Look for: Students work effectively as a team to measur…

3.A Collect data that support choosing the chemical reaction that has the ability to transfer the most energy to the food system.

and listen for

• Students work effectively as a team to measure and record temperature data vs. time by staying focused on their roles.
• Students calculate the maximum temperature change for each amount of substances in their group’s chemical reaction and report the appropriate sign (+ or - to indicate that the reaction caused an increase in temperature or a decrease).
• All groups, except those with cabbage juice and vinegar, identify that the magnitude of the temperature change increases as the amount of substances increases. The cabbage juice and vinegar group identifies that very little temperature change occurred regardless of the amounts of substances.
• Students identify that energy is being transferred out of the reaction system and into the thermometer when the temperature is increasing.
• Students identify that energy is being transferred from the thermometer into the reaction system when the temperature is decreasing.

What to do

• Remind students to take responsibility for their group roles and to support others as needed once their tasks are complete.
• If students are struggling to determine the maximum temperature change for the reaction that causes a temperature decrease and has a negative value (baking soda in vinegar), have them create a number line to see that temperature changes can occur in either direction.
• Ask questions about the direction of energy flow between each reaction and the thermometer to start students thinking about energy. This will help them with the questions at the end of the handout, Class Data for Chemical Reactions Lab.

Do not be concerned at this time if students are not able to explain the direction of energy transfer between the thermometer and the reaction system when the temperature decreases. If they cannot correctly identify the direction of energy transfer with this investigation, be patient with them. There are multiple opportunities for students to grapple with these ideas that are often counterintuitive.

Work in small groups to transfer data to the handout. As small groups are finishing their investigations, hand out Class Data for Chemical Reactions Lab and ask students to complete the rows for their group’s chemical reaction. Point out that Class Data for Chemical Reactions Lab provides instructions on how to determine the maximum temperature change. This will be a negative number (indicating a decrease in temperature) for groups investigating the baking soda and vinegar reaction. Provide additional support to those groups as needed.

Share data from small groups in a class data chart. Display slide K and enter class data directly into the whole-class data table as each small group shares their data. You could also create the whole-class data table on a whiteboard or chart paper. Ask students to add data to their own copy of Class Data for Chemical Reactions Lab as groups share.

In this part of the lesson the suggested roles are responsibilities to ensure the lab gets completed with reliable data and within the allotted amount of time. There are three different amounts of substances each group will be testing and only one thermometer and scale per group. For this reason, the suggested roles at this moment are to help the group manage their work flow, rather than intellectual roles such as Idea Connector or Evidence Wrangler. However, using intellectual roles is encouraged during sensemaking sections of the lesson and throughout the unit.