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	Forensics Case 8 No Dumping: Using soil characteristics to link suspects to a crime scene

Activity Overview

In this activity, students measure pH, conductivity, and water absorbency of different samples of soil. They use these characteristic properties to identify soil samples. They use the physical and chemical characteristics of soil samples collected from suspects to determine whether a suspect had been at a scene of crime.

Before the Activity

Use TI Connect™ to download Vernier EasyData™ application

Connect Vernier EasyLink™ to the USB port of the calculator

Connect the pH sensor to the EasyLink port

Set up the EasyData application for data collection

See the attached PDF file for detailed instructions for this activity

Print pages 70 - 74 from the attached PDF file for the class

Print sample data and student work pages

Activity Downloads:

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During the Activity

Distribute the pages to the class.

Follow the Activity procedures:

Mix 100 ml of water with 50 g of the soil sample in a small beaker

pH and Conductivity

Place the pH sensor in the beaker and note down the pH of the solution

Replace the pH sensor with the Conductivity probe and set it for data collection

Place the Conductivity probe in the beaker and note down the conductivity of the solution

Physical Appearance and Water Absorbency:

Measure out 50 g of soil sample and place it on a filter paper

Examine the sample using a magnifying glass and record its physical appearance

Place the filter paper and the soil in a funnel, held over a beaker

Pour 100 ml deionized water over the soil and collect the filtrate in the beaker

Measure how much of the 100 ml water gets collected in the beaker and calculate the water absorbency

Repeat the steps for different samples of soil

Use physical and chemical characteristics of soil samples to identify the unknown soil sample and find the connection between victim, crime scene, and suspects

After the Activity

Students analyze the results and answer the Case analysis questions on the Evidence Record sheet.

Review student results:

As a class, discuss questions that appeared to be more challenging

Re-teach concepts as necessary

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