Separating Mixtures: Discovery

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Students will be able to discover the purpose behind separating mixtures.

Big Idea

Why do we want to know about separating mixtures?

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Purpose of Lesson:

 The purpose of this lesson is to let students discover that all substances originally come from the earth.  


Major Strategies to Watch for:

1) Probe for understanding-  This formative check is meant to uncover misconceptions that students might be holding onto that will impact their learning.

2) Kinesthetic Lab- In this hands on lab, students are mining chocolate chips from a cookie.  They have to make decisions about tools they will use and the impact on the land.

Ready. Set. Engage!

5 minutes

Learning Goal: Discover the purpose of separating mixtures.

Opening Question:  When do we separate mixtures in real life?

Students record their opening question on their learning goal sheet and are ready to start class 3 min after the bell has rung.  I reward students who get started early with ROCK STAR SCIENTIST tickets.  

This question connects science content with students real lives.  It is important for them to realize that they use science content all the time, even if they don't realize it.  Here are some of he examples my students came up with.

- Separating types of Jelly Bellies.

-Washing dishes

- Doing Laundry

Follow the links to learn more about the beginning of class strategies and ROCK STAR scientist tickets.  


5 minutes

The purpose of this video is to give students a chance to see how complicated it is to get a material like aluminum out of the ground.  I like to choose aluminum because it is used so often it is almost invisible! The students already gave their opinions on how aluminum is produced in the opening.  Now it is time for them to see the real process of How Aluminum is Made in this video.

When the video is complete, I ask the students what surprised them about the video.  Most of the students talk about how complicated the process is and how much equipment and work it takes to get aluminum.  


5 minutes

I start each unit with a pre-assessment to open up the student thinking and help uncover misconceptions. This allows be to modify my teaching, compact curriculum, form appropriate groups, and measure growth. By far the best formative probes I've found are by Page Keeley. She's written several books of probes including Uncovering Student Ideas in Science Volume 1, 2, 3 and 4. This is a Which Substances Come From the Earth? formative probe that I wrote based on the Page Keeley probes.

In this probe I am trying to uncover the misconceptions that students have about where materials come from.  It is very common for students to believe that some materials are natural and others aren't.  The reason this can be a dangerous misconception is that if students don't understand that all substances come from the earth, than they can not accurately analyze the effects that human activity has on the planet.  

Discovery Activity

10 minutes

The purpose of this Cookie Mining activity is to show students some of the effects that pulling substances from the earth can cause.  Students will get to choose one of these tools to try to excavate the chocolate chips from a cookie.  You can find a full description of the Earth Science Week Cookie Mining lab activity. The lab includes decisions that the students have to make involving the economics of mining that makes this a very well-rounded activity.  

Below is a video of students "excavating" their mine.


Here are some pictures of the finished mines and the products.  Students get "paid" for whole and partial chocolate chips. 

At the end the students have to try to put the cookie back together, simulating land reclamation. If students are not able to put the land back together they are "fined" by the government.    


7 minutes

The Chocolate Chip Cookie Mining activity has a lot of opportunity for rich discussion.  You have the chance to explore the concept that all substances come from the Earth originally, that methods have to be used to separate the materials from the Earth, and that these methods could be harmful to land and people.  

Some of the questions that I use during the discussion are:

  • What did we learn about mining from our chocolate chip cookie experience?
  • How did we separate the chocolate from the cookie?
  • What were some problems with the separation?
  • Would there be better ways of separating the chocolate from the cookie? 

I prefer to use a circle discussion format for this activity. It is a great way to equalize the classroom and bounce ideas from one person to another.  

For me, the last question is the most important. I'm trying to get students to realize that physically separating substances (like picking out chocolate chips) might not always be the best way. This is a chance for students to brainstorm different ideas. For example, one student came up with the idea of adding water to the cookie to make it mushy. Some of the students thought this might also break up the chips, but some thought it would work. If you have time, you can have students experiment in class. Another way to let students experiment is to let them do this at home for extra credit or homework and report their findings to the class.


2 minutes

Closing Statement: Today in class we looked at how we separate mixtures to get materials from the Earth.  

Closing Question:  Explain this statement-  All materials we use are made from natural ingrediants. 

Closure depends greatly on timing and is not as easy to plan in advance as opening.  You can find more information about how I manage closure here.