Topic: Preparation of hydroxides

Target group

Elementary school student (grades 7. and 8.)

Core curriculum:

Elementary school. Chemistry.

VI. Hydroxides and acids. Pupil:

2) designs and conducts experiments, which may result in obtaining hydroxide (soluble and sparingly soluble in water), anaerobic and oxygenic acid (e.g. NaOH, Ca(OH)Indeks dolny 2₂, Cu(OH)Indeks dolny 2₂, HCl, HIndeks dolny 3₃POIndeks dolny 4₄); saves the corresponding reaction equations in the molecular form.

General aim of education

The student learns the methods and designs and conducts experiments that can lead to the preparation of a hydroxide.

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• exchange and describe the methods for obtaining hydroxides and record the corresponding reaction equations;

• give examples of metals and metal oxides reacting with water;

• identify reaction products of active metals with water.

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. The teacher announces a film entitled „Testing the behavior of sodium towards water”. He asks students to formulate a research question and hypothesis and write them in the form in an abstract. After watching the video, a summary of observations and conclusions is made, which should also be included in the form.

2. The teacher writes on the board the equation of reaction that took place during the experiment, explaining its mechanism. Then he writes down a verbal scheme of this method of obtaining hydroxides: active metal + water.

3. Students read a fragment explaining the method of obtaining hydroxides. They analyze the illustration showing the directions of changes in the activity of metals in the group of lithiums and beryllium.

4. The teacher recalls the participants of the classes to the abstract and asks for familiarization with the experiment's instruction „Testing the behavior of a given oxide”. The teacher divides students into groups and distributes appropriate equipment, glass and reagents to perform the experiment. Students - with the help of the teacher - formulate a hypothesis and a research question and write them on the form in the abstract. Then they follow the instructions. They record the observations in the form. The teacher asks questions in relation to the observations noted. He initiates a discussion, the conclusions of which students write on the form.

5. The teacher asks a willing student to write on the board the equation of reaction that took place during the experiment (if there are no volunteers, he writes the equation on the board himself), and then explains its mechanism.

6. The teacher announces a movie titled “Preparation of hydroxide sparingly soluble in water”. He instructs his students to write a research question and a hypothesis in the form provided in the abstract. Then he plays the video and the students note their observations and conclusions and record the equation of the reaction that occurred during the experiment shown in the movie. Selected people present the results of their work.

7. 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.

Summary

1. The teacher asks a willing student to summarize the lesson from his point of view. He asks other students if they would like to add anything to their colleague's statements.

Homework

1. Carry out task number nr 4.1.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Preparation of hydroxides

Hydroxides are obtained as a result of the reaction of active metals with water (metals from the 1st and 2nd groups of the periodic table, except for beryllium). As a result, bases (aqueous solutions of hydroxides) are formed and hydrogen is produced.

$\text{ active metal oxide }+\text{ water }\to \text{ hydroxide }$

Alkali metals react with water more violently than alkaline earth metals. Magnesium reacts with water at increased temperature. Within the group, the activity of metals increases with the increase of the atomic number (this is related to the distance of valence electrons from the nucleus). The metals of other groups of the periodic table (e.g. copper) are less active and do not react with water. Hydroxides of metals from the 1st and 2nd groups of the periodic table are obtained by other methods.

Another way of obtaining hydroxides is the reaction of active metal oxides (belonging to the 1st and 2nd group of the periodic table, except for beryllium), called basic oxides, with water.

$\text{active metal oxide + water → hydroxide}$

These reactions generate bases – aqueous solutions of hydroxides.

• Hydroxides are chemical compounds made of metal cations and hydroxide anions whose general formula is ${\text{M(OH)}}_{\text{n}}$.

• Hydroxides are obtained as an effect of the reaction of active metal oxides (basic oxides) with water and of some metals with water.

• Solutions of hydroxides that are easily soluble in water (all hydroxides of metals from the 1st group of the periodic table and selected metals from the 2nd group) are traditionally called bases.