A Good Cup O' Joe

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Objective

SWBAT describe the law of conservation of matter and apply that to making tea and coffee.

Big Idea

What happens to coffee beans when they are crushed and heated to make a cup of coffee? The science behind coffee (and conservation) will be discovered in this lesson.

Engage

5 minutes

I start the lesson by playing the Do You Want To Go To Starbucks parody:

 

Students relate to it not only because they are familiar with the movie, "Frozen", but also because many of them make daily trips to Starbucks with their friends or parents. Even if they don't actually drink coffee, they all know many people who do!

I ask the students to guess what food we may be learning about today, to which all of them will quickly respond, "Coffee"! Next, I ask if they have ever stopped to think about the science behind their favorite coffee or coffee-like drinks. Naturally, most haven't, but that ends today! I introduce today's topic, explaining to the students that we will learn today about this delicious beverage how science makes it what it is!

Explore

10 minutes

To activate prior knowledge, I have students watch the Diffusion Animation we studied in the lesson about Bacon and diffusion. I ask the students to Turn and Talk, discussing how diffusion may take place during the brewing process. Students will usually be able to figure out that the coffee grounds, milk, sugar, and other ingredients diffuse into the hot water, spreading into less dense areas.

Next, I pass out a small Dixie-type cups of both fresh and roasted whole coffee beans* to each table group, as well as small samples of warm, black coffee to each student. I allow students to touch, smell, and even taste (if they choose) samples from all of the cups. While they are investigating the beans, I play the How It's Made - Coffee video to explain how coffee is made.

Next, I post the following questions:

  • Coffee comes from beans which are crushed and added to hot water. Can you feel/taste the ground beans in a cup of coffee? 
  • What happens to the beans when added to the coffee? Are they still in there?
  • In addition to diffusion, what processes do you think the coffee undergoes in order to go from cherry to bean to drink?

 

*If you plan ahead, you can also order unroasted beans and coffee plants/cherries for students to investigate. These are usually available on Amazon.

Explain

15 minutes

Now that we have learned a basic understanding of how coffee is made, I want students to investigate the basic ideas behind the Law of Conservation of Matter. While we will investigate this concept in more detail in future lessons, I at least want them to develop a working definition for now, so they can apply it to the chemistry of cooking.I break the students into groups of 2-3 and have them do some research on the concept. After conducting their research, I have the students work together to create a drawing or diagram that illustrates the law.

After giving students approx 30 minutes to research and create their model, I have each set of partners share their work with the class. I purposely select students with a stronger understanding to share first, which allows the students with weaker connections to revise their models prior to sharing. As each group shares, the class provides feedback to help each other revise their understanding (as necessary).

Next, I pass out the Coffee Handout* and have students partner read, highlighting the connections between coffee, diffusion, and the law of Conservation of Matter. We discuss the concepts as a class after reading.

*The information presented in this handout was adapted from the blog, “The Science of Food”, by Scott McQuery.

 This video gives you important information on demonstrations that help students to understand the conservation of matter.


Elaborate

30 minutes

Now that students have a solid grasp of the concepts of diffusion/conservation and how they relate to coffee, it's time to enjoy a warm, frothy beverage!

*For this activity, I usually elicit the help of parent volunteers to make sure students are working safely and using proper hygiene practices.

I start by having each student wash, dry, and sanitize their hands. Then I send them to 4-5 stations around the room, each of which is equipped with:

  • Coffee maker -OR- 1 carafe/hot plate with hot water
  • Disposable coffee cups
  • Spoons and/or coffee stirrers
  • Variety of tea bags and powdered instant coffee mixes, such as International Cafe, etc.
  • Paper towels or napkins
  • Hand sanitizer
  • Oven mitt (This might not get used, but it provides a safe way to move pans and other hot materials)
  • 1-2 parents

Each students gets the opportunity to mix powders and create their own custom beverage.

Evaluate

10 minutes

Once the students have all had a chance to create their drink, I pass out the Coffee Questions Exit Ticket for students to complete before leaving for the day. This document will help me to assess their knowledge and clarify and misunderstandings they have at the beginning of the next class. It also allows me to determine if the students' understanding is clear enough to apply to other situations.