Title: Thermal expansion of liquids

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

Class VII – physics

IV. Thermal phenomena. Pupil:

5) analyzes qualitatively the relationship between temperature and average kinetic energy (chaotic motion) of molecules.

The general aim of education

Students demonstrate thermal expansion in liquids.

Criteria for success

• explain what the thermal expansion of liquid is;

• carry out an experiment showing the thermal expansion of a liquid;

• discuss the unique thermal expansion of water.

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, workshop method, direct observation, indirect observation.

Individual work, work in pairs and group work.

Teaching aids

• abstract;

• interactive or traditional board;

• tablets/computers;

• things needed to carry out the experiment: tacks, pencils, plastic drinking straws, plasticine, bowl, heat‑resistant dish, blue dye, red dye, cold and hot water, plastic bottle with a cap of 1l or 1.5l (one set for a pair);

• alcohol thermometer;

• Galileo thermometer;

• mercury thermometer;

• mini flip charts.

Lesson phases

Introduction

1. The teacher asks a student to explain what the thermal expansion of a substance is, based on gasses for example.

2. 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 instructs students to discuss the principles of safe experimenting.

2. The teacher introduces a film showing an experiment illustrating the thermal expansion of liquid. He instructs the pupils to read the research question and hypothesis together. Students write them in the form provided in the abstract. The teacher displays the film.

3. Students, working in pairs, conduct the experiment in accordance with the film. Each pair records their observations and conclusions.

4. The teacher asks the students to read out their observations, and then identifies the most accurate observations.

5. The teacher asks students to look in the abstract for practical examples of the use of thermal expansion of a liquid. The teacher demonstrates different types of liquid thermometers:

• alcohol thermometer;

• Galileo thermometer;

• mercury thermometer.

Presenting the mercury thermometer, he points out that mercury is a metal.

6. The teacher asks students to read a section of the abstract on the thermal expansion of water and respond in writing to the question: „Why is water not used to indicate temperature in thermometers?” Volunteers read the answers, and the other students use their mini flip charts to assess them (green card means correct answer, red card – incorrect).

Summary

1. Students independently perform an interactive exercise.

2. The teacher asks students to finish the sentence: „After today's lesson I will remember ...”.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Thermal expansion of liquids

Liquids can also undergo thermal expansion, although to a slightly lesser extent than gases. To see this in action, just look at the liquid in a thermometer. This is perhaps the most famous example of a practical use of thermal expansion.

How are fish able to survive winter when the water freezes? It is possible due to the unique thermal expansion of water. When cooled, water reduces its volume. However, after lowering the temperature to below 4°C, it again increases in volume. Therefore, when it has a temperature of 0°C ice forms on the surface, but in the depths the water is still liquid and the fish can swim.

• Thermal expansion (temperature) is a change in the volume of substances due to a change in their temperature.

• Thermal expansion of substances is related to the increased rate of motion of particles as the temperature increases.

• Thermal expansion mostly effects gases, but can also occurs in liquids and solids.

• Thermal expansion must be taken into account when designing buildings and machinery.