Organising demonstration and practical

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Organising Demonstration and Practical



Giving demonstration has become an important activity these days, after the IT age has ushered in. This is a situation where the teacher organizes the apparatus and materials and make them work. He will have arranged the demonstration in such a way that every body in the audience can see the working. It can be a computer or a mobile or preparation of chlorine gas or working of a thermo meter. The Lecturer plans it well and students enjoy seeing the working. The visual is always better than mere listening in a lecture situation.

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  1. Meaning of demonstration, functions of a demonstration
  2. Criteria of a good demonstration
  3. Requisites of a good demonstration
  4. Advantages of good demonstration
  5. Meaning of practical/development of skills
  6. Organisation of practical work
  7. Criteria of good practical work
  8. Assessment of practical work

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After going through this unit you will be able to:

  1. Define a demonstration
  2. List the advantages of a demonstration
  3. Enumerate the criteria of a good demonstration
  4. Define the practical work in a laboratory
  5. Plan to organize good practical work
  6. List the criteria of a good practical
  7. Construct test items to assess the practical work

Meaning of demonstration

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Demonstration means ‘to show’ or give the proof of, to prove or establish the truth. In a science or arts class demonstration implies showing the apparatus, arrange them in proper order so that it works. To give a demonstration means to show that required thing with verbal presentation to make the point clear or show how the machine works. It can be a water purifier or vacuum cleaner or laboratory apparatus.

Functions of a demonstration

  1. To solve a problem: a) To find V when P & T are given b) To find the specific gravity of liquid/body
  2. To explain or make clear by analysis: Role of a catalyst
  3. To verify substantiate the review: a) Acid + Base = Salt + Water b) In the absence of light no starch is formed
  4. To supply an application: a) Hyperacidity & antacids b) Newton’s II law of motion c) Multiple reflection (360/Ø – 1) = n.
  5. To evaluate student’s achievement: a) Effect of varying light in intensity on photographic plate & growth of a plant b) Reaction of magnesium powder and ice-no reaction, Add dry ice reaction takes place. Hence dry ice acts as a catalyst. (Even water, ice, steam also act as catalysts).
  6. To create a problem: Effect of iodine on the growth of tad poles. They die, because, all halogens are poisonous.
  7. To show methods & techniques.
  8. To display objects and specimens

Requisites of a good demonstration

The following must be kept in mind before doing the demonstration, by the lecturer.

  1. Physical facilities like demonstration table, light or darkness, Gas/Water/Burner facilities. Benches/Desks arranged in stairs/gallery, and a good black board.
  2. Apparatus and chemicals:Apparatus must be large, simple, improvised and reserve set, if the demonstration fails. Chemicals must be pure, clearly distinguishable and substitute if the demonstration fails
  3. Purpose of the demonstration must be clear to the teacher.

a) Teacher must have the list of apparatus & chemicals

b) Principles, theories and formula related to the demonstration

c) Observations

d) Graphs

e) Inference

f) Applications (Problem solving)

g) Important points (Precautions)

Merits of good demonstrations

The following merits can be listed in case of good demonstrations.
  1. Demonstration make the ideas concrete
  2. Students learn better and they retain it for a long time
  3. It is economic as the lecturer shows the adjustment of apparatus and the theory or law can be taught to a large number of students.
  4. It is cheaper than individual laboratory method
  5. Learning will be better even though it is slightly costlier than lecture method
  6. There is higher degree of motivation in students, and concentration will be better. (Visuals are remembered for a long time compared to the words)

Organisation of Practical work

Meaning of practical work

Practical work is opposed to mere theory, practical work is doing the established method, or practicing the skill. In a pre-university college, practical work is supplementary to the theory that is taught. Practical work is arranged in the colleges and students go to the laboratory in groups and do the practical there. The exercises are more in the form of verification than open – ended inquiry type. But these exercises develop the skills of laboratory work.

The skills are developed in four stages

  1. Demonstration by a master crafts man
  2. Imitation by the students
  3. Practice and Correction by the lecturers
  4. Internalization, where students automatically do the experiments and the skills are interwoven in the practical work. The pre-university students do these experiments and learn the skills well.

Organisation of Practical work The lecturer with the help of an attendar has to plan for the activities in the laboratory. The number of students who will be attending the laboratory will have to be kept in mind, while arranging for the sets of apparatus required and the amount of chemicals needed. The special reagents that are required, the light/darkness needed, etc must be kept in mind while arranging for the special type of experiments. The lecturer will have made arrangements as to who will work where, so that there will not be any confusion what so ever.

Assessment of Practical work

Assessment of Practical work Practical work can be assessed through a paper – pencil test. The parameters that can be tested are the following.

  1. Were the apparatus and chemicals available?
  2. Were the apparatus clean and usable?
  3. Were the chemicals clean and fresh?
  4. Were there reserve sets of apparatus if there was any problem?
  5. Were there substitute chemicals, if the chemical used failed to work.
  6. Was the teacher ready with list of observations, graphs applications, etc.,
  7. Was there opportunity to pose the problem and search for the answer?
  8. Were there avenues to raise the questions and look for the responses?

Key activities and assignments

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  1. Students can be asked to plan for a demonstration and demonstrate well to the other students.
  2. Students can be asked to list the criteria to assess a good demonstration
  3. Students can be asked to plan practical work in science laboratory
  4. Students can be asked to list the criteria to assess good practical class.
  5. Plan a demonstration in the area of your specialization list the apparatus/chemicals or whatever that is needed, suggest how to do it well.

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Criteria of good practical

The criteria of good practical could be looked into like this.

  1. Lecturer must have planned well and rehearsed well in advance or must have good knowledge of how it is done, the precautions to be taken, etc
  2. The aim of he practical work must be made clear to the students
  3. It should be done in a scientific way.
  4. Difficult points must be stressed in the beginning and can be put on the blackboard.
  5. It should be a cooperative venture of both lecturer and the students.
  6. The practical work must be followed by question and answer or discussion
  7. Time or the season must be kept in mind by the lecturer.
  8. If an experiment fails, the lecturer must convert it to a problem and try to find the causes with the students.

Criteria of a good demonstration

  1. Planned & rehearsed well in advance. a) Apparatus b) Observations c) students trained to help the teacher d) Confidence Ex. NH4 NO2 – N2 + H2O. Only water will remain. So fresh solution must be used.
  2. The demonstration must be clear & speedy. Visible to all students, it should be over within 45 minutes depends on different types of reactions.a)Instantaneous reactions–NaOH + HCl b)Delay reactions - KMnO4 + glycerin.c)NaHSO3 + KI03 + (Starch) → cracker
  3. Aim of the demonstration should be clear to the teacher
  4. It should be done in a scientific way - Arrangement of apparatus must be from left to right, labeling must be checked before hand. No hard and fast rule that while weighing weights must be kept in the right pan. When we are weighing 40 grms of Na2CO3, it can be had on the right pan.
  5. Important and difficult points should be stressed and explained well.
  6. It should be a cooperative venture of both teacher and students
  7. It should be followed by question & answer or discussion.
  8. Time & season must be kept in mind.a)Static electricity experiments will not be successful on rainy days, as production and discharge will be fast
  9. Failure – Then convert it into a problem and find out the causes
  10. It should pose problems and make provision for solving it – It should provide a chance to exercise their abilities to observe, explain, analyse, verify and review.

11. It should be followed by question & answer or discussion.
Salt Hot Cold
Zinc Yellow White
Mercuric Oxide Yellow White
Sulphur Yellow Red

b) NaCl + AgNO3 → AgCl + NaNO3. In summer white AgCl becomes light grey, green, brown and black.