For the class: 1 roll of masking or freezer tape.
Given a set of experiments related to the property of elasticity, the student will:
1. Identify which variable relates to the property of elasticity that is being changed.
2. Accurately predict the effect of a specific change in a variable on the distance the rubber band travels (its elasticity).
3. State the relationship between the change in the variable and its effect on how far the rubber band will travel.
Give the students Direction and data sheet 1, one 7-9 cm. rubber band, the ruler and the meter stick. Have students mark out 8-10 meters on a hallway floor with masking or freezer tape. Suggest that they measure the distance their rubber bands traveled from the nearest meter marking, adding the distance from that mark to the value of the mark itself.
Then ask each group to measure their rubber band at rest, laid alongside their rulers. Be sure the rubber band is pushed or laid flat next to the ruler. Have them record the length of their rubber band in the space provided on Data sheet 1. Also have students place a zero in the column labeled distance traveled.
Next, show students how to loop the rubber band over the edge of the ruler and stretch it out the appropriate distance (length at rest plus 1 centimeter for the first try). Make sure they shoot it form the top edge of the ruler. Also make sure they shoot it with the ruler on the floor and at the edge of the first mark. Students may need to experiment to get consistency.
Observe each group carefully on their first try. Make sure they are all following the procedure consistently. Then ask the students to continue shooting and recording until their data sheets are filled in.
When you return to the classroom, give students graph paper and ask them to graph their data using the length traveled (in meters) on the vertical axis. Then ask them to describe their results in short statements below their graphs.
Ask students to share their statements about the data on their graphs. (Their graphs should show greater distance with greater stretch, up to a point, where it should level off or decline). Then ask students to tell you what variable they changed in their experiments. (They should tell you they changed the amount they stretched their rubber bands). Then ask them to tell you what effect the amount of stretch of the rubber bands had on the distance traveled.
Next, ask students what they noticed about the rubber band’s size and shape after they shot it? Was it about the same size and shape? Then tell students that the ability of the rubber band to stretch and return to it’s previous shape and size is called elasticity.
A. Tell students that they are now going to investigate how the thickness of the rubber band affects it’s elasticity and the ability to shoot it. Give students the three rubber bands that are the same length but different thicknesses along with Data sheet 2.
B. Ask students to pull back each rubber band 5 cm. from it’s resting position.
C. Have students record their results on Data sheet 2. After recording data, students should graph their results and write statements that describe the relationship between the variable of thickness and distance traveled. (Graph thickness along the horizontal axis and distance on the vertical axis). Discuss as a class.
Give groups of students a 7-9 cm. rubber band. Ask them to record how far it will shoot when it is stretched, double it’s length at rest. Then ask them to cool the rubber band in ice water bath for two minutes. They should shoot the rubber band at double it’s length at rest, as soon as it is taken out of the ice water bath and record it’s distance. Finally, they should place the rubber band in a hot water bath (hot water out of the tap) for two minutes. They should again shoot the rubber band at double it’s length at rest as soon as it is taken out of the hot water bath and record it’s distance. Have them write statements that describe the relationship between temperature and elasticity. (They should observe that the coldest rubber band should go further than the room temperature rubber band. The heated rubber band should not go as far.)
Here are a set of experiments that Maria and Juan conducted:
Experiment A: Shot a 3mm. wide rubber band 4 cm. in length by pulling it back 5 cm. It traveled 7.3 meters.
Experiment B: Shot a 3mm. wide rubber band 7cm. in length by pulling it back 5cm. It traveled 5.6 meters.
Experiment C: Shot a 3mm. wide rubber band 15 cm. in length by pulling it back 5 cm. It traveled __?___ meters.
Question 1: What variable related to the property of elasticity is being changed in Maria and Juan’s experiment?
Question 2: Predict how far you think the rubber band went in experiment C.
Question 3: State the relationship between the variable that was changed and the distance the rubber band traveled.
Assessment key for teacher:
Question 1: The variable is the length of the rubber band.
Question 2: The rubber band actually went 2.8 meters; accept anything between 2.0-3.0.
Question 3: The shorter the rubber band, the further it traveled. You were able to deform a shorter rubber band more or stretch it tighter.
Directions and Data Sheet 1
Measure a 7-9 cm. rubber band at rest. Record it in your data table below. Then place a zero in the column labeled distance traveled. Place the rubber band at one end of your ruler, at the top. Stretch it out the required length. Make sure your ruler is at the first mark and is resting on the floor. Carefully release you rubber band. Have your partner measure how far it went by counting the meters plus the number of cm. past the last meter mark. Then fill in the table with the total length of your stretch (in cm.) and the distance traveled (in meters).
Length of stretch (cm.) Distance Traveled (m.)
At rest __________ ___________
+1 cm. __________ ___________
+2 cm. __________ ___________
+3 cm. __________ ___________
+4 cm. __________ ___________
+5 cm. __________ ___________
+6 cm. __________ ___________
+7 cm. __________ ___________
+8 cm. __________ ___________
Now graph you data as your teacher directs. On the back of your graph write a statement that describes your results.
Directions and Data Sheet 2:
Use the data sheet below to record data related to how far rubber bands of various thicknesses travel. Pull back each rubber band 5 cm. Measure the thickness in millimeters and record it in the space provided. Then record how far it traveled when you pulled it back 5 centimeters.
Thickness of band (mm) Distance Traveled (m)
No. 1 ___________ ____________
No. 2 ___________ ____________
No. 3 ___________ ____________
Now graph your results as your teacher directs. On the back of the graph, describe the relationship between the variable of thickness and the distance traveled.