Topic: The neutralization reaction part 1

Target group

Elementary school student (grades 7. and 8.)

Program basis:

Primary school. Chemistry.

VII. Salts. Pupil:

3. writes the equation for the salt reaction (acid + hydroxide (eg Ca(OH)Indeks dolny 2₂), acid + metal oxide, acid + metal (1 and 2 groups of the periodic table), hydroxide (NaOH, KOH, Ca(OH)Indeks dolny 2₂) + nonmetallic oxide, metal oxide + nonmetallic oxide, metal + nonmetallic) in molecular form.

General aim of education

The student explains the nature of the neutralization reaction

Key competences

• communication in the mother tongue;

• communication in foreign languages;

• mathematical competence and basic competences in science and technology;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• to show in molecular and ionic form (full and truncated) the equation of the reaction between hydrochloric acid and sodium hydroxide taking place in an aqueous solution;

• to explain what the neutralization reaction is about;

• to indicate substances that undergo neutralization.

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;

• sets for building particle models.

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.

3. Health and safety – before starting the experiments, students familiarise themselves with the safety data sheets of the substances that will be used during the lesson. The teacher points out the need to be careful when working with them.

Realization

1. The teacher introduces pupils to the topic of the lesson and asks to conduct (or watch a film with a recorded experiment) the problem‑verification experiment „Experiment: sodium hydroxide + hydrochloric acid” according to the instructions described in the abstract and the suggestion included in the methodical commentary. First, students formulate a research question and hypotheses, write them in the form in an abstract. Then they perform the experiment in accordance with the instructions and under the teacher's control, carefully observing the changes taking place. After completing the research activities, group leaders present the effects of their work. Students with the help of a teacher formulate the conclusions that result from the experiment, write them, eg. „As a result of adding acid to the base (or base to acid) neutralization takes place - the reaction of the alkaline solution (or acidic solution) changes to neutral.” . The teacher, writing down the course of this reaction in the molecular form on the board, explains its mechanism. Then he asks students (working in the same groups) to build on the ball models the course of the reaction equation according to the scheme written on the board. He checks the correctness of this task.

2. Later in the class, the teacher asks the students to write on the board the equation of electrolytic dissociation of hydrochloric acid and sodium hydroxide in order to remind the breakdown of these chemical compounds into ions under the influence of water. Then he writes the equation of the neutralization reaction in the ionic form, going to the shortened ionic form. He explains why this reaction is called a neutralization reaction.

3. To consolidate the knowledge, the teacher can once again use the resources from the abstract presenting the equations describing the course of reactions and display them successively on the interactive whiteboard. Students write them to notebooks. In order to fix messages, they work with an interactive illustration of the full ionic equation.

4. On the basis of the equation of the reaction of hydrochloric acid with sodium hydroxide, the students with the help of a teacher define the reaction of neutralization and write it in a notebook.

5. The teacher asks students (work in pairs) to do interactive exercises in abstract.

Summary

1. 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. In this way, students consolidate information learned during the lesson and practice listening comprehension.

2. 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. Carry out exercise number nr 7.

Methodical Comment

Suggestion for instructions in abstract - experiment 1. I suggest for each group to give a different indicator: phenolphthalein, methyl orange, the red cabbage decoction, berry juice, decoction of red geranium petals to observe that in each case the characteristic color reaction appears neutral.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

The neutralization reaction part 1

Sodium hydroxide reacts not only with hydrochloric acid, but also with other acids, e.g. sulfuric acid, nitric acid or phosphoric acid. All water‑soluble hydroxides behave in a similar manner.

The reaction between sodium hydroxide and hydrochloric acid can be represented by the equation:

HCl + NaOH → NaCl + HIndeks dolny 2₂O
hydrochloric acid + sodium hydroxide → sodium chloride + water

We know that water soluble hydroxides and acids in the aqueous solution undergo a dissociation process:

HCl + HIndeks dolny 2₂O → HIndeks dolny 3₃OIndeks górny +⁺ + ClIndeks górny -^-
(simplified: $\text{HCl }\stackrel{{\text{H}}_{\text{2}}\text{O}}{\to }{{\text{H}}^{\text{+}}\text{ + Cl}}^{-}$)

hydrochloric acid

$\mathrm{NaOH}\stackrel{{\text{H}}_{\text{2}}\text{O}}{\to }{\mathrm{Na}}^{+}+{\mathrm{OH}}^{-}$

sodium hydroxide

Therefore, ions take part in the reaction between these substances. So write down the equation with their use:

HIndeks dolny 3₃OIndeks górny +⁺ + ClIndeks górny -^- + NaIndeks górny +⁺ + OHIndeks górny -^- → ClIndeks górny -^- + NaIndeks górny +⁺ + 2HIndeks dolny 2₂O

Such a record of the course of the reaction is called complete ionic equation.

Note that during the reaction of sodium hydroxide with hydrochloric acid only two ions react: hydronium cation and hydroxide anion, which together form a water molecule. Let us omit the non‑reacting ions in the reaction equation:

and write the equation that describes the proper processes occurring during a chemical reaction:

HIndeks dolny 3₃OIndeks górny +⁺ + OHIndeks górny -^- → 2HIndeks dolny 2₂O

This way of presenting the course of the chemical reaction – using only the ions involved in the reaction – is called net ionic equation.

As we remember, hydroxide anions are responsible for alkaline reaction, while hydrogen cations - for acid reaction. The pH of the solution formed after the reaction of sodium hydroxide with hydrochloric acid was neutral. That is why the reaction between the acid and the hydroxide was called the neutralization reaction. Sometimes it is referred to as a neutralization reaction. Its essence is based on combination of hydrogen cations with hydroxide anions and the formation of water molecules.

• The reaction of sodium hydroxide with hydrochloric acid generates sodium chloride.

• The transformation involving the reaction of hydroxide anions with hydrogen cations, resulting in neutral water molecules, is called the neutralization reaction.

• In aqueous solution, the hydroxides react with acids.

acid, base, neutralization reaction, full ionic record, shortened ionic record