Chemistry lesson scenario

Lesson plan elaborated by: Krzysztof Błaszczak

Target group:

Elementary school student (grades 7. and 8.)

Core curriculum:

Elementary school. Chemistry.

VI. Acids and bases. Student:

8) analyses the formation process and the effects of acid rains; suggests measures to limit their formation.

Gymnasium

6. Acids and bases. Student:

9) analyses the process of formation of acid rains and their effects; suggests measures to limit their formation**.**

Abstract title:

3.9. Acid rains

1. How acid rain arises

Link to lesson:

https://www.epodreczniki.pl/reader/c/141001/v/33/t/student‑canon/m/iw47AIdQ7O

Topic: Where do acid rain come from?

Time: 45 min

Aim of the lesson:

The student analyses the process of acid rains formation

Criteria for success:

• you will explain the concept of acid rain

• you will indicate oxides of non‑metals, which contribute to the formation of acid rain

• you will determine the pH of the acid rain

• you will discuss the process of acid rain formation

• you will write down relevant reaction equations indicating the acid rain formation

Key competences:

• communicating in the mother tongue

• communicating in foreign languages

• mathematical competences and basic scientific and technical competences

• IT competences

• learning to learn

Acquired and improved skills:

• using the digital textbook

• communication

• computer literacy

• research and investigation

• creative thinking and acting

• cooperation

• conducting experiments

Teaching aids:

• computers with speakers and internet access

• multimedia resources contained in the abstract

• multimedia projector

• interactive whiteboard / blackboard and chalk

• Methodology Guide or green, yellow and red sheets of paper

• equipment, laboratory glassware and reagents for the experiment described in the methodological commentary

Methods / techniques:

• problematic: didactic discussion

• exposing: the film

• programmed: using the computer, using an e‑textbook

• giving: elements of the lecture

• practical: experiment

• stoplight technique for student self‑assessment, and thus determining the level of mastery of the discussed issue on an ongoing basis

• technique of summary sentences

Forms of work:

• collective activity

• team work

• individual activity

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 stoplight technique. He presents the aims of the lesson on a multimedia presentation in the student's language 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.

3. Health and safety - before experiments, the teacher familiarises students with the characteristics of the substances used during the lesson

Realization

4. The teacher, introducing students to the topic, asks them to find in the internet movie - „Acid rains”. Before the screening, he asks to pay attention to the chemical compounds that contribute to the formation of acid rain during the movie. After the movie, he asks about names of such compounds.

5. The teacher displays a movie „Obtaining acid rain” from the abstract. Before the screening, he asks students to formulate a research question. Then students discuss their observations with their classmates: they conclude that combustion of sulphur‑containing carbon provides the atmosphere with huge amounts of sulphur dioxide, which is the main cause of acid rains.

6. The teacher explains the process of acid rain formation paying attention to wet and dry depositions.

7. The teacher asks volunteers to write appropriate equations for obtaining oxoacids on the board, based on their knowledge and skills. The other students copy the equations to the notebooks.

8. The teacher, one week prior this class, asked students to collect rainwater and bring it to school. The students will conduct “Acid rain pH test” experiment during the lesson, working in pairs, according to the instructions described in the methodical commentary. Before the experiment, the teacher gives students worksheets and appropriate glassware and reagents. The participants formulate a research question and hypotheses, write them in the worksheets. After the experiment, they discuss the observations, and then draw conclusions and note them down in the worksheets.

9. Students - with teacher’s help - define the „acid rains” term and write it in notebooks.

10. The teacher asks students to perform interactive exercises in abstract as their homework.

Summary

11. In the summary of the lesson, the teacher asks students to finish following sentences:

• It was important for me…

• I got to know...

• I understood that…

He can use an interactive whiteboard in abstract or instruct students to work on it.

Multimedia:

I. Interactive exercises - crossword, pairing

II. Movie “Obtaining acid rain”

III. Logs for notes and observations made during the experiments

IV. Interactive whiteboard for lesson evaluation and self‑assessment of the student's knowledge

Methodical commentary:

Student experiment „Acid rain pH test” - a problem‑verification experiment

List of required materials/teaching aids

Laboratory equipment and glassware: beaker, pipette

Reagents: rainwater, methyl orange or a universal indicator strip

Performance of the experiment

1. Pour a few cmIndeks górny 3³ of rainwater in a beaker.

2. Immerse a universal indicator strip in a rainwater or add a few drops of methyl orange into it.

3. Observe the changes.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

How acid rain arises

Acid rains are acidic (pH <5.6). Wet deposition arises as a result of absorption by the vapor in the air of gaseous air pollutants, primarily sulfur dioxide, nitrogen oxides and carbon dioxide. Dry deposition in the form of oxides - mainly sulfur - is combined with water usually on moist surfaces of plants, structures and water surface. In industrial areas, acid rains components may include hydrochloric and hydrogen sulfonic acids in addition to oxides.

Carbon dioxide reacts with water to form carbonic acid.

COIndeks dolny 2₂Indeks dolny (g)_(g) + HIndeks dolny 2₂OIndeks dolny (l)_(l) → HIndeks dolny 2₂COIndeks dolny 3₃Indeks dolny (aq)_(aq)

Carbonic acid then dissociates to give the hydrogen ion (HIndeks dolny 3₃OIndeks górny +⁺) and the hydrogen carbonate ion (HCOIndeks dolny 3₃Indeks górny -^-). The ability of HIndeks dolny 2₂COIndeks dolny 3₃ to deliver HIndeks dolny 3₃OIndeks górny +⁺ is what classifies this molecule as an acid, thus lowering the pH of a solution.

HIndeks dolny 2₂COIndeks dolny 3₃ + HIndeks dolny 2₂O → HIndeks dolny 3₃OIndeks górny +⁺ + HCOIndeks dolny 3₃Indeks górny -^-

Sulfur dioxide reacts with water to form sulfurous acid.

SOIndeks dolny 2₂Indeks dolny (g)_(g) + HIndeks dolny 2₂OIndeks dolny (l)_(l) → HIndeks dolny 2₂SOIndeks dolny 3₃Indeks dolny (aq)_(aq)

Substances in the upper atmosphere then catalyse the reaction between sulfurous acid and oxygen to form sulfuric acid.

2HIndeks dolny 2₂SOIndeks dolny 3₃Indeks dolny (aq)_(aq) + OIndeks dolny 2₂Indeks dolny (g)_(g) → 2HIndeks dolny 2₂SOIndeks dolny 4₄Indeks dolny (aq)_(aq)

Nitrogen dioxide reacts with water to form a mixture of nitric and nitrous acid.

2NOIndeks dolny 2₂Indeks dolny (g)_(g) + HIndeks dolny 2₂OIndeks dolny (l)_(l) → HNOIndeks dolny 3₃Indeks dolny (aq)_(aq) + HNOIndeks dolny 2₂Indeks dolny (aq)_(aq)

Substances in the atmosphere then catalyse the reaction between nitrous acid and oxygen causing the formation of more nitric acid.

2HNOIndeks dolny 2₂Indeks dolny (aq)_(aq) + OIndeks dolny 2₂Indeks dolny (g)_(g) → 2HNOIndeks dolny 3₃Indeks dolny (aq)_(aq)

• Sulphur and nitrogen oxides are emitted into the atmosphere as a result of human activities (combustion of fuels, industry) and from natural sources (volcanic eruptions, forest fires).

• Acid rains arises as a result of the reaction of some oxides (${\text{SO}}_{\text{2}}{\text{, N}}_{\text{x}}{\text{O}}_{\text{y}}\text{, C}{\text{O}}_{\text{2}}$) with water.

Acid deposition, acid rains, wet decomposition, dry decomposition