Examining the Properties of Dry Ice

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Objective

SWBAT research and observe the properties of dry ice.

Big Idea

In this high-interest lesson, students will learn about the properties of dry ice through research and investigations.

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 Edudemic.com, 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 discussing the properties of dry ice. Students then explore the properties of dry ice by conducting an investigation. At the end of the lesson, students reflect and apply their new understanding of dry ice properties by writing a conclusion to today's investigation. 

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.  (lessons 3 & 4)

5-PS1-3. Make observations and measurements to identify materials based on their properties.  (lessons 1 & 2)

Scientific & Engineering Practices

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

Science & Engineering Practice 1: Asking Questions and Defining Problems - Student ask questions and explain cause & effect relationships.

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 the cause and effect relationships when placing dry ice 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)

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!  

Focus

15 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!

Dry Ice Poster 

Prior to the lesson, I set up a dry ice teacher demonstration station at least 8 feet away from student desks, Dry Ice Materials:

  • dry ice in a brown bag, inside a closed container to keep it from disappearing too quickly 
  • two plastic tubs inside aluminum pans
  • pair of gloves
  • a cup of dish soap 
  • a ladle for handling the dry ice
  • a bottle of green food coloring 
  • a piece of yarn (about 1.5 ft long)

Students can hardly wait to see what's in the brown paper bag! When I announce that we will be observing the properties of dry ice today, loud cheers fill the room! 

I pass out a half sheet of paper to each student so that students can create their own Dry Ice Poster (Student Dry Ice Notes) while I create a class poster on the front board (Teacher Dry Ice Poster). I find that students learn more when posters are constructed in front of them instead of explaining a poster that was created by the teacher before the lesson. 

I write "Dry Ice" in a circle at the center of the poster. Turn and talk: What is dry ice? I love listening to student responses, "Dry ice is frozen liquid nitrogen," and "Dry ice is the dry form of frozen water." 

We discuss responses as a class. Then, I write on the teacher poster and explain: Dry ice is frozen carbon dioxide. Can anyone tell me what carbon dioxide is? (CO2 is a gas that humans exhale. Also, plants need CO2 for photosynthesis.) 

Again, adding on to the poster, I explain: Here's what's really special about dry ice.... one of physical properties is that it is very, very cold. In fact, it is -109.3 degrees Fahrenheit. Water freezes at 32 degrees Fahrenheit! Students point out that dry ice is over three times colder than frozen water. 

Referring to the States of Matter Poster from the lesson, States of Matter Part 1, I continue: Do you remember how ice, or solid water, turns into a gas? It melts into water. Then it evaporates and changes into water vapor (which is water in the form of gas). In order to change from a solid to a gas, ice must change to a liquid first. For example, if you put ice in a pan on the stove, it melts into water, and then it turns into a vapor.

Well, another property of dry ice is that when it is exposed to heat, it changes from a solid into a gas. It skips changing into a liquid. This is called sublimation, when a substance can directly change from a solid to a gas!  

Now that you understand some of the properties of dry ice, turn and talk... why would you use dry ice to send a package in the mail? Here's the conversation that resulted: Why Use Dry Ice? Following this class discussion, we completed the dry ice poster by adding "Often times dry ice is used to keep packages cold in the mail.  This is because it avoids the liquid mess left when you use regular ice." 

Explore

30 minutes

Investigative Question

At this point, I ask students to use what they know about dry ice to think of questions they would like to investigate. I am really impressed with some of their questions: Developing an Investigative Question. At the end of this discussion, I guide to the question that we will be investigating today, "Why does dry ice create fog (condensed water)?" Students write this question on a new investigation template page in their lapbooks: Investigation Question & Observations Before.

Revisiting Condensation

We review the process of condensation before continuing. I use two models to help students remember this challenging concept. Model #1: Liquid droplets forming on the outside of a cold glass: As the water vapor in the air next to the glass is cooled, causing the water vapor to condense and form droplets. Model #2: Cloud & fog formation: As water vapor cools, water droplets form in the air, producing clouds or fog.

Observations Before 

Slipping on the gloves, I hold up a piece of dry ice in the ladle and I show students a tub of hot water. What are you observing before we place the dry ice in the hot water? Students agree that the sides of the tub are fogging up and condensation is gathering on the inside walls of the tub. They also point out that frost is collecting on the ladle. (Due to the coldness of the dry ice the condensation immediately freezes.) Students take notes on their investigations template: Investigation Question & Observations Before.

 

Reflect & Apply

30 minutes

Observations After 

Now, for the big moment! I drop the dry ice in the tub and hold it up for students to begin making observations. This is the conversation that follows: Bubbling Discussion. (Teacher Note: When watching this video, I noticed that I said, The dry ice is melting. What I should have said is: The dry ice is sublimating (turning from a solid into a gas). To prove this, we could have also observed that the water level did not rise before and after.)

Student observations include, "There are carbon dioxide bubbles," "Fog is spilling out of the tub," "I can hear the bubbling," "The dry ice is disappearing." Here's a student example of the Observations After & Conclusion.

Conclusion

Following our class discussion of observations, students moved on to the conclusion. For example, one student wrote, "Dry ice creates fog because the cold carbon dioxide bubbles come up and make the air cold which causes water vapor to condense and turn into fog." 

Teacher Note: Some students thought that the liquid water turned into fog. (In order for this to happen, the water would have to heat up and evaporate.) It's the water vapor in the air condensing because the bubbles of carbon dioxide are so cold. 

Fun Extension Part 1

I hold up a bottle of green food coloring and ask students: What questions do you have now? One student asks, "What will happen if we add food coloring to the tub?" Another student wonders, "Will the bubbles turn green?" A final student wants to know if the fog will be green too. 

After Adding Green Dye, I hold up the bubbling container so students can have a closer look. The class is surprised that the fog isn't green! 

Eventually, the dry ice disappears and the bubbling stops. Of course, students want to know if I have more dry ice and if we can "do it again!"

Fun Extension Part 2

We have one more piece of dry ice. This time, we are going to place the dry ice in the tub. Then, I'm going to soak a piece of yarn in dish soap. I drag the piece of yarn across the top of the tub, making sure to leave soap on all the edges. (I also placed the tub in a deep aluminum pan.) 

Here's what happened: Soap Bubbles. I ask the students to turn and talk: What's inside the soap bubbles? (carbon dioxide gas and condensed water vapor - fog)

Student Work

Here are a couple examples of student work from today's investigation: