their misconceptions have changed.  One group thought that the pencil would conduct electricity when tested lead to lead.  I have got this to work before, but could not today.  The pencils may have been too long.  Another group believed that the nickel would conduct electricity but not the penny.  They did not believe that copper was a good conductor so we discussed how wires and even cooking pots sometimes have copper on them because it is a good conductor.  

After identifying any wrong predictions that were made, I have each group share their entire list of conductors with the class so that we can compare what each group has.  Everything was the same for all groups, the only conductors were the paper clip, the penny, the nickel, and the aluminum foil.     

                                       

Wrap Up

10 minutes

Comparing properties of Conductors:

We briefly discuss the properties that all items in the T-chart have in common.  Students tell me they are all metals, they are all solids, they keep their shape, etc.  I ask if anyone can think of a substance that is not a solid that will conduct electricity.  Students are not able to name any.  I ask them if I touched electricity if it would run through me.  They tell me it would, and I point out that we are good conductors.  I add that water is also a good conductor which is why you should not be swimming in the pool when it is lightening.    

We also compare the items in the list that are not good conductors.  I feel it is important to take note of what types of items are not good conductors as they should be able to identify these are well.   Students say materials such as wood and plastic are not good conductors.  I ask them if they can name other materials that are not good conductors.  The need some hints to help them.  I tell them that the soles of shoes and tires on bikes and cars are made of a certain material that does not conduct electricity to help protect us.  They are able to identify the substance as rubber.   After that, a student asks about glass and another asks about tile.  I tell them both are poor conductors of electricity.   

Assess for understanding: 

I give each student a Conductor Exit Ticket to complete to check for understanding.  I divide these into three categories: -1 Proficient, -2 Almost, -3 Needs Reteaching.  Because all groups correctly identified the items that conducted electricity and were able to compare them stating that they were all metals, I assumed that the results from the exit ticket would be nearly 100% proficient.  I was quite surprised to see how many exit tickets were in the almost pile, there were 24 out of 40.  There were not many in the needs reteaching pile, only 4.  The most surprising results were that there were only 12 out of 40 students in the proficient pile!  

In order to demonstrate proficiency, students had to correctly draw the wires to complete the circuit at the top, and they had to identify the items at the bottom of the page that were good conductors (the metal nail file, and the penny.  

                                     

                                         Photo of Exit Ticket Demonstrating Proficiency

If students correctly completed the circuit at the top, but did not identify the correct conductors at the bottom, they received the almost proficient marking.  Students who correctly identified the good conductors at the bottom but did not complete the circuit correctly, also received this marking.  

    

   Photo 1 of Exit Ticket that Almost Got It                                Photo 2 of Exit Ticket that Almost Got It

For students to need complete reteaching, they would have had to have made errors in completing the circuit, and identifying the items that are good conductors from the bottom portion of the exit ticket.  

                                         

                                                Photo of Exit Tickets That Need Reteaching