WEBVTT

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[Music]

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Teacher: Not too long ago, we did this experiment that had to do with density, okay.

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Now, we added a liquid to water, and what happened when that liquid was more

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dense than the water, can anybody tell me over here?

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Student: It floated to the bottom.

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Teacher: It floated to the bottom or it -- ?

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Student: Sank.

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Teacher: It sank to the bottom, that's right.

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When things are more dense, they kind of are heavier and they go down, okay.

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What happens if they are less dense, Brandy?

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Student: They float.

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Teacher: They float on top, don't they?

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They are kind of on the surface.

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But what happens if something has the same density of water, Danielle?

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Student: They kind of mix together with the water.

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Teacher: They kind of mix together; we don't see any difference to it.

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There is nothing floating on top.

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There is nothing on the bottom of that, right?

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Okay. So, we are going to investigate the concept of thermal layering, and to understand that,

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you have to remember the information that we learned

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in our science experiment that dealt with density.

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Teacher: We want you to pretend that this is a lake here in Michigan,

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in the-we are going to pretend it's a lake in the summertime.

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How many of you have ever been swimming in a lake in Michigan?

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Alright, okay.

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What does it feel like when you first jump in the water, Cassidy?

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Student: Like, when you go further out into the lake,

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the water will get colder because it gets deeper.

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Teacher: The deeper the water is, the colder it is, right?

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So, where is your warmer water at in the lake?

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Student: Near the shore.

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Teacher: Near the shore, which is usually the upper layers, right, the top of the water.

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If warm water is less dense than hot water,

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if I add cold water to our lake, where is it going to be, Noah?

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Student: In the bottom.

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Teacher: It will be in the bottom, okay.

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Well, I want you to notice I have a container here, and I have blue food coloring in here,

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and this is going to symbolize the cold water that we are going to add to our Michigan lake.

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I am going to lay this into the lake and I want you to pay attention

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where this cold, blue water settles in the lake.

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Just watch this water for a minute.

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What do you notice that this cold water is doing in our lake?

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What do you notice that it's doing?

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What do you think, Joanna?

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Student: It's kind of clouding up.

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Teacher: It's clouding up.

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And where is it staying for the most part?

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Where is our bluest water, the most blue water?

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Where do you think it is?

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Luke?

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Student: At the bottom.

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Teacher: It's at the bottom of the lake, so our coldest water,

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the bluest water in our lake is staying down here at the bottom, isn't it?

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Okay, alright.

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Now, if I were to add hot water to our lake, where do you think it would be, Tori?

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Student: It would probably go, float up to the top.

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Teacher: Okay, very good.

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It would stay at the top or float to the top, now, wouldn't it?

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Now, let's think about this.

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When we have lakes here in Michigan, do we go around adding hot water to them?

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No. How do those upper layers get warm like that?

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What causes them to be warm like that, Avery?

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Student: The sun.

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Teacher: The sun.

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The sun is what is responsible for actually heating that upper layer, isn't it?

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Okay. So, let's take some hot water to our lake.

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We are going to cover it up and do something very similar to what I just did

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with our cold water, but I am going to wear gloves because this jar is very, very hot.

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So, I want you to watch this and I am going to do this as gently

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as I can, so I don't disrupt my layer.

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Now, you see, our bluest layer is still at the very bottom, right?

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Bluest water is at the bottom.

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Let's just gently lay this in here.

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Now, watch carefully what happens.

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Cassidy, what do you notice?

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Student: The red of the liquid is staying at top,

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so like the warmer water is covering up mostly,

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not like the bottom because the bottom is supposed to be more colder than the warm water.

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Teacher: Okay.

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Now, we are thinking about a summer lake in Michigan, okay.

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We are talking about a summer lake in Michigan.

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So let's picture a side cut of this lake.

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Okay. Here is our lake.

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And you talked about the three layers, is that right?

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Okay. Now, let's think about, our warmest layer is going to be up here.

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Fifteen degree Celsius is about what this middle layer will be here in the summer in a lake.

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Okay. So, anybody want to take a guess about what it might be here, because 15 is about,

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if it were three to one, maybe this would be about 45 degrees.

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We are not going to swim in the water that's 45 degrees.

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What do you think it might be, Noah?

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Student: 20 degrees.

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Teacher: Actually, you are really, really close.

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It would probably be about 25 degrees Celsius, okay?

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And then, this bottom layer down here would be about six degrees Celsius.

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And this is just on an average small lake here in Michigan, okay?

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Now, we have our warmest layer on top, our coldest layer on the bottom.

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Where in our summer lake are we going to find our most dense layer?

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Let's see, what can we come up with?

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Avery, what can you come up with?

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Student: It's going to be at the bottom.

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Teacher: It's going to be at the bottom,

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and this is going to be our coldest water or our warmest water?

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Student: Coldest.

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Teacher: Coldest water.

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So where is the least dense layer?

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What do you think, Sarah?

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Student: The top.

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Teacher: The top, very good.

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And is this our coldest layer or our warmest layer?

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Student: Our warmest.

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Teacher: Our warmest layer, so in a summer lake in Michigan,

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the warmest water is the least dense.

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[Music]