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Asia-Pacific Forum on Science Learning and Teaching, Volume 10, Issue 2, Article 2 (Dec., 2009) Mızrap BULUNUZ Undergraduate and masters students' understanding about properties of air and the forms of reasoning used to explain air phenomena |
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Asia-Pacific Forum on Science Learning and Teaching, Volume 10, Issue 2, Article 2 (Dec., 2009) Mızrap BULUNUZ Undergraduate and masters students' understanding about properties of air and the forms of reasoning used to explain air phenomena |
Activities Analyzed for Reasoning Method with correct Model-based Reasoning Included
Activity
Question
Elements of correct Model-Based Reasoning
The empty box candle snuffer
Explain the snuffing of a candle with a sudden hit to the box top.
There is air in the box and it occupies space.
With a hit to the box, the volume of the box decreases and air is forced out from the box hole snuffing the candle
A paper ball in the neck of bottle
Explain what happens when you blow hard into the neck of bottle.
The air in the bottle occupies space, air passes quickly into the bottle faster than the ball and then the extra air pressure pushes the ball out.
Test-tube in test tube
Explain why the small test-tube moves upwards against gravity.
The gravity and atmospheric pressure both act on the small test-tube when they are up side down. The dripping water creates a partial vacuum and atmospheric pressure pushes the small test tube upwards against gravity.
The inverted glass of water
Explain what happens to the paper card when a glass of water is inverted.
The atmospheric forces acting upward on the paper card is greater than the downward gravitational forces.
Two cups on a balloon
Explain what happens if the open ends of two cup placed on opposite sides of the balloon while it is inflating
The volume of the gas inside the cup increases and its pressure decreases as the curve of the balloon flattens. The atmospheric pressure acting on the outside of the cups balances the gravitational forces on the cups.
Linked syringes
Explain what happens when the plunger of one syringe is pushed and pulled.
When the plunger is pushed in, confined air moves to the second syringe. When a plunger is pulled out, the gas volume of that syringe increases the pressure decreases. The other plunger is pushed by atmospheric pressure.
Marshmallow and small balloon in a syringe
Explain what happens when the plunger is pulled out or pushed into the syringe while the nozzle is blocked with your finger
Push the plunger in, the pressure of the confined gas increases and the gas pressure inside the marshmallow and balloon increases so they shrink.
When the plunger is pulled out, the pressure of the confined gas in the syringe decreases and the marshmallow and balloon expands.
Leaping ping-pong ball
Explain what happens when you blow at a small angle into the cup with the ping-pong ball
The blow angle over the first cup creates flows of air across and in that cup. The flowing air has less pressure than stationary air, so the ping-pong ball is lifted and moved within this air current. It “jumps” to the other cup.
Blowing through a straw
Explain what happens when you blow through the horizontal straw
The flowing air has less pressure than stationary air. The pressure decreases over the top of the vertical straw. The water is pushed up by atmospheric pressure on the water surface and sprayed out of the vertical tube.
The ping-pong ball over hair dryer
Explain what will happen when you place a ping-pong ball over a hair dryer
The forces of the moving air balances gravity to keep the ball suspended. The lower pressure of moving air compared to the pressure of the stationary air keeps the ball from moving side ways.
Cartesian diver
Squeeze the bottle and watch what happens to the dropper. Release your hand. What happens? Can you explain why this happens?
When the bottle is squeezed, the air in the dropper is squeezed in and more water gets into the dropper. This makes the dropper heavier or denser than water and it sinks.
Illustrations by Christopher Jarrett and Karen Kimble
Copyright (C) 2009 HKIEd APFSLT. Volume 10, Issue 2, Article 2 (Dec., 2009). All Rights Reserved.
