Teachers and families across the country are facing a new reality of providing opportunities for students to do science through distance and home learning. The Daily Do is one of the ways NSTA is supporting teachers and families with this endeavor. Each weekday, NSTA will share a sensemaking task teachers and families can use to engage their students in authentic, relevant science learning. We encourage families to make time for family science learning (science is a social process!) and are dedicated to helping students and their families find balance between learning science and the day-to-day responsibilities they have to stay healthy and safe.

Interested in learning about other ways NSTA is supporting teachers and families? Visit the NSTA homepage.

Sensemaking is actively trying to figure out how the world works (science) or how to design solutions to problems (engineering). Students do science and engineering through the science and engineering practices. Engaging in these practices necessitates that students be part of a learning community to be able to share ideas, evaluate competing ideas, give and receive critique, and reach consensus. Whether this community of learners is made up of classmates or family members, students and adults build and refine science and engineering knowledge together.

We're featuring How does the hot air balloon take off? in honor of National Hot Air Balloon Day, celebrated annually on June 5. 

While most of us might think about hot air balloons in the context of festivals and rides, they have also played a large role in scientific discovery. Did you know that in addition to hot air balloons being used to collect data about Earth's atmosphere, knowledge gained from sending humans to great heights in hot air balloons made space exploration possible? Check out this Hot-Altitude Balloon Innovation article to learn more.

How do clouds form? Hot air rises! Why is it warmer at the top of the stairs than at the bottom of the stairs? Heat rises! How does the hot air balloon take off? Hot air/Heat rises!

Do these responses sound like ones your students might give? In today's task, How does the hot air balloon take off?, students engage in science and engineering practices and the thinking tool of the flow of energy and matter (crosscutting concept) to figure out what is "rising" and how the science ideas of energy transfer and the movement of matter can explain this and other phenomena.

Say to students, "I have a video that shows a puzzling phenomenon that I want to explore with you. Some of you may have experienced this phenomenon before."

Tell students to create a T-chart with the left side labeled Noticings and the right side labeled Wonderings. Ask students to record observations and questions that arise as they watch the video.

Show the Hot Air Balloon Takeoff video (above). You may choose to show the video multiple times. Consider showing the video at 1.5 speed after the first viewing (Settings > Playback speed > 1.5).

Note: The loud noise in the beginning of the video is made by the fan used to inflate the balloon. The fan is visible in the lower left corner of the screen at about 1:35. Consider pausing the video to point out the fan to students.

Ask students to share their observations with a partner or small group. Then ask students to share their observations (or those shared by a partner or group member) with the whole class. Record student observations on a class poster (or any place where observations can be accessed by all students.) If questions arise while students are sharing observations, capture them on a second poster.

Tell students, "Many of you have questions about how hot air makes the balloon go up (they've likely noted the balloon is quite heavy). Does it make sense to investigate this question first?"

Tell students they are going to investigate a phenomenon related to the hot air balloon taking off.

Materials

• 1 empty plastic bottle (2-liter or smaller)
• 2 6-quart tubs (can be smaller if using a small plastic bottle)
• 1 small container of soap bubble solution (2 parts water: 1 part dish soap)
• cold water (can use ice water, but cold tap water also works)
• hot water (do not use boiling water) An adult should pour hot water for students.

Student Directions

1. Fill one tub with cold water until the water is about 3 inches deep.
2. Fill the second tub with hot water to the same depth as the cold water tub.
3. Seal the air in the plastic bottle with a thin film of soap bubble solution (turn the bottle upside down and set the opening in the soap bubble solution, then tip the bottle right-side up and set it on the table).
4. Observe the bottle on the table.
5. Place the bottle in the cold water and observe what happens (if the soap bubble film breaks, reseal the bottle with the soap bubble solution and repeat).
6. Place the bottle in the hot water and observe what happens (if the soap bubble film breaks, reseal the bottle with the soap bubble solution and repeat).
7. Repeat the process a second time, and record what you observe when you place the bottle in each tub. Use pictures, symbols, and/or words.

Assign students to small groups of three or four. Give each group one piece of poster (chart) paper. Instruct the groups, "Create a group model to explain your observations of the bottle with the soap bubble film in water, on the table, and in cold water." Share the model scaffold (below) with the groups and ask them to transfer the scaffold to their group's poster paper.

Note: Using this scaffold will make it easier for students to compare their group model with other group models.

As you move from group to group, consider using the discipline-specific probes below to deepen students' thinking.

If students are having a difficult time getting started, ask them the following questions:

• What absolutely needs to be represented in your model?
• What's in the bottle? (Can it get out/can more get in? Why do you say so?)
• Why would it make sense to show the same number of gas molecules in the second and third bottles as you've shown in the first bottle system?

If students are telling you heat is rising, state the following:

• You said that heat is rising...let's go back a bit. Tell me what happens when you first put the bottle in the warm water (The bottle gets warm.) Okay, now the bottle is warm; what happens next? (The air gets warm.) So now the air is warm...what is the warm air doing?
• [Follow-up to questions above] Do you think all of the air is at the top of the bottle? Have you been outside on a hot day? Was there air near the ground? What's your evidence?
• How did the warm water make the bottle warm? Does the hot water have energy? How is the energy of the water making the bottle warm? (How is the energy of the bottle making the gas molecules warm?)

If students are not representing forces and/or energy, ask these questions:

• How could you represent the transfer of energy between the water and the bottle? The bottle and the air?
• How are you representing the speed of the gas molecules?
• How might you represent what happens to molecules when they collide with other molecules? With the sides of the bottle? With the soap bubble film?

Consider allowing students 15–25 minutes to create their group models.

Ask student groups to post their models so that other groups can view them (gallery walk).

Tell students to observe at least three other group models and

• record one similarity and one difference between their model and the group model they are observing, then
• place an adhesive note next to a component, interaction, and/or representation on the model they are observing that they would like to add to their own group model.

Provide students an opportunity to revise their group models at the end of the gallery walk.

Tell students, "Let's work toward consensus on a model that explains our observations of the bottle with the soap-bubble film in hot water, on the table, and in cold water."

Draw three bottles on chart paper, making sure to put the bottles in the same order as the model scaffold students used to create their group models.

Ask students to look at their models and their notes on similarities and differences between their group model and the three other group models they observed and be ready to share the components and interactions inside the bottles that the class consensus model should include. Likely student responses and teacher follow-up questions are listed below.

• Air. How should we represent air? When representing the molecules that made up the air in the bottle after cooling and after warming (assuming soap bubble film doesn't break), how many dots should we draw? Why?
• Show air particles (molecules) moving the fastest in the warmed bottle and the slowest in the cooled bottle. How should we represent the speed of air particles?
• Air particles are far apart in the warmed bottle and close together in the cooled bottle. How can we communicate the mechanism for air particles being far apart in the warmed bottle and close together in the cooled bottle?
• Draw the soap bubble film flat on the middle bottle (table), in the shape of a bubble on the warm bottle, and sunken in on the cool bottle. (Save follow-up questions for a discussion about air outside the bottles.)

Say to students, "We're all mentioning that the air is warm in this bottle (point to bottle in warm water) and cool in this bottle (point to bottle in cold water). How does the air warm up (cool down)? How can we represent this on our class model?"

• Show the water molecules touching the bottle. Show the air molecules touching the bottle. Why is showing the water touching the bottle important? How is water touching the bottle (air touching the bottle) related to transferring energy?
• Use a different arrow than the motion arrow to show forces. Where should I draw those arrows? Do I need one or two arrows to represent the interaction between a water molecule and a bottle particle (bottle particle and air particle)? What size(s) should the arrows be?

Focus students' attention on the soap bubble films. Point to the bubble inside the cool bottle, and ask, "What caused the change in motion of this soap bubble film in the cool bottle?"

• It sunk because the air inside isn't moving fast. What happened at the moment the film began to sink?
• When something changes motion, it means the forces on it are unbalanced (total force isn't zero). Are the forces acting on this soap bubble film (point to bottle on the table) balanced? What forces are acting on the film? What is changing in the warmed bottle? Cooled bottles?"

Say to students, "So it seems we have to include air particles on the bottles in our consensus model to explain our observations. Do you think we'll need to include the air outside the hot air balloon to explain the balloon's motion?"

Ask students to make a claim about how the hot air balloon takes off from the ground and to support that claim with evidence from observations of the phenomenon (video) and from the class consensus model explaining observations of the bottle with the soap bubble film in the warm water, on the table, and in the cool water.

Consider different ways students might share their evidence-supported claims with one another or with the whole-class learning communities:

• Students draw a model to explain how the hot air balloon takes off and send a picture of the model to you. Upload student models on Miro and share the link with students. Ask students to compare their models with at least two other models, noting similarities and differences. Give individual students an opportunity to revise their models—sharing their reasoning for changes/additions—and resubmit them to you for feedback. Note: The free version of Miro only allows the account holder to upload images. Consider keeping the modelers anonymous so that (1) students compare models without judgment and (2) you can provide public feedback to students using adhesive notes when students send you their revised models. Collective feedback could support all students in moving their thinking forward.
• Students record an oral presentation of their evidence-supported claim using an app such as Flipgrid or TikTok, then share it with the class. Assign students to small groups and ask them to respectively provide feedback to each group member by citing relevant evidence from data (see top of section) and posing questions that will support the sharer in elaborating on their ideas.
• Students write their claims and supporting evidence on a shared Google Doc. Make a copy of the Google doc and set the access permission to "comment only." Share the link to the Google Doc and ask students to respectively provide feedback to two classmates by citing relevant evidence from data (see top of section) and posing questions that will support the sharer in elaborating on their ideas using the comment feature.

Share other ideas for students to respectively provide and receive critiques below.

NSTA has created a How does the hot air balloon take off? collection of resources to support teachers and families using this task. If you're an NSTA member, you can add this collection to your library by clicking Add to My Library, located near the top of the page (at right in the blue box).

The NSTA Daily Do is an open educational resource (OER) and can be used by educators and families providing students distance and home science learning. Access the entire collection of NSTA Daily Dos.

The How does the hot air balloon take off? task is adapted from the OpenSciEd Weather, Climate, and Water Cycling Unit (Lesson 5: What happens to the air near the ground when it is warmed up?).