Summary

In this demonstration, students will observe the chemical process that occurs when making cheese. Students will be become more familiar with fundamental chemistry terms while making important observations.

Grade Level

Elementary School

NGSS Alignment

This demonstration will help prepare your students to meet the performance expectations in the following standards:

• 5-PS1-4: Conduct an investigation to determine whether the mixing of two or more substances results in new substances.
• Scientific and Engineering Practices:
  • Engaging in Argument from Evidence

Objectives

By the end of this demonstration, students should be able to

• Identify when a change occurs by using observations during a procedure.
• Differentiate between a chemical and a physical change.
• Define various terms that are related to the cheese-making process.

Chemistry Topics

This demonstration supports students’ understanding of

• Observations
• Mixtures
• Chemical reactions
• Chemical Change
• Physical Change
• Acids and Bases
• pH

Time

Teacher Preparation: 30 minutes
Lesson: 45 minutes

Materials

• Hot plate
• 4 Cups whole milk
• 1 cup buttermilk
• 1/3 cup heavy cream
• Mesh Strainer
• Cheese cloth
• Projector Computer (with internet access), pencils, post-it notes, and Teacher made Graphic Organizer with 3-different boxes for pictures and explanation.

Safety

• Always use caution around open flames. Keep flames away from flammable substances.
• Always be aware of an open flame. Do not reach over it, tie back hair, and secure loose clothing.
• Do not consume lab solutions, even if they’re otherwise edible products.
• Food in the lab should be considered a chemical not for consumption.

Teacher Notes

• This demonstration was originally planned with second graders in mind but could still have a great impact for elementary grades 3-5.
• The teacher will make ricotta cheese while the students observe the process.
• Before explaining what cheese is made of, the teacher will begin by polling the students and asking them a few discussion questions: Do you love cheese? When have you had cheese? Are there different types of cheese?
• Prior to completing the demonstration, it would be helpful for the teacher to familiarize themselves with the background information provided by Science News for Students about the chemistry of cheese.
• The following vocabulary words can be defined in the “Power Words” section of Chemistry Gets Cheesy. These would be helpful for teacher background knowledge and to be able to explain to students during the demonstration depending on their grade/ability level:

• A simple homemade recipe for Ricotta Cheese can be found here. This recipe could easily be cut in half to use fewer ingredients.
• Follow the cheese recipe, and while doing so it would be helpful to integrate the following information:
• Explain that milk is an emulsion, there are tiny fat particles dispersed throughout the watery milk. Milk also contains a combination of water, fat, carbohydrates (sugar), and protein.
• The cheese-making process isn’t simply turning liquid milk into a solid form—this would be a physical change like water freezing to ice. When we make cheese we add an acid (in our case we’re adding buttermilk and cream to the milk) which changes the pH level and helps the liquids turn to solid.
• Adding an acid and then heating is what denatures the protein and causes clumping. This is a chemical change/reaction.
• Make sure the students can see as you scoop the curds from the whey.
  
• Students shouldn’t eat in the lab. If you would like students to taste it, perhaps you could recommend that they try it at home with a parent, and document the process as an extension.
• Students will complete a Before-During-After chart to organize their observations. The teacher should then compile all observations from students as a class and discuss the process.
• After the demonstration, the teacher could show the students the short video (~ 5 minutes), The Chemistry of Cheese, from the NBC Cheeseburger Chemistry series as a cumulative activity.
• Finally, students can complete the analysis questions (post-video) and share answers as a class.