[1]
Purpose
To give students an opportunity to draw a model that explains dissolving.
Description
Ask students to again draw the cup of water using their super strong glasses [2], this time after the salt is added. Students can make their drawings on the “After” cup on this task sheet [3].
[4]
Questions to Ask Students
- Describe your drawing. What does each part represent?
- How does this drawing compare to the one you made earlier of the water before the salt was added?
- How does your new drawing explain what happens when salt is stirred into a glass of water?
Student Thinking
Some students may believe that matter is continuous rather than made up of particles (Nakhleh & Samarapungavan, 1999; Nakhleh, Samarapungavan, & Saglam, 2005; Renström, Anderson, & Maron, 1990) [5]. Students with a continuous view of matter will likely not have any particles in their drawings, in particular their drawing of water before salt is added. Because many students believe that salt “disappears” when stirred into water, pay careful attention to how they represent the salt in their drawings both before and after being stirred into the water. If students draw particles, are they visible in the “after” drawings? How do they compare to the particles in the “before” drawings?
Some students may use the word “dissolve,” but don’t assume they have an accurate understanding of the term. Ask students to explain what they mean by the word, but do not correct their ideas at this point.
Implementation Tips
- The drawings will help the teacher understand what students think about matter at the beginning of the pathway and be alert for opportunities for students to challenge their thinking.
- Collect and keep the drawings, or ask students to keep the drawings (for example, in their science notebook), so they will be able to compare their thinking from early to late in this driving question pathway.
- If resources are available, this experience could be done by students in pairs or small groups rather than as a demonstration.