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Purpose
[stextbox id = “info”] To help students become aware of their initial thinking about how particles fit together in different substances. [/stextbox]Description
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Part 1: Fill two graduated cylinders with 50 mL of water each. Ask a volunteer to look at the graduated cylinders and confirm that there is 50 mL of liquid in each. Have students predict what the total volume would be if you poured all of the water into a single graduated cylinder. Pour the two into one cylinder and show them that the volume is 100 mL.
Part 2: Next, fill two graduated cylinders with 50 mL of rubbing alcohol each. Again, ask for predictions about the combined volume. Pour the two together and have students observe that the combined volume is again 100 mL.
Part 3: Finally, fill one graduated cylinder with 50 mL of water and 50 mL of alcohol. Ask students to predict the total volume when the two are poured together into one cylinder. Pour the two together; this time the students will see the volume is less than 100 mL.
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Safety Tips
[stextbox id = “info”] Use safety goggles when pouring alcohol. We recommend that only the teacher pour alcohol. Also, as a rule, students should not eat or drink in a science activity. This rule is especially important here because rubbing alcohol looks just like water.[/stextbox]
Questions to Ask Students
[stextbox id = “info”]- What do you predict will happen when these are poured together? Why did you make that prediction?
- How can you explain the total volume when the liquids were poured into a single graduated cylinder?
Student Thinking
[stextbox id = “info”]- 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 [3]).
- Students with a particle understanding often think that there is no space between particles—i.e., the particles are packed too tightly together to allow for empty space (Benson, Wittrock, & Baur, 1993 [3]).
- Most students who do believe there is space between particles believe it is filled with a continuous substance (such as air or water) (Beerenwinkel, Parchmann, & Gräsel, 2011; Lee, Eichinger, Anderson, Berkheimer, & Blakeslee, 1993; Novick & Nussbaum, 1978, 1981 [3]).
Implementation Tips
[stextbox id = “info”]- Students may suggest that some of the liquid spilled, so it may be useful to allow a few volunteers touch the dry surface where the pouring occurred.
- It may be helpful to keep the cylinders with 100 mL of water and alcohol from Parts 1 and 2 out so students can compare these with the cylinder from Part 3.
- If you do not have the time or materials to conduct this activity, you can show your students this video clip from Bill Nye the Science Guy, Season 5, Episode 8: Atoms. https://www.youtube.com/watch?v=84k206qaVRU [4]. To avoid short-circuiting the learning, show the video with the sound off.