BACKGROUND

From the experience of teaching lower secondary science, science teachers often face problems in the use of teaching aids or apparatus to implement activity-centred teaching strategies. One of the reasons for this is that the schools cannot afford to acquire the needed apparatus or the equipments were insufficient in number to provide individual practical work. Plastic materials were chosen as the main medium for our construction since they are by far the most abundant form of discarded materials and therefore easily available. With the world resources diminishing it is necessary to inculcate in our pupils the need to fully utilize our natural resources and recycle our synthetic products so as to further safeguard our environment.

OBJECTIVES

1. To realise our country’s aspiration to raise the quality of science education.

2. To emphasize and implement innovative teaching strategies to further enrich the science programmes in schools.

3. To use the teaching aids or apparatus to implement activity-centred teaching strategies. One of the reasons for this is that the schools cannot afford to acquire the needed apparatus or the equipments were insufficient in number to provide individual practical work.

4. To inculcate the attitude to fully utilize natural resource and to recycle synthetic materials so as to safeguard or conserve the environment. Plastic materials were chosen as the main medium for the construction since they are by far the most abundant form of discarded materials and therefore easily available.

BENEFITS FOR TEACHING-LEARNING PROCESS

1. The apparatus can be easily prepared or constructed by teacher and/or pupils.

2. It inculcates confidence in teachers of their ability to build the simple apparatus and not to rely entirely on purchase through school funds.

3. The improvised teaching aids made of locally available plastics are “user-friendly” and pedagogically effective by virtue of the use of familiar items.

4 It promotes creative and innovative thinking when one has to think about ways to reuse and recycle in the context of teaching-learning process.

APPARATUS/ MATERIAL

(1) Solar and Lunar Eclipses (Diagram 2-1D)
Discarded PVC tube, plastic lunch box, sand, ping pong ball, plastic door knob, rubber band

(2) Water Filter (Diagram 2-2D)
2 soft drink bottles (1.25 litre), cotton wool, big stone, charcoal, small stone, sand, fine sand, plastic tube

(3) Cartesian Diver and Water Fountain (Diagram 2-3D)
Plastic ball point pen cap, plasticine, plastic bottle, plastic cap, water, rubber cap

(4) Light Reflection (Diagram 2-4D)
Round ice cream plastic container, mirror, black paint, plastic glue

(5) A Simple Submarine (Diagram 2-5D)
Plastic bottle, plastic stopper, rubber tubing, rubber band

(6) Simple Action and Reaction Cart (Diagram 2-6D)
Plastic pencil case, soft drink plastic bottle 1.25 litre, balloon, string

(7) Respiratory Model (Diagram 2-7D)
PVC tube, plasticine, plastic bag, balloon

(8) Siphon (Diagram 2-8D)
Plastic bottle mineral water 1.5 liter, rubber cork, beaker, retort stand, plastic tube

(9) Water Clock (Diagram 9)(10) Simple Fire Extinguisher (Diagram 2-9D)
Plastic soft drink bottle, water, bottle cap, rubber stopper, cellotape

(10) Simple Fire Extinguisher (Diagram 2-10P)
Plastic bottle with plastic spray nozzle, soap solution, sodium bicarbonate solution, potassium aluminium sulphate solute [KAl(SO₄)₂]

CONSTRUCTION OF TEACHING AIDS

(1) Solar and Lunar Eclipses (Diagram 2-1D)

The support rod is made from discarded PVC tube and the base is made from a discarded plastic lunch box filled with sand for stability. A plastic sphere is used for the ‘Sun’ a ping-pong ball acts as the ‘Earth’ while the ‘Moon’ is a small plastic solid sphere from a discarded toy. The part joining the ‘Earth’ and the plastic platform is a discarded plastic door knob. The rubber band acts as the driving belt between the ‘Sun’ and the ‘Earth’ - ‘Moon’ assembly. The construction time is just over 3 hours at a cost of just RM3.00.

(2) Water Filter (Diagram 2-2D)

Two soft drink bottles (1.25 litres capacity) which are truncated at the bottoms are joined together back-to-back. This acts as the filtering vessel. The media are then put in sequence, starting from  the coarse layer to the fine layer. A layer of cotton wool is placed at the top to make it more compact. All the materials except the cotton wool and charcoal, are easily obtainable without incurring  any cost. Production cost is the cost of the cotton wool and the charcoal which is RM3.00.

(3) Cartesian Diver and Water Fountain (Diagram 2-3D)

The diver is made from the plastic cap or a section of the stem of a plastic ball-point pen. Plasticine is used to fill up the cap or stem as weight and for balancing purposes. The diving vessels are mineral water plastic bottles. Cost of production is less than RM1.00, the cost for the plasticine used.

A bigger capacity mineral water bottle is used to build the water fountain. Except for the rubber stopper all parts are plastic. Cost of production is RM1.00 which is the cost of the rubber stopper.

(4) Light Reflection (Diagram 2-4D)

The semi-circular cover and the back plate are cut out from a round plastic ice-cream container. Two sets of corresponding holes are made along the curvature of the cover, ranging from 25^o to 75^o, taking the center point of the base as the reference point. The inside of the apparatus is painted black to avoid any undesirable reflection of light. A flat rectangular mirror, the only non-plastic component, is centrally placed on the base. the hole set up costs RM6.00 (cost for the mirror, plastic glue and black paint).

(5) A Simple Submarine (Diagram 2-5D)

Any mineral water plastic bottle with air tight plastic stopper can be used to build the body of the submarine. Two holes (approx. 5mm dia.) are bored in the stopper for the insertion of the two tubings, one of which is tied to the body of the submarine while the other being free, is for sucking out air from the bottle. The cost of making this teaching aid is RM1.60.

(6) Simple Action and Reaction Cart (Diagram 2-6D)

A plastic pencil case is used as the base of the cart while a thin and light plastic sheet, cut-out from a soft drink plastic bottle (1.25 litres capacity) is used for the body. A screen holding the balloon is also made up of a thin hard plastic sheet with a cut-out hole for holding the balloon. The plastic ‘spring’ is essentially a plastic rod glued to a small plastic sheet. Cost of production is about RM2.00.

(7) Respiratory Model (Diagram 2-7D)

The thoraxic cavity is a middle portion of a soft drink bottle (2 litres capacity). The PVC pipe acts as the trachea, while two sections of the stem of a ball-point pen act as the bronchi. A thin and strong plastic bag acts as the diaphragm. Balloons act as lungs. The production cost is RM2.00.

(8) Siphon (Diagram 2-8D)

A 1.5 litres capacity mineral water bottle is used. The bottle can be held tight in the inverted position by the improvised plastic retort stand. Rubber stopper is the only non-plastic component. The only cost is the cost of the rubber stopper and a meter of plastic tubing which is RM1.50.

(9) Water Clock (Diagram 2-9D)

Two plastic soft drink bottles (1.25 liters capacity) are joined together mouth to mouth. This is made possible by fitting a rubber stopper with a single hole to each bottle. The two stoppers are then joint with a 6cm glass tubing. The only expenditure is the cost of the rubber stopper and a roll of cellophane tape which is RM1.50.

(10) Simple Fire Extinguisher (Diagram 2-10D)

The plastic bottle, complete with the plastic nozzle, is used to construct the body of the foam-type fire extinguisher. The two tubes placed inside the bottle are cut-out sections of two plastic tubes. The plastic rods act as support for the plastic tubes when the bottle is inverted. The production cost is just the cost of the chemicals used in the production of the foam. Other materials used were obtained without any cost.

IMPLEMENTATION

(1) Solar and Lunar Eclipses (Photos 2-1P & 2P)

This is a simple but effective model showing the position of the Sun, Earth and Moon in the solar and lunar eclipses. By just moving the plastic support platform around the ‘Sun’ the ‘Earth’ will not only move around the ‘Sun’ but it will rotate about its own axis, with the ‘Moon’ automatically orbiting around it.

(2) Water Filter (Photos 2-3P & 4P)

Cloudy water (preferably with small visible particles) is poured into the open end of the bottle. The translucent plastic bottle enables the pupils to see the various filtering elements from course to fine particles). After a short wait clear water will be seen to drip slowly into the clear plastic trough.

(3) Cartesian Diver and Water Fountain (Photos 2-5P & 6P)

This simple to make Cartesian Diver is also very simple to operate. To ‘sink’ the Diver just press the sides of the bottle, to surface it release the pressure on the sides. A simple water fountain can be constructed by blowing air into the water in the bottle. By clipping the tube with a clothes peg the air is compressed in the water. Removing the peg will result in water gushing out from the bottle.

(4) Light Reflection (Photos 2-7P & 8P)

Place a light source (e.g. lighted candle) on the outside of the apparatus near any desired hole on one side of the curved surface. The pupil will be able to see the image by looking into the correct corresponding hole on the other side of the curved surface. This can be used to teach the Second Law of Reflection of Light.

(5) A Simple Submarine (Photos 2-9P & 10P)

Put the apparatus in a bucket of water and suck the air through the longer piece of plastic tubing. Water will fill the bottle and as the weight of the bottle becomes heavier than the bouyant force of the water, the bottle will start to sink. Now blow air through the other tubing. Due to air pressure water will be forced out of the bottle which will then rise up to the surface again. This explains the principle of the submarine.

(6) Simple Action and Reaction Cart (Photos 2-11P and 12P)

This simple apparatus can be used to show Newton’s 3rd Law of Motion. The external force needed to move the plastic cart in the opposite direction can be obtained from the release of the air from the blown-up balloon, or from the backlash of the released plastic ‘spring’.

(7) Respiratory Model (Photos 2-7P & 8P)

This respiratory model can be used to teach the way animals with lungs breathe. The volume of the thorax (plastic jar) is increased by pulling down the diaphragm (plastic bag). Air will rush in to inflate the lungs (balloons). Air is forced out by pushing the plastic bag upwards, depleting the balloons.

(8) Siphon (Photos 29P & 10P)

Pressure of the trapped air in the inverted plastic bottle forces the water down into the empty beaker, thus increasing the volume and decreasing the pressure of the trapped air. Atmospheric pressure will then force more water up into the bottle. Water forced in can be seen coming out as a water fountain above the water level of the inverted bottle. Coloured water would increase the visibility of the passage taken by the water.

(9) Water Clock (Photos 2-11P & 12P)

Simple in design but effective in teaching the concept of time recording, the water clock uses the regular dripping of water from one bottle to another to record time interval, in this case, 5 minutes. It can be modified to record other time intervals. Coloured water is used to enhance visibility and attractiveness.

(10) Simple Fire Extinguisher (2-13P & 14P)

This teaching aid shows the principle of the foam-type fire extinguisher. The translucent plastic bottle permits the three different chemicals to be visible in separation when the fire extinguisher is not in use (upright position). On inversion of the bottle the three chemicals were allowed to react and the product would be a foamed output, shooting out of the nozzle.