Title: Substance transformations

Supplementary material for use in lessons in the group of natural sciences (nature, biology, chemistry, geography, physics), additional classes, science clubs. It can serve as a resource for expanding knowledge, preparing students for science competitions.

Author: Zyta Sendecka

Target Group

Pupils of the 7th grade of primary school.

Core Curriculum

7th grade of primary school - chemistry

III. Chemical reactions. Student:

1) describes and compares physical phenomenon and chemical reaction; gives examples of physical phenomena and chemical reactions taking place in the human environment; designs and conducts experiments illustrating the physical phenomenon and chemical reaction; based on observations, it classifies transformations to chemical reactions and physical phenomena.

The general aim of education

Students explain how chemical and physical changes differ, as well as the reversible and irreversible processes and give examples.

Criteria for success

• explain how chemical and physical changes differ;

• show examples of chemical and physical changes encountered in everyday life;

• on selected examples you will discuss reversible and irreversible processes.

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;

• Social and civic competences.

Methods/forms of work

Talk, work with the text, work with film, mind map, indirect observation.

Frontal work and individual work.

Teaching aids

• abstract;

• interactive or traditional board;

• tablets/computers;

• sheets of paper in A3 format;

• colored markers.

Lesson phases

Introduction

1. The teacher gives the subject and the purpose of the lesson in a language that the student understands as well as the criteria for success.

Realization

1. The teacher explains to students the rules of making notes in the form of a mind map.

2. The teacher asks pupils to read two sections of the abstract: „Physical changes” and „Chemical changes” and they create mind maps on A3 format sheets of paper based on each. The teacher monitors the accuracy of the task, gives advice, and draws attention to the principles of making mind maps.

3. The teacher introduces a movie entitled „Comparison of physical and chemical transformations of a piece of paper” and explains the ideas presented in it. He asks students to write down the research question and hypothesis in the form provided in the abstract. Then displays the movie.

4. Students on their mind maps note the different changes observed in the film. Green color notes physical changes, and the red color notes chemical changes. Volunteers read their notes, the teacher corrects any mistakes.

5. Students independently perform an interactive exercise, checking their ability to distinguish physical changes from chemical changes.

6. Students, using the illustration „Examples of reversible and irreversible processes”, explain in their own words the notion of a reversible and an irreversible process. Then they compare their definitions with the explanations in the „Glossary” and, if necessary, make corrections.

7. Students independently perform an interactive exercise strengthening their knowledge about the reversible and irreversible processes.

Summary

1. The teacher asks students to finish the sentence: „In today's lesson, I have learned ...”.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Substance transformations

When we prepare ice for drinks, we pour water into special containers, which we then put in the freezer. Due to the low temperature, the water freezes (solidifies), taking the shape of the container. However, water in the ice cube remains water, it only occurs as different states of matter.We can say that we have observed a physical change.

Physical changes include processes consisting in changing the shape of the substance (eg crushing), changes in the physical states (eg solidification, melting, condensation, evaporation) and formation and separation of mixtures. Physical change can also be the change in the speed of movement.

In addition to physical changes, there are also chemical changes around us. As a result, new substances are created with different properties than the original ingredients. Chemical transformation occurs, for example, when lighting a match, rusting metal surfaces, spoiling food and the darkening of peeled apples. It can also be seen by looking at a burning candle, which becomes smaller every minute.Why is this happening? Wax or stearin, from which candles are made, during combustion, change into other substances which are then dispersed into the air.

Sometimes it is difficult to say whether there has been a physical or chemical change. It is helpful to carefully observe the whole process and examine the properties of the resulting substances. Let's check, for example, how two substances often used in cooking are dissolved in water: sugar and baking soda.

Many interesting examples of chemical reactions in our environment can be observed during cooking. Cooking is accompanied by complicated chemical processes.

Ice melts when its surroundings have a temperature higher than 0°C. As soon as the temperature drops, the water will freeze again. This is often observed during in the winter, when the cold days are intertwined with days of thawing. We say that the process of changing the state of water from solid to liquid is a reversible process. All changes of it’s state are reversible processes.

In our kitchen we can see an example of an irreversible process. When we cook or fry an egg, it changes its appearance and hardens.In no way can the egg be restored to its original form and properties. Irreversible transformations are, for example, cooking, frying, baking, and burning various substances. Corrosion is also irreversible, i.e. the destruction of metal objects under the influence of environmental conditions.

• In nature, there are physical changes, in which substances do not change their properties, and chemical changes, in which new substances are created.

• The processes occurring in nature may be irreversible, such as burning or cooking dishes, or reversible, such as evaporation and condensation.