[1]
Purpose
To give students an opportunity to draw a model that explains the conservation of weight during phase change (that is, weight stays the same during phase change).
Description
Have students draw what they would see in the ice cube and liquid (contained in the plastic baggie) if they had super strong glasses [2], more powerful than the most powerful microscope.
Questions to Ask Students
- Describe what’s in your drawing. What does each part represent?
- How could you use what you drew to explain your prediction about the weight of the ice cube before and after melting?
- How are your drawings for the ice cube and liquid different from your first ones, if at all?
Student Thinking
- Many students believe matter (in this case water) is continuous rather than made up of particles (in this case water molecules) (Benson et al., 1993; Nakhleh & Samarapungavan, 1999; Renström et al.,1990; Séré, 1986) [3]. These students are likely not to include water particles (or any other kind of particles) in their drawings.
- They may also think particles are IN substances (water particles in a body of water) (Beerenwinkel, Parchmann, & Gräsel, 2011; Lee et al., 1993; Novick & Nussbaum, 1978, 1981) [3], which should also be evident in their drawings.
- Students may think that there is NO space between particles (Benson et al., 1993; Özmen, 2011; Özmen & Kenan, 2007) [3].
- Students may not understand that the particles are constantly moving, even in ice (Herrmann-Abell & DeBoer, 2011; Lee et al., 1993) [3].