Soils
Lesson 4
When Soils Get Wet
Students will moisten samples of each soil type to observe how it behaves when wet. Then they will try to make a ball from each soil type to test properties of plasticity/cohesiveness of each soil when wet.
3. Lesson set up and Management
SYSTEMS 1.1-Properties: Understand how properties are used to identify, describe, and categorize substances, materials, and objects and how characteristics are used to categorize living things
GLE 1.1.1 Understand simple properties of common natural and manufactured materials and objects: Sort common materials and objects using a simple property and Identify and describe the differences between common natural and manufactured materials and objects using properties.
GLE 1.1.5 Understand physical properties of Earth materials: Sort rocks based on size, shape, and other physical properties and Explain how some Earth materials are used by living things.
INQUIRY 2.1-Investigating Systems: Developo the knowledge and skills necessary to do scientific inquiry
INQUIRY 2.2-Nature of Science: Understand the nature of scientific inquiry
• Every soil component has unique properties that can be identified using simple tests.
• Simple test can be performed to describe and identify soil components.
• Observations can be recorded, organized and interpreted to draw conclusions about soil composition.
3. Lesson set up and Management
Materials:
Spread newspaper drop cloths on desks or tables underneath the paper towels. The towels will absorb most of the water but the newspapers make for an effective way to clean up. Just fold in the edges when done and discard.
Take some time to show students how to drip water from eyedroppers slowly, one drop at a time, to cut down on "splash" related messes.
One student drips a drop at a time while the other student counts drops. |
The ball test with sand. |
The ball test with clay. |
The ball test with humus. |
Student Management:
Have one student in the partnership be the water-getter and drop-cloth-spreader while the other goes through the distribution line to get other supplies. This will save time and give everyone something to do. Reverse the jobs at the end of the lesson.
When students attempt to make sand into a ball, it will not remain in a ball. Humus will often make a ball but it will easily crumble with mild pressure. Clay forms a firm ball which is all but impossible to break unless it is struck or dropped (and often it will not break even then). Scientists use both a ball test and a ribbon test to assess soil type. In the ribbon test, you squeeze the wet ball upward through your thumb and forefinger to feel for smoothness.
Clay Ball |
Sand Ball |
Humus Ball |
Teachers should continue to add to the class chart either with a different-colored marker or by having students write what they learned on a post-it and putting it on the chart. If using the post-it method, the teacher should then talk through the chart, grouping like post-its or removing duplicates.
As the post-its are discussed, the teacher should point out that many students are seeing the same things. This speaks to the notion of repeated trials in an investigation. In a good investigation, scientists repeat trials to insure that they have consistent results and not just a fluke that is not repeatable. In the type of investigation done in Soils each partner's work becomes that "repeated trial." Ideally, students would repeat their own work but there is not enough time in the typical classroom day. Therefore this is a good place to point out the need to try an investigation more that once, and that having many people do the same investigation in the same way is a kind of repeated trial.
If students see differing results (which is not likely here) it becomes a good time to address two INQUIRY EALRS about the Nature of Science:
EALR/GLE 2.2.1-Understand that all scientific observations should be reported accurately even when they contradict expectations
EALR/GLE 2.2.3-Understand that similar investigations may not produce similar results
Writing Support:
Alternate record sheets such as these provide students with greater opportunity to write their investigative results. See Alternative Record Sheets 4-A and 4-A/5-A.
Reading Support:
A read-aloud resource book such as The Amazing Dirt Book by Paulette Bourgeois can give students some unusual facts about wet sand and clay. These facts include such information as why people take mud baths, and what to do if you fall in quicksand. A good fiction book about sand is Sophie's Castle by Heather F. Levine. It is the story of a little girl building a sand castle and what happens when the tide comes in.