In this lesson students will analyze the effectiveness of different brands of antifreeze/coolants and their ability to protect an engine in cold climates. Students will conduct a lab investigation to examine the freezing point depression in samples that have been diluted with distilled water. Students will also determine the specific heat capacities of antifreeze/coolant products as compared to pure water and explain how it relates to thermal energy transfer in the internal combustion engine.
This lesson 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-PS3-4: Plan and conduct an investigation to provide evidence that the transfer of thermal energy when two components of different temperature are combined within a closed system results in a more uniform energy distribution among the components in the system (second law of thermodynamics).
- Scientific and Engineering Practices:
- Analyzing and Interpreting Data
- Engaging in Argument from Evidence
By the end of this lesson, students should be able to:
- Draw conclusions from experimental data in which they compare and contrast different antifreeze/coolant products.
- Support conclusions with valid arguments based on experimental evidence.
- Explain the process by which an internal combustion engine is cooled.
- Relate the cooling process to thermal heat transfer and heat capacity.
This lesson supports students’ understanding of:
- Colligative properties (freezing point depression)
- Specific heat capacity
- Thermal energy transfer
Teacher Preparation: 30-45 minutes
- Engage: 60 minutes
- Explore: 2 hours
- Explain: 30 minutes
- Elaborate: 30 minutes
- Evaluate: 60 minutes
- 4 Different brands of antifreeze/coolant (full strength)
- Thermometer or temperature probe with appropriate computer interface
- 100-mL beakers
- Ring stand and clamps
- 100-mL graduated cylinders
- Rock salt
- Crushed ice
- Stirring rods
- Nalgene or other non-glass beaker
- Electronic balance
- Always wear safety goggles and aprons when handling chemicals and glassware 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.
- Ethylene glycol SDS
- Propylene glycol SDS
- This resource could be used as a post-AP Chemistry exam activity.
- Engage: Essential questions should be presented to students:
How does the cooling system in an internal combustion engine work?
- Students will be given a diagram that illustrates how the cooling system works in an internal combustion engine.
- Students write a brief explanation of the purpose for each component.
- What is the best antifreeze/coolant for an automobile engine? What criteria should be considered when selecting one brand over another?
- On the first day of the lesson, students will be presented with a request from an automobile dealer in northern Vermont to analyze different brands of antifreeze/coolant so that they can make recommendations to their customers.
- Students will engage in a brainstorming session in which they will identify key factors to consider when selecting an antifreeze/coolant product.
- How do products containing propylene glycol compare with those made with ethylene glycol?
- Students will research the properties of both compounds and prepare a table of advantages/disadvantages or pros/cons of each one.
- Explore: Students perform both of the included lab investigations.
- Explain: Students will discuss and analyze experimental findings from investigations.
- Elaborate: Students will integrate essential questions and initial research into a coherent explanation of their experimental findings.
Evaluate: Student groups will prepare and submit a product, in the format of their choosing to present their experimental findings and make the connection to the cooling system in an internal combustion engine. (For example: Students could produce a narrated pictorial account of their investigation, a video, or commercial that advertises the product that gave the optimal results).
- This information focused on the history of the Water Cooling System in Model T Ford engine may be helpful for a teacher to review before the lesson.
- This diagram of a cooling system may be helpful to share with students.