Forensics Problem Based Learning Scenario

As an FBI Forensics Special Agent, you are often asked to classify unknown substances found at the scene of a crime. Recently the FBI has found 7 mystery substances that need classification. Your mission is to test the 7 unknown materials so that all of their characteristics can be described. Below is a partial list of what may be tested:

· State of matter

· Color

· Shape

· Texture

· Melting point

· Freezing point

· Density

· Composition (one material or more than one material)

· pH

· Hardness

· Flammability

· Reactivity

· Solubility in water, alcohol, vinegar or other solvent

Once the characteristics of the unknown material have been determined, develop a flowchart, an organizer, a guide, a concept map, a table, or a dichotomous key so that each material can be identified.

Test the reliability of your chart by having another group of special agents use YOUR key to classify the substance. That is, another group of agents should be able to take an unknown substance and use your chart with 100% accuracy to identify the substance.

Forensics PBL Teacher Notes

MYSTERY POWDERS

To get students thinking about classification, use the Mystery Powders activity as an anticipatory set. In the Mystery Powders activity, students will use an existing key to determine five single powders assigned. The activity may be extended so that students can identify a mixture of three powders using this key.

Preparation

· The teacher should give each student 2 g samples of the following powders: talc, baking soda, salt, corn starch and baking powder. Each sample should be labeled “powder 1”, “powder 2”, up to powder 5. Film canisters work well for storage.

· Students will test each mystery powder with three materials, water, iodine and vinegar, and watch for reactions. Drop plates work well for the small amount of powder sample needed for each test. The liquids can be placed in labeled dropper bottles for easy use and storage. Students will compare the reactions to the numbered powders with the “known information” chart. On the chart, + means a reaction occurred, - means that a reaction did not occur.

· Teachers can expand the activity by mixing talc, cornstarch and baking soda to make an unknown substance. Students must test the substance and deduce which powders are in the mixtures. There is a blank at the bottom of the lab for the students interested in this enrichment activity.

FORENSICS ACTIVITY

Students may get mired down in trying to IDENTIFY the materials. This activity is to CLASSIFY the materials. They do not need to find the identity, they only need to describe it using physical and chemical properties.

Some of the materials to be used as unknowns include the following:

Salt
Sand
Limestone
Baking soda
Sugar
Copper sulfate
Iron filings
Citric acid powder
Crushed chalk
Copper powder
Water
Isopropyl alcohol
Vinegar
Ammonia
Corn starch
Talcum powder
Glycerine
Corn syrup
Marble chip

It may be advisable to use 4 solids and three liquids in the investigation, so that it takes more than two or three characteristics to classify the substance.

Problem Based Learning

Forensics Scenario

Ideas

Facts

Learning Issues

Action Plan

Test the following:

State of matter

· Color

· Shape

· Texture

· Melting point

· Freezing point

· Density

· Composition (one material or more than one material)

· pH

· Hardness

· Flammability

· Reactivity

· Solubility in water, alcohol, vinegar or other solvent

What type of chart will best describe the characteristics found for the materials?

Materials can be described by physical and chemical properties.

Different materials have different physical and chemical properties.

Same materials have alike physical and chemical properties.

These properties can be organized on a chart so that other experimenters can determine their classification in the same way.

How can we safely observe properties?

What type of chart best describes the information obtained?

How can others use the chart to determine the classification of the mystery substances?

Forensics PBL Suggested Sequencing

Day	Objective	Activity
1	Students will use a key to identify substances based on their properties.	Mystery Powders Activity.
2	Students will understand forensics PBL scenario and begin to form an organization system.	Introduce PBL scenario. Brainstorm facts, ideas and learning issues with students. Groups begin identifying properties of matter.
3	Students will get a more complete idea of their organization system. Students will decide what type of chart they will use to organize their information.	Groups finish identifying properties of matter. Groups identify how they will classify matter. Groups will choose the type of chart to organize their information.
4	Students will test their chart for accuracy.	Students finish making their chart, develop a key and test it within the group.
5	Students will evaluate other groups’ charts.	Groups trade charts and test to see if their ideas match the key.

Forensics Problem Based Scenario

Types of Charts

Concept Map

Students can draw by hand on butcher paper or use the computer program “Inspiration” to construct concept maps.
One of the most straightforward concept maps is a webbing. Students take a main idea and place it in the center of the map. Other ideas and facts can be branched off from the center.

Table

Students can make a standard data table much like the one given in the mystery powders investigation.

Flowchart

Students can use different geometric figures to identify different physical or chemical characteristics. For example, triangles can identify the state of matter, while squares identify the texture.
Lines should connect the characteristics so that it leads the investigator to the correct classification.

Organizer

Students can use graphic organizers such as Venn diagrams to display the information

Suggested Materials List

The materials required will vary according to the

experiments developed by the students.

Required for all groups:

· 2 g samples of the following powders: talc, baking soda, salt, corn starch and baking powder labeled “powder 1”, “powder 2”, up to powder 5

· Labeled dropper bottle of:

· Water

· Iodine

· Vinegar

· Drop plates (so that small amounts of powder samples can be used for each test).

Materials to be used as unknowns include the following:

Salt
Sand
Limestone
Baking soda
Sugar
Copper sulfate
Iron filings
Citric acid powder
Crushed chalk
Copper powder
Water
Isopropyl alcohol
Vinegar
Ammonia
Corn starch
Talcum powder
Glycerine
Corn syrup
Marble chip

Name ___________________

Mystery Powders

Objective: Identify unknown powders using lab skills.

Procedure:

1. Obtain the 5 mystery powders labeled powder 1, powder 2, powder 3, powder 4 and powder 5 from your teacher. You will be testing each powder for the reaction it has with iodine, vinegar and water.

2. Place a small amount of each powder in a spot plate and test each powder with drops of iodine, vinegar, and water. Record your observations in the data table labeled Testing Data.

3. Using the Known Information table at the top of page 2, identify each powder and record it in the Testing Data table in the column labeled identity.

4. Check your answers with your teacher. If your answers are correct, your teacher will give you a mixture of powders.

5. Test the unknown mixture with iodine, vinegar and water.

6. Identify the powders in the unknown mixture of powders and record them in the data table at the bottom of page 2 labeled Mixture Data.

Testing Data

	Vinegar	Iodine	Water	Identity
Powder 1
Powder 2
Powder 3
Powder 4
Powder 5

Known Information

	Vinegar	Iodine	Water
Baking Powder	+	+	Fizzes
Cornstarch	-	+	Gummy mixture
Talcum powder	-	-	Floats on water
Baking Soda	+	-	Pasty mixture
Salt	-	-	Dissolves in water

Mixture Data

Powder 1
Powder 2
Powder 3
Powder 4
Powder 5

My unknown is a mixture of _______________________________

How I discovered which powder or powders are in my unknown:

Name________________________ Date____________________

Company Name_________________

Materials and Procedures

This is a detailed list of instructions, which describe how to replicate your procedure. The reader should be able to follow your procedure using your written directions. The procedure can be in paragraph form or written as a list of steps. Any complicated steps should have a diagram to help illustrate the details. No personal pronouns such as "I", "we", or "you" should appear in the procedure. All writing must be in past tense.

Example:

Wrong: First you must add 10 millimeters of water to the beaker. Then I stirred the mixture for 10 minutes and watched for the color change.

Right: First 10 millimeters of water was added to the beaker. The mixture was stirred for 10 minutes and observed for any color change.

Below is a checklist to guide your materials and procedures.

___No pronouns were used (I, you, we)

___Written in past tense

___Uses only complete sentences

___Mentions the types of materials used

___Is specific and gives exact amounts (500 grams, 50 mL, etc.)

___Explains how observations were taken and from where

Name _____________________ Date __________________

Group Name ______________

Reflection on Procedures

The purpose of a reflection is to look back on your experience and try to identify the things that went well and the things that did not go well. In the future, you will try to keep doing the things that went well and try to change the things that did not go well.

1. Name 3 things that went well with your procedure.

2. Name 3 things that could have gone better with your procedure.

3. Name one thing you think you did well as a member of your group.

4. Name one thing you can improve upon the next time you are put in a group.

Rubric

Forensics PBL Chart – for student use

Chart tests at least 6 different properties of matter _____/15

Properties chosen to describe the matter are accurate _____/15

Others correctly using the chart get the same

classification as the key _____/10

Type of chart helps to organize the classification _____/5

Chart is readable, spelling is correct, there are

complete ideas expressed, creative _____/5

TOTAL _____/50