Title: Mixtures

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.

Lesson plan elaborated by: Zyta Sendecka

Target Group

Pupils of the 7th grade of primary school.

Core Curriculum

7th grade of primary school– chemistry

I. Substances and their properties. Student:

5) describes the characteristics of homogeneous and heterogeneous mixtures;

6) mixes and selects the method of separating the mixture components (eg, filtration, distillation, separation of liquid in the separator); indicates these differences between the physical properties of the mixture components that enable it to be separated.

The general aim of education

Students give examples of mixtures and suggest ways to separate their components.

Criteria for success

• give four examples of mixtures;

• discuss the differences between a homogeneous and heterogeneous mixture and show examples of such mixtures in your environment;

• suggest ways to separate the mixture components.

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, laboratory method, direct observation.

Frontal work, individual work and work in pairs.

Teaching aids

• abstract;

• interactive or traditional board;

• tablets/computers;

• items needed by the teacher to demonstrate the difference between homogeneous and heterogeneous mixtures: fruits for a salad (e.g bananas, mandarins and apples) and juice in a carton of the same fruits; cutting board, knife, glass salad bowl, blender, glass;

• items needed to carry out the „Observation 1” by the students: water, a small bag of sand, a few small pebbles, a strainer, chalk, a teaspoon, a plate, four glasses, two funnels, a filter paper;

• Student flip‑board.

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.

2. The teacher asks volunteers to discuss the rules of behavior in the laboratory.

Realization

1. The teacher presents two sets of the same fruits (eg bananas, mandarins and apples). Then he cuts one set into small pieces. He puts them in a salad bowl and mixes them. Fruit from the second set which are blended and moved into second bowl. The teacher asks students to write down the differences between the two sets in their notebooks. Volunteers read their observations.

2. The teacher pours the juice made from the same kind of fruit into a glass,. Students explain how juice differs from previous blended and cut fruit.

3. The teacher puts a piece of paper in front of a fruit salad salad bowl with the words „heterogeneous mixture”, and before a glass with juice - a card with the words „Homogenous mixture”. He instructs students to explain the following terms with their own words:

• mixture;

• heterogeneous mixture;

• homogeneous mixture.

Volunteers or students chosen by the teacher read their definitions. The best ones are written on the board.

4. Students independently perform an interactive exercise to check their ability to distinguish heterogeneous mixtures from homogeneous.

5. The teacher discusses methods of separating the components of mixtures:

• filtration;

• evaporation;

• sieving.

6. The students in pairs separate the mixtures according to the instructions in the abstract („Observation 1”). In their notebooks, they record the type of each mixture and the methods, in which they separated their components.

7. The teacher introduces the film. He instructs students to make notes while watching, which type of mixture has been separated and the name of the method used.

8. The teacher asks volunteers to present their observations.

Summary

1. The teacher asks students to answer the question: „What does the air have in common with mineral water?”.

2. The students independently perform an interactive exercise strengthening the knowledge about the methods of separating the mixtures.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Mixtures

In nature, very rarely can single substances be found. More often we are dealing with mixtures. A mixture is formed when we mix at least two different substances together.

Mixtures can be formed of solid substances, liquids or gases. Particles in the mixture do not change their properties. However, the mixture formed by them may differ in properties from their components.If, for example, you mix table salt and water, you will get a mixture that has a lower melting point than pure water, but the properties of the ingredients of this mixture remain the same.

Sometimes, when we mix two substances, eg water and sand, we can distinguish the components of the mixture.We then we have a heterogeneous mixture. We see that the sand slowly sinks to the bottom. The situation is different when mixing table salt with water. The salt dissolves in water and we get a clear liquid. If we are unable to distinguish the components of a mixture, it is a homogeneous mixture.

The components of many mixtures can be separated. The separation method is selected based on the properties of the components.

The mechanical method consists of separating the ingredients by hand or with the help of tools. Mechanical separation can be used on a heterogeneous mixtures of solids. The process consists of removing larger pieces of a substance with tweezers or sieving the mixture. If one of the components of the mixture is liquid, then we can use filtration. It consists of filtering a heterogeneous mixture through an appropriate filter. The filter keeps the solids and the liquid flows into the container under it.

It is more difficult to separate the components of a homogeneous mixture. One of the methods that can be used for a mixture of homogeneous solid and liquid, is evaporation. It consists of heating a mixture, the result of which is that the liquid, e.g. water, turns into steam, and a solid substance remains in the container (in this way the salt in salt water can be obtained).

It happens that after mixing, the substances take up less space than each of them separately. This is because particles of different substances have different sizes. If they are mixed, smaller particles fill the space between larger ones.

• Mixtures are formed by combining two or more substances.

• Mixtures are divided into: homogeneous and heterogeneous.

• The components of homogeneous mixtures can not be distinguished by the naked eye or magnifying glass, whereas in heterogeneous mixtures we can distinguish at least one component.

• Depending on the nature of the components forming the mixture, a variety of methods may be used for their separation, e.g. mechanical separation, filtration and evaporation.