Investigating Water Molecules

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SWBAT describe how matter (in this case, water) is made of particles too small to be seen.

Big Idea

Students investigate water molecules by completing five investigative tasks. Using observations and models, students are able to describe how they know there are tiny particles in water.

Lesson Overview

Inquiry Based Instructional Model

To intertwine scientific knowledge and practices and to empower students to learn through exploration, it is essential for scientific inquiry to be embedded in science education. While there are many types of inquiry-based models, one model that I've grown to appreciate and use is called the FERA Learning Cycle, developed by the National Science Resources Center (NSRC):

1. Focus

2. Explore

3. Reflect

4. Apply

A framework for implementation can be found here

I absolutely love how the Center for Inquiry Science at the Institute for Systems Biology explains that this is "not a locked-step method" but "rather a cyclical process," meaning that some lessons may start off at the focus phase while others may begin at the explore phase. 

Finally, an amazing article found at, How Inquiry-Based Learning Works with STEM, very clearly outlines how inquiry based learning "paves the way for effective learning in science" and supports College and Career Readiness, particularly in the area of STEM career choices. 

Unit Explanation

In this unit, students will begin by exploring the properties of matter. Then, the class will investigate the mass of matter before and after physical and chemical changes by conducting investigations and constructing graphs. 

Summary of Lesson

Today, I open the lesson by asking students to discuss higher-level thinking questions. Students then explore water molecules by completing and observing five investigative tasks. At the end of the lesson, students write an evidence-based argument, using their observations to support the idea that water has particles (molecules) that are too small to be seen. 

Next Generation Science Standards  

This lesson will support the following NGSS Standard(s):

5-PS1-1. Develop a model to describe that matter is made of particles too small to be seen. 

5-PS1-3. Make observations and measurements to identify materials based on their properties. 

Scientific & Engineering Practices

For this lesson, students are engaged in Science & Engineering Practice:

Science & Engineering Practice 2: Developing and Using Models

Students utilize multiple models to describe the scientific understanding, "water is made of particles too small to be seen."

Crosscutting Concepts

To relate ideas across disciplinary content, during this lesson I focus on the following Crosscutting Concept

Crosscutting Concept 2: Cause and Effect 

Students examine cause and effect relationships as they complete investigative tasks. For example, if I add food coloring to still water, it mixes up. This shows that there are tiny particles moving around in water. 

Disciplinary Core Ideas

In addition, this lesson also aligns with the following Disciplinary Core Ideas

PS1.A:  Structure and Properties of Matter

Matter of any type can be subdivided into particles that are too small to see, but even then the matter still exists and can be detected by other means. A model showing that gases are made from matter particles that are too small § to see and are moving freely around in space can explain many observations, including the inflation and shape of a balloon and the effects of air on larger particles or objects. (5-PS1-1)

ELA Integration

To add depth to student understanding, when I can, I'll often integrate ELA standards with science lessons. Today, students will work on meeting CCSS.ELA-LITERACY.RI.5.7: Draw on information from multiple print or digital sources, demonstrating the ability to locate an answer to a question quickly or to solve a problem efficiently. In this lesson, students will be using multiple resources to locate key information involving an environmental issue. 

Choosing Science Teams

With science, it is often difficult to find a balance between providing students with as many hands-on experiences as possible, having plenty of science materials, and offering students a collaborative setting to solve problems. Any time groups have four or more students, the opportunities for individual students to speak and take part in the exploration process decreases. With groups of two, I often struggle to find enough science materials to go around. So this year, I chose to place students in teams of two or three! Picking science teams is always easy as I already have students placed in desk groups based upon behavior, abilities, and communication skills. Each desk group has about six kids, so I simply divide this larger group in half or thirds. 

Gathering Supplies & Assigning Roles

To encourage a smooth running classroom, I ask students to decide who is a 1, 2, or 3 in their groups of three students (without talking). In no time, each student has a number in the air. I'll then ask the "threes" to get certain supplies, "ones" to grab their computers, and "twos" to hand out papers (or whatever is needed for the lesson). This management strategy has proven to be effective when cleaning up and returning supplies as well!  


20 minutes

Matter Unit Lapbooks

To provide students with a method to keep track of their research and thinking during our unit on matter, I followed these steps to create lapbooks for each student. 

1. I folded each side of a file folder inward to create a booklet that opens from the center: File Folder.

2. Next, I made copies of Lapbook Templates on colored paper (purple, yellow, green, and orange). I made sure to have enough copies so that each student would have 4 graphs, 6 research notes, 8 investigations, 18 vocabulary words (9 sets of 2 words), and the 4 pictures.  I also copied the Other Research Pocket onto blue card stock paper so that students would have a place to put loose papers. 

3. Then, I stapled the templates into each lapbook: Inside the Lapbook.

4. Before starting our unit on matter, I asked students to help personalize their lapbooks. Students used a glue stick and tape to secure the blue research pockets on the back (Student Research Pocket Example). Then, they decorated the cover: 


Creating these lapbooks helps build excitement and student ownership!

Higher Level Questions

I want to inspire interest in today's lesson and capitalize on student curiosity, so I pose two higher level thinking questions for student teams to discuss. I ask students to use whiteboards and markers to keep track of their thinking.

Question 1: If you could be any type of matter, which type of matter would you be and why? Please use information from our poster to think of reasons why you would want to be a particular type of matter. 

After about 3-4 minutes, we discuss team decisions as a class. Student responses are very thoughtful and supported with evidence: 

  • "I wouldn't want to be a solid because solid molecules really can't move that much. If I was a liquid, I would be able to move way more freely."
  • "I would want to be a gas because gas molecules get to go wherever they want and I like to travel."
  • "I would not want to be a solid because if my friends were solids, we would have close bonds." 


Question 2: Again, please reflect upon your research and our class poster to answer this next question. What is most important about matter?  

Again, after about 3-4 minutes, students share their ideas. 

  • "The most important thing about matter is that everything on Earth is made of matter."
  • "We wouldn't be alive without matter. For example, the human body is made up matter. There's iron, potassium, hydrogen, and water in our body."
  • "Oxygen is matter and we need oxygen to live." 


Balloon Popping Video

To get students thinking about the presence of particles in matter that are too small to be seen, I show students the following video a couple of times. The first time, students simply observe what happens. After watching the video for a second time, I ask students to turn and share what they think is happening! 


Class Discussion

After a few minutes, we discuss the balloon popping video as a class. 

What are you observing here? 

  • "The water stays in a group." 
  • "The water is still the same shape of the balloon." 
  • "The water looks like a solid because the water stays together." 


Who can hypothesize why the water in the balloon stayed together? 

  • "Maybe because when the water was in the balloon, the balloon shaped it and when it was popped, the water just fell out." 
  • "The water held it's shape."
  • "The molecules got pushed together when they were in the balloon. Then when it popped, they're still kind of together."


Are water molecules attracted to each other? How is this evidence that water is made up of molecules?  

  • "The water molecules are attracted to each other until they hit the floor. Then they'll separate because of all the pressure. The atoms are attracted to each other, which means that they won't let go until something impacts them. 



40 minutes

For the exploration portion of today's lesson, students investigate the molecules in water by completing five investigation tasks. Then, students will use their observations to construct an argument supporting the idea that water has tiny particles (molecules) that are too small to be seen. 

Teacher Note: NGSS Standard 5-PS1-1 states, "Develop a model to describe that matter is made of particles too small to be seen." While this standard does not address cohesion (the sticking together of water molecules), adhesion (water molecules sticking to other substances), and diffusion (water molecules mixing due to their motion), understanding the behaviors of molecules helps students prove the actual presence of molecules. 

Creating Investigation Task Booklets

Prior to today's lesson, I created a Water Investigation Task Booklet for each science team by printing Water Tasks onto card stock paper and cutting the paper into thirds: Creating the Water Molecule Booklets

I also set out Beakers of Water and assembled investigation tubs for each team (Team Tubs) with the following Team Tub Items:

  • Stapled Booklet of Investigation Tasks
  • Paper towels
  • Food coloring
  • Pipettes
  • Magnifying glasses
  • Toothpicks 
  • Copies of the Water Maze placed in sheet protectors (students will use the blank back side as their "mat")


Introduction of Verdict

To provide a purpose for today's investigations, we discuss how a jury collects evidence to support a verdict.

I explain: Today, you're going to be the jury and what you are going to be deciding is if water has tiny particles (or molecules). Can you see them? (No) But can we observe models, like a water balloon popping, and determine if they are there or not, knowing that water molecules stick together? 

I refer to the Blue Pocket Chart and share: At the end of today's lesson, we are going to write a paragraph together and it's going to start off: We, the people of room 161, find water ______ of having tiny particles (molecules). Then we're going to list our evidence from our investigations. 

Investigation Format

Sometimes students rush through investigations. I want students to take their time. I also want to avoid having some groups finished while others are still investigating. For this reason, I explain that I will ring a bell when it's time for students to move on to the next investigative task. 

After explaining the contents of the tub and distributing supplies, students begin investigating. About every five minutes, I ring the bell, which is often followed with, "Ah, man!" as my students can't get enough of hands-on learning experiences such as these. 

Monitoring Student Understanding

Once students begin working, I conference with every group. My goal is to support students by asking guiding questions (listed below). I also want to encourage students to engage in Science & Engineering Practice 7: Engaging in Argument from Evidence

  1. What patterns have you noticed? 
  2. Why do you suppose ____? 
  3. Does this task help prove that water has particles that are too small to be seen? Why or why not? 
  4. What do you think is going to happen? 
  5. Can you explain what you think is happening? 
  6. Has your thinking changed? 
  7. What evidence do you have? 
  8. How did you decide _____?
  9. How do you know water is a liquid?
  10. What conclusion can you draw about ____?


Task 1: Take a Closer Look

1. Place a drop of water on your mat.
2. Look closely at the drop of water with a magnifying glass.
3. Discuss your observations: What do you notice?


Students Observations During Task 1:

  • I see little dots. Those must be the water molecules. (Another student: I think the dots are pockets of air.)
  • The drop of water moves when I blow on it. The water molecules are moving as a group. They are sticking together. 
  • When poked with a pencil, the drop didn't pop.
  • When I moved the drop, it didn't leave a wet trail on the mat.  


Task 2: One Droplet

1. Using your pipette (pie-pet), gently squeeze a drop of water out without letting the droplet fall.
2. Experiment with how far you can get the drop to hang without letting the droplet fall.
3. Discuss your observations: What is happening? Why do you think this is happening? 


Students Observations During Task 2:

  • It takes a long time for the drop to fall.
  • The molecules are trying to stick together. 
  • The molecules are sticking to the end of the pipette.
  • The water molecules in the drop are clinging onto the water molecules in the pipette.


Task 3: Separating Water
1. Make a big drop by placing 6 droplets altogether on your mat.
2. Move the big drop around on your mat using a toothpick.
3. Try to break the big drop of water into 6 smaller drops of water.
4. Discuss your observations: What is happening? Why do you think this is happening?  


Students Observations During Task 3:

  • The water molecules are attracted to each other and are sticking together.
  • This isn't easy. It's hard to separate a big drop into smaller drops.
  • If you use the side of the toothpick, it's easier. The water molecules are more attracted to the side of the toothpick instead the tip of the toothpick. 
  • I did it! I put the drops back together! 


Task 4: Water Drop Race
1. Dry your mat off and flip it over to the Maze.
2. Place a drop of water at “Enter.”
3. Race your partner! Drag the whole droplet through the maze.
4. The first to the “Exit” is the winner.


Students Observations During Task 4:

  • The smaller the drop, the easier it is to move.
  • There are lots of dead ends!



Task 5: Colored Water
1. Make sure the water in your beaker is still.
2. Add one drop of food coloring to the water. Do not stir.
3. Discuss: What is happening? Why do you think this is happening? 
4. Add up to 10 more drops of food coloring.
5. Continue discussing your observations.  


Students Observations During Task 5:

  • Yes! Food coloring! I call it! 
  • The food coloring is moving around.
  • All of the water is changing color.
  • The more food coloring you put in, the darker the water is. 
  • The whole container of water changes color because the water molecules move around and stirs itself. 


After completing all five tasks, we clean up and students are now ready to apply what they've learned! 

Reflect & Apply

30 minutes

Sharing Findings

Now that students have built meaning and understanding by observing, questioning, and exploring, it is important to provide students with the opportunity to share their findings. For this reason, I pass out a lined sheet of paper to each student. Then, referring to our Blue Pocket Chart, I ask students to write the following topic sentence at the top of their lined sheets of paper: We, the people of room 161, find water (guilty) of having tiny particles (molecules). 

Here's what we're going to do. As a class, we are now going to write a paragraph on our Blue Pocket Chart. Your paragraph doesn't have to look exactly like the class paragraph, but it can. So you can be inspired by other students' ideas or you can write your own. Using your observations, how do you know that water is guilty of having tiny particles? 

I reread the topic sentence and ask students: Who can tell me what that next sentence could be?A student offers, "I know this because the investigation we did proves it." I hand this student a marker and a sentence strip so that she can add it to our class paragraph in the blue pocket chart. 

Another student shares and writes the next sentence, "Because when there are two droplets of water close together, the droplets combined to make a bigger droplet, which means the molecules combined."

Through this sharing and writing process, multiple students in the class help write the Class Paragraph (Close Up Views: Part 1 of Paragraph & Part 2 of Paragraph). Here's the final result:


We, the people of room 161, find water (guilty) of having tiny particles (molecules).

I know this because the investigation we did proves it.

Because when there are two droplets of water close together, the droplets combined to ma a bigger droplet, which means the molecules combined.

The molecules in water are attracted to each other.


There was an investigation where we put a drop of food coloring in still water and it stirred up all by itself, which shows that molecules are moving around. 

In my research, I learned that molecules in liquid stick together, so when you move the water it sometimes stays together.

Another investigation is if you fill a water balloon with water and pop it, for a second, the water held it's shape. This is because the molecules were packed together in the balloon. When it popped, the molecules still sort-of stuck together.

Another experiment that we did is we put a drop of water at the beginning of a maze and drug it through with a toothpick. The hardest part was finding my way out of the maze. This shows that the water molecules are attracted to each other.

If you are not convinced that H2O is guilty, of having tiny particles, H2O is a compound molecule. The H2 in H2O means 2 hydrogen and the O means 1 oxygen, which is the "tiny particles" called molecules.

This just goes to show that water is guilty of having molecules. 

Student Paragraphs

Here are a few examples of student verdicts: 


Teacher Note: This was definitely a higher level lesson for 5th grade students! Had we only used one model (such as separating a drop of water), the idea that water is composed of tiny particles (that are attracted to each other), would not have been as clear. However, by using multiple models, this complex scientific concept made more sense to students. In fact, I was impressed with how well students were able to grasp this concept!