Topic: Sugars - application of polysaccharides

Target group

Elementary school student (grades 7. and 8.)

Core curriculum:

Elementary school. Chemistry.

X. Chemical substances of biological importance. Pupil:

10) gives examples of the presence of starch and cellulose in nature; gives summary models of these compounds; lists differences in their physical properties; describes the meaning and uses of these sugars; designs and conducts experiments to detect the presence of starch with iodine solution in various food products.

General aim of education

The student discusses the use of starch and cellulose.

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• describe the presence of starch and cellulose;

• give summary formulas of polysaccharides;

• what properties and applications are starch and cellulose.

Methods/techniques

• expository

  • talk.

• activating

  • discussion;

  • mind map.

• 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;

• interactive whiteboard, tablets/computers;

• sheets of gray paper;

• colored markers.

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 initiates the discussion and asks the students questions: Which plants contain the most starch? Which contain the most cellulose? Which of these two chemical compounds can be obtained on an industrial scale? .

2. The teacher divides the students into groups, distributes sheets of paper and markers. Students, using various sources of knowledge (e.g. e‑textbook, textbook, internet), develop the issue of the application of starch and cellulose. They present the issue using a mind map, poster or infographics. They can also use the sketchbook in an abstract.

3. Group leaders present the results of team work. The teacher evaluates its effects and, to summarize the issue, presents on the multimedia board the illustrations: „Application of starch” and „Application of cellulose”.

4. Students arrange crosswords based on issues learned during the lesson. They exchange the crosswords in pairs and solve them.

5. Students carry out exercise number 1 and exercise number 2. The teacher discusses the correct solutions with them.

Summary

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

2. 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 exercise number 3..

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Sugars - application of polysaccharides

Polysaccharides are complex chemical compounds composed of many residues of simple sugars. The most well‑known polysaccharides are starch and cellulose. Recall the most important messages about these.

Starch is used primarily in the food industry. Due to the texture of the mixture of starch and water, it serves for the production of jelly and pudding. It is also used for the production of adhesives, medicines and cosmetics.

Cellulose also has a wide range of applications, mainly in the paper industry. It is also used for the production of varnishes, adhesives, explosives and artificial silk. In addition, it is used in the pharmaceutical industry, for the production of medicines (e.g. suppositories).

• The most widespread polysaccharides are starch and cellulose with a molecular formula of $\text{(}{\text{C}}_{\text{6}}{\text{H}}_{\text{10}}{\text{O}}_{\text{5}}{\text{)}}_{\text{n}}$.

• Starch has a granular structure and occurs mainly in potatoes, cereal grains, rice and corn.

• Cellulose is the basic building material of plants. It has a fibrous structure; occurs, among others in wood and cotton.

• Starch and cellulose are white solids. Starch weakly dissolves in cold water, while in hot water it forms starchy pap. Cellulose does not dissolve in water; it is flammable.

• Iodine testing is used to detect starch in food products – reaction of starch with iodine, resulting in a dark‑blue coloration.

• Starch undergoes hydrolysis in the human body: it breaks down into dextrins and then into glucose molecules. Man does not digest cellulose.