Topic: Metal alloy

Target group

Elementary school student (grades 7. and 8.)

Core curriculum:

Primary 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 explain the use of metal alloys and discuss their applications

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• to explain why, instead of metal, its alloy is often used with other chemical elements;

• to give examples of applications of metal alloys in everyday life;

• to indicate in the periodic table chemical elements metals from which utility alloys are obtained;

• to classify metal alloys as homogeneous mixtures and describe some of them: bronze, brass, steel, duralumin;

• to design experiments to compare the properties of metals and their alloys.

Methods/techniques

• activating

  • discussion.

• expository

  • talk.

• programmed

  • with computer;

  • with e‑textbook.

• practical

  • exercices concerned.

• exposing

  • exposition.

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. Teacher introducing students to the subject, reports that metals can be fused together. Foots with the desired properties and melting temperature lower than the melting point of the individual components are then obtained. Sometimes non‑metals are also added to alloys.

2. The teacher informs students that they will watch the film „Study of the properties of the alloy and its components”. He asks them to formulate a research question and hypotheses before the screening and write them in the observation diary in abstract (or in previously prepared work cards / in notebooks). After watching the material, the students and the teacher set the observations and write them - similarly they make the conclusions from the forum discussed on the forum.

3. The lecturer displays on the multimedia board an illustration of the „Timeline” from the abstract and asks students to analyze the information contained therein. He also instructs them to recall the history of the stone, bronze and iron ages - initiating the discussion.

4. The teacher presents on the multimedia board the gallery „Metal alloys” from the abstract. The composition and use of particular alloys is analyzed. Students compare the melting temperatures of individual metals and their alloys, using the periodic table of elements and chemical tables.

5. The teacher informs students that they will watch the film „Obtaining Wood's alloy” - before this happens, they formulate a research question and hypotheses and write them in an abstract. Observations made during the projection and jointly determined conclusions after getting acquainted with the film material are also to be saved in the form in the abstract.

6. At the end of the lesson, the teacher asks students to do interactive exercises - individual work.

Summary

1. The teacher asks the students to finish the following sentences:

   • Today I learned ...

   • I understood that …

   • It surprised me …

   • I found out ...

   The teacher can use the interactive whiteboard in the abstract or instruct students to work with it

2. 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.

2. Make at home a note from the lesson using the sketchnoting method.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Metal alloy

While listening to the organ recital, it is worth considering what the most important elements of the organs – pipes – are made of? Most often it is a tin and lead alloy. The sheet of metal building the pipes may have different tin contents, and the percentage of this element in the alloy is determined by the so‑called tin‑assay. It can be value from 1 to 16. Tin‑assay in subsequent samples can be calculated by multiplying 6.25% by assay “number” (assay 1 contains 6.25% of tin, 2 - 12.50% of tin, 3 - 18.75% of tin, etc.). Assay 16 means there is no lead added, only tin (100%) is included in this material. It is rarely used and it has mainly decorative qualities. The higher the tin content, the lower the density and the lighter the colour of the alloy. However, the more lead, the greater the density of the alloy, and the colour is darker.

In the lower part of the organ pipes, the walls are often thicker than at the top. Due to this, these withstand the high pressure of the pipe body on its lower part, which prevents its deformation (flattening). Sometimes large pipes are made of zinc - lighter and cheaper than lead, however, then the emitted sound has lower quality and their surface is dull and does not have gloss, as zinc in the air undergoes passivation. Brass instruments, such as trombone or trumpet, are most often made of brass, i.e. copper and zinc alloy, rarely of noble metal. Alto flutes can be produced from the so‑called gold brass (with a high content of copper), due to which these are lighter than traditional instruments and have optimal sound.

Guitar manufacturers also use metal alloys. They are constantly looking for new ways to make the strings of these instruments last longer and have better sound qualities. Most of the currently produced strings for electric guitars are made of nickel steel, ensuring good sound quality. The current news are strings made of stainless steel – very strong, durable and hard.

Why are the guitar strings coated with plastics? Formerly the guitar strings were produced from processed intestines of animals, nowadays nylon strings are used most often in classical guitars, and in the rest of them – string made of steel or bronze. Dirt, sweat and grease covering the strings while playing expose them to corrosion.

Therefore, these are protected against impurities by covering them with plastic coatings.

As a result of the melting of two or more different metals homogenous mixtures called alloys are obtained. Both metals and alloys obtained from these have metallic gloss.

Alloy i.e. a mixture of metals or metal with non‑metal elements, it is obtained by melting the components and then cooling the obtained mass.

Iron due to its properties is the most useful metal. It is the main component of commonly used steel, which is obtained from crude steel (produced in a huge furnace from iron ore) and refined with metals: manganese, nickel or chromium. This alloy is used in the construction of bridges, skyscrapers, ships, offshore platforms, cars, trains, roofs or in the manufacture of cans. For manufacturing, among others elements of the construction of aircraft or beverage cans, another alloy is used – duralumin.

Alloy usually has different properties from its building blocks, in some cases even a small number of additives significantly affects its properties. Typically, the alloys are more resistant to air and water, as well as harder and more mechanically durable than pure metals.

• The properties of the alloy depend on its composition and the method of its manufacture.

• Metal alloys are obtained just as other mixtures by mixing two or more metals, after fusing them together and cooling the obtained mass.

• The alloys differ from the metals creating them with their properties, e.g. hardness, durability, ductility and melting points (generally lower in the case of alloy). Metal alloys are more resistant to corrosion than metals.

• Steel is an iron alloy with an admixture of carbon, which provides greater hardness and durability of the alloy and reduces its forgeability and ductility. Achieving specific properties, e.g. corrosion resistance, requires the addition of chromium to the steel, e.g. stainless steel contains 11 – 14% of chromium. Steel prepared in this way is used for the manufacture of machine parts, rails, knife blades, tools, concrete reinforcements, building elements.

• Brass is an alloy of copper and zinc (up to 40%) and additions, e.g. lead, aluminium, tin, manganese, iron, chromium and silicon. Brass is useful for cold forming, for example during the production of ammunition shell‑case. Coins, medals, candlesticks, cups, padlocks, mortars, monuments, decorative elements (buckles, door handles, weights, bells, fittings, picture frames), fixtures, equipment resistant to seawater, screw propellers, ammunition are made of brass. Elements of the machines are also made of brass – in the machine, automotive, electrotechnical, shipbuilding, precision and chemical industries. An important application of brass is the production of musical instruments.

metal alloys, bronze, brass, duralumin, steel, cast iron, Wood’s alloy