Lesson Plan

Sinking and Floating Water

Density of water

Students will be able to make a claim about how water's temperature affects its' density using accurate diagrams.

NEXT GENERATION SCIENCE STANDARDS*: (PS1.A) Matter can be described and classified by its observable properties.


1. Research and information fluency - students apply digital tools to gather, evaluate, and use information. 

2. Creativity and innovation - students demonstrate creative thinking, construct knowledge, and develop innovative products and processes using technology. 

3. Critical thinking, problem solving, and decision making - students use critical thinking skills to plan and conduct research, manage research, solve problems, and make informed decisions using appropriate digital tools and resources. 


*"Structure and Properties of Matter." Next Generation Science Standards. National Academy of Sciences, n.d. Web. 13 Nov. 2015.

**"ISTE Standards for Students." Standards for Students. International Society for Technology Education, 2007. Web. 13 Nov. 2015.

Grades 3
All Notes
Teacher Notes
Student Notes


Activity: Presenting

"Welcome to a new day of science! I am excited to continue learning about the different properties of water. So far we have learned about how water either beads up or is absorbed, how water has surface tension, and how the temperature of water affects whether it expands or contracts. Today we are going to explore more about how the temperature of water affects one of its properties; Density. First, we need to figure out what density is." 


Activity: Exploring


There are two pieces  of cakes displayed on the doc camera.  One of these cakes is denser than the other. Can anyone guess which one?

TECH TOOL: Use your QR code sheets to hold up A for cake A and B for cake B. I am going to hold up my phone and scan every ones answers. They will appear on the screen! 

The denser an object is, the closer the parts of that object are. In this cake example, this angel food cake is very light and fluffy. The inside of the cake is spread out, not packed together. The pound cake, on the other hand, is very dense. It is heavy and the inside of the cake is packed together. Not just cake is dense though! Every single thing on earth has some level of density.

3 min.

Can everyone stand up for me? We are going to do a movement that will help us remember what more dense means.

[Demonstrate crouching down and making a tight ball with arms and legs]

Right now, we are more dense because our parts are closer together!

Now if an objects is less dense, its’ parts are farther away from each other. Can everyone make a star with their body?

[Demonstrate making a star]

Now, we are less dense because our parts are farther away from each other!

[Have the students do TPR with those movements with their entire body a few more times.]

2 min.

Let’s record these definitions in our glossary! Feel free to draw a picture if that helps you remember the words.


6 min.

I have another example that will help us learn more about density. I want to know if an objects density, or how close or far apart an objects parts are, will affect whether or not it sinks or floats. I have 4 objects, a cork, a penny, a stopper, and a bead.. The penny and the rubber stopper are denser than the cork and bead. You can see the parts of the cork, even see where there is just air. The penny, on the other hand, is completely solid.  

[Display objects with labels on doc camera-cork, bead, penny, stopper]

Do you think the density of each of these objects will determine whether or not it sinks or floats in this water? Scout and Chloe are passing out a handout that asks that question.

[Read handout aloud to class/show on doc camera]

“Will an objects’ density affect whether it sinks or floats?

Yes, I think an objects’ density will affect whether it sinks or floats.

No, I don’t think an objects’ density will affect whether it sinks or floats.

I think this because…”


TECH TOOL: I just want to get a quick read on what you have predicted, so when I call out an object use your QR codes again to answer. If you think this object will float, hold up the A side. If you think the object will sink, hold up the B side. 

[Scan room for answers]

Let’s see what happens!

[Test each object under the doc cam]

This demonstration is showing an example of density. Remember how I said that every single thing has some level of density? Water has density too! So, if an object floats in water, the object is less dense than water; if an object sinks in water, the object is denser than water.

Let’s explore this idea more. The wooden bead and the cork floated. So, are these objects less dense or denser than water? Turn and talk with your table. Thumbs up when you have come to a conclusion.

[Call on a few tables to make sure they understand]


The stopper and the penny sunk in the water. Are these objects less dense or denser than water? Turn and talk with your table, thumbs up again when you have come to a conclusion.

[Call on the rest of the tables to make sure they understand]

Today we are going to be experimenting with water to answer the following question: Does the density of water change when its’ temperature changes?  

First, we are going to see if hot water has a different density then room temperature water. After that, we are going to see if ice water has a different density then room temperature water.


Activity: Investigating

These are the materials that we are going to be using today during our experiment. Each pair of scientists (your partner is the scientist sitting next to you) will have a cup full of room-temperature water. You will also have a small vial full of hot water that you will lower into the cup of room-temp water, then pin to the side with a clothes pin. Scout and Chloe are going to pass out the cup and the vial with no hot water, I want each partner to practice lower the vial into the room-temp water.

[Give each partner within the pair number 1 and 2; Scientist 1 will lower the vial today, Scientist 2 will on Wednesday]

 The key to this experiment is to lower the vial in slowly and steadily. It also needs to remain straight up and down the entire time.

[Demonstrate to the class how to do it]

You have the next 2 minutes to take turns lowering the vial into the cup. Scout, Chloe and I are going to walk around and see how you are doing.


Awesome job scientists! Thumbs up if you feel confident to start the experiment? Today, Scientist 1 is going to lower the vial. Wednesday, when we continue our experiment, Scientist 2 will get to lower the vial.


Here are the worksheets to record your observations on. I would like for each of you to draw a picture of what you observe, and label each thing you draw. After this experiment, we will share our diagrams and talk about what makes a good scientific diagram.


We are going to come around and fill your vials with hot red water. Remember; lower the vial steadily and straight up and down. Scientist 2 should be recording what they see while Scientist 1 is lowering the vial. Don’t forget to clip your vial to the side of the cup. Remember, we are doing this to answer the question, “Will the temperature of water change its density?” So, if the hot water is denser than the room temp water, it will act like the penny! If it is less dense than room temp water, it will act like the cork!


[Let students work for a good 10 minutes observing and drawing their diagram.]


Ok, eyes on me in 5, 4, 3, 2, 1. Awesome, thank you! Let’s move down to the carpet for the next part.

Now that we have completed the first experiment, let’s discuss our findings. What happened to the hot water in the vials?

[Call on a few students, write answers on the board]

Now, taking what we learned earlier in the day, why do you think the hot water floated to the surface?

[Call on few more students, write on the board]

How many pairs found the same thing? Interesting…well tomorrow we are going to investigate further with cold water. Before I let you go to recess I need to see your diagram work sheet glued into your science notebooks! That is your ticket to leave. –

Thanks for your hard work today, I will see you Wednesday!

 End of Day 1


Day 2

Happy Wednesday! Who can remember the word we learned on Monday?

[Call on student]

That’s right, density! Ok, let’s review the movements we did… everybody stand up! Ok, show me...more dense!

Show me less dense!

Now let’s do it Slo-Mo! Mooorrreeee dense…Leeeessssss dense…

Great work! Since we are standing up, go ahead and grab your science notebooks and meet me on the carpet.

Who can give me an example of a very dense object?

What about a less dense object?

Those are great examples! I am also thinking of a pinecone, which isn’t very dense, and a pebble, which is very dense!

[Transition time to carpet approx. 2 min]

On Monday we looked at what happens to hot water when it is placed in room temperature water. Let’s review what we observed!

What happened when you lowered the vial of hot water into the room temperature water? Why did that happen?



Each of you drew a diagram to show what you observed happening to the water.

I noticed that [Student x] had a really great diagram and I asked them to share it with the class.

[Have that student come up and explain their diagram.]

Student x, I love how you used the red pencil to show the different temperatures of the water. Also, the labels you used are wonderful! Every part of this diagram has a name.

Scientists use diagrams to communicate the information they have learned. Scientists use color, details, and labels to communicate clearly. Diagrams are great because they are giving the same amount of information as a paragraph, but you get to have a visual and see how the experiment worked.

When I say Go, take the next 6 minutes, move back to your desks, and make any changes to your diagram so it has color and labels and clearly states the information you gathered from your experiment. Ready and Go!

Ok, excellent work, I love the changes you have made to your diagrams!


We are now going to do the second part of our experiment where we answer the question; will ice water change the density of water? Monday we saw that hot water floated to the surface because it was less dense than room temp water. I wonder what will happen with the ice water…


This experiment is just like Mondays, except this time Scientist 2 is going to be the person lowering the vial into the water! Do you remember how to do it? What are some tips?

[Remind students to lower straight and slowly]

Now that we have gone over the way scientists draw diagrams, keep that in mind while you are drawing this diagram!

[Students begin experiment part 2]



Formative assessment questions:

What is happening to the ice water? Whoa, why do you think that is happening?


Is this the same thing that happened to the hot water? How is it different?


Activity: Conversing

Alright, we have completed part 2! Let’s return to the carpet to discuss our findings! What happened to the cold water in the vials?

[Call on students]

Why do you think it stayed in the vial?

[Call on other students/write on board answers that make sense and fit with learning target]



Thinking back to the initial floating and sinking demonstration that I showed you, talk to the person next to you about these questions.

Which water was more dense than room-temperature water?

Which water was less dense than room-temp water?

Ok, so think about this question, which is denser, hot water or cold water? How do you know this?

[Class conversation]


Activity: Assessing

Synthesis: Water has many different properties, and today and Monday we learned about yet another one. Can anyone make a claim about water and density? Use your glossary words and the notes that we have recorded to form your sentence.

Connections: How do our diagrams help us come up with a claim? What do these diagrams tell us?


Reflection: Keeping everything we have talked about in mind, let’s return to the question you had on your What I know about Water worksheet a few weeks ago…Scout and Chloe are going to pass out the worksheets while I read this aloud.


Fox and Beaver are swimming in Lake Whatcom and notice the temperature on the surface is different from the bottom of the lake. Is the surface hotter or cooler than the bottom? How do you know? Draw a diagram to answer.


Superb work today Scientists! I will collect your worksheets when you are finished.


End of Day 2


Activity: Other — Listening


Time to split up into stations! We are going to work with a few different apps that will give us some more insight into density. 

[Number off the kids so there are three groups]

Station 1: Scientists, you will be working with the apps Video Science and Paper. Look at the TASK CARD that is at your station. 

Station 2: Scientists, you will be using the Camera app on the iPad and the app Skitch to add comments to your pictures. Follow the instructions on the TASK CARD that is at your station. 

Station 3: Scientists, you will be using the app Word Clouds by ABCya and the app Explain Everything. Follow the instructions on the TASK CARD that is at your station.