Topicmc7121ba5a90d2baa_1528449000663_0Topic

Electrical and thermal conductionthermal conductionthermal conduction in solids

Levelmc7121ba5a90d2baa_1528449084556_0Level

Second

Core curriculummc7121ba5a90d2baa_1528449076687_0Core curriculum

I. The use of physical concepts and quantities to describe phenomena and to indicate their examples in the surrounding reality. The student:

3) distinguishes the concepts: observation, measurement, experiment; conducts selected observations, measurements and experiments using their descriptions;

4) describes the course of the experiment or the demonstration; distinguishes the key steps and procedures and indicates the role of the instruments used.

Timingmc7121ba5a90d2baa_1528449068082_0Timing

45 minutes

General learning objectivesmc7121ba5a90d2baa_1528449523725_0General learning objectives

Explaining the electrical and thermal properties of solids.

Key competencesmc7121ba5a90d2baa_1528449552113_0Key competences

1. Recognition of electrical conductors and insulators.

2. Recognition of thermal conductors and insulators.

3. Determining the differences in the internal structure of thermal and electrical conductors and insulators.

Operational (detailed) goalsmc7121ba5a90d2baa_1528450430307_0Operational (detailed) goals

The student:

- recognizes electrical and thermal conductors and insulators,

- specifies the differences in the construction of electrical and thermal conductors and insulators.

Methodsmc7121ba5a90d2baa_1528449534267_0Methods

1. Learning by observation.

2. Teaching by experimenting.

Forms of workmc7121ba5a90d2baa_1528449514617_0Forms of work

1. Individual work.

2. Work with the whole class.

Lesson stages

Introductionmc7121ba5a90d2baa_1528450127855_0Introduction

Task 1

Answer the questions:

a) How do we divide solids due to their physical properties?
b) How are the molecules arranged in crystalline solids and amorphous solids?

Answer:

a) Among solids, we distinguish between bodies with a crystalline structurecrystalline structurecrystalline structure and an amorphous structure. The crystalline solids may be in the form of monocrystals and polycrystals.
b) Molecules in crystalline solids are arranged in an orderly manner. Molecules in amorphous solids are arranged in a disordered manner.

Task 2

View the photo gallery and answer the questions:

a) Which of the bodies shown in the pictures according to you can conduct electric current?
b) Which of the bodies shown in the pictures according to you can conduct heat well?

[Illustration 1]

Answer:

a) Bodies conducting electric current are a gold bar shown in picture 1 and copper shown in picture 2.
b) Bodies conducting heat are a gold bar shown in picture 1 and copper shown in picture 2.

Conclusion:

Bodies conducting electric current also conduct heat well.

Proceduremc7121ba5a90d2baa_1528446435040_0Procedure

Experiment 1

Electrical properties of solids.

Research problem:

Demonstration of the ability of solids to conduct electric current.

Research hypothesis:

Solids can be electrically conductive.

What will be needed?

a) 1,5 V or 4.5 V battery;
b) three wires with terminals;
c) 1.5 V or 4.5 V light bulb in a holder;
d) items subjected to electrical conduction tests (plastic spoon, metal knife, piece of paper, coin, etc.).

Instruction:

a) Ask for help from an adult at home to connect all elements of the electric circuit as shown in the figure below:

[Illustration 2]

b) In place of the knife, put the remaining items in sequence. Make a note of the measurement result in the table.

[Table 1]

Observation:

If there is metal between the wire terminals, the bulb is on. If there is plastic between the wire terminals, the bulb does not light up.

Conclusion:

a) The metals conduct electricity and the plastics do not conduct electricity.
b) Due to the electrical properties of solids, we can divide into two groups: conductors and insulators of electric current.

Task 3

View the Geogebra applet „Thermal conductivitythermal conductivityThermal conductivity of different materials”.

[Geogebra applet]

Task 4

Using the above applet, enter the missing values of thermal conductivity into the given table.

[Table 2]

Task 5

Assuming that the thermal insulatorinsulatorinsulator is a material with a thermal conductivity $\lambda <10\frac{W}{m\cdot K}$
(Note: the Greek letter $\lambda$ - we read as „lambda”) divide the materials from the table into thermal conductors and thermal insulators.

Answer:

Thermal conductors are: aluminium, copper, tin.
Thermal insulators are: plexiglas, ordinary glass, wood.mc7121ba5a90d2baa_1527752256679_0Thermal conductors are: aluminium, copper, tin.
Thermal insulators are: plexiglas, ordinary glass, wood.

Conclusion:

a) Good thermal conductors are good electrical conductors.
b) Thermal insulators are also electrical insulators.

Task 6

Determine the molecular structure of a substance that is a good electrical conductor. Explain your choice.

Answer:

Substances that are good electrical conductors have an internal ordered structure, they are crystalline substances (crystals or polycrystals).

Good contact between molecules is needed for good conduction. The crystalline substances fulfil this condition due to the high density of particles.

Lesson summarymc7121ba5a90d2baa_1528450119332_0Lesson summary

- Due to the electrical properties, solids can be divided into two groups: electrical conductors and electrical insulators.
- Solids can be good or bad thermal conductors.
- Usually, good electrical conductors are good thermal conductors (e.g. metals).
- The electrical conductors have a crystalline structure.mc7121ba5a90d2baa_1527752263647_0- Due to the electrical properties, solids can be divided into two groups: electrical conductors and electrical insulators.
- Solids can be good or bad thermal conductors.
- Usually, good electrical conductors are good thermal conductors (e.g. metals).
- The electrical conductors have a crystalline structure.

Selected words and expressions used in the lesson plan

amorphous solidamorphous solidamorphous solid

conductorconductorconductor

crystalline solidcrystalline solidcrystalline solid

crystalline structurecrystalline structurecrystalline structure

electric current conductorelectric current conductorelectric current conductor

insulatorinsulatorinsulator

polycrystalpolycrystalpolycrystal

thermal conductionthermal conductionthermal conduction

thermal conductivitythermal conductivitythermal conductivity

thermal conductorthermal conductorthermal conductor