যেকোনও পরীক্ষার আসল কথা হল প্রক্রিয়া ও প্রক্রিয়াকে অনুসরণ করে প্রমাণ ৷ যেকোনও বৈজ্ঞানিক তথ্য বা তত্ত্ব সঠিক হলেও গ্রহণযোগ্য হবে না, যতক্ষণ তা বৈজ্ঞানিক পরীক্ষার মাধ্যমে প্রমাণিত হচ্ছে ৷ এক্সপেরিমেন্টের মাধ্যমেই বিজ্ঞানের নতুন নতুন দিক আমাদের সামনে খুলে যায় ৷ বিজ্ঞানকে আরও এগিয়ে যেতে নির্ভর করতে হয় পরীক্ষা-নিরীক্ষার উপরই ৷ বিজ্ঞানকে আরও ভালভাবে জানতেও সাহায্য করে এক্সপেরিমেন্ট ৷
বৈজ্ঞানিক সূত্র ও তত্ত্বগুলি ভালভাবে বোঝার জন্যই নবম ও দশম শ্রেণীতে প্র্যাকটিক্যাল ক্লাসের উপর জোর দেয় CBSE ৷
Basically, the following skills are tested in practicals conducted in schools:
Practicals are generally conducted alongside the concepts taught in the theory classes. It is important that students have a good hold over the concept to crack the crux of a particular experiment. Without thorough understanding of the concept, it would be difficult to interpret the observations and results of the experiment.
Let’s now quickly take a look at some of the crucial experiments for CBSE 9 Science which you need to focus on in order to score well.
Preparation of stained temporary mounts of onion peel and human cheek cells
This experiment is based on the concept of the cell structure in plant and animal cells.
• In this experiment, it is important that you prepare a fresh mount.
• For onion peel, use glycerine instead of water to prevent the material from drying.
• The onion peel should not be overstained.
• For human cheek cells, scrape the inner lining of the cheek very gently to avoid any pricks.
• The toothpick should be properly cleaned before use.
• Draw neat and well-labelled diagrams of the cells indicating the cell membrane, cytoplasm and nucleus distinctly.
Identification of parenchyma, collenchyma and sclerenchyma tissues in plants and striped, smooth and cardiac muscle fibres and nerve cells in animals
This experiment is based on the concept of tissue structure in plants and animals.
• In this experiment, you should know about the structural details of each type of tissue.
• Just remember the morphology of the cells and identification will not be an issue.
Study of the external features of root, stem, leaf and flower of monocot and dicot plants
This experiment is based on the concept of characteristics of monocot and dicot plants.
• This practical will test whether you are clear on the differences between monocot and dicot plants.
• Look for the distinguishing characters in the root, stem, leaf and flower of the given specimen and classify it accordingly.
To establish the relationship between the loss in weight of a solid when fully immersed in tap water and strongly salty water, with the weight of water displaced by it taking two different solids
This experiment is based on the concept of Archimedes’ principle. It shows that the loss in weight of a body immersed in a liquid is equal to the weight of the liquid displaced. The loss in weight in very salty water is more as compared to tap water as salty water provides more upthrust.
• Study the theory properly as the experiment involves the application of concepts of flotation which you have learnt in theory.
• Ensure that the solid body is immersed fully in tap water/very salty water for taking readings of the spring balance.
• Note the zero error of the spring balance very carefully.
• Take care that the body immersed should not touch the bottom or sides of the tank.
• Ensure that the level of water in the overflow can is up to its brim.
To verify the laws of reflection
The laws of reflection of sound are the same as those of the laws of reflection of light, i.e. the angle of incidence is equal to the angle of reflection, and the incident ray, reflected ray and normal all lie in the same plane.
• Study the properties of sound thoroughly as it will be very helpful while performing the experiment and also during viva voce.
• Measure the angles very carefully.
• Use the spirit level to check whether the table top is perfectly horizontal; otherwise, you will not be able to hear sound.
• Hold the cylindrical pipe properly.
Separation of the constituents of a mixture
These experiments are based on the principle of filtration, distillation, sublimation and magnetic separation.
• Study the theory properly before performing any activity.
• Clean all the apparatus before use to prevent alteration.
To understand a chemical change
This experiment is performed to understand the concept of various chemical reactions. Chemical changes can be seen in the form of a combination reaction, decomposition reaction, displacement reaction, oxidation and reduction.
Some of the experiments to identify these changes include
• To observe the changes when an iron nail reacts with copper sulphate solution in water
• To carry out chemical reaction of zinc metal with dilute sulphuric acid and record the observations
• To study the heating of copper sulphate and record the observations
• To study the reaction of sodium sulphate with barium chloride in the form of their aqueous solutions and record the observations
Try and focus on this list of crucial experiments. Fix in your mind all possible precautions to be taken during each of these experiments so that you do not get stuck anywhere.
The practical examination pattern varies a bit subject-wise, but still, there are some common practices which can give you an edge. Remember these tips:
• Be thorough with the concept behind the specific experiment
• Learn the procedure to conduct the experiment
• Don't cram the readings
• Know the diagrams and circuit diagrams well
• Sharpen your senses
• Be confident
তাহলে পড়ুয়ারা আর প্র্যাকটিক্যাল পরীক্ষায় ভয় পেও না ৷ এই পদ্ধতি অনুসরণ করলে ভাল মার্কস আসবেই ৷ ভবিষ্যতের জন্য আমাদের শুভেচ্ছা রইল ৷