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Purpose
[stextbox id = “info”] To provide students with evidence that air (1) takes up space, and (2) is made of particles that have empty space between them.[/stextbox]
Description
[stextbox id = “info”] In front of the class, pull back the plunger on a syringe (without a needle), then push it in quickly. Repeat, but ask a student to put his or her hand about an inch in front of the syringe before you push in the plunger. Ask what the student felt. Pull the plunger back again. Give the syringe to a student and tell the student to put a finger firmly on the tip of the syringe and then try to push in the plunger. Ask the student what s/he felt. Let several other students try and describe what they felt. Finally, ask students to draw what they would see if they could look inside the syringe with super strong glasses [2] that are stronger than the strongest microscope (Gómez, Benarroch, & Marín, 2006; Loughran et al., 2004 [3]).
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Questions to Ask Students
[stextbox id = “info”]- What do you think is inside the syringe when I pull the plunger back? What is air made of? (Ask only if students say there was air in the syringe.)
- What was hitting your hand when I pushed the plunger in?
- When you put your finger over the tip of the syringe, why could you push the plunger in only part of the way?
Student Thinking
[stextbox id = “info”]- Students are likely to think that air is either nothing (Durmuş & Bayraktar, 2010; Stavy, 1988) or that it is continuous rather than particulate (Benson, Wittrock, & Baur, 1993; Séré, 1986) [5]. These activities will challenge both ideas. Air coming out of the syringe feels like something, not nothing. When students try to push the plunger in with their finger covering the tip, the resistance also challenges the idea that air is nothing. The fact that they can push it in part of the way suggests air is compressible, which contradicts the continuous model of matter.
- Students who understand that air is made of particles may be able to explain that air is compressible because the particles are surrounded by empty space.
Implementation Tips
[stextbox id = “info”]- The activity will be more convincing with a large syringe. You can purchase syringes at a drug store.
- Instead of doing this activity as a demonstration, you can provide pairs or small groups of students with their own syringes.