ETV “Junior Secondary Science” Programme

The Particle Model of Matter

Teachers’ Notes

Target Audience

Secondary 1 - 3

Duration

20 minutes

Production Aim

This programme is a teaching resource produced especially for enriching the classroom teaching of the Syllabus for Science (Secondary 1 – 3) prepared by the Curriculum Development Council (1998).

The content of the programme serves to illustrate the following parts of the Syllabus:

“Unit 6 – Matter as Particle

Topic 6.1 - States of matter

Topic 6.2 - Illustrations for the support of the claims of the particle

theory

Topic 6.3 - Particle model for the three states of matter

Topic 6.4 - Gas pressure

Topic 6.5 - Density

Topic 6.6 - Thermal expansion and contraction"

Key Points

1.  An introduction to the three states of matter.

2.  An illustration of the evidence in support of the claims of the particle theory.

3.  An illustration of the particle model for the three states of matter.

4.  An explanation of the origin of gas pressure in terms of kinetic motion.

5.  An introduction to density.

6.  An explanation of the expansion and contraction of matter.

Content Outline

This programme is divisible into 6 segments as follows:

1.  The Three States of Matter

A variety of objects are shown to illustrate the following principles:

(a) Matter exists in three states, namely solid, liquid and gas.

(b)  A solid usually has a fixed shape and volume.

(c)  The volume of a liquid is fixed but its shape may change to fit the shape of the container.

(d)  The shape and volume of a gas is easily changed under external forces.

2.  Matter is Made up of Particles

A smoke cell experiment is demonstrated to show the presence of particles in air. The audience is told that the tiny pinpoints of light observed in the smoke cell are the reflection of light from the smoke particles, and that the irregular movement of tiny pinpoints of light is the result of the smoke particles being collided by the air particles moving around them.

3. Particles and the Three States of Matter

An animated explanation of the arrangement and movement of particles in matter at different states is shown as the basis of the particle model of the Three States of Matter. Sugar dissolving in water and copper sulphate crystal in agar are used to demonstrate the phenomenon of diffusion.

The Brownian movement is demonstrated and an explanation is given. It is then used to explain the phenomenon observed in the smoke cell. When a British botanist Robert Brown in the 19th century examined pollen grains under the microscope, he noted that the pollen grains moved unceasingly and irregularly. This phenomenon is called Brownian movement.

4. An Pressure

Everyday examples, e.g. sipping liquid with a straw from a paper-packed drink, are used to show the existence of air pressure.

The kinetic theory model is used to explain the origin of air pressure. Air pressure is generated as a result of the collision of air particles on the surface of the container.

The use of a Bourdon gauge is demonstrated and its working principle is explained.

5. Density

The density of a substance is defined as mass per unit volume of the substance. Different matters have different densities. Density can be construed in terms of the particle model of matter. Everyday examples, such as a balloon floating in air, a piece of wood floating on water, and an iron cube floating on mercury are shown for illustration.

6. Thermal Expansion and Contraction

The phenomenon of thermal expansion and contraction is explained in terms of the particle model. Particles gain energy when heated or when temperature rises. The increase in energy increases the distances among particles, hence the object expands. The Tsing Ma Bridge is used as an example to illustrate the need to consider thermal expansion in its construction. The length of the bridge will increase or decrease as a result of expansion or contraction. This was taken into account in the design of the bridge.

Suggestions for Utilization

The teacher is advised to show the programme in one lesson. The teacher may spend 5 to 10 minutes at the beginning of each lesson to lead students to discuss with reference to the Preparation before viewing the programme part of the Suggested Activities. The teacher may then show the programme. After the show, the teacher may spend another 10 to 15 minutes to discuss with students with a view to consolidating the concepts and methods illustrated in the programme. The teacher is advised to refer to the Activities after viewing the programme part of Suggested Activities.

Suggested Activities

(The following activities are suggested for teacher’s reference only. The teacher may wish to use the activities according to students’ abilities, the learning environment of the class, and the teaching time available.)

Preparation before viewing the programme

(1)  The teacher may discuss with students on evidences of the existence of particles in matter.

(2)  The teacher may quote examples such as the rising of hot balloon to arouse students ' interest towards the learning of density.

(3)  The teacher may discuss with students on the purpose of dividing the surface of roads into blocks with gap in between.

Activities after viewing the programme

(1)  The teacher may guide students to recall the main points of the programme and present the particle theory of matter in their own words.

(2)  The teacher may demonstrate an experiment to show that when air is removed from a metal can by a vacuum pump, the can would be compressed by the atmospheric pressure.

(3)  The teacher may ask students to give everyday examples of the application of air pressure.

(4)  The teacher may ask students to give everyday examples of the application of thermal expansion and contraction.

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