Materials Included In Kit

Additional Materials Required

Safety Precautions

The materials used in this activity are considered non-hazardous. However, all may cause slight irritation to the skin or eyes. Avoid contact of all chemicals with eyes and skin. Follow all laboratory safety guidelines. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Please review current Safety Data Sheets for additional safety, handling and disposal information. Remember to wash hands thoroughly with soap and water before leaving the laboratory.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. The solid products of this reaction may be disposed following Flinn method #26a.

Lab Hints

• Enough materials are provided in this kit for 30 students working in pairs or for 15 groups of students. Both parts of this laboratory activity can reasonably be completed in 1–2, 50-minute class periods. The Prelaboratory Assignment may be completed before coming to lab, and the data compilation and calculations may be completed the day after the lab.
• Once the lava lamp reaction stops, additional antacid may be added to restart the reaction.
• As an extension, students may perform food dye or pen dye chromatography. Flinn Scientific products in this category include Radial Chromatography—Super Value Laboratory Kit (AP8687) and Candy Chromatography—Wet/Dry Inquiry Lab for One Period (AP9592).

Answers to Prelab Questions

1. List four known intermolecular forces.

   Hydrogen bonding, van der Waals, dipole–dipole, ion–dipole

2. Density plays an important factor in the lava lamp experiment. Oil and water are two components that are used. Define density and why it is an important concept in this experiment.

   Density, an object’s mass divided by its volume, is a characteristic property of a material. Solids that have the same physical appearance or objects of different shapes and sizes may be identified by their densities. The density of a sample is commonly expressed as g/cm³. There are two liquids in this experiment that are not miscible. The water is more dense than the oil; therefore, the water is the bottom layer, and the oil is the top layer.

3. What does a household lava lamp look like?
   

   A household lava lamp often has a lamp that heats the substances inside of the lamp. It is made of see through glass. There are often two liquids of different colors in the lamp. It forms bubbles that rise and fall due to being heated when plugged into an outlet.

4. List four dyes in Gobstoppers candy.
   

   FD&C Blue 1, FD&C Red 40, FD&C Yellow 5, FD&C Yellow 6

5. Which liquid will evaporate faster—water or ethyl alcohol?
   

   Ethyl alcohol will evaporate faster due to having weaker intermolecular forces. Water molecules hydrogen bond to each other, hydrogen bonding is a strong intermolecular force.

Sample Data

Answers to Questions

1. In the following space, draw the lava lamp experiment (use colored pencils if available) or paste a printed picture. Label all of the parts of the lava lamp.

2. What was the lava lamp’s overall reaction? Make sure these products are labeled in your figure in Question 1.

The lava lamp overall reaction is:
3NaHCO₃ + C₆H₈O₇ → C₆H₅Na₃O₇ + 3CO₂ + 3H₂O

3. Gobstoppers^® observations table

The experiment was very colorful, overall. The FD&C dyes are polar, and the water is polar; therefore, based on the principle that like dissolves like, the dyes readily dissolved in water over the progression of the experiment. Fainter and deeper colors were witnessed, this could be due to the dye molecules having various levels of polarity. An interesting observation, however, was that the dyes did not mix once they were dissolved. One hypothesis is that the candies contain other additives that prevent the dyes from mixing after they have dissolved in the water.

4. In the following space, draw the Gobstoppers Petri dish experiment. Use colored pencils if available. You may choose to paste a printed picture of the experiment as well.

Introduction

Have fun making your very own miniature lava lamp and learn about intermolecular forces, density and much more at the same time! Then a simple Petri dish experiment with Gobstoppers^® proves how candy dye molecules interact with water and reinforces intermolecular forces concepts—watch how the colors do NOT mix in the dish and hypothesize why. Both experimental setups are simple, and the resulting colors and observations will mesmerize!

Concepts

• Intermolecular forces
• Surface tension
• Consumer science
• Density
• Polar vs. non-polar
• Chemical reactions

Background

There are many educational concepts that can be learned from these two simple consumer science experiments. In both the candy and lava lamp experiments, intermolecular forces, often referred to as IMFs, are readily present. Intermolecular forces include dipole–dipole attractions, hydrogen bonding, dipole-induced dipole attraction, and London dispersion forces. All of these types of forces are electrostatic in nature. Electrostatic forces arise when the molecules contain or are capable of creating areas of charge separation. Dipole–dipole interactions occur only in polar compounds. The greater the polarity of the molecules, the larger the force of attraction between those molecules. Many compounds that contain an O—H or N—H bond exhibit a specialized form of dipole–dipole attraction called hydrogen bonding. Hydrogen bonding occurs in molecules where hydrogen is bonded to a highly electronegative atom (X). The difference in electronegativity between H and X creates a large charge separation in the bond.

δ–   δ+
X—H  

If the molecule also contains a highly electronegative atom with a lone pair of electrons, this lone pair is strongly attracted to the now partial positive charge on the hydrogen atom in a neighboring molecule. This is hydrogen bonding.

δ–   δ+      δ–  
X—H- - -:Y—

Because they possess strong intermolecular attractive forces, water and ethyl alcohol, for example, have higher melting and boiling points than similar-size nonpolar molecules. For different compounds to form solutions, the intermolecular forces between the molecules must be similar to allow for the separation and mixing of the two substances. Without this similarity, the substances will remain separated. Hence the phrase, “Like dissolves like.” There are only seven dyes approved by the FDA as additives in food. They are known as FD&C dyes. Take a close look at any candy food label, inspect the label closely for the Gobstoppers^® experiment. All FD&C-approved food dyes are charged, water-soluble organic compounds that bind to natural ionic and polar sites in large food molecules, including proteins and carbohydrates.

Finally, density and polarity are two key concepts that will be witnessed in the lava lamp experiment. The two liquids, silicon oil and water, are immiscible; they will not intermix to form a solution. Silicon oil is composed of hydrocarbons, which have a general chemical formula of C_NH_{(N x 2)+2}. The difference in electronegativity values between carbon and hydrogen is small. When they form molecules, electrons are almost equally shared within the carbon and hydrogen bond. As a result, the carbon hydrogen bond has little change separation or polarity. Hydrocarbon molecules are nonpolar and hydrophobic (water repelling) in nature, since water, H₂O, is a polar molecule. Oxygen and hydrogen have very different electronegativity values, causing an uneven distribution of electrical charge resulting in partial charges—a dipole. The geometry of water keeps the partial charges separated and causes water molecules to be polar. Since the electronegative oxygen atoms in water molecules have a partial negative charge, hydrogen atoms from other water molecules will be drawn to this negativity due to their partial positive charge—resulting in an attractive force called hydrogen bonding. Water molecules have greater attraction to one another due to hydrogen bonding than they do to other nonpolar molecules, such as hydrocarbons like the silicon oil. The strong attraction between water molecules causes them to be tightly packed in the liquid state. This means there will be more water molecules (mass) per unit volume of liquid compared to nonpolar liquids. The silicon oil and water liquids will be distinctly identified in this lab due to their immiscibility. Addition of FD&C food dye will add an appealing color to the lava lamp. The FD&C food dye is a polar substance, so it mixes readily with water. When the antacid tablet is added, the overall lamp oil reaction is:

3NaHCO₃ + C₆H₈O₇ → C₆H₅Na₃O₇ + 3CO₂ + 3H₂O

Witness these products in your very own lava lamp! The beautiful colors and evidence of these important concepts will be witnessed in these fun experiments. If the instructor allows, make sure to take a short video or image of the creations using a smartphone!

Experiment Overview

Each student pair will make their very own miniature lava lamp by following the procedure and will collaborate and share the lab equipment. Then they will follow the procedure to test the candy Gobstoppers^® in a Petri with a small amount of DI water. Collect observations the lab notebook.

Materials

Prelab Questions

1. List four known intermolecular forces.
2. Density plays an important factor in the lava lamp experiment. Oil and water are two components that are used. Define density and why it is an important concept in this experiment.
3. What does a household lava lamp look like?
4. List four dyes in Gobstoppers^® candy.
5. Which liquid will evaporate faster—water or ethyl alcohol?

Safety Precautions

The materials used in this activity are considered non-hazardous. However, all may cause slight irritation to the skin or eyes. Avoid contact of all chemicals with eyes and skin. Follow all laboratory safety guidelines. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Please review current Safety Data Sheets for additional safety, handling and disposal information. Remember to wash hands thoroughly with soap and water before leaving the laboratory.

Procedure

Part A. Make Your Own Lava Lamp

1. Obtain a 60-mL square bottle, remove the cap, and throw it away.
2. Fill the bottle ½ full with DI (deionized) or distilled water, about 30 mL.
3. Squeeze 2 to 3 drops of your choice of food dye color into the water in the bottle, gently swirling to mix.
4. Carefully add oil and fill to the neck of the bottle. The oil may be dispensed from the chemical bottle, or it may be transferred to a 50-mL beaker and then added to the bottle.
5. Using a spatula, carefully break an Alka-Seltzer^® tablet into 4 smaller pieces.
6. Drop one piece of the Alka-Seltzer into the bottle containing the water and oil.
7. DO NOT CAP THE BOTTLE! This may cause pressure build up inside the bottle, which poses a hazard.
8. Make observations in the lab notebook. If the instructor allows, take a short video of the lava lamp using a smartphone.
9. At the end of the class period, discard the lava lamp solutions according to the instructor’s directions.

Part B. Gobstoppers^® Petri Dish Science

1. Cover the bottom of a Petri dish with DI (deionized) or distilled water.
2. Select 5 different colored Gobbstopper candies. If enough colored candies are available, add 2 more to each color and move on to step 3.
3. Place the candies along the edges of the Petri dish (see Figure 1).

Student Worksheet PDF

14144_Student1.pdf