Topic: Metals – application, corrosion and passivation

Target group

Student of an eight‑year elementary school

Core curriculum:

Elementary school. Chemistry.

I. Substances and their properties. Pupil:

8) classifies elements into metals and non‑metals; differentiates metals from non‑metals based on their properties.

General aim of education

The student will discuss the use of metals and the process of corrosion and passivation

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• to show examples of the use of metals in everyday life;

• to explain what the corrosion process is and suggest ways to prevent iron products from rusting;

• to explain what the passivation process is and how it differs from the corrosion process.

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 experiments, the teacher familiarises students with the characteristics of the substances to be used during the lesson. He indicates the need to be careful when working with them.

Realization

1. The teacher, in order to remind the news from the last lesson, asks students to mention properties typical of metals.

2. The teacher divides the students into groups - he distributes sheets of paper and markers, asking for a conceptual map of the issue of using metals in the context of their properties. Students can use textbooks, abstracts and the internet. After finishing the work, its effects are discussed using the wall‑telling technique.

3. The teacher discusses the processes of destroying metals from which various objects are made, associated with the passage of time. These include the rusting of steel elements of various devices and structures, and the overlapping of copper products with patina. The teacher asks for examples of their environment illustrating the phenomenon of corrosion - discussion.

4. The lecturer informs students that they will watch the film „Rust: Prevention and treatment” - asks them to formulate and record in the diaries abstract observations of research questions, and then, after projections, observations and conclusions.

5. Students define the concept of corrosion. The teacher verifies the correctness of the definition proposed by the students and explains any errors.

6. The teacher explains what the process of overlapping copper products with patina - passivation. It asks students to give examples of passivation observed in their immediate surroundings or everyday situations.

7. The teacher initiates the discussion by asking: „What factors cause corrosion and passivation of metals and their alloys?”.

8. The teacher divides students into groups, distributes sheets of paper and markers, and then asks to present / save methods for protecting metals and their alloys against corrosion and passivation. Group leaders discuss the effects of work; the teacher sums up the activities.

9. At the end of the lesson, the teacher asks students to do interactive exercises from the abstract.

Summary

1. The student indicated by the teacher sums up the lesson, telling what he has learned and what skills he/she has been practicing.

Homework

1. Listen to the abstract recording at home. Pay attention to pronunciation, accent and intonation. Learn to pronounce the words learned during the lesson.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Metals – application, corrosion and passivation

Corrosion is a process of decaying materials caused by the action of air, water and other environmental factors. Destruction begins on the surface of the metal and progresses deeply, changing its properties. The most exposed to corrosion are seams with other metal, e.g. welding or soldering seams. Corrosion of iron and steel is called rusting. Objects made of copper, such as the roofs of historic buildings, over time are covered with a greenish coating called patina, which protects copper from further decaying. This process is called passivation.

Passivation is therefore a process in which a certain chemical active substance in a given environment creates a protective coating on its surface – a passive layer. The coating is tight and resistant to further reactions with the environment – thus protecting the substance from decaying.

Passivation can be:

• natural, resulting from properties of the metals in particular environment;

• artificial, triggered by a deliberate reaction, e.g. the formation of a passive layer consisting of, for example, chromium oxides to protect steel alloys (a passive layer consisting of oxides, mainly chromium oxides).

The passivation phenomenon is used, for example, in the transport of concentrated nitric acid in aluminium cisterns. The aluminium reacts with the acid, forming a protective coating on the walls of the tanker by passivation. It prevents further chemical reactions and does not affect the physical and chemical properties of the acid.

• Metals by the definition are characterized by: metallic gloss, thermal conductivity, electric conductivity, tenacity, ductility.

• Metals in a room temperature also have a constant state of matter (except mercury) and silvery‑white or silvery‑grey colour (with the exception of gold, copper).

• All metals, except noble ones (e.g. gold, silver, platinum), are subject of corrosion.

• Corrosion is the process of decomposition of materials caused by the action of air, water and other environmental factors.

• Passivation is the process of coating formation, for example on copper, which protects the metal against further destruction.

• Passivation concerns mainly metals and can be a natural process or caused intentionally by man.