Beacon Lesson Plan Library

Action Reaction: A Crushing Experience

Lois Walsh
Bay District Schools

Description

A dynamic laboratory activity in which students crush a cola can as 2 forces equalize. It is a demonstration of wind, weather fronts, action/reaction, or Charles' Gas Law.

Objectives

The student knows that temperature is a measure of the average translational kinetic energy of motion of the molecules in an object.

The student explains that all forces come in pairs commonly called action and reaction.

Materials

-1 to 3 empty Aluminum cola cans per student
-Heat source: hot plate, candle, alcohol burner, or propane burner
-Protective eyewear
-Beaker tongs
-Two tubs: one half filled with water and one for wet Al cans
-Beaker with water
-Eyedropper
-Gauze screen or other pad for a hot object

Preparations

1. Gather materials and set them up.
2. Read over procedure.
3. Review safety procedure and first aid.

Procedures

Introduction:
Forces come in pairs. Equilibrium is balance or equaling out of paired forces, so when there is an action there follows a reaction. An example of the concept being taught can be added here (See extensions). In this activity the addition of heat will increase the movement of the water molecules, their average translational kinetic energy of motion, inside of the cola can. The water will actually change states into a gas and rise. This will create an area of fewer molecules, less force/push and less pressure in the cola can. The cola can will then be inverted in the water closing the cola can and the situation of fewer molecules, less force/push and less pressure inside. The balancing of forces will be immediately.
Note: I recommend not to do a full demonstration of the lab to the class, but to allow the students to ‘discover’ the reaction themselves. (and to see their reaction!)

Safety: The heat source and cola can will get hot. Steam is very hot.

Directions:
1- The set up: Arrange the materials so the heat source and tub of water are side by side.
2- The cola can will need to be moved quickly from the heat source to the tub of water. As the cola can is moved it needs to be inverted and the top of the can immersed in the water, closing it off from the air outside of the can. So before any water is in the can, practice how to hold the can and invert it. (Palm up works best).
3- Place 5 to 10 drops or 1 ml of water in the cola can.
4- Hold it over the heat source until steam rises and the water in the cola can is boiling. Allow most of the water to evaporate.
5- Then quickly invert the can and plunge into the tub of water about 2 cm so the opening is underwater in the tub.
6- There should be an immediate result as the pair of forces balance out: the reaction. If the can does not crush, start over at step 3 with water and leave it over the heat longer in step 4.
7- Drain the water from the can and place the crushed can in the dispense tub.
8- Clean up and return materials.
9- Complete the lab report.
10-Assess the Lab Reports.
11- Return Lab Reports and review the sequence of events and concepts of the lab.

Assessments

Students will complete a laboratory report with 1) Title, 2) Purpose, 3) Hypothesis, 4) Experimental procedure summary, 5) Data consisting of drawings of the cola can before, after and during with labeling, molecules in and out of can, temperature, forces, and pressure, and 6) conclusion.

If done correctly, the report will confirm that forces work in pairs: there is an action and then a reaction. The report should also include that the increased movement of molecules, kinetic energy of motion, inside the can could be measured as a rise in temperature. The fewer number of molecules inside the can did not balance those outside the can, which resulted in an inward push (force), when the can was closed off.
Since this is a formative assessment, if not done correctly, those students could partner up to correct their lab reports and then the teacher and the class could orally review the concepts.

Extensions

Application:
The lab can be applied to several concepts:
-Air masses, and weather fronts
-How wind is created
-Gas Law involving pressure, temperature, and
volume (Charles' Law)
-Density of Matter
-Changes in the states of Matter
-How atoms behave with temperature
-For every action there is an equal and opposite
reaction
Extensions:
-The volume of the can before and after can be determined by filling it with water and then measuring the contents with a graduated cylinder.
-Each class could display the 'Best Crushed Can' with the name and period of the student. Extra cans(and time) will be needed for the students to experiment with.
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