Author: Penny Pleitikapich and Kathie Owens
Get the students interested in this lesson by asking them to share their experiences with bubblegum - who has ever blown a bubble that broke and plastered sticky gum all over your face? If Internet access and projection are available in your classroom the site www.bubblegum.com has animation and stories about what makes up bubblegum and how it is made. Showing part of this site to your students is an interest enhancer!
Pre-assess your students' understanding of physical and chemical changes (which they will discuss further after they have designed a test to measure the stretch-ability and bubble-ability of various kinds of gum). Pose a couple of examples - sugar dissolved in water, leaves changing color in the fall, paper burning, etc. and ask your students to decide whether these changes are physical and/or chemical. Ask students to predict what changes they think will happen to the bubble gum when it is chewed, stretched, and bubbles are blown.
Posed problem: How do various types of bubblegum perform when tested for stretch-ability and bubble-ability? How does the gum change from before and after chewing?
Assessment: Monitor the students' responses to your questions and their predictions for reasonableness. Be sure that they understand the posed problem.
Review with students what makes a "fair" test when doing a science experiment and safety procedures used in science investigations. Give students an opportunity to design the experiment to test for the stretch-ability and bubble-ability of various types of bubblegum or use the following suggestions.
- Mass each gum in its wrapper and record the mass of each gum. Unwrap the gum (SAVE THE WRAPPER), place it in your mouth, and chew it for three minutes. Before massing the gum again, predict whether the new mass will be more or less than the original mass. Put the gum back in its wrapper and mass the gum again. Record the new mass. Did the changes in mass support your predictions? Why or why not?
- Hold the end of the tape measure in one hand and your bubblegum in the other hand. Your partner should face you and hold the tape and bubblegum using the wrapper in opposite hands. Hold the gum in one hand next to the zero cm end of the tape that is in your other hand. Your partner should slowly back away from you and stretch the gum as far as it can go until it breaks. Record how far the gum stretched. Repeat this process with your partner's gum.
- Each member of the group should chew his/her gum again and after 3 minutes blow a bubble. Observe the relative sizes of the bubbles produced and record your observations in your science journal. NOTE: omit this portion of the investigation if the gum falls to the floor or gets contaminated during the stretch test. Alternative: give each student another piece of the same gum.
Have students compare their findings within the small group and make a bar graph of their stretch findings.
Assessment: Monitor students' work. Be sure students are proceeding safely and following authentic scientific procedures.
Students report their findings. Each team shares their data and their graphs from their science journals.
As a class, create a data chart of stretch-ability by brand of bubblegum. Which brand of gum had the best stretch? Have students report their observations about the size and appearance of the bubbles they blew. Ask students for their assessment of which brand of gum delivered the "best" bubbles.
Discuss the experimental process with the students. Help students identify the variables and the control. Ask students what variables may have affected the elasticity of the gum. Talk about errors that may have entered into the data collection process (for example, variations in the chewing process across the class). Ask students if they think that there many have been any variables in the gum itself that may have affected its elasticity.
Return to the discussion of physical and chemical changes begun in the opener. Ask students to identify any physical changes and chemical changes that occurred in this experiment.
Assessment: Have students work in their experimental groups. Ask students to summarize their findings in writings and what they have learned about scientific methods as a result of their work. Check their lab reports and graphs for accuracy and completeness.
Several suggestions are given:
- Ask students to write up additional test that could be performed on bubblegum and to predict the outcome.
- Ask students to write a letter to the manufacturer of bubblegum to report their tests and findings. They could include suggestions to the company to improve stretch-ability and bubble-ability.
- Have students research the ingredients in gum and how gumbase and rosin affect the stretch. See www.bubblegum.com
- Have students research the history of gum and how natural products were once used as chewing gum.
- Have students make a list of physical and chemical changes that they observe occurring around/in their homes. Using this list, have students make a mini-poster depicting some of these changes.
- Have students address the final assessment suggestion given in this lesson.
Assessment: Will vary depending on the teacher's choice of elaboration activity.