Activity 3.1 - Predictions about Soda Water Fizzing (20 min)

Tell students that in this lesson, they will be investigating what happens when soda water fizzes to learn more about how what happens to matter during chemical changes.

• Tell students that during the investigation, one of the goals is to learn about the chemical change that is happening. Display slide 3 on the 3.1 Predictions about Soda Water Fizzing PPT. Use this slide to overview what we mean when we say “chemical change.”
• Pour soda water into a Petri dish in the front of the classroom. Encourage them to take a closer look at the soda water if they are interested.
• With slide still open, draw the students’ attention to the Matter Movement Question and the Matter Change Question. Tell them that in this lesson they will be trying to answer these two questions about chemical change.

Display slide 4 of the PPT.

• Draw students’ attention to the slide and point out that the question is accompanied with “rules to follow” as well as ways to “connect atoms to evidence.”
• Emphasize the following rule about matter: Atoms are bonded together in molecules.

Display slide 5 of the PPT.

• Emphasize the following rule about matter: Atoms last forever.

Show slide 6 of the 3.1 Predictions about Soda Water Fizzing PPT. Pass out one copy of 3.1 Predictions and Planning Tool for Soda Water Fizzing to each student. Ask them to record their ideas as individuals for part A for the Matter Movement and Matter Change Questions for soda water fizzing.

• Remind students that these are just predictions, and that there are no wrong answers at this point. Encourage them to write down all their ideas on the tool.

Show slides 7 and 8 of the 3.1 Predictions about Soda Water Fizzing PPT. Discuss with students how a digital balance can be used to measure matter moving into or out of a system. Highlight that the mass of the system can be measured before and after a change happens in a system. Discuss the two possible conclusions students can draw from their observations:

• If the mass of the system increases, then matter must have moved into the system (remember the facts about atoms)
• If the mass of the system decreases, then matter must have moved out of the system.

Show slide 9 of the 3.1 Predictions about Soda Water Fizzing PPT. Discuss with students how BTB can be used to measure matter change in a system. Highlight that the BTB in a closed container can be observed before and after a change happens in the system. Discuss the two possible conclusions students can draw from their observations:

• If the BTB changes from blue to yellow, then a chemical change may be producing CO₂
• If the BTB changes from yellow to blue, then a chemical change may be using CO₂ as a reactant.

Show slide 10 of the PPT. Have students have complete Part B of their Prediction Tool. Have them focus on the matter movement and matter change as they make their predictions about what happens in soda water loses its fizz.

Divide students into pairs and tell them to compare and contrast their predictions with each other and to look for differences and similarities.

Give students 2-3 minutes to compare their predictions.

Display slide 11.

• Tell students that tomorrow they will discuss their predictions together as a class.
• Also, they will revisit their ideas after the investigation to see how their ideas changed over time.

Show slide 12 of the PPT and describe the instruments and materials necessary for carrying out the investigation. Have students begin planning their investigation. There are two main variations in how much control students can have over this planning process:

• Minimal student control: Discuss student ideas for how an investigation could be set up. Then have students follow the lab instructions for lesson 3.2
• Maximal student control: Students in the class develop their own consensus plans that will replace the lab instructions in lesson 3.2. Note the importance of having different student groups following the same plan so that they can come to a consensus about patterns in data in lesson 3.2 Some possible ideas of using lab materials are below.
  • Students might choose to add controls to the experiment, for example including both a Petri dish of yellow bromothymol blue (BTB) (made from blowing into the blue BTB with a straw) and a Petri dish of blue BTB to the chamber.
  • Students might also choose to set up a chamber with a Petri dish of blue BTB alone without the soda water fizzing