NCERT Class 10 Science Lab Manual – Introduction
Hands-on experience promotes curiosity, provides opportunity for discussion and enhances enquiry skills. This helps the students to relate things scientifically and make sense of what they learn. The experiments should be conducted in a scientific method, i.e., carefully collect the evidences by observation and draw a conclusion from these evidences.
- Experiments connect the theoretical world of textbooks to the real concrete world of experience.
- It helps in creating interest for science among students.
- It caters to the need of all types of learners, VAK, e., Visual, Auditory and Kinesthetic learners and enhances basic skills like enquiry skills, observation skills, manipulative skills, communication skills, skills of representing and interpreting data, etc.
- Brief Up the Students: Students should have brief knowledge about the experiment that will be conducted in the laboratory for the practical period before they leave their classroom for laboratory.
- Students must carry practical file/auxilliary copy, lab manual, stationery required (pencil, eraser, scale, protractor, compass, slide mounting material, pen, etc.)
- Discipline and Punctuality: On their way to laboratory the students should maintain silence. In the lab, they should be assigned a desk/work station and the place should be fixed/permanent for the academic session. A student should remain present for the practical work and reach lab on time.
A week for make-up of lost/absent experiments can be given to those students who were absent due to medical reason.
Each student should keep its work station and surrounding area clean and tidy, similarly the practical files should also be kept neat and tidy.
Knowledge of Apparatus
- All the apparatus should be handled carefully and keep them at their respective place.
- Each student should know how to select the right apparatus and correct way of using them.
While performing the experiments, record the data in your copy (practical file/auxilliary note book), analyse the data and try to draw conclusions. Do not manipulate the readings.
Reading: Take correct readings of the experiment performed by you.
Recording: Record the readings with pencil, write units. Show the readings to the teacher. If it is wrong you may do the experiment again and record the new readings by erasing the previous one.
Maintain your practical file neatly as shown below:
- Never taste any chemical in the lab.
- Never smell any gas released during a chemical reaction directly (sniff it or waft).
- Never touch chemicals.
- Never use cracked apparatus.
- Never enter the lab in the absence of a teacher.
- Always read the label on the chemical bottles before using it.
- Use very little amount of chemicals.
- You should know the main on/off connection of the gas (LPG/CNG).
- Use a test tube holder and a hard glass apparatus for heating experiments.
- Keep the mouth of the test tube away from your body.
- If you smell the leakage of gas, immediately report to the teacher.
- Stay away from concentrated acids. Use them only in the presence of a teacher.
- You should know the location of fire-extinguisher, first-aid box and call for a teacher during an emergency.
- Follow the general rules/instructions for the chemistry lab.
- Do not try to dilute the acid by yourself. (For dilution add acid into water)
- Do not open the tap completely as the water may come with pressure and splash over the work station area.
- Do not wash the hot apparatus immediately after heating as it may crack/break.
- Do not inhale gases or vapours directly. Always use your hand to waft fumes towards your nose.
- Always use clean apparatus.
- Wash the apparatus once the experiment is over.
- Do not throw the chemicals in sink or dustbin, use separate container to throw the chemical waste
- Keep the burners knob off when not in use.
- Use tongs to hold hot objects.
- Keep your work station clean.
Recording the Observations
- Enter all your observations in the practical file/auxilliary copy.
- Record your readings with pencil and get them cross-checked by your teacher.
- Maintain your practical file as instructed earlier.
- Before you start with the next experiment get your previous experiment checked.
Common Apparatus used in Chemistry Lab
First Aid in Laboratory
In Physics experiments we generally try to verify the laws, “establish the relationship”, “observe and compare things”
A student must have a thorough knowledge of the theory/concepts for performing the experiment. He should know about the apparatus required for the experiment and how to handle it.
- Record your readings neatly in the practical file with pencil.
- Mention the units for each reading.
- Repeat the observations and cross check the readings recorded. Do calculations to get the desired result.
Draw neatly labelled and proportionate diagram for the experiment.
Plot the graph wherever required. Label x-axis and y-axis properly.
Correct way of measu ring the angle of incidence and angle of reflection.
Discuss the doubts in the experiment and solve the MCQs all by yourself.
Least count of an instrument: It is the minimum value that can be measured by an instrument. For example, if a measuring cylinder as 10 divisions between 10 mL to 20 mL then least count of measuring cylinder is (20 – 10)/10 = 1 mL. So, we can measure minimum 1 mL using this measuring cylinder.
When the pointer of the measuring instrument don’t coincide with zero of the scale at rest, then the instrument has zero error.
1 kg = 1000 g
1 Newton = kg x 9.8 m/s2 (g = 9.8 m/s2)
1 kgf = 1 kg x 9.8 newton.
1 cc of water = 1 gf.
Common Apparatus used in Physics Lab
1. Spring balance
(a) It is used to measure the weight of an object.
(b) It has a graduated scale and unit marked on it.
(c) The unit may be kgf or N. The least count of spring balance should be studied and calculated before using it.
Sources of error
- The object/mass suspended should not oscillate/swing.
- Do not handle/hold the spring balance on its side, hold it only at the top hook.
- Parallax error — while recording the readings, the eye level and the reading should be parallel and coincide.
2. Measuring cylinder
(a) It can be of glass/plastic.
(b) Handle the glass measuring cylinder carefully.
(c) Read the graduated scale and find the least count.
Sources of error
- It should be clean and placed on the plain table.
- The scale marking should be readable.
- While recording the readings, for liquid read the lower meniscus.
- The eye-level and liquid level should be parallel.
3. Overflow can
(a) It is used to verily Archimedes principle. It can be made of in glass, metal or plastic.
(b) The outlet duct should not be blocked.
(c) It should be filled above the level of duct and allow the extra water to flow into a beaker, to get the desired level of water.
(d) It should be placed on plain table.
4. Tuning fork
(a) It is used in experiments of sound, it is made up of metal alloys. The vibration of tuning fork produces sound.
(b) The tuning fork is always held at the edge of the handle and banged on the rubber pad for vibrations.
5. Stop watch
It is used to record the time in seconds.
Follow the instructions given below for biology experiments.
Before you enter a lab, be prepared for the experiment and read about the experiment that has to be performed.
Read the experiments so that you get your thoughts organised about the experimental work and its reporting.
Keep your desk top/work station area neat and clean. Always wash your hands when you are finished with practical.
Be careful when you are working with blade, knife, cutter, scissors, etc.
Diagram: Draw neat, proportionate and labelled diagrams wherever required.
Read/observe the experimental work carefully i.e. specimens, slides, set-ups and record your observations in your practical file. Draw labelled diagram of each specimen in blank page on right hand page side.
Common Equipments Used in Biology Lab
- Microscopes: These are high powered, extremely expensive and sensitive pieces of equipment.
Our naked eye can see 0.2 mm object i.e., 200 micrometer size.
For objects smaller than 0.2 mm we use microscope.
There are different types of microscopes with different magnifying power.
(a) Hand lens: It is a biconvex lens mounted on a handle. It is based on the principle that when an object is placed between convex lens and its principal focus then an enlarged virtual image is formed. It is of different magnifying power 2X, 4X, 5X, etc.
(b) Simple (dissecting) microscope: It has a single lens system. A single lens is mounted on a metallic frame and it can be moved up or down or sideways to get a magnified image.
Its magnification ranges from 5X to 50X.
(c) Compound microscope: Commonly used microscope in lab is compound microscope. It uses visible light to help us observe the specimens. Two lenses of different power are used to obtain the desired magnification. The magnification is achieved when light rays from any source of light fall on the concave mirror which then reflects the light into the condenser tube allowing it to pass through the slide and then through two lenses which magnify the image of slide taken as specimen. The lens near the eye is called eye lens and the lens near the object is called objective lens. To calculate the total magnification of a specimen multiply the power of objective lens with the eyepiece:Objective lens can have power of 10X (low power), 40X (big) and 100X (very big power)
Eyepiece used is of order 10X
E.g. for calculation of the power of magnification.
- Slides: The permanent slides have a sample of blood, cell, muscles etc. with cover slips placed on it, these samples are fixed with a fixative on the slide.
Temporary slides are those slides which a student make while performing an experiment, e.g. stomata, cheek cells, onion peel, blood, etc.
- Petri dish: It is used to grow a culture or to carry out an experiment.
- Watch glass: It is used to keep and stain the specimen. Forceps Used to hold tissues or pick up the structures for slide.
- Needle: It is used to lift small cells or structures for slide.
- Brush: It is used to transfer delicate specimen from one apparatus to another.
- Dropper: Used to drop stain/water slowly during slide preparation.
- Stain: These are the agents that colour the structures of cell and allow us to see them more clearly.
- Stain: make invisible structures visible. Some common stains used are:
(a) Safranin: is used to stain slides made of plant structures.
(b) Iodine: Used to stain carbohydrates, flagella, nuclei etc. of the cells.
(c) Methylene blue: used to stain cells, tissues, etc.
(d) Eosin Y: used to stain cells, tissues, etc.
- Preserved specimens: The animal specimens are preserved in a glass jar with formalin solution used as a preservative. While studying the specimens, find out the characteristics in it by observing carefully, draw diagram for your understanding.