Mixtures: Characteristic Properties - Magnetism and Solubility

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Objective

Students will be able to identify the characteristic property of magnetism and solubility and use it them to separate two simple mixtures.

Big Idea

Separation. Getting the peas away from the carrots.

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Purpose of Lesson:

The purpose of this lesson is to give students a chance to experiment with solubility and magnetism. Throughout this lesson students will only get to a low level of understanding about these concepts because the big idea if for them to be able to use these properties to separate a mixture. This lesson can be done in one day if you manage pacing and leave less time for processing. It is easy to do in two days. The timing in the lab is for one day. 

Strategies used in this lesson:

1) Conclusion anchors-  Exemplars and explanation for the conclusions.

Ready. Set. Engage!

5 minutes

Learning Goal: Understand how different substances have different properties and that these properties can be used to identify and sort.

Opening Question: Give some examples of how substances can be different from each other.

The biggest misconception that students have about characteristic properties is that MASS is a characteristic property.  This misconception takes several attempts at correction through labs, scenarios and discussions.  

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.  

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

Hook

5 minutes

I start this day by introducing the substance sulfur to the kids. Most of my students have some familiarity with sulfur and have been to hot springs in the mountains or to Yellowstone. I put this picture up on the screen. 

I also put some plain sulfur on the table for the students to see. We start by talking about what the students already know and I push the conversation towards properties of sulfur.

  • It's yellow.
  • It has an odor. 
  • It forms a crust.
  • It floats on water.

Then I show the students two mixtures. One is sulfur and salt and one is sulfur and iron filings. The students get a chance to observe the mixtures and discuss how they would separate them. If you have magnifying glasses, this is a great time to hand them out so students can observe the mixtures more closely.  

Lab Prep

10 minutes

I remind the students before they start that they are investigating two important characteristic properties, magnetism and solubility. You have choices here on these words. Students probably have an idea of magnetism, but may not be clear on solubility. You can wait, and use these words in context or review the word meanings before you begin. 

This lab prep is pretty easy. At their desks students need clear plastic cups, plastic bags, magnets, and stir rods. Another way to make this lab more structured is to put beakers of water at the tables as well. Below is a video of an easy way to use plastic bags to keep your magnets clean.


I have the students get the lab write-ups ready for both labs before we start the separation. They need to write a title, purpose, hypothesis, and data tables. At this point my students are very capable of getting ready to write their own lab reports.  However, for students where the physical process of writing is difficult or those that need a scaffold, I use the lab templates solubility lab, magnetism lab

Collaborative Practice

20 minutes

This lab is pretty self explanatory to the students. They use water to separate the salt and sulfur and see that solubility is a characteristic property and use a magnet to separate sulfur and iron to see that magnetism is a characteristic property. 

I walk around and use a strategy called praise-prompt-leave. It is pretty self-explanatory; you praise something the students have done, give them the next prompt they need to move on, and then walk away. This is an easy way to add differentiation to your classes. By giving students the "just right" prompt you can add challenge for every student.  

Some important questions that I use to push student thinking are;

  1. What do you think makes sulfur float?
  2. What do you think makes iron magnetic?
  3. Would iron be magnetic under water?
  4. Would temperature change solubility?

Independent Practice

7 minutes

The labs are so simple and quick, this is a great time to focus on the conclusion writing.  At this point in the year, students should be able to communicate effectively using the sentence starters. Attached are some conclusion exemplars.  

Some students may be ready to write conclusions of their own and that is great. For the few students that are still struggling with the sentence starters, this is a great time to pull a small group and try to help them be self-sufficient in this area.  

Closure

3 minutes

Closing Statement:  "Today we worked on using two characteristic properties to separate simple mixtures." 

Closing Question: "How did characteristic properties help us separate the mixtures today?"


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.