In this lesson, students will review what they know about the three states of matter (solid, liquid, and gas). They will perform a word sort about states of matter and discuss how substances can exist in more than one state of matter. Following this they will contribute to a KWL (Know, Want to know, Learned) chart. The teacher will conclude the lesson with a demonstration using chocolate.
This lesson will help prepare your students to meet the performance expectations in the following standards:
- 5-PS1-2: Measure and graph quantities to provide evidence that regardless of the type of change that occurs when heating, cooling, or mixing substances, the total weight of matter is conserved.
- 5-PS1-3: Make observation and measurements to identify materials based on their properties.
- Scientific and Engineering Practices:
- Analyzing and Interpreting Data
By the end of this lesson, students should be able to
- Identify the three states of matter and provide examples of each state.
- Identify chocolate as an object that can be a solid or a liquid.
- Compare the melting point of chocolate and water.
This lesson supports students’ understanding of
- States of Matter
- Phase Changes
- Melting Point
Teacher Preparation: 15 minutes
Lesson: 30-45 minutes (allow additional time for chocolate to harden)
- Student Handouts
- Student activity sheet
- Student KWL sheet
- Student Word Sort
- Semisweet Chocolate Chips (one standard 12oz package with ½ of the chips at room temperature and ½ of the chips frozen)
- Plastic Spoon
- Microwave-Safe Bowl
- Ziploc Sandwich Bag
- Ice Cube Tray or Chocolate Mold
- Students should wash their hands thoroughly before leaving the lab.
- Food in the lab should be considered a chemical not for consumption.
- Liquid chocolate is hot and can burn the skin.
- Exercise caution when using melted chocolate. Students should not touch bowl with chocolate.
- Silicon ice cube trays/candy molds are recommended. They make clean-up faster and are easier than plastic trays to get the chocolate out of.
- If you are using thermometers with a paper backing, you will want to have a separate thermometer for the room-temperature and frozen chocolate. This makes your measurement more accurate since the chocolate can be difficult to clean off of the paper backing.
- If you are using a large ice cube tray, a plate and knife may be helpful for cutting chocolate into smaller pieces.
Before the Lesson:
- Pour half of the chocolate chips in a Ziploc bag and place in the freezer for a couple of hours, or overnight.
- Review the states of matter and have students complete the word sort (see student worksheet) or complete as a class on the board.
- Have students do a Think-Pair-Share with a partner and discuss how water and chocolate are similar, and how they can fall under more than one state of matter category.
- Ask students if chocolate is normally in a solid or liquid state. Have students give examples of when it can be liquid.After the discussion, tell students that today we will be changing chocolate from a solid to a liquid and then from a liquid to a solid.
- On chart paper, create a KWL chart about melting chocolate. Ask students what they already know and add it to the first column of the chart.Then create a list of things they want to know in the second column of the chart.
- Possible examples for What I KNOW:chocolate can melt in a car, chocolate can melt in my pocket, chocolate milk has liquid chocolate, etc.
- Possible examples for What I WANT to Know: How hot does it have to be to melt chocolate? How can you make chocolate into a solid again?
- Complete the demonstration (instructions below).
- Instruct students to complete the analysis and conclusion parts of the student activity.
- [Optional] Ask students if chocolate can exist as a gas. The typical answer is no. However, world-class chef Grant Achatz and his famous edible balloons may disagree.
- This article explains that Grant Achatz made “an entirely edible balloon made from green apple taffy and inflated with apple-scented helium.”
- Although this isn’t quite the same as a food existing as a gas, it is pretty close.
- This video shows Grant Achatz making the edible balloons.
- More detail and clips can be shown from Netflix’s Chef’s Table show, season 2 episode 1.
- Ask students if they think something similar can be done with chocolate. You may also have them come up with creative ways to make a potential chocolate gas.
- Put the room-temperature chocolate chips a microwave-safe bowl.
- Melt the room-temperature chocolate chips, stirring every 15-20 seconds to avoid overheating and to create a smooth consistency.
- Once the chocolate is melted and in a liquid form, use a thermometer to read the temperature. Be sure to keep thermometer in the middle of chocolate.
- Repeat steps 2-4 with the frozen chocolate chips.
- Ask students if it is possible to put the chocolate back into a solid form.
- After the discussion, spoon the melted chocolate into the ice cube tray and place it in a freezer or refrigerator (this will take 30-45 minutes).
- After the chocolate has frozen, remove it from the ice cube tray. Ask the students if they can see a difference between the chocolate that was originally room-temperature and the chocolate that was originally frozen.
- It should take the room-temperature chocolate approximately 1 minute total to melt in the microwave (don’t forget to stir periodically!)
- It should take the frozen chocolate about 2 ½ minutes total to melt in the microwave.
- It should take the melted chocolate 30-45 minutes to become solid in the freezer.
- The temperature of the melted chocolate should be around 94 or 96 degrees Fahrenheit (34-36 degrees Celsius).
For the Student
During this lesson, you will sort items according to their appropriate state of matter, and paste them into their proper category: solid, liquid, or gas. You will also take a close look at chocolate, which is normally a solid, but can also be a liquid.
These questions will be discussed with a partner, and then as a class.
- What is a state of matter?
- How can some substances change states of matter?
- What is a melting point?
- Wash your hands thoroughly before leaving the lab.
- Follow the teacher’s instructions for cleanup of materials and disposal of chemicals.
- Complete the word sort by cutting out the items and gluing them into the appropriate category.
- Complete the Know and Want to Know columns of the KWL chart.
- Watch the teacher demonstration and discuss observations on the melting chocolate.
- Record the time it took the room-temperature and frozen chocolate to melt in the table below.
- After the chocolate has melted record the temperature of the chocolate in the same table.
- Record what you learned in the L column of the KWL Chart.
- Complete the analysis and conclusion questions.
|Minutes to Change From a Solid to a Liquid||Temperature Measured After Melting||Notes/Observations|
- Why do you think we need to stir the chocolate as it melts?
- How is chocolate changing states similar and/or different from how water changes states?
- In this demonstration, chocolate chips were melted. How do you think the outcome would be different if we used a large chocolate bar instead?
Based on your observations, what did you learn about how chocolate changes states?
In a few sentences, explain how chocolate can change state and what states it can exist in. Be sure to include data from the results table in your explanation.