Topic: Saturated and unsaturated solutions

Target group

Elementary school student (grades 7. and 8.)

Core curriculum:

Primary school. Chemistry.

V. Water and aqueous solutions. Pupil:

5) defines the term solubility; gives the difference between saturated and unsaturated solution;

6) reads the solubility of substances from the solubility table or from the solubility plot; calculates the mass of the substance that can be dissolved in a given amount of water at the given temperature.

General aim of education

The student distinguishes between the concepts of saturated solution and unsaturated solution as well as dilute solution and concentrated solution.

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• distinguish between the terms: saturated solution, unsaturated solution, dilute solution and concentrated solution.

Methods/techniques

• expository

  • talk.

• activating

  • discussion;

  • brainstorming.

• 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.

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, using the illustrations in the abstract, explains the concept of saturated solution and unsaturated solution as well as concentrated solution and diluted solution.

2. The teacher, using the brainstorming method, asks students how to obtain an unsaturated solution from a saturated solution. He should get, among others such responses: heating the solution, adding more solvent. The teacher may ask another question and ask for examples of solutions used in everyday life, e.g. in the kitchen, which should be diluted before use.

3. The teacher, also on the principle of brainstorming, asks students about the methods of obtaining a saturated solution from an unsaturated solution. He should get, among others Answer: evaporation of water, addition of this substance, which is dissolved, cooling of the solution. A new concept will appear here - crystallization..

4. Students carry out the interactive exercises checking the level of knowledge learned during the lesson. The teacher initiates a discussion during which the correct solutions for all the exercises performed by the students are discussed.

5. The teacher plays the recording of the abstract. Every now and then he stops it, asking the students to tell in their own words what they have just heard.This way, students practice listening comprehension.

Summary

1. Students, working in small groups, create an infographic showing the issues learned during the lesson.

Homework

1. Develop a lap book containing issues learned during the lesson and bring your work to the next class.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Saturated and unsaturated solutions

If the maximum amount of solute is found in the aqueous solution and the next addition of substance is no longer dissolved, it is a saturated solution. Any other solution that does not reach saturation is referred to as an unsaturated solution.

Due to the relationship between the amount of substance dissolved from the temperature, the solution that is saturated at the lower temperature will no longer be at a higher temperature at which more substances can be dissolved.

Chemists also use the terms of solutions relating to the amount of substance dissolved in them. They stand out on this basis:

• concentrated solution, wherein the amount of solute is the same as in a saturated solution or slightly less;

• diluted solution, that is, a solution that contains at least several times less substance than a concentrated solution.

Each solution is saturated with a concentrated solution, but not every concentrated solution is saturated.
Each dilute solution is simultaneously unsaturated, but the unsaturated solution can be either a dilute solution or a concentrated solution.

• Different amounts of various substances dissolve in the same volume of water.

• A solution that contains the maximum amount of solute at a given temperature, and the next added portion of the substance does not dissolve, is called a saturated solution.

• A solution that at the given temperature does not contain the maximum amount of solute and in which it is possible to dissolve an additional portion of the substance, unsaturated solution.

• The diluted solution contains at least several times less substance than a concentrated solution.

• In a concentrated solution, the amount of solute is the same as in a saturated solution or slightly smaller.

• The maximum amount of substance that can dissolve in a fixed mass or volume of solvent at a given temperature and under constant pressure is called solubility. It can be expressed as the number of grams of substance that can be dissolved in 100 g of solvent at a given temperature and under consistent pressure.

• Crystallization is the reverse process to dissolve – occurs as a result of supercooling of steam or liquid or supersaturation of the solution (eg due to lowering the temperature of the saturated solution, removing the solvent by evaporation or distilling.