Topic: Sugars – glucose and fructose

Target group

Elementary school student (grades 7. and 8.)

Core curriculum:

Primary school. Chemistry.

X. Biologically relevant chemicals. Student:

7) names the elements whose atoms are part of molecules of sugars (carbohydrates); classifies sugars into simple (glucose, fructose) and complex (sucrose, starch, cellulose);

8) gives the molecular formula of glucose and fructose; tests and describes the selected physical properties of glucose and fructose; names and describes their uses.

General aim of education

The student classifies sugars and characterizes glucose and fructose in terms of structure, properties and application

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• what elements are made of sugars;

• to divide sugars into simple and complex ones;

• to explain what is the difference in the construction of glucose and fructose and write down their formulas correctly;

• what are the properties and use of glucose and fructose;

• how to plan and carry out experiments to check the reduction properties of simple sugars.

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.

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 students to the issue of carbohydrates - he may ask about their role in the human body (it was discussed earlier in biology), examples of occurrence in nature, etc. Presents the breakdown of carbohydrates by displaying a diagram on a multimedia presentation. He asks students to get acquainted with the interactive map presenting the photosynthesis diagram.

2. The teacher displays the summary and structural formulas of glucose and fructose. He explains the difference in their structural structure and justifies why total patterns do not differ from each other. Referring to this fact, he asks the students the question: „What elements make sugar?”.

3. The lecturer refers students to the abstract and asks them to find out information on the properties of glucose, instruments and substances needed to carry out the experiment. He also asks students to read the instructions for this experience.

4. The teacher divides the students into exercise groups and then asks for an experiment - testing the physical properties of glucose. Students write notes and conclusions on the form in an abstract.

5. After this practical part, the teacher asks the students the question: „Why do sugars have neutral reaction even though they dissolve in water?”. If the students do not respond, he guides them or tells them that „because they do not undergo electrolytic dissociation”.

6. The instructor recommends students, currently working in pairs, find information (internet, e‑textbook, abstract) on the importance and use of glucose and fructose (some pairs take on topic of glucose, and some - fructose). The pairs present the search results.

7. The teacher divides the students into exercise groups and then asks for an experiment - testing the physical properties of fructose. Students write notes and conclusions on the form in an abstract.

8. The teacher asks students to do interactive exercises in the abstract, which summarize the information about the properties of glucose and fructose.

Summary

1. The student indicated by the teacher sums up the lesson, telling what he has learned and what skills he/she has been practicing.

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

Sugars – glucose and fructose

Fats and proteins are important elements of our daily diet. These biologically important substances also include sugars called saccharides. These compounds are composed of carbon, hydrogen and oxygen atoms.

Due to the structure of sugars, we divide them into simple and complex ones.

One of nature's most common simple sugars is glucose – one of the products of the photosynthesis process.

What is the structure of the glucose molecule?

The molecular formula for glucose is ${\text{C}}_{\text{6}}{\text{H}}_{\text{12}}{\text{O}}_{\text{6.}}$ This formula also describes other compounds. This is why, in organic chemistry, structural, semi‑structural or skeletal formulas are most often used.

The second most commonly known simple sugar is fructose. Its molecular formula is the same as the formula of glucose ${\text{C}}_{\text{6}}{\text{H}}_{\text{12}}{\text{O}}_{\text{6}}$, but differs from it in terms of structure.

Fructose is found, among others, in fruit and honey. It is the sweetest and the most soluble sugar in water. It is used as a sweetener for people with diabetes.

How can you distinguish glucose from fructose?

Look at the structural formula of both monosaccharides and perform the experiment:

• aqueous solution of glucose,

• aqueous solution of fructose,

• sodium hydrogen carbonate ${\mathrm{NaHCO}}_3$,

• bromine water,

• pipette,

• test tube rack,

• test tubes.

1. Add to the test tube with a solution of glucose, a solution of sodium bicarbonate and then a few drops of bromine water.

2. Add to the test tube with a solution of fructose, a solution of sodium bicarbonate and then a few drops of bromine water.

3. Observe the changes that occur.

Glucose and fructose have identical molecular formulas, but a different arrangement of atoms in the molecule. In a fructose molecule, oxygen is combined with a double bond with carbon occurring within the chain and not with the final carbon, as is the case in glucose.

The different arrangement of atoms in the glucose and fructose molecule causes both sugars to have different chemical properties. Fructose is, for example, much sweeter. To distinguish glucose from fructose, bromine water should be added in the presence of sodium hydrogen carbonate. Bromine water will decolorize in the glucose solution.

• Sugars, also called saccharides, are compounds composed of carbon, hydrogen and oxygen atoms.

• Sugars are divided into simple and complex ones.

• Simple sugars include, among others, glucose and fructose. These compounds have the same molecular formula – ${\text{C}}_{\text{6}}{\text{H}}_{\text{12}}{\text{O}}_{\text{6 }}$, but they differ in terms of structure.

• Glucose is a white crystalline substance which dissolves well in water. Its aqueous solution has a neutral reaction.

• Glucose is the product of the photosynthesis process.

• The reaction of glucose with copper(II) hydroxide, under the influence of temperature, results in the formation of brick‑red sediment. This is a indicative reaction for glucose.