Pop Bottle Waves & Hair Dryer Ripples

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Objective

Students investigate how motion and wind create waves on water.

Big Idea

In this opening lesson, we explore what waves are all about as we observe, draw, and think about how waves are shaped and how they move and what creates them.

Observing the Phenomena of Water Waves

30 minutes

One of the wonderful things about NGSS is the permission to play in order to discover. Two liter bottles, some water and a classroom full of kids make for some great fun and dynamic learning about waves!  This lesson was simply opened up with me telling them that we were going to pay attention to water as we create constant motion and discover how waves move and move things.

Below is the list of materials for you to prepare and for students to bring to class.

Materials: Enough 2 Liter bottles with tightly fitting caps, per groups of 3 (to 4)  

Corks cut into ½ “ pieces.

1 1000 ML graduated cylinder,

Funnels

A Metronome (either a real one or go to 8notes.com and use that one. Put it through the sound system on the SB if using iPad.)

Blue or green food dye.

Paper towels for spills.

Blow-dryer & small tub of water.

Students need their iPad timer app & Camera/Video app

Data Chart/ Notebooks/ pencils

Procedure: I broke up my class in groups of three, putting people together by considering their teamwork abilities and personalities. This exercise demands that people work together with great team skills.  

Model: I started this investigation by modeling. It was important to model what I expected them to do first, so that they would know how to fill the graduated cylinder to 700 ml, pour it through the funnel into the bottle, in order to set up their wave bottle. I explained that I would be adding the food coloring to prevent any clothing stains. We discussed how much 1000 ml were and they guessed that the large graduated cylinder would fill up the bottle. They were surprised when it was only half. However, during that discussion, one person connected that 1000 ml must be one liter. I had hoped they would see this as it links in with a near future upcoming math unit!  So, I measured 700 ml, filled up the bottle just a little under half. I explained that this amount would give them the right amount of water to create some awesome waves. 

Divide jobs to fill bottles: I asked that the oldest student in the group fill the cylinder, the youngest pour the 700 ml and the third person video the process of them filling and pouring. (This little strategy is in place just to practice for upcoming procedures. One person will always be filming each time. It gets them cooperating right away and keeps students busy. When students finished, they brought me their bottles and I put the drops of dye in. They were so excited! I asked them to shake up the bottle to move the dye through the water and test the cap for leakage. 

Take turns by rotating: It was time to start! In order to keep everyone engaged and on task, one person was the timer, one was the “bottle rocker” and one was the videographer. I explained that that I would set the rhythm on the metronome and allow them to listen and feel the beat. Then, the timer will be set for 20 seconds and start when I give the signal, and the videographer should begin videoing the person rocking the bottle. I asked that they get the video so that we can see what is happening in the bottle. 

I set the metronome for 52 beats and began its ticking. I asked that the student hold the bottle very still on its side. Then, I gave them the go, the timer started and they started rocking the bottle to the beat of the rhythm.  As the rocking began, I coached them to watch carefully and asked them questions that keep them focused. After 20 seconds, I asked them to trade jobs and I set the metronome for 88 beats, and then 126 beats (notice this child's face). Things were really starting to change and I kept the questioning about their observations flowing as the metronome ticked.  At 144 we saw curls!

When all speeds have been completed, I asked them to push the small piece of cork in the bottle and repeat the process. Ask them to predict again based on what they noticed about waves. Add this to the board. Guide them in discussion as it unfolds about what they are seeing as the process begins again. We started at 52 beats with the cork as I coached them to notice where the cork is  in relationship to the water.  And again we sped up the beats to 88 and 126. As the waves started to increase and curl again at 126, I stopped them to predict at 144. They agreed it was going to dunk under the wave and not float.  As they began, the excitement peaked as the waves really curled upward toward the top and the cork moved below the wave as predicted! I told them that we would discuss why they thought this was happening after they looked at their movies and made official observational notes on their sheets. 

Recording the Data and Responding to the Phenomena

20 minutes

After all was done and filmed, students began watching their videos and recording their observations. This was a great way for them to really see the increase of the altitude as they watched them in order without and with the cork. Observing themselves again through the use of the video really made recording on data sheets much easier. There was no way they could have written what they were seeing had there been no video.  I roved and asked them to talk a little bit about their observations.  They really could see by watching the cork through each process how it moved and how the wave was responsible for where it was going in the bottle. We discussed how waves move things. This was their first observation of transfer of energy! 

As students finished up their observations at different rates, I called them up to the center counter to see yet another phenomena using a hair dryer and a tub of water. This little activity kept everyone busy as they waited for people to finish. Group by group, they began to congregate. I asked them what they were noticing to stimulate inquiry. Wonderful conversations about this phenomenon started to unfold. Wind made ripples that they discussed. Conclusions were drawn and debated. They were engaged and could relate well to what they were seeing as they worked hard to make sense of it all!  It was time to close our lesson and share thoughts.

Creating a Collaboration Board

15 minutes

I asked students to think about these questions and jot down their thoughts in their notebook. I wrote them on the board as I asked them out loud.

What patterns did you notice in the waves each time the metronome beat faster?

What patterns did you notice about the cork as the waves sped up?

What do you think caused the waves? 

Discussion began and rich ideas again began to emerge. We discussed figuring out what the cork was really doing and how it was moving. We also began to discuss how currents work and they related what they saw the cork do to rip tides. Most said that the cork was pulled under and then backward. Some related it to ocean beach experiences about what they were told about rip tides. This is an example of how using inquiry builds into amazing discussion that never would have happened if I had handed them reading material about waves. I asked one student to come to the board and draw waves on the board as he had witnessed them in the hair dryer experience. I wanted the students to connect to the visual he had sketched in his notebook.

To wrap it all up, I told them we would use all of our evidence to create a collaboration board using sticky notes, that would be centered around a sentence starter that I wanted them to finish as a group. I wrote,

The faster the wave the...

I know this because ... (what’s your evidence?)

I asked them to discuss their findings in their group, draw some conclusions using the questions they had answered above. Then, I wanted them to finish up the sentence I had written on the collaboration board started to come together. When the stickies were all up, I read each one to share.