Topic: Diffusion in liquids and in solids

Target group

Elementary school student (grades 7. and 8.)

Core curriculum:

Primary school. Chemistry.

I. Substances and their properties. Pupil:

4) explains the phenomena of diffusion, dissolution, change of state of aggregation;

General aim of education

The student explains the phenomenon of diffusion in liquids and solids.

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• explain what is the phenomenon of diffusion in liquids and solids;

• exchange examples of diffusion found in everyday life;

• explain what are the phenomena of diffusion, dissolution, mixing, changes in physical states.

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.

Realization

1. The teacher, referring to previous lessons, asks volunteers to define the following concepts: matter, mixture, advection and contraction. He also asks what properties matter has in various states and what diffusion in gases consists in.

2. The teacher announces a movie titled „Testing the dye behavior in a liquid”. He instructs his students to write a research question and a hypothesis in the form provided in the abstract. Then he plays the video and the students note their observations and conclusions. Selected people present the results of their work.

3. Students read the fragment titled „Diffusion in solids” and indicate differences between diffusion in gases, diffusion in liquids and diffusion in solids. They compare these phenomena with dissolution and mixing processes. The teacher complements students' statements, corrects possible mistakes.

4. Students, working in pairs, analyze the infographic presenting the features of diffusion and osmosis.

5. The teacher divides the students into groups. The task of each team is to provide as many examples of diffusion as they can find in everyday life. After the work, the group leaders present the effects of the activities.

6. Students carry out the interactive exercises checking the level of knowledge learned during the lesson. The teacher initiates a discussion during which the correct solutions for all the exercises performed by the students are discussed.

Summary

1. The teacher plays the recording of the abstract. Every now and then he stops it, asking the students to tell in their own words what they have just heard. This way, students consolidate information learned during the lesson and practice listening comprehension.

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. 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

Diffusion in liquids and in solids

Diffusion in solids is a process almost impossible to observe in everyday life. In order to investigate this phenomenon, an experience was carried out. Two thoroughly polished plates were placed on each other: one made of lead, the other one made of gold. They were pressed with a weight, and after five years of storing them at room temperature the following findings were made at the 1 mm thick interface between the two layers:

• particles of gold in the lead plate,

• particles of lead in the gold plate.

This experience confirms that the matters in contact with each other may interpenetrate. This proves that matter has a granular structure.

The Brazil nut paradox

During carriage by sea from South America to Europe, crates filled with various species of nuts were exposed to constant shocks. When the crates were opened, the largest and heaviest Brazil nuts were found on top.
Explanation:
A small difference in the size of two types of nuts causes the sinking of one type and the emerging of the other type to the surface – this is the „Brazil nut effect”

Diffusion leads to the formation of mixtures by changing the position of particles - some particles penetrate between the other ones. The mobility of particles, i.e. the ability to move, depends on the state of matter and temperature. Diffusion occurs in all states of matter – it is the fastest in gases, and the slowest – in solid substances. Diffusion in liquids may last from several hours to several days.

A special type of diffusion is osmosis, which takes place in aqueous solutions, penetrating the semi‑permeable membrane that separates two solutions with different concentration.

Osmosis proceeds spontaneously, from a solution with a lower concentration of dissolved substance to a solution with a higher concentration, i.e. it leads to the equalization of the concentrations of both solutions.

• Matter is made up of particles that are constantly in motion. Matter has a granular structure.

• The most important phenomena confirming the discontinuity of matter are: diffusion, dissolution of solids in liquids, mixing of liquids, changes of state of matter.

• Diffusion in gases and liquids occurs faster than in solids.