1. High tide and low tide is a natural phenomenon, which as far as our human memory can recall, plays an important part in our life .
   
   
2. In school, this topic is taught with Sir Isaac Newton's Law of gravitational Pull by the moon and the sun.
   
   
3. This phenomenon is not fully understood by the students due to

• normally, the topic has been taught in theory with the help of a chart only.
• in the process of learning, students have to recall their experience about the tide that they do not observe it in detail.
• some students living in inland region or certain locality do not experience this phenomenon.
• many students have misconception that the twelve hourly high and low tide circle is brought about by the gravitational force of the moon alone. It is not surprise that many adults are having this misconception too.
• the earth is too huge for us to be aware of its movement.
• they think that low tide experienced by them is due to the high tide water moving away from their place.
• they fail to relate the time taken by the moon's evolution with the time taken by the earth's rotation. This relationship plays an important part in the occurrence of this phenomenon.
• there are four elements responsible for this phenomenon. They are (a) the evolution of the moon, (b) the position of the tide, (c) the time and (d) the rotation of the earth. Normally, many students fail to construct a correct relationship among these four elements that contribute to the formation of high and low tide.
• no apparatus is available in market.
• students have not given an opportunity to construct this knowledge due to lack of proper device.

In view of this, a simple teaching aid has been improvised for students to study this topic through simulation method.

The main purposes of having this teaching aid are :

• to provide opportunity for students to carry out simulation experiment on this natural phenomenon.
• to provide students device to study the relationship between the movement of the moon, the movement of the earth and the positions of high tide and low tide area at a certain period of time.
• to enable students to relate laboratory activities with everyday life.
  
• to construct a true picture about the formation of high tide and low tide which is meaningful to them so that misconception can be eliminated.
• to provide an effective teaching aid for science teachers to teach this topic.
  

a. The teaching aids improvised are simple to make and at low cost but its effect in the learning process are obvious and encouraging.
b. It provides an opportunity for students to carry out simulation experiment. With the help of the aid, students can actually imitate and study :

• the rotation of the Earth
• the evolution of the Moon
• the position of high tide and low tide and
• the period of time involved in these changes (refer 3-P4, 3-P5, 3-P6, 3-P7 and 3-P8).

c. In this activity, students can easily construct a correct picture about the phenomena of high and low tide in their mind.

d. Students can draw conclusion through experimental results and not by theories.

e. With this study, science knowledge is related to our everyday life phenomenon.

f. For slow students, teacher can teach the topic by using transparency and overhead projector (refer 3-P4, 5, 6, 7 and 8). Thus, the phenomenon of high tide and low tide, which unceasing occurs in the ocean, has brought into action in classroom or laboratory.

g. This teaching aid is especially useful in the regions where students do not experience this phenomenon.

h. This activity enhances cooperative learning among students that the present educators have emphasized on (refer 3-P9).

Materials needed to prepare these teaching aid are :

a. transparent plastic sheets (210mm x 300 mm) - 4 sheets.
b. a metal pin.
c. different colour markers.

The methods for preparing the teaching aids are :

a. On each sheet of plastic sheet A, B, C, D, fixes a point.
b. On sheet A, draw a circle of radius 2.5 cm from the fixed point O (diagram A) to represent the Earth.
c. On sheet B, draw a circle of radius 2.6 cm from the fixed point and a feature of high and low tide is drawn outside the circle. Draw a small circle of radius 0.5 cm with a distance of 6 cm from the fixed point to represent the Moon.d. On sheet C, the drawing is the same as Diagram B.
e. On sheet D, draw a circle with radius 10 cm from the fixed point. Divide the inner edge of the circle into 24 equal arc and label them from 0 to 24 (diagram D) to represent the time of a day.

The following is the implementation of the teaching/guidance methods:

(I) Theory of constructivism

The research into children's conceptions shows that learning outcomes depend not only on the learning environment but also on the knowledge of the learner. Learning involves the construction of meaning. Meaning constructed by students is to a large extent influenced by their prior knowledge. Thus, learners have the final responsibility for their own learning. In view of this, a teacher can never learn for a student, and teaching is never more than the offering of opportunities for learning.

This teaching aid is a device to provide opportunity for students to construct the meaning of high tide and low tide phenomena based on their prior knowledge that they have learnt before. These prior knowledge are :

a. gravitational pull of the moon causes high tide.
b. there are 24 hours in a day.
c. the moon takes 29.5 days or 708 hours to complete one evolution around the earth.
d. the earth takes 24 hours to complete one rotation at its polar axis.

(II) Arrangement and usage of the teaching aids.

a. Students are provided with four plastic sheets with Diagram A, B, C and D on them respectively.
b. Base on their prior knowledge, they have to arrange the Earth, the Moon with the high tide in their respective position.

The outer circle will show the time of the high tide. The expected outcome of the arrangement is shown as follow:

(III) In order to observe the change of the water level for the tide, the change of time, the rotation of the Earth and the evolution of the Moon have to be studied.

• A pin is inserted at the point O.
• Diagram A representing the Earth is rotated at point O.
• Diagram C is added to the arrangement to show the new position of the Moon and the tide.
• The result of these movements will show a different setting of the position of the Moon, tide, the tree and the time.
• The expected outcome of the new setting can be shown as follow.

• When the Earth is rotating, it will bring the tree towards the low tide region at 0800 hour.
• Although the position of the Moon has changed too, it shows a little change only for it takes 708 hours to complete one evolution around the Earth. Because of this, the high tide is retained by the gravitational pull of the Moon (refer 3-P5).
• By continuous rotation of the Earth, the tree will experience low tide and high tide every six hourly, i.e. at 1100 hour-low tide (refer 3-P6); at 1700 hour-high tide (refer to 3-P7); at 2300 hour-low tide and high tide again in the next morning (refer 3-P8).
• This circle and the position of high tide and low tide can be studied by rotating the Earth diagram and the moon and tide diagram.

• The explanation on the concept of "high tide and low tide" could be made clearer if the simulation experiment is further illustrated by the use of filmstrips or CD-ROM which includes pictures that depict the real life situation.
  
  
• The suggested strategies to be carried out, i.e. cooperative learning (e.g. structural or conceptual approaches) should be explained in more details or specific.