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	Forensics Case 11 Ashes to Ashes: Using evaporation rate to identify an unknown liquid

Activity Overview

In this activity, students understand that evaporation rate is a characteristic property of a liquid. Based on this fact, they identify the solution and the likely accelerant in a case of arson. They compare the evaporation rates of the accelerants found with the suspects with those near the crime site.

Before the Activity

Use TI Connect™ to download Vernier EasyData™ application

Connect the EasyTemp temperature probe to the USB port of the calculator

Set up the calculator and the EasyData application for data collection

See the attached PDF file for detailed instructions for this activity

Print pages 96 - 100 from the attached PDF file for the class

Print sample data and student work pages

Activity Downloads:

(file types)

During the Activity

Distribute the pages to the class.

Follow the Activity procedures:

Place the temperature probe into a test tube containing a small amount of the accelerant

Collect temperature readings from the calculator screen, and observe the graph of temperature versus time

Record the maximum and minimum temperatures in the Evidence Record sheet, and determine the temperature change during evaporation

Repeat the steps with accelerant samples from the other suspects, and from the crime scene

Plot the data from all accelerants on the same graph, and compare them

Identify the suspect accelerant that creates a plot that matches the shape of the plot of the accelerant from the crime scene

After the Activity

Students understand the use of the evaporation rate as a characteristic property with which to distinguish different liquids from one other.
They 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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Subject Area:
Science : Forensics : Data Analysis
Science : Chemistry : Gases, Liquids and Solids
Math : Statistics : Data Analysis
Math : PreAlgebra : Probability, Statistics and Data Analysis
Math : Algebra I : Data Analysis
Math : Middle Grades Math : Problem Solving

Author:
Texas Instruments