8. Science Laboratory – Methodology of Teaching Science

8

Science Laboratory

CHAPTER OUTLINE
LEARNING OBJECTIVES

After reading this chapter, you will be able to:

  • Understand the importance of a science laboratory

  • List the various characteristic features of a science laboratory

  • Draw the design of an ideal science laboratory

  • Comprehend the expected actions from a science teacher in a science laboratory

  • Maintain the records of a science laboratory

  • Take appropriate measure, in case an accident happens in a science laboratory

  • Ensure safety measures in a science laboratory

INTRODUCTION

A well-equipped laboratory plays an important role in the effective and efficient science teaching. A major part of the time spent in learning has to be used for practical work, either in the class room for demonstration or in the laboratory, as an individual or as a member of a group.

Science helps in developing certain values like intellectual values, utilitarian values, cultural values, moral values and aesthetic values. These can be achieved only if the students get the opportunities to test the knowledge of the principles and theories through experiments and practical work. In other words, science teaching cannot be properly conducted without a good laboratory.

With the implementation of the improved science curricula in the various states, and as recommended by Kothari Commission (1964–1966) to implement the scheme ‘Science For All’ throughout the school stage, and also the work done by the N.C.E.R.T. in this respect, it has become imperatively important to implement different means of providing better teaching learning situations within the frame work of school education.

Physical facilities in science, perhaps, are those provisions in schools which facilitate the teacher and pupil to have ideal teaching-learning situations and to utilize them effectively with understanding in a simple and easier way to achieve the desired aims and objectives of science in comparatively less time. It is also to keep the students in touch with the developed advancements in science and to fulfill the individual needs of the students.

Resources are referred to as all those means that facilitate learning situations and are helpful in creating an atmosphere for learning. From this, we can conclude that by learning resources, we mean all those things such as people, programmes, instructions, materials, physical facilities, necessary equipments and tools, etc.

IMPORTANCE OF A SCIENCE LABORATORY

Science has gained almost unparalleled position in every field. Its evolution in the last few decades has necessitated the need of well developed students with a scientific attitude and for this we need a well equipped laboratory. Science teaching has now become less concerned in presenting factual knowledge or satisfying only knowledge aim. It is felt that only chalk and talk method makes science an uninteresting subject. Moreover, with only theory, students are like frogs in a well, totally unaware of experimental techniques.

An experimental study is indispensible to create scientific method of thinking among the students. Facts become everlasting if pupils perform experiments themselves, instead of memorizing like parrots. If a good teacher is the first most important requirement for teaching science, a well-equipped laboratory is the second most important requirement.

CHARACTERISTICS OF A GOOD SCIENCE LABORATORY

An ideal science laboratory and its essential features are depicted in Figure 8.1

 

 

Figure 8.1 Features of a Science Laboratory

 

I. Design of Science Laboratory: The design of a laboratory should be a cooperative exercise between the architects and those engaged in science education and administration. The plan and design of a laboratory must provide elements of flexibility.

  1. Shape: Most schools posses a rectangular shaped laboratory. An ideal laboratory for about 30 students should have a floor area of 89 m2 (960 ft2) which provides approximately 3 m2 floor area per pupil. Six factors are of particular importance while planning the lay out of a science laboratory. These factors clearly reflect the main attributes in science teaching i.e. pupils doing individual practical work, writing or watching a demonstration. The factors are:
    1. Linear bench shape: The provision of 1 linear meter of bench space per pupil is advisable.
    2. Circulation space: The provision of 1.7 meter of space between the ends of benches and walls to provide circulation space and room for wall furniture.
    3. Storage: Space for cup-boards and shelves in the laboratory for storage of apparatus and other materials is common.
    4. Permanent equipment: Space for installation of non-movable equipment like aqua, balance, oven, H2O bath.
    5. Wall space: Space for apparatus which needs to be fixed in vertical plane.
    6. Demonstration bench: Provision of a demonstration bench which is used for teaching, i.e., demonstration as well as individual practical work.
  2. Location

    There are several advantages in having all the science laboratories together to form a science block :

    • the movement of staff and apparatus is reduced.
    • availability of technical assistance is increased.
    • work of an inter-disciplinary nature can be developed easily.
    • Installation expenditure of services such as gas, electricity, water and drainage can be kept to a minimum.
  3. Laboratory Design Criteria

    A science laboratory must be designed for a variety of activities like :

    1. Practical work by individuals or small groups. These activities require the usual range of services near fixed or movable work benches.
    2. Study activities like writing experiments, making observations and drawing diagrams. Recommended height of working surface for seated work in 75 cm and for stool is 50 cm.
    3. Lecture/Demonstration : It can be done at an ordinary work bench or a special demonstration bench which has space to receive a trolley.
    4. Discussion : Movable tables which can create space for a class discussion advantageous for discussion.
    5. Audio-visual aids : Using a projector or a T.V. Viewing of films through a projector requires dim light in the laboratory, therefore, fire-proof black out curtains should be present.
    6. Display/exhibition areas; For displaying charts, models, projects, etc., provision of pin board areas at all places is essential.
    7. Storage : A laboratory should have a store room with preparation areas from which material can be sent to the laboratory. The store room should contain cupboards and drawers or trays for storage. Some lockable cupboards should be present particularly for storing expensive or dangerous items.
    8. Preparation area : It should be provided with the usual services such as gas, sink, etc. A part of bench top should be covered with fire resistant material.
  4. Services

    The services include gas, electricity and water supplies. A laboratory must have permanently fixed services in fixed benches or service stations along the sides of the laboratory. There should be 2 or 3 additional service stations for electricity and gas in the middle of the laboratory. For lighting, there should be lamps at each bench to facilitate microscopic work.

     

  5. Safety Measures
    1. Design of the laboratory should be such that all pupils can be supervised easily while doing practical work.
    2. The laboratory floor should be resistant to minor spillage. It can be polished or varnished, but must not be slippery. It must also be free from cracks.
    3. The wall and floor fitting must not protrude unnecessarily into laboratory working space.
    4. Provision must be made for the storage of pupils’ bags, etc., that may be removed while doing the practical work.
    5. It must be possible to open windows and to lower any blinds without climbing benches to do so.
    6. The design of a laboratory should be such that the teacher has ready access to main gas, water and electricity controls which should be located near exit doors of the laboratory. Pupils should also know the position of controls to deal with emergency.
    7. First aid kit must be provided in adequate number and should kept at accessible places. Pupils must be aware of the location and content of the kit. They must also be aware of its usage.
  6. Audio-visual Aids

    Various audio-visual aids recommended for science laboratory are illustrated in figure 8.2. They are :

     

     

    Figure 8.2 Types of Audio-visual Aids

  1. Chalkboard: Chalkboard is a board with a surface that allows chalk to rub off a stick on to the board. Most commonly used chalk board is the black board, but other colors, particularly green, are also used.
  2. Placement of the chalkboard: Lighting conditions change throughout the day and it is important that the light reflected from the chalk board surface does not prevent students from reading the information written on it. To ensure this, blinds must be provided on windows which can be pulled down for shielding against light. For adequate illumination, artificial lighting can be provided.
  3. Display board: Some wall space in laboratory must be given to pin board or other surface for display of articles, notices, etc.
  4. Wall charts: Wall charts can be made in the school by pupils or teachers or can be bought from commercial suppliers. Charts should not be over used. It will be ignored if used for a long time.
  5. Models: Models are used to convey an appreciation of three dimensional structure. Models can be static or working.
  6. Projector: Various projectors are used in schools like slide projector, film strip projector, over head projector and micro projector.
  7. T.V. and radio: T.V. telecast includes various programmes for schools. School time table should be adjusted according to the T.V. schedule.

II. Equipments: Some equipments are same for the Physics, Chemistry and Biology laboratories. But some equipments are specific to a subject.

  1. Equipments for Chemistry Laboratory: The recommended equipments for a chemistry laboratory are as under:
    1. Cupboards (wooden and steel).
    2. Wall board or black board.
    3. Demonstration table (8’X4’) with cupboards, water and gas points.
    4. Working tables with cupboards, shelves, water and gas points.
    5. Balance room should be attached to the laboratory.
    6. Sinks on each working table or at least two large sinks at the corners of the laboratory.
    7. A wooden box half filled with sand to be usea as a waste material box.
    8. A full cupboard.
    9. Acid proof drainage system.
    10. Shelves for reagent bottle on each working table and wall shelves for storage of reagent bottles.
  2. Equipments for Physics Laboratory
    1. Working tables of about 6’X3.5’X3’ with inside drawers.
    2. One demonstration table with water, gas and fitting.
    3. Blackboard at the back of demonstration table nicely painted.
    4. Sinks.
    5. Cupboards may be wooden or with glass pane.
    6. Stools.
    7. Separate balance room if schools can afford it. Otherwise projected platform windows or space in the walls may be used for keeping balances.
  3. Equipments for Biology Laboratory
    1. A long working table where 3-4 students can work comfortably. It should be along the walls so that ample light is available for microscopic study. Drawers should also there for keeping books, etc.
    2. Teacher's demonstration table should be facilitated with gas and water fittings.
    3. Stools.
    4. Blackboard.
    5. Shelves for keeping chemicals.
    6. Cupboards with glass pane, so that students can see the specimens frequently.
    7. Aquarium for keeping animals.

III. Basic Requirements of a Laboratory: Any science laboratory is incomplete without certain essential things. These requirements are given below :

  1. First Aid Box: It is a basic requirement of every laboratory. It should contain the following materials:
    • Bandages (3-4 rolls of different sizes), gauze, lint, cotton wool, leucoplast.
    • A pair of forceps, a pair of scissors, safety pins, glass dropper, two eye glasses.
    • Vaseline, boric acid power, sodium bicarbonate powder, a tube of burnol.
    • Sarson oil, olive oil, glycerin.
    • 1% acetic acid solution, 1% boric acid, 1% sodium bicarbonate, saturated solution of sodium carbonate.
    • Methylated spirit, rectified spirit, dettol.
  2. Apparatus: Every laboratory requires some apparatus for its functioning and to conduct experiments e.g. beaker, conical flask, test tubes stand, pipette, burette, Petri dishes, watch glasses, slides, microscopes, etc.
  3. Electrification of Laboratory: A good light system is very important factor in the laboratory for students’ tables, demonstrations tables and blackboard. A well lighted laboratory aids in better practical work.There should be some arrangement for darkening and controlling the intensity of light. Sufficient care should be taken of switches, fans and other electrical arrangements. No point should be left loose. There should be some arrangement for A.C. and D.C.
  4. Gas Supply: Gas supply is required for all laboratories, especially in chemistry laboratory, it is indispensible. There may be coal gas plant, kerosene oil gas plant or petrol air gas plant. Mostly air gas (petrol) plant is installed in schools as :
    • Its cost is low.
    • It is easy to handle.
    • It is easily available.

    A gas plant should be in a small room attached to the laboratory. Gas controllers should be fitted on every working table which can be used when required.

  5. Chemicals: Chemicals are one of the basic requirements of every laboratory especially in chemistry laboratory. In storage of chemicals the following methods are normally adopted:
    • Grouping the chemicals in a systematic way.
    • Arranging the chemicals and elements in an alphabetical order.
    • Numbering each bottle and jar and keeping an index book.
IDEAL SCIENCE LABORATORY DESIGN

Outline designs of Physics, Chemistry and Biology laboratories are given in figures 8.3, 8.4 and 8.5 respectively.

 

 

Figure 8.3 Physics Laboratory

 

 

Figure 8.4 Chemistry Laboratory

 

 

Figure 8.5 Biology Laboratory

GUIDELINES FOR TEACHERS

For smooth working in the laboratory, teachers should give due considerations to the following points :

  1. If a teacher follows the demonstration method to teach theory, he/she should remember the most important principle that practical work should go hand in hand with the theoretical work. Thus, if a class is doing theoretical work in chemistry, it should also do practical work in chemistry during the practical periods.
  2. An attempt should be made to arrange the practical work in such a way that each student is able to do the practical individually. Thus, for practical work, working individually is preferred in comparison to working in groups.
  3. In case of a large class, it is convenient to divide the class in a suitable number of groups for practical work. A practical group in no case should have more than 20 students. The limit on practical group is essential, otherwise the teacher will not be able to devote individual attention to the students.
  4. To save time on delivering a lecture about do's and don'ts in laboratory, card system is used. This card also contains printed instructions, apparatus required, etc. Students can complete the practical work according to the apparatus required and the instructions given in the card.
  5. The apparatus provided should be good so that the students get an accurate result, particularly, in those experiments in which the students are likely to compare the numerical value of the result with some standard values.
  6. A true and faithful record of each and every experiment should be kept by pupils. The record should be complete in all respects.
  7. To check the habit of ‘cooking the results’, teacher should see that students enter all their observations directly in their practical note book. The teacher should insist that the pupil do not go to the balance room without first entering the data in their notebook.
  8. Students should not be allowed to calculate results’ data on scrap paper.
  9. In practical notebooks the right hand page should be reserved for record while the left hand page should be left for diagram and calculations. This practice should be followed for assignment method also.
  10. The teacher should see that students complete their practical notebooks and should thoroughly check the account written by students.
  11. Whenever a student is required to make use of a piece of apparatus for the first time, it is the duty of the teacher to explain to the student, the working of the apparatus and the chemicals needed by him/her. He/she should also explain the reasons for necessary care and accuracy.
  12. A teacher should see that students find no difficulty in getting the apparatus and chemicals needed by them. In the absence of provisions of laboratory assistants, it is for the teacher that he/she arranges in such a way that things frequently needed by the students are easily accessible to them. The teacher should also emphasize proper and economical use of apparatus and chemicals.
  13. While working with larger groups and with limited apparatus, a teacher can act in many ways as given under :
    • He/she may use the assignment method.
    • He /she may allow students to work in groups.
    • He/she may devise alternate simple experiments and work with improvised apparatus.
    • He/she may allow use of home made apparatus.
  14. Whenever the teacher is required to draw up suitable laboratory directions or instructions for practical work by pupils, he/she should keep the following points in mind:
    • Beginners should be given detailed directions.
    • He /she should not tell the students what is actually going to happen.
    • The main aim of the experiment should be made clear.
  15. During a practical class, the teacher should observe all the children from his/her desk, otherwise chances of accidents are there. Even when the teacher has to move away from the desk, his/her power of control over the class should be such that students continue their work satisfactorily.
MAINTENANCE OF RECORDS

A science teacher is required to maintain the following records (Figure 8.6) :

 

 

Figure 8.6 Types of Records for Science Laboratory

  1. Stock register of chemicals: The register should contain the names of chemicals and their description. The record should be made in alphabetical order. There should be monthly and if necessary, weekly checking of the stock register. This will also serve as a stock register for consumable articles.
  2. Permanent stock register: This register should list all the articles, apparatus, equipments, models and specimens (with description) which are not breakable or non consumable and thus, permanent in nature. These are usually made of metal or wood or unbreakable hardware. These may also be listed alphabetically with other details such as date of purchase, number of quantity, name of manufacturer, etc. Any article or equipment out of order should be noted as such in the remarks column.
  3. Stock register for breakable articles: This lists all articles made of glass and china ware such as beakers, trough, thermometers and models of other breakable materials.
  4. Order register: This register should contain names of all the articles, apparatus, equipments, chemicals, specimens and models which are procured and received for use in the laboratory. The different columns in this register should indicate the date of order, order details, name of the firm, price, number or quantity purchased, date of delivery or receipt, date of payment, vouchers details and also remarks about the quality of the materials. It would be useful to have a copy of the vouchers attached in this register at its appropriate place. This register may have a section specially reserved for recording articles received grants or as donations.
LABORATORY DISCIPLINE

A teacher should try to maintain discipline in the laboratory and regulate the pupils while they are working in the laboratory. The following rules will help to avoid any accident in the laboratory.

  1. Admission to the laboratory in the absence of a teacher should be avoided.
  2. Teacher should not be late unduly.
  3. Teacher should address the whole class.
  4. Teacher should see that complete silence is observed during the instructions.
  5. Teacher should change his pitch at times to add interest to his/her talk.
  6. Teacher should make adequate preparation to keep the class busy.
  7. The teacher should see and remove all possible causes of trouble.
  8. Adequate apparatus should be made available.
COMMON ACCIDENTS AND THEIR REMEDIES

Laboratory is a place where accidents do happen often. Students may get hurt due to burns or cuts or gases. A science teacher should be able to identify the injury and do the needful. Various possible injuries and the suggested first aid have been given in figure 8.7. These are :

 

 

Figure 8.7 Common Accidents in a Science Laboratory

1. Burns

  1. Burns by dry heat (i.e. by flame, hot objects etc.). For slight burns apply Burnol and Sarson Oil. In case of blisters caused by burns , apply Burnol at once and rush to the dispensary.
  2. Acid burns : Wash with water and then with a saturated solution of Sodium Bicarbonate and finally with water. Even after this if the burning persists wipe the skin dry with cotton wool and apply Sarson oil and Burnol. In case of Concentrated Sulphuric Acid, wipe it from the skin before giving the above treatment.
  3. Alkali burns : Wash with water and then with 1% acetic acid and finally with water. Dry the skin and apply Burnol.

2. Cuts

  1. In case of a minor cut allow it to bleed for a few seconds and remove the glass piece if any. Apply a little methylated spirit or Dettol on the skin and cover it with a piece of Leucoplast.
  2. For serious cuts call the doctor at once. In the mean time try to stop bleeding by applying pressure above the cuts. The pressure should not be continued for more than five minutes. Minor bleeding can be stopped easily by applying conc. ferric chloride solution or alum.

3. Eye Injuries

  1. Acid in eye : At once wash the eye with water a number of times. Then wash it with 1% sodium carbonate solution by means of an eye glass.
  2. Alkali in eye; At once wash with water and then with 1% boric acid solution by means of an eye glass.
  3. Foreign particles in eye : Do not rub the eye. Wash it with sprinkling water into the eye. Open the eye and remove the particle by means of clean handkerchief. Again wash with water.

4. Poison

  1. Salts; If a solid or liquid goes to the mouth but is not swallowed, spit it at once and repeatedly wash with water. If the mouth is sealed, apply olive oil or ghee.
  2. Acids : Dilute by drinking lots of water or preferably with milk of magnesia.
  3. Caustic alkalis : Dilute by drinking water and then drink a glass of lemon or orange juice.
  4. Arsenic or mercury compounds : Immediately give an emetic, e.g., one table spoon full of salt or zinc sulphate in a tumbler of warm water.

5. Inhalation of Gases

Pungent gases like chlorine, sulphur-di-oxide, bromine vapours, etc., when inhaled in large quantities often choke the throat and cause suffocation. In such a case, move the victim to the open air and loosen the clothing at the neck. The patient should inhale dilute vapours of ammonia or gargle with sodium bicarbonate solution.

6. Fire

  1. Burning clothes : If clothes have caught fire, then lay the victim on the floor and wrap a fire proof blanket tightly around him. The fire in the burning clothes will thus be extinguished. Never throw water on the person as it will cause serious boils on his body.
  2. Burning Reagents : In case of fire on the working table, at once turn out the gas taps and remove all things which are likely to ignite. Following methods can be used to extinguish the fire:
    • If any bottle or beaker containing a liquid has caught fire, cover the mouth of the vessel with a clean damp cloth or duster.
    • Most of the fire on the working table can be extinguished by throwing water on it.
    • If any wooden structure has caught fire, it is put off by throwing water on it.
    • Never throw water on burning oil or spirit. Since it will only spread the fire. Throwing of a mixture of sand and sodium bicarbonate on the fire is most effective.
PRECAUTIONS IN A SCIENCE LABORATORY
  • Take special care with explosives, uncontrolled reactions and inflammable substances.
  • Heat inflammable liquid only in round bottomed flasks or steam /bath. Never heat such liquids on naked flames.
  • Don't drop lighted matches, sodium or phosphorus into waste boxes.
  • Take care that a large round bottom flask does not act as a lens when the sun rays fall on it as it may cause fire.
  • Gas supply pipes in physics laboratory should be of non magnetic material.
  • Never use concentrated acids unless specially or specifically instructed.
  • Do not mix chemicals aimlessly.
  • Do not taste chemicals without permission.
  • Pour liquids only down the sink.
  • Students should always be followed by the science teacher while working in a laboratory.
SUMMARY
  1. A well-quipped laboratory plays an important role in the effective and efficient science teaching.
  2. Only chalk and talk method makes science an uninteresting subject.
  3. An experimental study is indispensible to create scientific method of thinking among students.
  4. A science laboratory has 3 characteristic features :
    • Design
    • Equipments
    • Basic requirements
  5. The design of a science laboratory has 6 factors :
    • Shape
    • Location
    • Laboratory design criteria
    • Services
    • Safety measures
    • Audio-visual aids
  6. Some equipments are same for the Physics, Chemistry and Biology laboratories. But, some equipments are specific to a subject.
  7. The basic Requirements of a laboratory:
    • First aid box
    • Apparatus
    • Electrification of laboratory
    • Gas supply
    • Chemicals
  8. A science teacher should follow certain guidelines to ensure discipline in the laboratory.
  9. Laboratory records are of 4 types :
    • Stock register of chemicals
    • Permanent stock register
    • Stock register for beakable articles
    • Order register
  10. A teacher should try to maintain discipline in the laboratory and regulate the pupils while they are working in the laboratory.
  11. A laboratory is a place where accidents do happen often. Students may get hurt due to burns or cuts or gases. A science teacher should be able to identify the injury and do the needful. Some common accidents are:
    • Burns
    • Cuts
    • Eye injuries
    • Poison
    • Inhalation of gases
    • Fire
  12. Precautions must be taken, so that no untoward accident happens in the laboratory.
QUESTIONS
  1. How will you set up a science laboratory in your school?
  2. Discuss the characteristics features of a science laboratory.
  3. List various types of audio-visual aids needed in a science laboratory.
  4. How are the equipments in physics, chemistry and biology laboratory similar or different from each other?
  5. Explain the basic requirements of a science laboratory.
  6. What are the guidelines for a science teacher to ensure smooth working in a laboratory?
  7. Describe the role of a science teacher in the maintenance of the laboratory records.
  8. Mention some common accidents that may happen in a science laboratory and their remedies.
  9. What precautions are needed in a science laboratory?
  10. Why is a laboratory important for the teaching of science?