Lesson 1: What happens when a bath bomb is added to water (and what causes it to happen)?

Lesson 1 • Learning Plan Snapshot

Lesson 1 • Materials List

Materials preparation (120, plus 60+ (drying time) minutes)

Review teacher guide, slides, and teacher references or keys (if applicable).

Make copies of handouts and ensure sufficient copies of student references, readings, and procedures are available.

Gather chart paper, notecards, tape, and markers.

Download Communicating in Scientific Ways from the website and post in your classroom and/or add to students’ notebooks. It can be used as a poster or a handout.

Determine where to set up the Driving Question Board so that students can gather around it.

Print out this copy of all the Driving Question Board questions for all your classes, 1 per group of 2 students.

Trim all handouts to fit in science notebooks.

Prepare two pieces of poster paper for each class for the initial consensus models that you will co-construct. One poster is of the macroscopic view (the side view of the cups) and the other poster is of the microscopic view (with the five circles). You will create the two consensus models for each class. Note that the corresponding colors in both posters match the same parts of the system.

On day 2, for the Initial Consensus model: The colors chosen for the example poster included in the teacher guide for this class model were intentional in order to support students who are color blind to be able to differentiate between the different particles. Since we are working together to figure out what is happening at the particle level and what is different between the particles, it is important that all students can tell the difference between the different particles.

After your last class on day 3: Merge all the questions together on your Driving Question Board into categories that emerge across all your classes. After (or as) you do that reorganization of the board after this lesson, make a record of all the questions that are on the board so that you can print them out for students to reference in groups of three during class the next day. One way to do this is to take a high resolution photo of the board, and another way is to transcribe the questions on the board.

Day 1: Store-bought bath bomb investigation

• Group size: Whole class
• Setup

• For each class, place a clear bowl or container with fresh water in the middle of the Scientists Circle.
• Have 4 store-bought bath bombs to pass around (reused between classes).
• Have 1 additional bath bomb ready to be used up per class. (The most total bath bombs you will need are 4 + the number of class sections)
• Set up this equipment off to the side (in case it is requested): digital scale, digital thermometer

• Safety: Consider using an unscented bath bomb if any students have a scent sensitivity.
•  Disposal: All materials can be washed down the drain with cold or warm water.
• Storage: Store unused bath bombs in sealed or closed containers.

Day 1: Homemade bath bomb investigation

• Group size: Arrange students into 6 groups of 3–5 students
• Setup

• Make each of the recipes (A, B, C, and D) for the homemade bath bombs one day prior to this investigation. Watch https://youtu.be/q2UMxYmiUuI for instructions on how to make one of the bath bomb recipes. In addition, see Recipes for Homemade Bath Bombs for complete instructions for preparing these. Each recipe will just fill a mini ice cube tray. This will produce 160 bath bombs from each recipe, for a total of 640 bath bombs. For the investigations in this lesson, you will need enough for one bath bomb per student. The extras that you have left over after Lesson 1, can be stored in ziplock baggies or a sealed container for use in later lessons.
• Make four batches of recipe B. Save three batches for Lessons 2 and 5.
• Make sure students have access to the following items placed in a common area for this investigation:

• trays or paper plates with different bath bomb samples on them
• water
• 1 splash goggle per student
• paper towels

• Make sure you have supplies available so that every student gets at least one of the following:

• clear plastic cups (wash and reuse between classes)
• disposable pipettes (can be washed and reused between classes)
• toothpicks
• paper plates

• Set up this equipment off to the side, one per group, in case groups request them:

• digital scale and digital thermometer

• Safety: There are no safety concerns.
• Disposal: All materials can be washed down the drain with cold or warm water.
• Storage: Store unused bath bombs in sealed or closed containers.

Lesson 1 • Where We Are Going and NOT Going

Where We Are Going

This lesson is meant to draw out students’ prior experiences where they have seen solids dissolving in water (relatively common), and more specifically, where that coincides with the appearance of gas bubbles, which is less common (e.g., Alka Seltzer, dental retainer cleaning tablets). Competing explanations will come up for what happened to the solid and why the gas appeared. We hope to foreground all of these competing explanations in this lesson to provide motivation for ideas to pursue that are largely parallel to the ones that are part of what is planned for lessons in the first learning set of the unit.

Competing explanations include:

1. What happened to the solid: Some students will likely claim that the solid melted. Other students will claim the solid is dissolved. Assuming that students have developed the 5th grade DCIs related to both melting and dissolving, students should know that mass is conserved in both processes, and that particles of solids can break apart in both cases. They should also know that you have to warm something up (increase its temperature) to get it to melt (change from a solid to liquid). Therefore, you can leverage this line of reasoning to help students argue that we could determine if the solid melted or dissolved in the water by simply tracking the temperature of the stuff in the system before and after we mix them together. That argument can help motivate taking the measurement of temperature of everything in the system, either in Lesson 2 or in Lesson 4, if that didn’t already emerge in Lesson 1. The corresponding slight temperature drop that occurs after adding the solid bath bomb to the water should help provide evidence that nothing is melting in the system.
2. Where the gas came from: Students will identify the bubbles as an interesting aspect of the phenomenon, but don’t initially tend to think of those as being filled with gas. It is anticipated that a small amount of additional facilitation and questioning will be needed to help them make that connection (see the learning plan). One possible source students will suggest from their initial models is that those types of particles were there to start with (e.g., they were inside pockets/cavities within the solid bath bomb before it touched the water and were released when it dissolved). A second possible source other students will suggest is that those types of particles formed when the bath bomb (inter)acted with the water, but were not there to start with, and that some of the substances in the system reacted to form something new. This is an idea that the class will develop, and they will uncover additional evidence over the course of this unit after they eliminate other possibilities. A third possible source that students may raise (but is less commonly suggested) is that the gas is the result of the boiling of a substance that was in the system (the bath bomb in the water). There is no need to resolve whether this is happening until Lesson 5, even if your class has the temperature change data (from this lesson or Lesson 2) to refute this explanation. Boiling is a relatively new phenomenon that is not connected to any DCIs students will have developed around particulate models of matter in 5th grade. Understanding that boiling point is a property of a substance is a middle school DCI. In Lesson 5 of this unit, students will narrow in on potential candidates for the type of substances that the gas in the bubbles could be using. Property data will lead them to determine that it is not the result of any of the original substances boiling.

Students should be ready to make connections to what they figured out about the particulate nature of gases from their work in the OpenSciEd Unit 6.2: How can containers keep stuff from warming up or cooling down? (Cup Design Unit)and OpenSciEd Unit 6.3: Why does a lot of hail, rain, or snow fall at some times and not others? (Storms Unit). We want to use this initial consensus modeling activity to establish what students know about gases (that they are made of particles with lots of space between them). From this, we also want to further elicit what students should know about solids and liquids (particularly water) from a particle perspective. This will help build on what they figured out in the Cup Design Unit and Storms Unit. In particular, we want to help them recall that in those prior units, they figured out that solids and liquids are made of particles closely packed together. We also want to help them recall the idea that it can be helpful to represent different types of substances (e.g., water vs. plastic vs. other gases in the air) by representing them with different types of particles (e.g., different shapes or colors). This is something they did in the Cup Design Unit. We want to help them recall that we can keep track of the same substances (e.g., liquid water and water vapor) by representing the same type of particles (which we often call molecules, as in the case of water) as we did in the Storms Unit. Students should be reminded that these are important connections when developing the consensus model. All of this will culminate in helping students articulate two possible sources for the particles that make up the gas in the bubbles.

Where We Are NOT Going

It is not important in this unit that students understand whether dissolving is a physical change or a chemical reaction. It is not important that they figure out what happens to the particles that make up the solid bath bomb as the solid dissolves, beyond the idea that the solid is breaking into little pieces too small to see. It is, however, productive to represent dissolving in the consensus models as “breaking into pieces of matter too small to see and mixing into the water.” Do not try to label those as a specific kind of particle.

In the later part of the unit, students will figure out that the substances that made up the bath bombs were made of smaller particles that are atoms. If that idea is introduced by some students, you can, of course, record it, but don’t offer any more feedback regarding this possibility versus other ideas that are raised. Do not introduce the idea of atoms making up matter in this lesson, as this is the idea that is new in the middle school grade band. This unit is where that idea is developed for the first time in OpenSciEd, and later lessons will support students in constructing propositions for the idea of atoms making up substances according to the line of evidence they accumulate up to that point in the unit. In addition, though students will be modeling what happens when substances go through a chemical reaction (that the molecules break apart and the atoms rearrange to form a new molecule), the mechanisms underlying how this happens with bonds between atoms breaking apart and the different parts of the atom are above grade band.

Lesson 2: Where is the gas coming from?

Lesson 2 • Learning Plan Snapshot

Lesson 2 • Materials List

Materials preparation (30 minutes)

Review teacher guide, slides, and teacher references or keys (if applicable).

Make copies of handouts and ensure sufficient copies of student references, readings, and procedures are available.

Each pair of students will need one mini bath bomb cube or a broken piece of a bath bomb to observe closely in part 2 of this lesson. Any recipe (or a variety of them) will work for this exploration, and it is a good opportunity to use pieces of bath bombs that may have started to crumble already.

Note: To complete the labs in this lesson, each class will need 56 total bath bombs from Recipe B. (If you did not already prepare these when making others for Lesson 1, see the directions in Recipes for Homemade Bath Bombs to make them now. They will need several hours to dry before use.)

To save time during the lesson, you may choose to premake the poster “Arguing for (or Against) a Claim” to support the discussion for “Scaffold an argument about where the gas comes from” (Step 8).

Day 1: Crushing Bath Bombs

• Group size: Whole class
• Setup: You will need 8 mini bath bomb cubes from Recipe B (see the directions in Recipes for Homemade Bath Bombs). If you have some available, students may also want to test a sample of the store-bought bath bombs.
• Notes for during the lab: Use a book or other heavy flat object to crush the bath bombs inside the bag, being careful not to puncture the bag.
• Safety: There are no safety concerns.
• Disposal: All materials may be safely disposed of in the wastebasket.
• Storage: Store bath bombs in a sealed container or bag.

Day 1: Investigating Gas from Bath Bombs in a Bottle

• An example video of this lab is available at https://youtu.be/pOHajna6OR4 for your reference.
• Group size: Form 6 groups of 3 to 5 students each
• Setup: Each group will need 8 mini bath bomb cubes from Recipe B, so for 6 groups you will need 48 total. If you need to make additional mini bath bombs, the recipes and directions are in Recipes for Homemade Bath Bombs. Also, gather an empty 16.9 or 20 ounce soda or pop bottle with a screw-top lid for each group.
• Notes for during the lab: Groups will need access to water. It is recommended that students rinse their bottles after the lab for reuse in future classes.
• Safety: There are no safety concerns.
• Disposal: All products may be safely poured down the drain with water. Solids may be disposed of in the wastebasket.
• Storage: Store bath bombs in a sealed container or bag.

Lesson 2 • Where We Are Going and NOT Going

Where We Are Going

In the previous lesson, students came up with many questions about the phenomenon of gas bubbles appearing when a bath bomb is placed in water. Students will naturally wonder where the gas bubbles came from. Two competing initial explanations came out of the previous lesson for this phenomenon. One was that the gas was already in the solid bath bomb to start with. The other was that the gas is the result of some sort of matter transformation (e.g., reaction) of the stuff that was there to start with. Generating evidence to support or refute the first candidate explanation is the focus of Lesson 2.

In this lesson, the class begins recording key model ideas on a poster. Students should know from previous work in OpenSciEd Unit 6.2: How can containers keep stuff from warming up or cooling down? (Cup Design Unit) and OpenSciEd Unit 6.3: Why does a lot of hail, rain, or snow fall at some times and not others? (Storms Unit) and in learning connected with PS1.A DCIs from grade 5 that:

• Gases, liquids, and solids are all matter.
• Matter has mass and takes up space.
• All matter is made of particles.

This connection to prior knowledge is intentional so we can help students build a foundation on those key model ideas about particles, matter, and mass conservation at the beginning of this unit. Then, as the unit progresses, we can help students extend that thinking to develop evidence for a different kind of particle (the atom), which is a fundamental building block of larger particles (molecules) that make up matter. This reuse and extension of ideas is a key feature of developing a coherent learning progression for students over multiple years in NGSS.

Students will figure out that there is a new substance in the system; this substance is a gas and must come from some sort of matter transformation from some of the materials they started with. They also discover that the gas is not trapped in the bath bomb. By taking mass measurements in a closed system, students figure out that the gas comes from the substances in the system. Therefore, the matter loss that happens when the gas is released from an airtight container shows that the matter in the gas was all part of the matter that was there to start with.

Where We Are NOT Going

Although the previous lesson elicited student ideas about the particulate nature of gases, that is not the focus of this lesson. That understanding will be revisited and refined further in later lessons.

In the second investigation you are using a rigid airtight container to mass the system, rather than a baggie to ensure that the overall volume of the system doesn’t change measurably when the bathbomb mixes with the water. This volume change happens when using a baggy, and this would add a confounding variable when weighing the baggy, as it leads to an additional amount of upward buoyancy force on the system. This reduces the overall weight registered on the scale. Such a result would take time to reason out, and would not be a productive avenue of investigation at this point in the unit. This is why additional guidance is provided in the lesson to motivate using a rigid airtight container for recording the mass of the system.

Lesson 3: What’s in a bath bomb that is producing the gas?

Lesson 3 • Learning Plan Snapshot

Lesson 3 • Materials List

Materials preparation ( minutes)

Review teacher guide, slides, and teacher references or keys (if applicable).

Make copies of handouts and ensure sufficient copies of student references, readings, and procedures are available.

•  Cut an 8.5” x 11” piece of paper in half for words on the Word Wall.
• The words and definitions are:

• property--a characteristic of a substance that doesn’t change
• substance--made of one type of material throughout
• dissolve--when a solid dissolves in a liquid, the solid breaks apart into particles too small to see and it mixes completely in the liquid
• soluble--describes a material that can dissolve in a particular substance
• insoluble--describes a material that does not dissolve in something else
• mixture--a blend of two or more substances

• Also make a “Word Wall” sign.
• Your completed Word Wall at the end of this lesson will look something like the image to the right.

Day 1: Ingredients in Bath Bombs

• Groups: Form 10 groups of 2-3 students each
• Setup

• For each of your 10 groups, 10 small cups will be needed. Label each cup with one ingredient and its corresponding letter from the list below. You will save these cups for use in Lesson 4, as well. The following list of ingredients is common to many bath bombs. Ingredients that are not used or contaminated in this lesson will be saved and reused for lesson 4.

• A. coconut oil
• B. olive oil
• C. baking soda
• D. Epsom salts
• E. table salt
• F. sugar-free lemonade mix
• G. citric acid
• H. sugar-based lemonade mix
• I. sugar
• J. corn starch

• Place approximately 1 teaspoon of each of these ingredients into the small cups. Place a set in a small bin, and make 10 sets for easy transport.
• Each group of 3 students should have a complete set. Decide if you want to make a set per class or have students share a set with the next class. You have enough supplies for doing either.
• After this lab, keep these labeled cups and the ingredients for the next lab (Lesson 4). Replenish as necessary.

• Notes for during the lab: Monitor the groups and encourage them to avoid cross-contamination. If this happens, discard the cup and its contents into the trash.
• Safety: No safety concerns.
• Disposal: Any mixed or contaminated ingredients can be disposed of in the trash. Collect the uncontaminated ingredients and save the labeled cups to use Lesson 4.
• Storage: Store ingredients in their corresponding cups until Lesson 4.

Day 2: Investigating the Ingredients Mixed in Water

• Group size: Your class should work in groups of 2.
• Setup

• Rearrange the cups from the previous day so that pairs of students get two different ingredients. There is a pairing in the lesson that is suggested so that students do not get two ingredients that will make bubbles when mixed with water if accidentally combined. We don’t want that to happen until Lesson 4.
• Students will need two larger clear cups and access to water.
• Notes for during the lab: Have paper towels available for accidental spills.

• Safety: There are no safety concerns.
• Disposal: All materials can be disposed in the trash or washed down the drain with cold water. Rinse the larger clear cups to use in the next class.
• Storage: Store ingredients separately in sealed or closed containers.

Lesson 3 • Where We Are Going and NOT Going

Where We Are Going

In this lesson students begin to explore what is in the bath bomb that could be creating the gas by examining the ingredients individually both before and after adding to water. Students will test substances for their properties and will examine data that list one of its properties (melting point). Students will acquire scientific vocabulary such as solubility, viscosity, etc., to describe characteristic properties of substances that can be used to identify them. They find that individually adding the substances to water does not produce a gas, which motivates them to combine ingredients in the next lesson.

Where We Are NOT Going

Students will not measure the boiling point or melting point of substances. They also will not measure or calculate density at this time. In this unit we will not be exploring pressures’ relationship to boiling of a substance. We will assume boiling points are constant.

Lesson 4: Which combinations of the substances in a bath bomb produce a gas?

Lesson 4 • Learning Plan Snapshot

Lesson 4 • Materials List

Materials preparation (35 minutes)

Review teacher guide, slides, and teacher references or keys (if applicable).

Make copies of handouts and ensure sufficient copies of student references, readings, and procedures are available.

Trim handouts to fit science notebooks.

An optional material to copy for students is Lemonade Mix Labels, which shows the ingredient lists for both lemonade mixes. These lists are also displayed on slide N, but you may choose to provide this copy to your students and reuse it across classes.

Day 2: Combinations of Ingredients lab

• Group size: form 10 groups of 2–3 students each
• Setup:

• A video of the setup for this lab is available at https://youtu.be/ByhU5pzoZ4s .
• Make a solution of each of the following substances by stirring 2 T of each ingredient into 250 mL of water. If you were able to collect uncontaminated leftovers of these ingredients after Lesson 3, use those to make these solutions. Ingredients are labeled here by the letter of the cup in which they’ll be distributed.

• C. baking soda
• D. Epsom salts
• E. table salt
• F. sugar-free lemonade mix
• G. citric acid
• H. sugar-based lemonade mix
• I. sugar
• J. corn starch
• (Ingredients A and B are coconut and olive oils; they are not mixed into solution.)

• Obtain 9 sets of 10 small (3 oz) plastic cups, for a total of 90 cups, and label each set A through J. You should already have sets of small cups labeled like this saved from Lesson 3.
• Obtain 10 large (5 oz) plastic cups and label them A through J (a single cup for each letter). Since each group will test a single ingredient in combination with all the others, each group will have a larger amount of the single ingredient that they will test repeatedly.
• Pour 100 mL of each solution into its corresponding large cup (labeled C through J).
• Pour about 10 mL of each solution into the corresponding small cups (labeled C through J).
• Pour about 100 mL of olive oil into the large cup labeled B. Pour about 10 mL of olive oil into each small cup labeled B.
• Scoop out about 3 tablespoons of coconut oil into the large cup labeled A and 1 teaspoon of coconut oil into each small cup labeled A.
• Label a different bin for each group, numbered 1–10.
• You are now ready to prepare bins of cups for each group to use for testing. Put a different large cup in each bin and add smaller cups for the other solutions as follows:

• Bin 1: large cup of A (coconut oil) and small cups B-J
• Bin 2: large cup of B (olive oil) and small cups A and C–J
• Bin 3: large cup of C (baking soda solution) and small cups A–B and D–J
• Bin 4: large cup of D (Epsom salts solution) and small cups A–C and E–J
• Bin 5: large cup of E (table salt solution) and small cups A–D and F–J
• Bin 6: large cup of F (sugar-free lemonade solution) and small cups A–E and G–J
• Bin 7: large cup of G (citric acid solution) and small cups A–F and H–J
• Bin 8: large cup of H (sugar-based lemonade solution) and small cups A–G and I–J
• Bin 9: large cup of I (sugar solution) and small cups A–H and J
• Bin 10: large cup of J (corn starch solution) and small cups A–I

• Add a disposable wooden coffee stirrer to each of the cups labeled A (large and small) for scooping and spreading coconut oil.
• Label 90 disposable pipettes, 10 each with each letter B–J. To avoid rubbing off the labels during use, write in permanent marker below the bulb, or make flags of tape with the letters on them. Add a set of labeled pipettes (one of each letter) to each bin. When you prepare for classes to follow, keep these pipettes with their corresponding cups and bins. The goal is not to cross-contaminate the pipettes.
• Reuse the bins for transport of materials to the next class.

• Safety: Be sure students wear splash goggles during this investigation.
• Disposal: All materials can be washed down the drain with cold or warm water. Cups can be saved and reused for next year.
• Storage: Unused solutions F, H, I, and J may be stored in a closed container in a refrigerator for up to one week. The other solutions you prepared may be stored on a shelf for the duration of the unit if they are in a closed container.

Lesson 4 • Where We Are Going and NOT Going

Where We Are Going

This lesson begins with identifying a new key model idea that was discovered in the previous lesson.

• Properties don’t change for a substance.

After this lesson, you can start referring to this phenomenon as something that “produces” a gas, rather than simply saying it causes a gas to appear. This is because we now know that the gas wasn’t something that was there before. We know the combination of substances that caused it to form, and we know that matter is conserved in this process.

Lesson 5 will help students narrow down a list of candidate gases that could be in the bubbles based on their property data.

Where We Are NOT Going

It is not yet important that students determine that this is a chemical reaction. At this point, they only have a partial understanding of this idea: that certain combinations of substances, when mixed together, may cause a new substance to form. But they will need some additional data to support their new understandings about this idea.

It is not important that students understand the role of water in this process. Students already know that water causes baking soda to dissolve (break into smaller pieces), and that it does the same for citric acid. It could be reasonable to assume that one or both substances must be broken down into smaller pieces in order for the gas to appear.

Lesson 5: What gas(es) could be coming from the bath bomb?

Lesson 5 • Learning Plan Snapshot

Lesson 5 • Where We Are Going and NOT Going

Where We Are Going

This lesson is focused on figuring out the identity of the gas that comes from a bath bomb. This is accomplished by using the properties of density and flammability for several common gases.

Students should be able to draw on their experiences with helium balloons and experiences with thinking about how the particle density of air changes with temperature in the OpenSciEd Unit 6.3: Why does a lot of hail, rain, or snow fall at some times and not others? (Storms Unit), to reason whether helium will float or sink in air and how the reported density value for it in grams per mL (compared to air) is related to those predictions.

Students will narrow down ten possible candidate substances to three substances by the end of this lesson. The written explanation that students will construct at the end of this lesson targets a portion of MS-PS1-2: “Analyze and interpret data on the properties of substances before and after the substances interact to determine….” In this PE, students are trying to develop an argument for whether a chemical reaction occurred. While they will do this fully in future lessons, right now, they are developing a precursor argument that will become part of the foundation for that.

Words we earn: In this lesson students will be introduced to the property of flammability. After analyzing data in a property chart for gases, as a class, flammability of two different gases will be tested in the classroom. This will help to develop a meaning for the word flammability. In addition, another property of gases included on the data chart is density. As a class the density of two different gases as compared to air will be tested. This will help to develop a meaning for the word density as a property. Both flammability and density will be added to the Word Wall in this lesson.

Where We Are NOT Going

Students will not calculate the density of a gas. They will compare relative densities based on evidence of sinking and floating of that gas in room air. Density will be calculated for different substances when they work with clear liquids in later lessons.