Topic: Ubiquitous silica

Target group

High school / technical school student

Core curriculum

New core curriculum:

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

XI. Applications of selected inorganic compounds. Pupil:

1) investigates and describes the properties of silicon oxide (IV); lists varieties of silicon oxide (IV) found in nature and indicates their uses;

2) describes the glass production process; its types, properties and applications.

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

XI. Applications of selected inorganic compounds. Pupil:

1) investigates and describes the properties of silicon oxide (IV); lists varieties of silicon oxide (IV) found in nature and lists their uses;

2) describes the glass production process; its types, properties and applications.

Old core curriculum:

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

XI. Applications of selected inorganic compounds. Pupil:

5. investigates and describes the properties of SiOIndeks dolny 2₂; lists the SiOIndeks dolny 2₂ variants found in nature and indicates their uses.

General aim of education

The student discusses the physical and chemical properties and use of silica.

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• to study and describe the physical and chemical properties of silicon dioxide;

• to exchange the types of SiOIndeks dolny 2₂ found in nature and determine their application;

• to explain why quartz glass is used for the production of laboratory crucibles and lamps used in medicine for the treatment of, among others, skin diseases (mainly psoriasis and acne);

• to justify the storage of hydrofluoric acid.

Methods/techniques

• expository

  • talk.

• activating

  • discussion;

  • brainstorming;

  • mind map.

• exposing

  • film.

• 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 informs students that they will work brainstorming. Their task is to gather information about silicon dioxide. The students give their suggestions, and the moderator writes them on the board in the form of a mind map according to the instructions of colleagues. After the creative phase, ideas are verified. Then the teacher displays the scheme „The occurrence of silicon dioxide in nature” and analyzes it with students who, if necessary, supplement the mind map.

2. The teacher refers students to the abstract and asks you to read the instructions for the „Physical properties of silica” experiment. It divides students into groups, distributes the right equipment, glass and reagents to perform the experiment. Students formulate a research question and hypotheses and write them on the form in an abstract. Then they follow the instructions. They record the observations in the form. The teacher asks questions in relation to the observations recorded. It initiates a discussion, the conclusions of which students write on the form.

3. The teacher announces a movie. He instructs his pupils to write a research question and a hypothesis in the form provided in the abstract. Then he plays the video and the students note their observations and conclusions. The teacher points the person who shares his insights and explains the reasonableness of the conclusions noted.

4. Then the teacher and the students discuss the reaction of the silica under the influence of heating with salts, with carbon, with magnesium and with hydrofluoric acid. Willing/selected students write the appropriate equations on the board, and the other students supplement them if necessary. The teacher watches over the correctness of the task.

5. The teacher divides the students into two groups and distributes sheets of paper, markers. He asks one group to work on the application of silicon dioxide, and the second group on the issue of silicon as an element of life and electronics. Students can use abstracts, textbooks and the internet. Group leaders present the effects of work. The teacher summarizes the activities of students.

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

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. Prepare 5 questions about the area that could be found on the test of the lesson.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Ubiquitous silica

The outermost and best‑known layer of the Earth's rock is the Earth's crust. Only 11 elements occur in it in an amount greater than 0.1%, which is as much as 99,895% of the mass of this part of the globe. Watch the video from the e‑textbook and find out what elements the earth's crust consists of.

The second most‑spread element in the earth's crust is silicon, and silicon dioxide , commonly known as silica, is as common as water. Silica is the main component of sand, rocks and soils. In nature, we encounter it both in a crystalline form, with an ordered internal structure (as quartz, tridymite and cristobalite), as well as in the non‑crystalline form, i.e. amorphous (in the case of e.g. agates, opals, jasper, onyx, diatomaceous earth). These varietes are characterized by the lack of an ordered internal structure.

From the earliest times people have used the unusual properties of silica. A mineral called flint, thanks to its hardness, was used to strike a fire. It is brittle, and its shards have sharp edges, which is why it was used by the Paleolithic people as a raw material for the production of stone tools. Today flint is a raw material used in the ceramic industry and used for the production of paints. Coatings with silicate paints are durable, resistant to moisture and have high mechanical resistance. They are completely non‑flammable and resistant to the development of microorganisms. From striped flint due to the rarity of its occurrence, aesthetic values and appropriate hardness, original jewelry and decorations are created.

Melted quartz upon slow cooling creates so‑called quartz glass, which is used for production of, among others, lamps in solariums, hospital rooms, fiber optics, laboratory crucibles. Quartz crystals have piezoelectric properties. When we place them in a variable electric field, these crystals shrink and expand, emitting ultrasounds. Ultrasounds allow to obtain images of various objects, which was used in sonars – to locate icebergs, schools of fish, as well as in medicine - for USG examination. Quartz crystals are also used for the production of extremely accurate clocks and lighters and igniters – due to the piezoelectric effect, which consists in the formation of electric charges on the surface of this crystal, due to mechanical stresses. As a decorative stone it is used in jewelry. In the optical industry, it is used for the production of lenses and prisms.

Sand is the basic component of mortar and cement and a raw material for the production of ceramic products, as well as various types of glass, e.g. window, decorative, water. In addition, silicon and its alloys are obtained from sand, it produces carborundum (SiC – hard grinding material).

Silicon is a dark gray solid with a metallic gloss. It creates crystals similar to diamond crystals. It is a semiconductor. It is a hard element (6.5 on the Mohs scale) and fragile. It has a high melting point (1863 K), during which it reduces its volume, similar to water. It is not chemically active. Does not react with water nor acids, except for hydrofluoric acid. At room temperature, silicon reacts only with fluorine to form silicon tetrafluoride – ${\text{SiF}}_{\text{4}}$. After heating, it reacts with other halogens, with oxygen and nitrogen, so that at temperatures of about 1000 K oxide is formed ${\text{SiO}}_{\text{2}}$ and nitride${\text{Si}}_{\text{3}}{\text{N}}_{\text{4}}$, and at temperatures above 2300 K it reacts, among others with carbon, forming a carbide. At high temperatures, it also reacts with metals, forming silicates, e.g. ${\text{Mg}}_{\text{2}}\text{Si}$. In solutions of bases, silicon is dissolved with the evolution of hydrogen.

• Silicon dioxide occurs in nature in crystalline form, mainly as quartz, and amorphous as opal and diatomaceous soil.

• Silicon dioxide is a solid, crystalline, colorless, insoluble in water and other common solvents. It is a substance with a high melting point and high hardness.

• Silicon dioxide has low chemical activity; it does not decompose under the influence of high temperature, it does not react with water, acids (except for hydrofluoric acid), after heating it reacts with oxides and hydroxides of metals and with few elements, e.g. with carbon, magnesium. It is classified as an acidic oxide.