Topic: Calculation of concentration and solubility

Target group

Elementary school student (grades 7. and 8.)

Core curriculum

Elementary school. Chemistry.

V. Water and aqueous solutions. Pupil:

7) performs calculations using the following notions: solubility, percent concentration (mass percentage), mass of substance, solvent mass, mass of solution, solution density (using solubility table or solubility plot).

General aim of education

The student calculates the percentage concentration of solutions using the solubility plot

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• calculate the percentage concentration of a saturated solution at a given temperature using a solubility chart;

• determine the solution solubility based on the percentage of saturated solution at a given temperature.

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;

• 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. The teacher, introducing students to the subject of classes, states that the interpretation of the solubility curves and the calculations used allow to predict the mass of the substance that will be released from the saturated solution during its cooling. Thanks to them, it is also possible to determine the mass of the solvent to be added to the indicated solution in order to obtain a suitable solute concentration. It is also possible to set the percentage of saturated solution at a given temperature.

2. Students, working in pairs, analyze the scheme „Solubility curves of solid substances” and the table in the abstract. Selected pairs discuss their observations.

3. Then students perform exercise number 1 and exercise number 2 on the use of solubility of substances to calculate the percentage of solution. The teacher initiates a discussion during which the correct solutions are discussed.

4. The teacher plays the presentation placed in the abstract. The teacher discusses the calculation of the solubility of a substances in a saturated solution with a known percentage concentration. Students do exercise number 3. The teacher makes sure that the task has been correctly completed and gives feedback.

5. Students do exercise number 4 themselves. Volunteers comment on the solution, the teacher completes or corrects the students' statements.

Summary

1. The teacher briefly presents the most important issues discussed in class. He answers the additional questions of the proteges and explains all their doubts.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Calculation of concentration and solubility

The solution saturated at a given temperature contains a defined amount of solute in a given mass of solvent. On the basis of these values, the percentage concentration of the solution can be calculated.

The more mass of solute falls on a specific mass solvent, the percentage concentration of the solution is higher. Due to the fact that the solubility of solids usually increases with temperature, the concentration of the saturated solution of these substances also increases.

If at a given temperature we know the percentage of saturated solution of a substance, then we can calculate the solubility of this substance at a certain temperature.

• Based on the knowledge of the solubility of the substance, the percentage of saturated solution can be calculated.

• Knowing the percentage concentration of a saturated solution of a substance, you can calculate its solubility.