SOIL AS EVIDENCE DATA TABLES NAME___________________________________ Total Number of Layers Height of Sand Layer (mm) Height of Silt Layer (mm) Height of Clay Layer (mm) Total Height of All Layers (mm) % of Sand
In Soil % of Silt In Soil % of Clay In Soil
Farm Soil Vehicle #1 Vehicle #2 Vehicle #3 Vehicle #4
Table 1 – Soil Texture Test Results
pH Color of Dry Soil Unusual Material in Soil Appearance With UV
Light Farm Soil Vehicle #1 Vehicle #2 Vehicle #3 Vehicle #4
Table 2 – General Soil Characteristics
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Blacks Reds/Pinks Whites Yellows/Browns Others Clear Reds/Pinks WhitesMilky Yellows/Browns Other Total Sand Particles Counted Farm Soil Vehicle #1 Vehicle #2 Vehicle #3 Vehicle #4
SOLID/OPAQUE COLORS TRANSLUCENT/CLEAR COLORS
Table 3 – Microscopic Examination Of Soil Results – Large Sand Particle Color Counts
Table 4 – Microscopic Examination Of Soil Results – Large Sand Particle Color Percentages
Blacks % Reds/ Pinks % Whites % Yellows/ Browns % Others % Clear % Reds/ Pinks % Milky Whites % Yellows/ Browns % Other % Farm Soil Vehicle #1 Vehicle #2 Vehicle #3 Vehicle #4
SOLID/OPAQUE COLORS TRANSLUCENT/CLEAR COLORS
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Farm Soil Vehicle #1 Vehicle #2 Vehicle #3 Vehicle #4 Soil Texture Soil pH Color Of Soil Unusual Material In Soil
UV Light Results Large Sand Particle
Color Percentages Sand Particle Edges
% of Large And Small Soil Particles
Table 6 – Summary of soil test results. Which vehicle’s soil most closely matches the Farm Soil? (dots indicate a close match to the Farm Soil)
Table 5 – Characteristics of sand particles.
Sand Particles Have Mostly: *Rounded Edges
*Sharp Edges
*Some Rounded/Some Sharp Edges
Weight Of Larger Soil Particles (g) Weight Of Smaller Soil Particles (g) Total Weight Of All Soil Particles (g) % Of Larger Soil Particles In Soil Sample % Of Smaller Soil Particles In Soil Sample Farm Soil Vehicle #1 Vehicle #2 Vehicle #3 Vehicle #4
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QUESTIONS – SOIL AS EVIDENCE NAME____________________________________ Use your analysis of the Farm Soil Sample and Vehicle Soil Samples to answer
Questions #1 - #6
1. Did you discover a Vehicle Soil Sample that you believe is a perfect match to the Farm Soil? (yes or no)
_______________
2. If you answered “Yes” to Question #1 – Which vehicle contained soil that perfectly matched the Farm Soil?
_____________________________________
If you answered “No” to Question #1 – Which vehicle (or vehicles) contained soil that was the closest match to the Farm Soil?
____________________________________
3. Which person would you most likely search out as a prime suspect in the farmhouse robbery? (give their name)
____________________________________
4. List the test (or tests) you considered to be the MOST useful in helping you match the Farm Soil to the soil located on one of the a vehicles.
5. List the test (or tests) you considered to be the LEAST useful in helping you match the Farm Soil to the soil located on one of the vehicles.
6. Do you think your MOST useful test list (from Question #4) and LEAST useful test list (from Question #5) would stay the same every time you tried to match up evidence soil samples? (yes or no)
________
Explain your answer.
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7. Explain how can you tell the difference between Sand, Silt, and Clay?
8. You complete a Soil Texture Test and find THREE different soil particle layers in the soil texture tube.
Which soil particle would be found in the top (uppermost) layer?____________________ Which soil particle would be found in the middle layer?_____________________
Which soil particle would be found in the bottom layer?_____________________
9. Describe how soil might be collected and used as evidence at the following crime scenes you are investigating.
9A. You are investigating the possibility that several horses discovered in a trailer were stolen from a stable 150 miles away. Describe how soil could be collected and used as evidence in this case to help prove the horses were stolen from the stable.
9B. A body has been discovered in a wooded park. You believe the victim may have been murdered in another area of the park, then moved to this location. Describe how soil could be collected and used as evidence in this case to help prove the victim was murdered in another area of the park.
9C. A suspect has been arrested for murder, however, the victim’s body has not been located – and the arrested suspect refuses to talk. A search of the suspect’s car turns up a shovel covered with fresh dirt and a pair of muddy boots. Describe how soil could be collected and used as evidence to help locate the body of the victim.
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10. You are talking to a rookie C.S.I. agent describing a crime you solved several years ago. You explain that the crime scene contained a sample of soil and you decided this soil evidence must have come from the suspect’s muddy shoes. You took a closer look and noticed some sort of plant, animal, or human product material in the soil sample. You quickly identified this unusual material in the soil sample, and you immediately knew where you should go searching for the person that committed the crime. Sure enough, this material allowed you to narrow your search down to a more specific location - and within a day you had a suspect in custody. The rookie is
impressed and asks you what you found in the soil, and how it helped you narrow down the location of your search. Finish the story below (be creative – there is not one correct answer) and tell the rookie what you found in the soil sample and how it helped you narrow down the location of your search.
11. Return you thoughts back to the farmhouse robbery you solved in this Training Lab. List any unusual material (plant, animal or human product material) you observed in any of the Vehicle Evidence Soil Samples (list “None” if nothing was observed in a sample). Then, based on any unusual materials you observed, attempt to describe a general location where you think this soil sample may have come from.
Unusual Plant, Animal, or Human Product Material Found
In Soil Sample
Possible Location Where Soil Sample Originated Vehicle #1 Soil Sample Vehicle #2 Soil Sample Vehicle #3 Soil Sample Vehicle #4 Soil Sample
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TEACHER NOTES
Lab Activity:
Training Lab: Soil As Evidence
Equipment To Prepare:
4 different soil samples to represent the soil removed from the 4 Vehicles. See “Preparing The Soil Samples” section later in the Teacher Notes.
1 soil sample to represent the Farm Soil. The soil sample must match one of the Vehicle Soil Samples. See “Preparing The Soil Samples” section later in the Teacher Notes. 5 glass or clear plastic vials each with caps or stoppers/every group throughout the day –
for soil texture tests. We use 25mm x 95mm glass vials with screw tops (such us Science Kit 63565M08 or Wards Natural Science 17W0169), however, any clear, flat-bottomed vial or cylinder will work. Screw tops will work better than rubber stoppers (they usually end up leaking). Remember, each group will need their own set of 5 texture tubes throughout the day (tubes can’t be re-used throughout the day because the soil texture test requires 24 hours of settling time).
labels/tape to label soil texture tubes – cut paper in small squares for students to tape to their tubes.
1 plastic spoon/group – for students to pick up soil samples as needed
1 small millimeter ruler/group – to measure layers in soil texture test (day 2)
10 – 13 x 100mm test tubes in test tube rack (or similar holder)/group – used to test the pH of the soil samples.
1 or 2 dropper pipettes/group – to move liquids associated with the pH test
1 soil separating screen/group – for students to separate large sand particles from smaller sand particles. We use tea strainers/infusers for our soil separating screens (tea strainers are made with very fine screen, which works perfectly for separating soil particles. Tea strainers/infusers can be purchased cheaply at Walmart or similar stores. A tea strainer often comes as a screen “ball” made of two halves that open up (to place the tea leaves inside). Completely separate the two halves (it is easy to take them apart) and you now have TWO soil separating screens! You can also purchase soil sieves from Science Supply Companies (these are usually five plastic containers that sit on top of each other – each container contains a screen in its bottom with progressively smaller holes. A soil sample is placed in the top, shaken, and the particles of soil will be separated by size – the top container will contain rocks, the next pebbles, the next sand, the next silt/sand, and the bottom clay). This Training Lab has been written using tea strainers as the soil separating screens. 1 plastic petri dish (or similar container)/group – students can put large sand particles in
the bottom half and small sand particles in the top half of the dish for observing. Rinse out and use from year to year.
1 needle probe or small paintbrush/group – to move sand particles around while observing white photocopy paper – to use with soil separating screen. Also, students will be able to
see sand particles better if they place white paper under their petri dish on the stereomicroscope (they are easier to see against a white background). Also, to use when weighing the larger and smaller soil particles.
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1 stereomicroscope (dissecting microscope)/group – to view and count sand particles electronic or accurate manual balances (triple-beam or cent-o-gram) – set up 2 or 3
weighing stations around the room for all groups to use when weighing large and small soil particles from the soil samples. Include paper squares at the stations for students to place their soil samples on when weighing.
blacklight /longwave UV-A light station – for students to view soil samples with UV light. It is easiest to place the soil samples in a location of the room with the UV light source
– preferably in an area away from bright light. You could allow students to go to the station as individual groups, or have all groups observe at one time. Turning out the lights in the room makes it easier to observe any fluorescence. Longwave UV-A light sources can be purchased from many Science Supply Companies (such as Wards Natural Science 29W3010 or 29W3005) SAFETY NOTE: UV-A light is usually considered safe for short exposures, however, we recommend that students wear UV safety goggles when using this station – and students should never stare into the light. You also may encounter students with UV sensitive skin. Skin irritation may result if these students get their skin too close to the light. UV safety goggles – have several pairs of safety goggles around the UV light station.
Many safety goggles (that you may already have) are rated for UV-A protection – otherwise, they can be purchased from any Science Supply Company
soil texture solution station – fill 2 or 3 beakers with soil texture solution and place in the front of the room (students will get soil texture solution from this station)
distilled water station - fill 2 or 3 beakers with distilled water and place in the front of the room (students will use the distilled water for their soil pH tests)
universal indicator solution station – place a bottle of universal indicator solution in the front of the room (students will use drops of this solution when testing soil pH). Universal indicator solution is a common pH indicator and can be purchased from just about any Science Supply Company. Some bottles contain a color chart that allows students to make a match and determine a solution’s pH. A color/pH chart has also been included in the Training Lab for students to use. Note – not every bottle of Universal indicator solution contains the exact same color chart (we have two different bottles at our school with slightly different charts). As long as your students use the same color chart for all soil samples it should not be a problem. soil disposal station – for students to dispose of wet soils (from texture test and ph tests).
Place a plastic bucket (or similar container) by the sink for disposal of all wet soil samples. This will prevent students form pouring soil down your sink and possibly stopping it up. The liquid in the bucket can be carefully poured down the sink. Let the soil dry out and place it in the trash.
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Solutions To Prepare:
soil texture solution – mix 15 grams of Calgon brand bath powder + 285ml tap water. Each group will use approximately 80ml-100ml of the solution (to place in their five soil texture tubes). Calgon bath powders (such as “Ocean Breeze”, “English Garden”, “Island Escape”) can be purchased in stores like Walmart. Calgon is a bath powder/water softener that contains the chemical Sodium Hexametaphosphate – the
chemical used for professional soil texture testing. The Calgon product you find might be a colored powder (usually blue or pink). This color will NOT affect the soil texture results.