Topic: Types of cleaning agents

Target group

High school / technical school student

Core curriculum

New core curriculum:

High school and technical high school. Chemistry – basic level:

XXI. Chemistry around us. Pupil:

9) indicates the chemical nature of the components of glass cleaning agents, pipe clearing, cleaning metals and jewelry in terms of the uses of these products; explains the removal process impurities with these agents and describes the principles of their safe use.

High school and technical high school. Chemistry – extended level:

XXI. Chemistry around us. Pupil:

9) indicates the chemical nature of the components of glass cleaning agents, pipe clearing, cleaning metals and jewelry in terms of the uses of these products; explains the removal process impurities with these agents and describes the principles of their safe use.

Old core curriculum:

High school and technical high school. Chemistry – basic level:

XXI. Chemistry around us. Pupil:

8) points to the chemical nature of the components of glass cleaners, pipe cutting, cleaning metals and jewelery in terms of the use of these products; explains what the process of removing contaminants by means of these means and describes the principles of their safe use.

General aim of education

The student explains what the process of removing impurities with cleaning agents is.

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn;

• mathematical competence and basic competences in science and technology.

Criteria for success
The student will learn:

• what detergents are and what their properties and application are;

• what the main ingredients of cleaning agents are, what properties they have and how to use them safely and effectively in everyday life.

Methods/techniques

• expository

  • talk.

• activating

  • discussion.

• exposing

  • film;

  • exposition.

• programmed

  • with computer;

  • with e‑textbook.

• practical

  • exercices concerned.

Forms of work

• individual activity;

• 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 introduces students to the issue of cleaning products as substances intended to remove dirt from various types of surfaces. These include many chemical compounds, e.g. phosphates (V), chlorine compounds, silica, sodium hydroxide. The most important components of cleaning agents are anionic and cationic surfactants.

2. The lecturer announces a movie entitled „Effect of detergents on water”. He instructs his pupils to write a research question and a hypothesis in the form provided in the abstract. Then it displays the video and the students record their observations and conclusions. The teacher indicates the person who shares his insights and explains the reasonableness of the conclusions he has made.

3. The teacher conducts - in the form of a show - an experiment, according to the instructions in the abstract („Effect of enzymatic and non‑enzymatic powder on proteins”). Before joining the action, he asks the students to formulate a research question and a hypothesis and write them in the form in an abstract. After the experiment, a summary of observations and conclusions is made, which should also be included in the form. If for any reason the show can not be performed, the teacher displays the film in the abstract.

4. Students will get acquainted with the content of the abstract. They discuss different types of cleaners and explain in their own words the meaning of the terms detergents and zeolites.

5. Students perform the interactive exercises. The teacher makes sure that the tasks has been correctly completed and gives feedback.

Summary

1. Teacher asks: If there was going to be a test on the material we have covered today, what questions do you think would you have to answer? If the students do not manage to name all the most important questions, the teacher may complement their suggestions.

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.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Types of cleaning agents

Detergents are chemical compounds that currently are used for washing more often than soaps. These compounds have a structure similar to soaps, are made of a polar and a non‑polar part and fulfill a soap‑like role in the cleaning and washing processes – they produce foam, remove dirt. They are further characterized by certain properties that make their use more beneficial – they also retain excellent cleaning and foaming properties regardless of the degree of water hardness.
The term detergent originates from the Latin word detergens – cleaning.

Like soaps, detergents reduce the surface tension of water, i.e. they are surface‑active compounds. However, detergents do not form precipitates with magnesium and calcium ions, because their salts are soluble. Detergents (like soaps) have long non‑polar hydrocarbon chains (tails) linked to polar groups (heads).

Aqueous solutions of detergents are less susceptible to pH changes – these are the properties of anionic detergents with negatively charged sulfate functional groups.
Cationic detergents are often bactericidal and their ability to change the surface pH is used in the production of softeners and hair conditioners.
In amphoteric detergents, positive and negative charges may be present in the surface‑active (head) part.
In nonionic detergents, the hydrophilic part has no charge, but it demonstrates polar properties.

Detergents are components of commonly used body cleaning (shampoos, bath liquids), laundry (powders, gels) and cleansing (lotions, cleansing milks) preparations, therefore the production of detergents is one of the basic branches of the chemical industry. The detergents available on the market are mixtures. Most of them contain various additives, such as fillers (to increase the volume), anti‑foaming agents and bleaching agents.

The main ingredient of washing powders are detergents that remove most of the dirt. In addition to detergents, washing powders also contain water softeners, bleaches and enzymes.
Water softeners are to prevent precipitation of sparingly soluble calcium and magnesium salts. In the past, a compound called sodium hexametaphosphate was used for this purpose, but it was found that its effect on the environment was harmful. Currently, zeolites are used as water softening substances allowing to reduce the amount of phosphates added to the washing powders.

Zeolites are aluminosilicates of metals from the 1st and 2nd groups distinguished by an unusual porous structure, and thus unique properties. An example of the effect of zeolites is the removal of calcium ions from hard water. Given their extraordinary ability of ion exchange, zeolites replace sodium ions with calcium ions (they capture and retain them in their pores). In this way, they remove them from the water and the water becomes soft.

Modern washing powders contain enzymes (biocatalysts) in their composition. Due to enzymes, these washing powders have the ability to quickly break down the organic compounds forming stains on clothes and should remove stains such as juice, egg, blood, grass (containing proteins in its composition).
The enzyme washing powders contain primarily enzymes that break down proteins (proteases), sugars (e.g. amylase, cellulase) and fats (lipases).

The glass is characterized by low resistance to scratches, therefore the products for cleaning glass (windows, mirrors) usually have the form of a water solution of surfactants and do not contain abrasives. On the other hand, they contain volatile (easily evaporating) compounds, e.g. ammonia ${\text{NH}}_{\text{3}}$, acetic (ethanoic) acid ${\text{CH}}_{\text{3}}\text{COOH}$ or ethanol ${\text{C}}_{\text{2}}{\text{H}}_{\text{5}}\text{OH}$, which are intended to prevent streaks.

Before using any cleaning agents, read the information on the composition and the rules of safe use provided on the label. Keep cleaning products away from children. When using those that contain toxic, irritating or corrosive substances, avoid splashes, eye rubbing, skin contact.

• Synthetic detergents (like soaps) are surface‑active substances that allow for effective removal of dirt in cleaning and washing processes.

• Currently, many types of preparations are used for washing and cleaning. Their carefully selected composition has to guarantee efficiency.

• Some of the cleaning agents have corrosive or irritating properties. Therefore, read the instructions carefully and use the recommended precautions during use, e.g.: use protective gloves.

• Even a small concentration of detergents and other cleaning ingredients in water reservoirs impedes the process of water purification, and especially sedimentation of suspensions, which causes the degradation of the natural environment, therefore the aim is to make the detergents used biodegradable.