What does a 2-bottle system have in common with the Solar System? While this question may at first seem like a silly riddle, it calls attention on the concept of a system. Both the solar system and the 2-bottle system have physical boundaries, and both have components that interact within those boundaries.

The components within the three 2-bottle systems increase their interaction shortly after the lights are turned on. Students will notice changes at the start of this investigation. After sharing their initial understanding of a system, they focus on the components of the closed 2-bottle system and the now open mini-lake system. They end the class by carefully observing their "home" 2-bottle system and making drawings that record the initial changes. This is the first in a series of observations that document changes in the 2-bottle systems.

By the end of this investigation, students will understand that systems have components that interact within boundaries. They'll be able to describe the components of the 2-bottle systems and their mini-lake, and start to understand the transformations of the components within the systems.

Learning Goals

• Understand that a system has components that interact within the system boundary
• Start to understand the interaction of the components within the 2-bottle systems

Sequence of experiences
1. Ask the question	All Class	10 Mins
2. Observe the 2-bottle systems	Small Groups	10 Mins
3. Make meaning	All Class	15 Mins
4. Weigh the mini-lakes*	Pairs	10 Mins

* If possible, have students weigh the mini-lakes before school starts, or during a lunch period, to have additional time during this investigation.

Materials and Preparation

For the class:

• Post the investigation question in a place where all students can see it.
• 3 2-bottle systems

For each group:

• 1 digital scale
• 2 mini-lakes