Summary

In this lesson, students explore the science behind chemical reactions as well as the processes used by chemical engineering principles to develop new materials. The idea that mixing two substances can result in an explosion, the release of gas, and the formation of an entirely new substance is both fascinating and mysterious to most young students. Many students are also attracted to the idea of inventing new substances with different and exciting properties. The lesson begins with a reading of Dr. Seuss’ book Bartholomew and the Oobleck. Students then explore what happens when two different substances are mixed and a chemical change occurs. They then extend the investigation further by experimenting with different combinations of substances to make “oobleck” (slime).

This is a simple investigation that introduces or expands on the concept of chemical reactions, but does not go into details of the composition of the substances or the reaction that occurs.

Objectives

By the end of this lesson, students should be able to:

• Describe and compare physical properties of various substances.
  
• Explain that when two or more different substances are mixed a new substance with different properties may be formed.
  
• Identify the difference between a chemical change and a physical change.
  
• Describe possible negative effects of substances that are engineered by humans.
  
• Describe ways that chemical engineering can make life better or worse.

Chemistry Topics

This lesson supports students’ understanding of the following topics in chemistry:

• Matter
• Chemical reactions

Time

Teacher Preparation: 30 minutes

Lesson:

• Single Day lesson: 50 minutes
• Multiple Day Extension or Investigation: This topic of study could be easily adapted into a 5-day format

Materials

Single Day Instruction (small sample for each student):

• Water (average class, 1 liter)
• Borax-based detergent (such as 20 Mule Team Laundry Soap) (1/4 cup)
• White glue (2 to 3 oz. per student)
• Stirring sticks (craft sticks or popsicle sticks – 1 per student)
• Small 2-3 ounce paper or plastic cup (plastic bags will also work—1 per student)
• Green food coloring (1-2 drops per student cup; ¾ bottle for 1 gallon of glue)
• Mixing flask or container (for borax solution)
• Eye dropper (for adding borax solution to glue—1 per student or team)
• Science journal
• Optional:
  • for engagement and connections to reading: Bartholomew and the Oobleck by Dr. Seuss
  • for engagement, motivation, and atmosphere: Erlenmeyer flasks and graduated cylinders filled with food colored borax solutions; candle; magician or sorcerer’s costume
  • safety equipment such as goggles, gloves, aprons (see safety note)

Multiple Day Extension or Investigation:

• Computers and other resources for conducting research
• Corn starch or other substances as required to produce different types of slime
• Balance
• Graduated cylinders
• Rulers, tape measures, meter sticks, etc. (for measuring)

Safety

• Candle Burning: A hurricane lamp enclosure can be used to surround the open flame. You could also use a battery-operated candle.
• Chemicals: While these are not dangerous chemicals, white glue and borax solution should not be eaten. Students should be instructed that they should be responsible with the slime they create, including instructing younger children not to eat it and putting it away when finished.
• Although this activity is specifically designed for “at home use” with children, the single and multiday activities provide the opportunity to introduce lab safety to young students. For example, it is important that the students be allowed to investigate using their senses. Chemists do not feel, smell, or taste substances unless they are absolutely sure that the substances are safe to examine in this way.
• When running the multiday activity/investigation, the students must wear safety goggles, rubber gloves, and aprons.

Vocabulary Terms

• Chemical change
• Chemical reaction
• Solid
• Liquid
• Polymer
• Engineering
• Chemical engineering

Keywords

Oobleck, slime, silly putty, polymer, polymerization, elastic, non-Newtonian liquid

Teacher Notes

• One box of detergent with borax (such as 20 Mule Team) will last many years.
• Consider buying glue in gallon jugs.
• Throughout the activities, encourage students to record their observations using both words and drawings.

Science Background

The process of making slime involves both physical and chemical changes. Mixing borax with water creates a borax solution. No chemical reaction takes place during this step. Mixing food coloring and water with glue creates a mixture. For the most part, water is just mixing with the glue, but there is some reaction occurring between the water and glue. Mixing the borax solution with the glue mixture, however, involves a significant chemical reaction.

School glue is a substance known as polyvinyl acetate (PVA). PVA itself is a polymer, a long chain of repeating molecules, or monomers. PVA is made of C ₄H₆O₂ monomers.

Borax is sodium borate, Na2B4O7 •10H2O. When borax and school glue are mixed, a more complex polymer forms. The borax molecules bond to the PVA chains, linking them together. This causes the glue to become less like a liquid and more like a solid.

The slime created is a type of non-Newtonian fluid. Newtonian fluids, like water, respond in the same way to stress regardless of the rate at which the stress is applied. Water has the same viscosity (resistance to flow) regardless of how forces are applied to it. It has a very low viscosity whether it is poured slowly or hit hard and quickly with a hammer. Non-Newtonian fluids, however, respond differently, depending on whether the stress is applied quickly or slowly. Slime has a low viscosity and will flow easily under the slow, gradual stress of the force of gravity but a high viscosity, causing it to break under the quick stress of being hit with a hammer.

Additional Resources:

• Non-Newtonian liquids
  • On Dr. Seuss’s Famous Non-Newtonian Fluid
  • Non-Newtonian fluids
• Polymers:
  • Kids' Macrogalleria
    
• Slime:
  • The Incredible Secret Formula Book by Shar Levine and Leslie Johnstone Pure Slime by Brian Rohrig
  • Pure Slime by Brian Rohrig
  • Silly Putty: Synthesizing a Polymer

Preparation

• Mixing the borax with water and pouring the solution into eyedropper bottles takes about 20 minutes (multiple small group or individual).
  
• Organizing the remaining supplies and materials for the reading and activity takes approximately 10 minutes, and is best accomplished before the instruction is to take place.