In this lesson students will learn about the properties of glass, and relate those properties to the new engineering design of glass in a car.
This lesson plan will help prepare your students to meet the performance expectations in the following standards:
- HS-PS1-1: Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms.
- HS-PS1-2: Construct and revise an explanation of the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.
- HS-PS1-3: Plan and conduct an investigation to gather evidence to compare the structure of substances at the bulk scale to infer the strength of electrical forces between particles.
- HS-PS2-6: Communicate scientific and technical information about why the molecular-level structure is important in the functioning of designed materials.
- HS-ETS1-2: Design a solution to a complex real-world problem by breaking it down into smaller, more manageable problems that can be solved through engineering.
AP Chemistry Curriculum Framework
This lab supports the following unit, topic and learning objective:
- Unit 3: Intermolecular Forces and Properties
- Topic 3.3: Solids, Liquids and Gases
- SAP-6.A: Represent a given chemical reaction or physical process with a consistent particulate model.
- Topic 3.3: Solids, Liquids and Gases
By the end of this lesson, students should be able to
- Compare and contrast the properties of laminate glass and Corning® Gorilla® Glass.
- Design an experiment to examine the properties of sugar glass.
- Explain why car design benefits from stronger, lighter glass.
This lesson supports students’ understanding of
- Physical Properties
- Periodic Table
- Experiment Design
- Scientific Method
Teacher Preparation: 30-45 minutes
- Engage: 10 minutes
- Explore: 60-80 minutes (Part 1), 90 minutes (Part 2)
- Explain: 70 minutes
- Elaborate: 45 minutes
- Evaluate: 60-100 minutes
For each lab group
- 8-10 Tea Light candles with metal bases. (Note: metal base is all that is needed; the candle is not needed for experiment.
- Corn syrup
- Digital candy thermometer (or have available high temperature digital thermometers that can measure up to 150 ⁰C.)
- Porcelain evaporating dishes (70 mL capacity)
- Stirring rod
- Crucible tongs
- Ring stand
- Utility clamp
- Hot plate
- Electronic balance
- Weighing boats
- Always wear safety goggles when handling chemicals in the lab.
- Students should wash their hands thoroughly before leaving the lab.
- When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.
- Exercise caution when using a heat source. Hot plates should be turned off and unplugged as soon as they are no longer needed.
- Use caution around hot evaporating dishes, and their contents; they are a significant burn hazard.
- Do not consume lab solutions, even if they’re otherwise edible products.
- Food in the lab should be considered a chemical not for consumption.
- This resource could be used as a post-AP Chemistry exam activity.
- Engage: Show Corning ® Video, “The Glass Age—Part 2: Strong, Durable Glass.” Optional: Start video at 6 minutes, and play until end (Total Length of segment to show = 4 minutes)
The entire Corning video is excellent, but is 10 minutes long. It starts with a discussion of Gorilla® Glass in smart phones. It is suggested to just show the last part of the video starting at about 6 minutes, since this is the focus on windshields. Some students may ask about the difference between Gorilla ® Glass and bullet-proof glass. Bullet-proof (more correctly called bullet-resistant) glass is a composite material, composed of layers of glass and polymer. See the following:
Explore: Since we cannot make glass in the lab, we are going to use a model for glass made from sugar. Before doing the lab, it would be helpful to have a discussion with the class about models; e.g., the use of an atomic model as an explanation for atomic theory.
The lab is designed as a two-part lab. Part 1 is a directed lab with a cookbook recipe. The students will learn the technique of sugar glass making and cast some samples for testing. In Part 2, the students will extend their knowledge and experiment with making different sugar glasses by changing temperatures and proportions of ingredients. Part 2 is an inquiry lab, and students can adjust the composition, process and/or testing of their sugar glass as needed. Depending on your students’ abilities, and their prior experience with inquiry labs, you may choose to do the “Explain” piece of this activity before conducting the inquiry portion of the lab.
Lab groups can be any size that is practical. The limiting factor is the number of lab benches and likely the number of hot plates available.
Advise students that the boiling sugar solution is a burn hazard since it has to reach temperatures well above 100 ⁰C. Be careful with the boiling sugar, as it will rapidly rise in temperature as it boils. If it turns brown, it has caramelized, and must be discarded.
Keep in mind that the samples must be cooled before testing, so you need to plan for doing the testing on a different day than sample preparation. If you have a double lab period, it was found that samples cooled thoroughly within 20 minutes. If you do not have a double lab period, let the samples cool overnight at room temperature.
The recipe given in Part 1 is very reproducible for a good glass. Groups may want to collaborate on finding the limits of the sugar/water/corn syrup ratio. For example, it is possible to make a glass from just sucrose and water, but it is prone to crystallization. Too much corn syrup will lead to a gummy material which is difficult to remove from the metal base. The literature reports that good glasses are obtained using a 2:1 ratio of sugar to corn syrup, with approximately 10% water. See the following resource for an in-depth analysis: "Building a Low Cost, Hands-on Learning Curriculum for Glass Science and Engineering Using Candy Glass."
Students may also calculate the density of the candy glass. The literature (reference given above) suggests constructing a pycnometer if the samples are irregularly shaped. If the samples as constructed in the lab below are used, and are regular cylinders, their volume may be calculated using geometry. Water displacement cannot be used as the samples absorb water.
As an extension, you can also have the students explore how different heating and stirring methods impact the properties of the candy glass.
Explain: Students are asked to research the properties of laminate glass in a windshield using web sites such as How Products are Made: Automobile Windshield.
Students are then asked to research the properties of Gorilla® Glass in a windshield using websites such as Corning Gorilla Glass.
After their research, they can write an essay, or use technology to make a Prezi, PowerPoint, or video that compares and contrasts conventional windshield glass with Gorilla® Glass. Students will then share their papers or videos/PowerPoint’s with another group for comments.
- Elaborate: This can be done on paper, poster board, or by using technology. Groups can research and develop their ads in one day, and then present them the next day to the rest of the class.
2. Students are asked to research the advantages of lighter and stronger windshields, and then work with a group to develop a promotional ad (can be written, illustrated or done using technology) for lighter and stronger windshields in a car.
If you want to explore new technology for presentations, you can suggest students use Audacity (a free open source software for recording and editing sounds; available for free download at audacityteam.org) or Camtasia (software that allows you to create finished videos from screen recordings; free trial but full use software is not free).
- Evaluate: Lab reports should be collected for evaluation. Ads should be assessed at teacher’s discretion.