The ANTZ Go Marching

Separation of Mixtures: Properties in Matter

This lesson was originally designed and intended to address 8th grade physical science standards but can be adapted to any higher level chemistry courses.

INTRODUCTION (for students):

Scientists around the world face challenges in keeping the air we breathe clean and the water we drink and the food we eat safe. Close monitoring are needed to control the qualities of the things we take for granted in our daily lives. Often times, a lot of work are needed to treat the problem of contamination. The strategy behind finding a resolution for these problems, however, is simple and something most of us are capable of doing after some basic investigations.

BACKGROUND:

In developing sensing devices, a selective medium is usually employed to collect the compound(s) of interest and ease detection. To achieve selectivity, compound(s) of interest must be differentiated from other contaminants. One differentiation mechanism is to make use of the physical properties of the mixture.

In the following lesson, students will observe separation of mixtures. Separation will occur based upon differences in physical properties. Two different mixtures are proposed for variation in the depth of content coverage desired and the materials available.

The proposed lesson plan addresses the physical science strands and is intended for 8th grade.

Arizona Grade 8 Strand 5: Physical Science Concept 1: Properties and Change of Properties in Matter PO 1. Identify different kinds of matter based on the following physical properties:  States  Boiling point  Solubility PO 5. Classify mixtures as being homogenous or heterogeneous PO 7. Investigate how the transfer of energy can affect the physical and chemical properties of matter MATERIALS:

Basic mixture

 5 grams of sand  5 grams of salt  5 grams of iron filings  5 grams of wood chips  Bottle of water  Magnets  Tweezers  Pipettes  Coffee filters  Paper towels  Beakers  Hot plates  Thermometer  Magnifying glass  Computer  Test tubes  Funnels

Personal Protective Equipments / Precautions:

 Lab Coats  Goggles  Heat Gloves * Be sure to tie back long hair.

Advanced mixture

 20mL of water  20mL of acetone  20mL of ethanol  5 grams of sand  5 grams of salt  Tweezers  Hot plates with accurate temperature control  Pipettes  Coffee filters  Thermometer  Magnifying glass  Computer  Paper towel  Beakers  Test tubes  Funnels

Personal Protective Equipments / Precautions:

 Lab Coats  Goggles  Heat Gloves  Chemical fume hoods * Be sure to tie back long hair TIME REQUIRED:

This lesson plan will require between 2 to 5 school days dependent upon the depth of content coverage desired.

PROCEDURE:

BASIC MIXTURE

1. Provide students with the mixture 2. Allow student (in groups) some time to make observations 3. Have a class discussion on the observations and the things they noticed and know about the individual components can be use for separation 4. Have students generate hypothesis (in groups) on how the mixtures can be separated based on their observations and the discussion (The iron filings can be separated with a magnet. The wood chips can be separated by adding water to the mixture and picking the floating wood chips from the top. The sand can be separated by pouring the water/sand/salt mixture through a coffee filter or a paper towel. The remaining water and salt can be collected in a beaker and heated on a hot plate until all of the water evaporates.) 5. Provide materials for students to test out their hypothesis 6. Have student reflect on their separation plan 7. Conclude lesson with a discussion of what happened and label terms if necessary 8. Discuss benefits of separation (and how separation relates to detection)

ADVANCED MIXTURE

1. Provide student with a “real-world” scenario (example given below)

Example Scenario: You are all chemists/engineers who live in the same town and work for the same company. A river runs through your town and the water comes from three smaller rivers that pass through three big cities. Recently, your town ran out of drinking water and your non-chemist, non-engineer neighbors have been drinking the water from the river. A few days later, many of your neighbors started feeling sick. You suspected the river water and half of you went to City No. 1 and the other half went to City No. 2 to see what is in their river. In City No. 1, you saw that a factory is right next to the river and they have been putting chemicals in the river. In City No. 2, the other half of you saw that the water appears to be clean but have a lot of sand in it. You are now asked to come up with a way to separate the chemicals from the water in City No. 1 and the sand from the water in City No. 2.

2. Pre-assessment: Have students spend 5 minutes discussing ways to separate the components from the water in their groups 3. Have students share with the class what they came up with 4. Demonstrate separation of a binary water / acetone mixture by heating the mixture above acetone’s boiling point and below 100°C 5. Have students make observations and discuss what they think happened 6. Discuss how by noting the temperature (boiling point) at which the chemical became a gas, we can determine what chemical was in the water 7. Optional: Discuss other 8th grade science concepts (i.e. the changes in states from liquid to gas during heating, boiling point of acetone versus boiling of water, mixture classification, transfer of heat energy, physical changes versus chemical changes) 8. Continue to scenario to identify components in the mixture (continuation of example given below)

Example Scenario (continued): A separate group of chemists/engineers went to City No. 3 and found that ethanol and salt are in their river water. That means a mixture of water, ethanol (isopropanol), acetone, salt, and sand is in the river that runs through your town. Remember, your town is out of drinking water, so you must clean the river water and separate all the chemicals, salt, and sand from the river water to have drinking water!!!

9. Provide students with a mixture of water, ethanol or isopropanol, acetone, salt, and sand 10. Allow student (in groups) some time to make observations and research on the internet about the different components 11. Have students generate hypothesis (in groups) on how the mixtures can be separated based on the principles from the demonstration and the brief discussion on separation by differences in boiling point (The sand can be separation by using filters, i.e. coffee filters, paper towel. The salt will dissolve in the mixture. As the mixture is heated, acetone will vaporize, followed by ethanol or isopropanol. Lastly, water can be boiled off or let stand to vaporize to obtain salt crystals.) 12. Provide materials for students to test out their hypothesis 13. Have student reflect on their separation plan 14. Conclude lesson with a discussion of what happened and label terms if necessary 15. Discuss benefits of separation (and how separation relates to detection) ASSESMENT:

Have students propose separation technique for a different mixture

Example: Love Canal Scenario  http://www.epa.gov/history/topics/lovecanal/01.htm  http://www.health.state.ny.us/environmental/investigations/love_canal/  refer to the human toxicity of chemicals section at http://www.health.state.ny.us/environmental/investigations/love_canal/lctimbmb. htm for a summary of chemicals found in the Love Canal)