Instructional goals: Students will be able to: (1) understand the complex nature of soil (components of different layers, and the creatures living in the soil), and (2) see different types of soil including sandy soil, clay soil, loamy soil.
Grade level: Grade 7, 8
Duration: 50-75 minutes
Instructional Materials:
1. Soil samples from 3 uniquely different sites
2. Garden trowel
3. Extension activity: Erlenmeyer flask, funnel, soil samples Note: Soil samples will work best if they are collected from a deep source so the organic matter; horizon A, and perhaps horizon B are visible (Garbage bags work best.). Activity must be done in autumn or spring.
Worksheet: Eureka B, Questions 7, 8, 9 EN 20
QEP POLs for secondary cycle 1 relevant to the concept of soil profiles: Classifies soils based on their composition (e.g. sand, clay, organic material)
Children’s preconceptions relevant to the concept of soil profiles: Students often think that soils are uniform in composition, and that all soils are the same (soil is “dirt”).
Assessment Items to explore or uncover students’ preconceptions around the concept of soil profiles:
Question 1. Below is the diagram of a soil profile. Which layer contains the most organic material (organic materials can be remains of plants and animals and their waste products)?
A. B. C. D.
(Retrieved from MOSART, Earth Science Test, Item form #821, Q3)
Question 2. What is true about all soils?
A. All soils are the same color and texture.
B. All soils contain weathered rock.
C. All soils do not contain air.
D. All of the above.
(Adapted from MOSART, Earth Science Test, Item form #821, Q9)
Description of the Lesson
The following activities have been designed to address students’ prevalent alternative frameworks, some of which you might discover by using the two multiple choice items above
Step 1 of The Lesson: Eliciting Student Thinking/ Intuitive Models
This step involves two activities (i.e., Activity #1 – Picture the soil! and Activity #2 – Activity #2: Think-Pair-Share), in order to elicit students’ prior knowledge and understanding of this topic.
Activity #1: Picture the soil!
(1) Prepare 1 sample of soil bag and have students observe the bag.
(2) Tell students a story: “Hello, we have this bag full of soil today. Now, I want you to imagine that we have a special machine that could magnify a very little spot in this bag of soil, just like what you see on your worksheet.”
(3) Distribute the worksheet #1 (please see Appendix A) and continue with the story by saying: “In your worksheet, you see the circle on your worksheet? I want you to draw in the circle what you think you might be able to see in the soil.”
(4) Allow students to draw on the worksheet. Teacher may circulate the classroom and probe for their explanation. While teachers circulate, try to choose 3-4 students’ models that best represent the class’s diverse ideas. Teacher can ask the following questions in order to probe for their explanation further:
Can you tell me why you draw these?
What happens if it rains?
Do you think what you draw will change or no?”
(5) Once students complete with drawing, teachers can share the models chosen and have students to explain. For example, teacher can ask: “Student A, can you please explain what you drew? I see that you draw circles here, what do they represent? Does anyone else have similar pictures than Student A? If so, do you want to add anything else on Student A?”
(6) After sharing the models, teacher summarizes points that were brought up by students and create a consensus model. Teacher can say: “Based on your ideas, let’s build a class model! Many of you had circles representing soil atoms and different layers of circles. So, do we agree that there are different layers of soil? Many of you also drew worms. Do we want to add worms on our class model?”
Based on students’ response, teacher can add or change class consensus model. Teacher can ask the following questions to guide the discussion:
Student A said we have different layers in soil, how would you represent this in drawing? Can you come and draw?
Does everyone agree that we have different layers?
Does anybody else have different ideas?
If there are conflicting ideas, try to include both, or turn to class for a vote.
The goal of Activity #1- Picture the Soil! is to help teachers to elicit students’ diverse ideas before the lesson. In the next Activity #2: Think-Pair-Share, students will be invited to make observation of different types of soil. The goal is to further press for students’ prior understandings in a deeper level with regards to different types of soil and composition of soil
Activity #2: Think-and-share
This activity allows students to share their prior understanding of the composition of soil with other students in a deeper level. By engaging in observation and argumentation, students have opportunities to explore and explain their ideas. Teacher can probe for students ideas with the guided questions provided in students’ worksheet.
In this activity, the students will: (1) think individually about the question and write their answer on a paper, (2) pair with a partner and discuss their answer and ideas, and (3) share their ideas with the class. Students are encouraged to write emerging ideas during the discussion in their Scientist Journal which is used as an evaluation for understanding (If students do not have scientific journal, they can write them down on a piece of paper). Details are described as follow:
(1) Think individually: Collect 3 samples of soil from 3 uniquely different sites. Then introduce today’ driving Question: What happens when you dig deeper and deeper into soil?
Invite students to observe the bags of soil individually. Here teachers can direct students to touch and feel the different types of soil by saying: “Here are three different bags of soil. I want you to touch the soil. Look at the colours. I want you to try to answers on your worksheet while you are observing the soils.”
While students are observing different samples of soils, they will also be invited to write their observation on their worksheet (Please see Appendix B). The worksheet includes the following questions:
What is soil made up of?
What colours are the soils?
What stuff can you find in soil?
Are all soils the same?
Are soils uniform, or the same as you dig deeper into the soil?
After students fill out the worksheet with answers, the individual responses will be submitted to teachers. The purpose of this step is to help teachers get a sense of students’ predominant ideas related to this topic.
(2) Pair with a partner: Ask students to pair with a partner and discuss their answers and ideas. Teachers can circulate the classroom and press for further explanation. For example, teachers can ask: Do you both think that soils are made up of different rocks? Why? Have you seen soils with different rocks? Why do you think that they are rocks?
(3) Share their ideas with the class: To engage students in a whole class discussion, teacher can distribute a few sheets of post-it to each team. Ask students to write down their ideas on post-it (answers for the questions on the worksheet)
Have a chart ready on the board (or a chart paper) for each question. With students’ responses posted on the board, teachers can start categorize to see the difference and similarities found within students’ responses.
Once written down the similarities and differences on the board, teachers can go back to the class consensus model made during Activity #1– Picture the soil! to see if students wants to change, add, remove any parts from the class model based on their discussion from Activity #2–Think-and-share. Teachers can ask the following question: “Many of you think that soils are same as you dig deeper; how can we represent this idea in our model? Should we colour all soils in the same colour? Are there anyone think that soil changes colours as we dig deeper? If so, do you agree if we add extra colour to our class model? Raise your hands if you agree. Is there anything else we want to change in our class model?” Note: While working on the class model, please include legends. Also remember to refrain from evaluating students’ responses at this point.
Step 2 of the Lesson: Collecting and Making Sense of Data
In order to help students make sense of soil profiles, teacher invites students to dig through the bags of soil from top to bottom. Teacher asks students to describe differences in color, texture, and various components (small stones, organic matter, sand clay). Ask students to write down their observation on the worksheet #1 (please see Appendix A).
Have students examine the texture of the soil by dampening a small handful of soil and rubbing it between fingers. If the soil is sticky, there is a high clay content. If the soil is rough and grainy, there is a lot of sand in the soil. If the soil is neither sticky nor grainy, then the soil is silty (loamy). Teachers can ask the following question: Do some soils have more pores or spaces in them?
Create a table (same as the one from the worksheet #1) on a board. Discuss their observations and write students’ responses on the board. Note: teachers can tally. e.g., Colour- brown 5, black 5, mixture of brown and others 6
Have students go through the soil to look for living organisms. Teacher then writes on the board the living organisms found by students, such as small snails, worms, ants, small beetles and other insects.
Step 3 of the Lesson: Developing Evidence-Based Explanations
Ask students to analyze the relationships between soil colour, texture, and living organisms in small groups. Teacher can circulate the room to press for descriptions and observations. Teachers can ask the following questions to guide students to notice patterns.
What happens when the colours of soil gets darker?
Are there more living organisms found in the soil?
Why do you think that is?
Post a summary table of all the groups findings on a chart. Teacher then leads a discussion about the similarities and differences in the group analysis. Teacher can use the following strategies:
Ø Orienting students to each other’s thinking: For example, teacher can ask: Do you agree with what Student A said? and Why?
Ø Pressing for explanation: For example, teacher can ask: Group A and B, both of you said if the colours of soils are darker, there are more living organisms in the soil. Why do you think so?
Students’ discussions might include:
Soils with a lot of leaf litter and organic matter have more living organisms
Soils that are rough with a high sand content have many pores, but fewer living organisms.
Step 4 of the Lesson: Extension & Application
Teacher can conduct a follow up activity to further engage students in thinking that soil is made up of distinct layers – horizons – and each layer has its own characteristics that make it different from all of the other layers. The procedures of this activity are as follow:
(1) Fill an Erlenmeyer flask ⅔ with water. Using a funnel, add soil to the water. (This could be messy).
(2) Shake the Erlenmeyer. Let the soil settle overnight.
(3) The organic matter will stay on top of the water while the heavier particles of sand will sink to the bottom. The layers of silt and clay might be visible resting on top of the sand and gravel.
This activity allows students to understand that the characteristics of each horizon play a very important role in what the soil is used for. For example, the top layer of soil is made up of living and decomposed materials like leaves, plants, and bugs (organic material); this layer is very thin and is usually pretty dark. Under the top layer of soil is the layer made up of minerals and decomposed organic matter and it is also very dark in color; this is the layer that many plants roots grow in. Below the top layers is a layer of soil that has clay and mineral deposits and less organic materials than the layers above it; this layer is also lighter in color than the layers above it. Lastly, the bottom layer of soil is made up of slightly unbroken rock and only a little bit of organic material is found here; plant roots are not found in this layer.
Step 5 of the Lesson: Evaluation
Three strategies can be used to do a post-assessment to examine students’ understanding and application of the concepts learned through the activities described above; they are:
(1) Draw the soil profile: Have individual students draw coloured soil profiles of the three (which refer to the first activity) soils, including living organisms. All components should be labelled.
(2) Case study: Which soil is best for an apple tree to grow?
Give students the following scenario: Mr. Kim is trying to open? an apple farm here in Quebec. He wants to find out in which region in Quebec, his apple tree will grow “better”. He hired a group of soil scientists (you and your group) to figure out which regions he should start building his apple farm. You had been given three soil samples; each soil sample is from a different region in Quebec (Soil number 1 from region 1.. and so forth.. ). Based on your analysis so far, where do you suggest Mr. Kim could open? his apple farm?
Ask students work in groups of 3-4 and try to create a portfolio. Students’ portfolio should include the following:
Soil profiles created from the activities: based on the profile, find out which soil has the most number and diversity of living organisms
Students should research which type of soil apple tree would “prosper?” the most. (e.g., focusing on texture, colours, living organisms etc.) – Case study….
A letter to Mr. Kim which include students’ suggestion regarding the appropriate soil (#1, 2, 3) and their reasons for the suggested soil type (e.g., evidence from their lab activities- texture, colours, etc.)
(3) Post-assessment questions: Administer the same two questions that were given before the lesson to see if students’ responses have changed. Teacher can use the clickers to obtain students’ responses. If the school does not have clickers, teachers can ask thee questions in the class and ask students to raise their hands for their answers. Teachers can also ask students to write their answer on a piece of paper and put them in a box. Teacher will then write some responses on a board (or a chart paper) for discussion.
After administering the test, share the data with students and ask students for the explanations. Sample guiding questions are: We see that many of you choose option C as an answer. Can anybody share why they chose letter C? What is your evidence for saying that? Note: You may re-voice their explanations and write their response on a board.
This lesson plan is inspired by the following resources:
