Topic: Higher carboxylic acids

Target group

Elementary school student (grades 7. and 8.)

Core curriculum

Primary school. Chemistry.

X. Chemical substances of biological importance. Pupil:

1) gives names and draws semi‑structural (group) formulas of long‑chain monocarboxylic (fatty acids) saturated (palmitic, stearic) and unsaturated (oleic) acids;

2) describes selected physical and chemical properties of long‑chain monocarboxylic acids; designs and conducts experiments that will distinguish oleic acid from palmitic or stearic acid.

General aim of education

The student acquires knowledge and skills about the topics discussed in the classes

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• what the name of the higher carboxylic acids means;

• to name higher saturated carboxylic acids (palmitic and stearic acid) and unsaturated (oleic acid);

• to write down the formulas of higher carboxylic acids (palmitic, stearic and oleic acid);

• what are the properties of higher carboxylic acids;

• what application higher carboxylic acids have;

• to design experience to distinguish oleic acid from palmitic or stearic acid.

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 uses the reverse lesson method. Students answer the questions asked, e.g. what the name „higher carboxylic acids” means; why their synonyms are fatty acids; what is the classification of acids due to the state of aggregation; what is the classification of acids due to the construction of the carbon chain; what are the summary formula of palmitic, stearic and oleic acids (in this case, the teacher can show or instruct students to work with the active scheme from the abstract); where there are higher carboxylic acids; what use have higher carboxylic acids.

2. The instructor divides the students into groups. Distributes work sheets, equipment, glass and reagents according to instructions for the experience regarding the properties of higher carboxylic acids from the abstract. Students perform experiments, write notes in the work sheets, discuss lessons with the teacher.

3. The teacher performs - in the form of a teaching show - Experiment 2 based on instructions from the abstract. Pupils formulate observations and conclusions, and then note them in the work sheets. The teacher writes the equation on the board and at the same time explains the reaction mechanism. For the consolidation of the message, it displays an equation on the interactive whiteboard and summarizes the illustration of different types of soaps.

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

5. The teacher instructs the students to do the remaining interactive exercises in the abstract.

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. Listen to the abstract recording at home. Pay attention to pronunciation, accent and intonation. Learn to pronounce the words learned during the lesson.

2. Make at home a note from the lesson using the sketchnoting method.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Higher carboxylic acids

Carboxylic acids, among others the acetic acid $\text{C}{\text{H}}_{\text{3}}\text{COOH}$ or butyric acid ${\text{C}}_{\text{3}}{\text{H}}_{\text{7}}\text{COOH}$, due to the small number of carbon atoms in the hydrocarbon chain, are classified as lower carboxylic acids. Higher carboxylic acids are compounds containing a long carbon chain (a dozen or so carbon atoms) as well as the group $\text{– COOH}$ which is characteristic of carboxylic acids.

Higher carboxylic acids are also called fatty acids. Fat molecules contain radicals of fatty acids.

Remember the concept of organic saturated and unsaturated compounds. Do you recall which hydrocarbons are classified as saturated, and which as unsaturated?

There are saturated and unsaturated fatty acids.

Saturated higher carboxylic acids include palmitic acid that has the following formula: ${{\text{C}}_{\text{15}}\text{H}}_{\text{31}}\text{COOH}$, as well as stearic acid ${\text{C}}_{\text{17}}{\text{H}}_{\text{35}}\text{COOH}$. In the molecules of these acids, there are single bonds between carbon atoms. Oleic acid ${\text{C}}_{\text{17}}{\text{H}}_{\text{33}}\text{COOH}$ contains a double bond between the 9th and 10th carbon atoms, which is why it belongs to unsaturated organic compounds.

Stearic and palmitic acids melt at low temperatures. Carboxylic acids undergo the combustion reaction. They burn with a yellow flame – like the one we observe while candles burn.

Exercise summary
In order to distinguish stearic or palmitic acid from oleic acid, use bromine water ${\text{Br}}_{\text{2(aq)}}$ or a solution of potassium permanganate ${\text{KMnO}}_{\text{4}}$. The molecules of unsaturated oleic acid contain a double bond and therefore discolor the bromine water and the solution of potassium permanganate. What is more, this reaction produces a white solid – saturated stearic acid. It transitions into a saturated acid, which we observe as a change in the state of the substance from liquid to solid. Higher carboxylic acids introduced into water with the addition of methyl orange do not change the color of the indicator because they do not dissolve in water and do not undergo the process of electrolytic dissociation.

Fatty acids play an important role in obtaining soaps.

The salts of higher carboxylic acids, e.g. palmitic, stearic and oleic, are soaps.

• Higher carboxylic acids are acids containing long carbon chains.

• Higher carboxylic acids are also referred to as fatty acids because fat molecules contain the radicals of these acids.

• Saturated fatty acids include palmitic and stearic acids.

• Oleic acid is an unsaturated fatty acid.

• Soaps are the salts of higher carboxylic acids.