Topic: Ethyne and alkynes - hydrocarbons with multiple bonds between carbon atoms

Target group

Elementary school student (grades 7. and 8.)

Core curriculum

Elementary school. Chemistry.

VIII. Compounds of carbon with hydrogen – hydrocarbons. Student:

5. creates general formulas of homologous series of alkenes and alkynes (based on the formulas of subsequent alkenes and alkynes); writes the total formula of the alkene and alkyne with the specified number of carbon atoms; it forms the names of alkenes and alkynes based on the names of the corresponding alkanes; draws structural and semi‑structural (group) formulas of alkenes and alkynes with straight‑chain atoms up to five carbon atoms.

General aim of education

The student explains the concept of alkynes and unsaturated hydrocarbons.

Key competences

• communication in the mother tongue;

• communication in foreign languages;

• mathematical competence and basic competences in science and technology;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• what the terms: alkynes, unsaturated hydrocarbons mean;

• to draw structural and semi‑structural formulas of alkynes;

• to write down general formulas of homologous alkynes.

Methods/techniques

• activating

  • discussion.

• expository

  • talk.

• exposing

  • film.

• programmed

  • with computer;

  • with e‑textbook.

• practical

  • exercices concerned.

Forms of work

• individual activity;

• activity in groups;

• collective activity.

Teaching aids

• e‑textbook;

• notebook and crayons/felt‑tip pens;

• interactive whiteboard, tablets/computers;

• sets for building particle models;

• methodician or green, yellow and red cards.

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. Students read the fragment „Ethyne and other alkynes” from the abstract. Volunteers define the concept of unsaturated hydrocarbons and alkynes.

2. The teacher presents and discusses the illustration showing the summary formula of the ethyne, the model of its molecule and the structural formula. He writes the general formula for alkynes on the board and explains how to create the names of alkynes using the table in the abstract.

3. The teacher announces a movie „Obtaining ethyne”. Instructs students to write a research question and hypothesis in the form provided in the abstract. Then displays the video and the students write down their observations and conclusions in the form in the abstract. Volunteers read them. The teacher encourages young people to discuss, referring to the presented conclusions.

4. The teacher divides the students into groups. He distributes kits for building particle models and asks you to create model formulas for the first five alkins. Then he checks the correctness of the task.

5. Students perform Task 3 from the abstract. The teacher verifies the correctness of the drawn structural formulas, corrects possible errors and provides feedback.

6. Students perform an interactive exercise. The teacher makes sure that the task has been correctly completed and gives feedback.

Summary

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

2. 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. 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

Ethyne and alkynes - hydrocarbons with multiple bonds between carbon atoms

You already know alkenes, unsaturated hydrocarbons. The other group of compounds are compounds in which molecules there is one triple bond between carbon atoms, the others are single bonds. These are alkynes, also called acetylenes. The simplest representative of alkynes is ethyne, commonly referred to as acetylene.

The names of alkynes are formed from the corresponding names of alkanes, replacing the ending -ane into -yne.

If the triple bond occurs between the first and the second carbon atoms, the following entries -1- appear in the names, starting with the butyne:

• Unsaturated hydrocarbons are hydrocarbons in which molecules between carbon atoms in addition to single bonds there is one double bond (alkenes), and hydrocarbons in which molecules between carbon atoms have one triple bond (alkynes).

• Alkenes form a homologous series with the general formula of ${\text{C}}_{\text{n}}{\text{H}}_{\text{2n}}$.

• Alkynes form a homologous series with the general formula of ${\text{C}}_{\text{n}}{\text{H}}_{\text{2n-2}}$.