- Have students reflect on what they already know about matter by having them respond in their journals to the following questions:
*"What is matter? Give two examples of matter and two examples of non-matter."*

OR "*Solids, liquids and gases each have measurable mass. What parts of this statement do you agree with? Disagree? Explain your answer in detail."*

- Introduce the activity to the students:
- If chemistry is the study of matter then to understand chemistry they must first understand what matter is. Through this activity students will collectively define matter.
- By defining the term as a group, students will start to develop into a community of scientists. Science has its own language, but this language is built, collectively by the practicing community of scientists who agree on definitions for the terms they are using.

- Explain the activity:
- Each pair will receive a set of “items”. The students' task is to work together and discuss whether each item is or is not matter. Ask students to discuss why they think the item is or is not matter and to challenge each others' thinking.
- Have students create a table to categorize their items: Matter, not matter or unsure
- Based on their categorizations, ask students to come up with properties the things in the matter category have in common (and that apply to all matter). Ask students to make a list of these properties. What about things that are not matter or that they are unsure about?

- Have students report out

Stress that the following two big ideas are critical to this and other report-outs:

- Constructing an argument and defending a position – as students share their conclusions with the class, challenge them to explain why they made that decision. What evidence do they have?
- Thinking critically and being skeptical. Explain that you want them to be working as a community and to really push all of their thinking. Encourage students to direct their report-out to the group, not to the teacher. Encourage students to ask one another questions.

- Ask a team to get the class started on this report out. Perhaps by sharing what item had the most interesting discussion for their pair. Why? And what does this tell us about matter? Leave this discussion solely student-centered at this time. Have pairs report out, challenge and question each other, share their difficulties categorizing certain item etc. Refrain from judging, correcting or giving the "right" answer. Instead, probe students' ideas by asking "Did anyone else have trouble categorizing this item? Why?". "How did other pairs categorize this item? Why?". Highlight students' confusions, difficulties and controversies.
- After all "tricky" items have been discussed (see
*Instructor background*section above), ask students to share if they were able to find common characteristics of items in the matter category as well as of items in the non-matter category. Ask students: "If something is not matter - what is it?" - Collect responses about characteristics of matter/non-matter on blackboard/overhead while students report out. Again, don't comment just yet - just record. Challenge students' responses by asking the class "Does everyone agree with this?," "Is that characteristic true for all items in the matter category?" etc.
- Add and cross out characteristics of matter until all students agree that ALL matter shares those common characteristics.
- Based on that list of characteristics, ask students to create a definition of matter that everybody can agree on. Write down the definition on a wordwall or large poster to refer back to during later lessons.
- Share some textbook defintions of matter and have students compare these definitions to theirs. Are those definitions useful for them? Do they give them any more insights?

- While students work in pairs, sorting the items, walk around, listen in on their discussions and ask probing questions to get a sense of students' understanding of matter.
- The discussion of students' placement of items will reveal students' misconceptions and internal struggles about the concept of matter.
- The pre-activity journal reflection can be repeated at the end of the class to determine how students' ideas might have changed.

Have students repeat their pre-activity journal reflection at the end of the class to determine how students' ideas might have changed.