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Notes for teachers

In this lesson, the students will explore how soil fertility affects electrical conductivity. They will measure the electrical conductivity of different types of soil and see which one has the highest level.

The students will perform experiment and find out if

any type of soil can conduct, or

carry an electric current.

Record their observations on their digital Science Investigatory Journal

List of Materials

200g of sand

200g of clay

400g of loam

50ml of liquid fertilizer

800ml of water

4 beakers

1 DC12V battery

3 jumper wires with crocodile clips at both ends

2 copper electrodes

1 milliammeter/multimeter

1 digital weighing scale

1 measuring cylinder

1 ruler

1 clock

For recording:

Digital Science Investigatory Journal

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Standards

Science and Engineering Practices

ask questions and define problem
plan and carry out investigations
analyze and interpret data
use mathematical and computational thinking
construct explanations and design solutions
engage in argument from evidence
obtain, evaluate and communicate information

Standards

Science

Standard 8.P1U1.2 Obtain and evaluate information regarding how scientists identify substances based on unique physical and chemical properties.

ELA

Common Core ELA Standards

• Grades 7: Writing W.7; W.8

• Grade 7: Speaking and Listening 4.SL.1b-d

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Objectives:

The students will describe how electrical conductivity affects soil function

The students will explain how soil fertility affects electrical conductivity.

The students will list down and describe problems related to electrical conductivity.

The students measure soil electrical conductivity and interpret results.

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Agenda (lesson time)

I will allow two class periods for this activity.

Introduction (10 minutes):

Start the lesson by having the students fill out the KWL chart on their prior knowledge about soil fertility and electrical conductivity.
Engage students by having them watch a video about electrical conductivity

Explain to students that they will be performing an experiment and measure the electrical conductivity of different types of soil and see which one has the highest level.
Remind the students to record their observations in their digital Science Investigatory Journal and must observe the standards of writing.

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Intro/Driving Question/Opening

Do you think soil and energy could go together? How is that possible?

What is soil electrical conductivity?

What kind of soil conducts electricity the best?

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Hands-on Activity Instructions

Let's Do the KWL Chart!

In Dyad, have the students work on the first and second columns of the KWL chart, share and discuss ideas.

Hook Me Up

Have the students watch a video about soil electrical conductivity and let them fill out the last column of the KWL chart. Allow sharing of ideas with their partners. Then proceed with the unlocking of terms (saline soil, sodic soil, nitrification, denitrification, electrolytes)

Ask students to make some predictions about the electrical conductivity (salinity) of the soil in your area based on the climate and soil texture of the area.

Introduce the Scenario

Ken, an agronomist was consulted by a farmer concerned about how soil fertility affects electrical conductivity and

what kind of soil conducts electricity the best?

Measuring Soil Electrical Conductivity

For this experiment, the independent variable is the type of soil used – sand, clay, loam and loam mixed with fertilizer. The dependent variable is the conductivity of the soil. This is determined by measuring the current conducted in the soil using a multimeter. The constants (control variables) are the amount of soil in the beaker, the amount of water added, the temperature of the environment (which will remain at room temperature), the battery voltage and the distance between the electrodes.

Produces

Step 1. Dry the samples of sand, clay and loam under the sun or in an oven, to remove moisture.

Step 2. Label the 4 beakers ‘sand’, ‘clay’, ‘loam’ and ‘loam with fertilizer’.

Step 3. Measure out 200g of each type of soil and place in the appropriate beaker, Then, measure and add 200ml of water into each beaker. Add 50 ml of liquid fertilizer to the beaker marked ‘loam and fertilizer’.

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Hands-on Activity Instructions

Continuation...

Step 4. Leave the beakers aside for 30 minutes. This will allow the soil to absorb the water, as well as allow the mineral salts to dilute.

Step 5. Insert 2 copper electrodes 5 cm apart in one beaker. Connect the ammeter and the DC12V battery to the electrodes. Record the current measurement in your record sheet.

Step 6. Repeat step 5 with the remaining beakers.

Group Activity / Interpreting Soil Electrical Conductivity

Form a group of four. Use your observations and answer the following questions: Make your claim and provide evidence.

a. Which type of soil has the highest level of electrical conductivity?

b. Which type of soil has the lowest level of electrical conductivity?

c. What happens if the electrical conductivity is too low?

d. What happens if the electrical conductivity is too high?

Discussion

What can electrical conductivity tell us about soil?

2. How does soil fertility affects electrical conductivity?

3. Do you think your soil test could explain why some plants look better than others?

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Assessment

Students (in group of four) come up with a slide presentation on the following:

1. How does soil electrical conductivity affect plant growth?

2. What are the factors affecting soil electrical conductivity?

3-2-1 Exit Ticket

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Differentiation

Online video can be provided for students who need additional information about the lesson and for those who learn better through visual.

The experiment may be repeated by adding different types of minerals to the soil samples and subsequently comparing their electrical conductivity.

Remediation

Extension/Enrichment

The experiment may also be modified to measure the effects of other factors on electrical conductivity, eg. by varying the amount of water added, the temperature of the environment, or the pH of the soil.

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