Introduction:

Introduce the idea of separating a mixture by having students brainstorm times when separating a mixture was important to them.  

Have students share their ideas and prompt them to think about the types of physical properties they used to separate that mixture.  

For example: Many students will say that they have separated the M&M's from trail mix.  

Ask them: "What physical properties did you use to get the M&M's out of the mix?

Possible answers include: color, shape, size, texture

Explain that sometimes the need to separate a mixture can be life and death- examples include separating pure water from contaminants or separating blood components for use in medicine.  Play the video "Blood Component Processing" linked here and discuss how the blood center uses the physical properties of the various parts of blood to separate them.

Blood Component Processing Video

Lab Set-up Day 1

Materials: 

Goggles, beakers, aluminum pie pans, coffee filters, screens (I took pieces of window screen and made a border with duct tape), hot plate, spoons, paper plates, water, small cups, popcorn kernels, salt, iron filings, sand, small plastic snack bags, a balance.  You may also want to provide other materials as students see a need for them. 

Day 1 Teacher Instructions:

Objective: Students will collect data about the physical properties of the substances that will be in their mixtures.

For each lab station, I provide the following in a container( a dish pan or storage bin works well for this):

Lab Sheet

small labeled cups with samples of salt, sand, iron filings, and popcorn kernels

250 mL beaker

Magnet in plastic baggie

Two spoons

Paper plate

Magnifying glass

Access to water (we have a sink in the lab that students use as needed)

2 Metric rulers

Make sure to have students wear goggles throughout this lab as small particles and glasswear are being used.

Day 1 Student Instructions

Have students work to fill in pages 1 and 2 on the student activity sheet:

     - Finding the physical properties of each component that will be in their mixtures

     - Listing other physical properties not being tested

     - Planning the procedure they will use

     - Gaining teacher approval for procedure

Lab Set-up Day 2

Day 2: Teacher Instructions

Before class, prepare a baggie with one mixture for each group of students.  

The mixture should include:  

 10g salt

10g sand

15g popcorn kernels

5g iron

Place community materials in a central location.  Students can use and return materials.  Materials you include will vary depending on your lab, but I have had success with the following: aluminum pie pans, screens, coffee filters, funnels, beakers, spoons, water, paper plates, balances, kettle with hot water, and tweezers.

I also have a hot plate that I use and I boil student materials as they ask me to.  For safety reasons, I don't have students in my classes use the hot plate themselves.

Give each group a mixture and have them begin their procedure as planned on the previous day.  As students work, circulate to facilitate their procedures.  Remind students to note any procedural changes they make as they work.  I find it works well to ask students leading questions such as, how do you plan to get the salt out of the water?  Where is your sand now?  

After students separate their mixtures, they should be sure to measure their recovered pure materials.  This might need to wait until the next day as some materials may need to be dried or boiled to recover the pure material.

Be sure to leave at least 10 minutes to clean up at the end of the lab activity.

Day 2: Student Instructions

Students will separate their mixtures 

Students will measure the pure materials recovered and calculate percent recovery for each component of the mixture

Assessment

Have students answer the post-lab questions on the student activity sheet provided.