Melting+Chocolate

= Melting Chocolate =

by Chris Fennig and Ben Gambler

This lesson is appropriate for grades 4-8 with a focus on melting points, the factors that affect them, and ancient civilizations.

The state standards that will be focused on are 3.4.7 A, 3.7.7 B and 3.8.7 A. In addition, state standards 3.2.7 B and 3.2.7 C building off of 3.2.4 C. The national standard of properties and changes of properties in matter is covered. Students will also use appropriate tools to gather, analyze, and interpret data, which is another standard in NSES.

** Objectives ** ** Content Explanation: ** 2,600 years ago Mayans drank chocolate. Called the cocoa tree //cacahuaquchtl.// Chocolate comes from //xocoatl// meaning "bitter water." Cocoa pods symbolized life and fertility. Used in religious rituals and for currency. Materials, Equipment, Set-Up ** Activity: ** ** SAFETY: ** Risk of being burnt by a hot plate or hot glassware. Use caution around the entire set-up. Handle the beaker with care as it will be hot upon removal from the hot plate. Any broken glassware will be reported to the teacher immediately. Students are**NOT** to eat any of the chocolate. Goggles will be worn at all times. Procedure: Part I:   Part II: ** Body of Lesson ** 1) Engagement: (5 minutes)   a) So who here likes chocolate? b) What is your favorite type of chocolate?   c) Did you know that there are many different types/ways to make chocolate? d) What is melting? What about a melting point?   2) Exploration: What causes melting points of chocolate to differ? (7 minutes) a) We will explain to them how chocolate is a mixture of a number of things, including fats. By varying the amount of each ingredient will change the final type of chocolate you produce. The materials above will be used in the melting point determination of various types of chocolate. This will demonstrate how different chocolates with varying fat contents affect the melting point. Students will determine the melting points of various chocolates. If time permits, they will also explore how the amount of chocolate present affects the melting point. This stage will teach them about melting point as an intensive property of matter.   3) Explanation: (3 minutes) a) Upon completing of the lab, we will ask students to graph their data and explain how the fat content of the chocolates affects the melting point.   4) Evaluation: (5 min) a) We will ask the students questions about the different stages of the experiment and why particular results were observed.   5) Elaboration a) If there is additional time, we will further explain how the fats contained within the chocolates take on different structures upon heating/cooling cycles.  ** References: **
 * 1) 1. Students will be able to define melting point and find a melting point.
 * 2) 2. Students will be able to explain what affects the melting points of various chocolates.
 * 3) 3. Students will be able to explain how structure affects properties of a substance.
 * (3) Hot plates
 * (6) Beakers
 * (6) Temperature Probes
 * (6) Computers (with Inspiration program)
 * (6) Goggles
 * (3) Stirring rods
 * Chocolate bars
 * 1) 1. Break one rectangular section of a chocolate bar into four pieces, each approximately 2 cm by 1 cm, and place them in the beaker. Insert the temperature probe between the chocolate pieces. Place the beaker onto the hot plate. Each group will test different sets of chocolate and compare data.
 * 2) 2. Slowly dial up the hot plate while watching the chocolate to see when it melts. Upon its melting, record the temperature.
 * 3) 3. Dial the hot plate back down to 0. Remove the probe from the beaker and clean the chocolate from both.
 * 4) 4. Repeat steps 1-3 with all types of chocolate bars available.
 * 5) 5. Plot a graph of the melting point of each chocolate bar vs. its unsaturated fat content. How do they correlate?
 * 1) 1. Break a rectangular unit of chocolate (any bar that still has at least five squares left) into four pieces. Place two into the beaker. Insert the temperature probe between the chocolate pieces. Place the beaker onto the hot plate.
 * 2) 2. Dial up the hot plate slowly while watching for the chocolate to melt. Record the temperature when it melts.
 * 3) 3. Dial the hot plate down to 0. Remove the probe from the beaker and clean the chocolate from both.
 * 4) 4. Repeat steps 1-3 using 4, 6, and 8 pieces of chocolate. Each piece should be approximately 2 cm by 1 cm.
 * 5) 5. Graph the melting point vs. number of chocolate pieces. How do they correlate?
 * 1) 1. The Nuffield Foundation and Royal Society of Chemistry. "Chocolate and Structure." //Practical Chemistry//. __ [] __
 * 2) 2. Sokol, Gail. "Chapter 19: Chocolate." //About Professional Baking//. Clifton Park, NY: Delmar Learning, 2006.