Topic: Soil – composition and properties

Target group

High school / technical school student

Core curriculum

New core curriculum:

High school and technical high school. Chemistry – basic level:

XXII. Elements of environmental protection. Pupil:

1) explains what the sorption properties of soil in plant cultivation and environmental protection consist in; describes the effect of soil pH on the growth of selected plants; plans and conducts research on soil acidity and testing soil sorption properties.

High school and technical high school. Cheistry – extended level:

XXII. Elements of environmental protection. Pupil:

1) explains what the sorption properties of soil in plant cultivation and environmental protection consist in; describes the effect of soil pH on the growth of selected plants; plans and conducts research on soil acidity and testing soil sorption properties.

Old core curriculum:

High school and technical high school. Chemistry – basic level:

XXII. Elements of environmental protection. Pupil:

1) explains what the sorption properties of soil in plant cultivation and environmental protection consist in; describes the effect of soil pH on the growth of selected plants; plans and conducts research on soil acidity and testing soil sorption properties.

General aim of education

The student discusses the composition and properties of the soil.

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• to define the concept of soil;

• to describe the composition of the soil;

• to explain what sorptive properties of the soil consist in and indicate factors affecting the soil sorption properties;

• to explain how soil pH can affect the growth and development of plants;

• to give examples of plants and their requirements for soil pH;

• to plan and conduct soil acidity testing and study soil sorption properties.

Methods/techniques

• expository

  • talk.

• activating

  • discussion.

• programmed

  • with computer;

  • with e‑textbook.

• practical

  • exercices concerned.

Forms of work

• individual activity;

• activity in pairs;

• activity in groups;

• collective activity.

Teaching aids

• e‑textbook;

• notebook and crayons/felt‑tip pens;

• interactive whiteboard, tablets/computers.

Lesson plan overview

Introduction

1. The teacher hands out Methodology Guide or green, yellow and red sheets of paper to the students to be used during the work based on a traffic light technique. He presents the aims of the lesson in the student's language on a multimedia presentation and discusses the criteria of success (aims of the lesson and success criteria can be send to students via e‑mail or posted on Facebook, so that students will be able to manage their portfolio).

2. The teacher together with the students determines the topic – based on the previously presented lesson aims – and then writes it on the interactive whiteboard/blackboard. Students write the topic in the notebook.

3. Health and safety – before starting the experiments, students familiarise themselves with the safety data sheets of the substances that will be used during the lesson. The teacher points out the need to be careful when working with them.

Realization

1. The teacher uses the text of the abstract for individual work or in pairs, according to the following steps: 1) a sketchy review of the text, 2) asking questions, 3) accurate reading, 4) a summary of individual parts of the text, 5) repeating the content or reading the entire text.

2. The teacher presents and discusses the photo gallery. Students analyze the illustrations and answer the teacher's questions.

3. The teacher plays the recording of the abstract. Every now and then he stops it, asking the students to tell in their own words what they have just heard.

4. The teacher announces the experiment „Soil properties”. Students formulate a hypothesis and a research question in an abstract form. After the experiment, students jointly discuss observations and conclusions, which they then write in the form in an abstract..

5. The teacher announces the experiment „Sorption properties”. Students formulate a hypothesis and a research question in an abstract form. After the experiment, students jointly discuss observations and conclusions, which they then write in the form in an abstract..

6. The teacher announces the experiment „Soil reaction”. Students formulate a hypothesis and a research question in an abstract form. After the experiment, students jointly discuss observations and conclusions, which they then write in the form in an abstract..

7. Students carry out the interactive exercises checking the level of knowledge learned during the lesson. The teacher initiates a discussion during which the correct solutions for all the exercises performed by the students are discussed.

Summary

1. The students consolidate the acquired information, discussing it with their nearest neighbors („tell your neighbor” method.

2. The teacher displays the criteria for success and asks the students to assess their skills acquired during the classes.

Homework

1. Carry out task number 6.1.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Soil – composition and properties

The composition of soil depends on the type of rock being the substrate and undergoing (physical and chemical) soil formation processes, the amount of humus and the diversity of organisms living in it. Approx. 45% of the soil volume is made of mineral substances, approx. 25% of gases, 25% – of water and 5% – of organic substances.

Soil formation is a continuous process including:

• weathering of minerals in the rock substrate under the soil layer: physical weathering – the breakdown of rocks caused by water, wind and temperature fluctuations, chemical weathering – reactions of minerals that make rocks with water and carbon dioxide, leading to the formation of simpler, water‑soluble compounds;

• biological weathering – transformation of biological matter, mainly plant matter, reactions involving microorganisms leading to the formation of humus (organic matter formed resulting from incomplete decomposition of plants and animals).

The following types of sorption can be distinguished:

• mechanical sorption, which consists in the retention in the open spaces of the soil of particles and microorganisms contained in soil solutions and suspensions;

• physical sorption – the process of retaining water and gases (carbon dioxide and nitrogen oxides) by fragmented solid components of soil;

• chemical sorption – the process of retaining ions contained in the soil solution by way of the reaction of digestion and precipitation of sparingly soluble salts.

Plants have different degrees of tolerance of soil acidity. Soil with pH close to neutral (6.6 to 7.2) or slightly acidic pH (5.6–6.5) is best for crops. It was found that the decrease in soil pH in the arable layer below 5 results in a decrease in crop yields. Forest plants grow normally in soils with a pH of 4.5 – 5.5.
In Poland, over 80% of arable soils are acid soils that require liming, i.e. fertilization with alkaline calcium compounds (calcium fertilizers).

• Soil formation is a continuous process including among others, weathering of minerals in the in the rock substrate under the soil layer, reactions involving microorganisms, metabolism of biological matter, mainly plants.

• Weathering of minerals is a set of physical, chemical and biological processes occurring with the participation of living organisms. An important role in the course of these processes is played by water flowing through the soil and dissolving mineral components. The weathering processes take place in the environment with low acidity.

• Soil has strong sorption properties, i.e. the ability to absorb gases and vapors from the air, particles or ions from solutions as well as microorganisms and fine particles from suspensions in the soil.

• Most plants thrive on soils with neutral or slightly acidic pH.