Topic: Electrolytic dissociation of salt

Target group

Student of an eight‑year elementary school

Core curriculum:

Elementary school. Chemistry.

VII. Salts. Pupil:

4) writes the electrolytic dissociation equations of water‑soluble salts

General aim of education

The student writes the electrolytic dissociation equations of water‑soluble salts

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn;

• mathematical competence and basic competences in science and technology.

Criteria for success
The student will learn:

• to write down the equations of the salt electrolytic dissociation process.

Methods/techniques

• activating

  • discussion.

• expository

  • talk.

• 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.

Realization

1. By introducing students to the subject of classes, the teacher displays an abstract film „Testing solubility of salt in water” on an interactive whiteboard. Before this happens, students formulate a research question and hypotheses, and then write them on the form in an abstract. They observe changes during the experiment being watched, discuss about them, jointly draw conclusions about salt solubility hypotheses and write them in the form.

2. The teacher refers students to the abstract. He asks you to read the text and analyze the „Where to get information which salts are soluble in water” - work in pairs. Then, he gives students examples of salts containing a specific cation and anion (eg, calcium cation and sulphate anion) and asks you to indicate, based on the salt solubility table, whether the salt is soluble or sparingly soluble in water. Selected students provide answers.

3. The instructor instructs the group to familiarize themselves with the instructions of the experiment „Do aqueous solutions of salt conduct electricity?” and analyzed the interactive illustration. Students write their observations and conclusions in the form provided in the abstract. Selected people read them, the teacher corrects mistakes, explains any doubts.

4. The teacher discusses a table describing the electrolytic dissociation process of the selected salts, explains how to write the equations of individual reactions.

5. Students, working individually or in pairs, perform interactive exercises. Volunteers discuss the correct solutions. The instructor completes or straightens the charges of the charges.

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

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. Execute task 3.1.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Electrolytic dissociation of salt

The salts do not dissolve in water to the same extent. Among them, there are salts very well soluble in water, such as, for example, potassium nitrate, and those that do not dissolve in it barely at all - e.g. barium sulphate. The same metal can form salts that are both well and sparingly soluble in water, e.g. calcium chloride and calcium carbonate. Similarly, salts containing the same anion of an acid residue may have different solubilities, e.g. calcium carbonate and sodium carbonate.

Information on whether the salt will dissolve in water can be found in the solubility table. It will allow us to assess whether a given salt is well, sparingly or virtually insoluble in water. To determine this property for the selected salt, read the record at the intersection of the cation column with the row of anion (ions forming the salt of interest).

All known salts of sodium, potassium, ammonium and all known nitrates are very well soluble in water.

Water‑soluble salts are electrolytes, their aqueous solutions conduct electricity. Under the influence of water, these disintegrate into the ions forming them, i.e. metal cations and anions of the acid residue. This process, as we remember, is called electrolytic dissociation.

During the dissolution of sodium chloride, polar water molecules release the ions from the crystal of the salt: sodium cations and chloride anions that can carry electric charge (electrons); due to this, the sodium chloride aqueous solution conducts electricity.

• There are salts that dissolve in water and salts that are sparingly soluble or practically insoluble in water.

• Aqueous solutions of salt conduct electricity - salts are electrolytes.

• Salts in water are subject to electrolytic dissociation, i.e. these disintegrate (dissociate) into metal cations and anions of the acid residue.