LABORATORY APPARATUS - USES

LABORATORY APPARATUS - HOW TO USE AND WHAT ARE THEIR ADVANTAGES ?

1, I am ‘Test tube’…..!

A test tube is a clear glass or plastic container that is much longer than its wide, commonly has a U-shaped bottom and has an open top.  Glass and special plastic test tubes are also non-reactive.  Many metals react with all sorts of chemicals in ways that would ruin an experiment or sample. 

Chemists use test tubes to mix, heat and/or hold small quantities of chemicals for assays and laboratory experiment.  Biologists use them to culture and handle various organisms, fluids, and samples.

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2.  I am ‘Beaker’

 

A Beaker is a common container in most labs.  It is used for mixing, stirring, and heating chemicals.   It is generally a cylindrical container with a flat bottom.  Most also have a small spout to aid pouring.  Beaker is distinguished from a flask, by having straight rather than sloping slides.  Beakers are available in glass, and also in metal, plastics.  

Any experiment which yields a liquid product uses a beaker to catch the liquid.

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3. CONICAL FLASK

SK’mCAn Erlenmeyer flask also known as a Conical Flask or a titration flask, which features a flat bottom, a conical body, and a cylindrical neck.  It is named after the German Chemist Emil Erlenmeyer (1825-1909), who created in 1860.

Erlenmeyer flasks have wide bases, with sides that taper upward to a short vertical neck.  They may be graduated, and often spots of ground glass or enamel are used.  It differs from the beaker in its tapered body and narrow neck.  Depending on the application, they may be constructed from glass or plastic in a wide range of volumes. The mouth of the Erlenmeyer flask may have a beaded lip that can be stopped or covered.

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4.  I am watch glass….

A watch glass is a circular concave piece of glass used in chemistry as a surface to evaporate a liquid., to hold solids while being weighted, for heating a small amount of substance and as a cover for a beaker.  It can be used to prevent dust or other particles entering the beaker, the watch glass does not completely seal the beaker, so gas exchanges still occur.  When used as an evaporation surface, a watch glass allows closer observation of precipitates or crystallization.

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5. PIPPETTE

Pipette or pipet is a laboratory tool commonly used in chemistry, biology, and medicine to transport a measured volume of liquid. 

Pipette works by creating a partial vacuum above the liquid –holding chamber and selectively releasing this vacuum to draw up and dispense liquid. 

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6. RUBBER STOPPERS

•Rubber stoppers in the labs are used frequently to plug flasks and test tubes.  Its purpose is to prevent liquids, and gases, escaping from their containers and also to prevent contaminants from entering the containers.
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7. ROUND BOTTOM FLASK/ROUND BOTTOMED FLASK

   

   A GLASS FLASK USED IN LABORATORY FOR HOLDING CHEMICAL LIQUIDS AND SOLUTIONS, WHICH HAS A SPHERICAL SHAPE BODY FOR UNIFORM HEATING AND HAS CYLINDRICAL NECK. IT IS ALSO KNOWN  AS A BOILING FLASK, MOST OFTEN USED WHEN HEATING SOLUTIONS, PARTICULARLY FOR DISTILLATION. 

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8. FUNNEL

Glass funnels can be used to guard against spillage when pouring chemicals from one vessel to another, can be fitted with filter to separate solids from liquids. 

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9. GRADUATED CYLINDER

•A graduated cylinder also called as measuring cylinder, used to measure the volume of liquids.  It is used accurately to measure the volume of chemicals for use in reactions.

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CONCENTRATE ON THESE.......FROM THE EXPERIMENTS......

A QUICK REVISION USING THESE QUESTIONS.....BASED ON EXPERIMENTS .....

TYPE THE ANSWER IN THE BOX 

1. WHEN CURRENT IS PASSING THROUGH THE MAGNETIC NEEDLE IS

2. MAGNETIC NEEDLE IS DEFLECTED ONLY DUE TO

3. WHEN CURRENT PASSES THROUGH A COPPER WIRE OR A CONDUCTOR IT PRODUCES

4. THE DISTANCE BETWEEN CONVERGED OR DIVERGED POINT TO SURFACE IS CALLED

5. THE LINE JOINING THE CONVERGED OR DIVERGED POINT TO PINS IS CALLED

6. WHEN ALL PINS POSITIONS ARE EXTENDED BACK OR FRONT THEY WILL MEET AT A POINT THAT POINT IS CALLED

7. WHEN WE BEND A PIECE OF RUBBER CHORD OUTWARDS THE PINS ARE ORIENTED SUCH THAT ALL PINS FROM EACH OTHER FROM A POINT OR TEND TO FROM A POINT

8. WHEN WE BEND A PIECE OF RUBBER CHORD INWARDS THE PINS ARE ORIENTED SUCH THAT ALL HEADS OF PINS OR

9. WHEN OBJECT IS PLACED VERY NEAR TO CONCAVE REFLECTING SURFACE THE IMAGE FORMED IS

10. TO GET POINT SIZE IMAGE THE OBJECT SHOULD BE PLACED INFRONT OF A CONCAVE MIRROR,

11. ON REACTING WITH SODIUM SULPHATE WITH BARIUM CHLORIDE, THE PRECIPITATE FORMED IS

12. THE END PRODUCTS FORMED AFTER REACTION BETWEEN CALCIUM OXIDE AND WATER

13. THE METAL CARBONATES AND HYDROGEN CARBONATES ON REACTING WITH ACIDS AND BASES GIVE

14. TO GET SAME SIZE IMAGE, THE OBJECT SHOULD BE PLACED INFRONT OF A CONVEX LENS IS,

15. THE FOCAL LENGTH OF A CONVEX LENS, WHEN KEPT IN WATER [INCREASE/DECREASE]

16.LEAST DISTANCE OF DISTINCT VISION AND ANGLE OF VISION OF A HEALTHY PERSON, ARE

17. THE REASON FOR SPLITTING OF WHITE LIGHT INTO SEVEN COLORS IS

18. LIGHT EMITTED BY SODIUM THIO SULPHATE WHEN REACTED WITH SULPHURIC ACID,

19. BATTERY CONVERTS

20. THE FACTORS OF RESISTANCE ARE

21. EFFECTIVE RESISTANCE WHEN RESISTORS ARE CONNECTED IN

22. WHEN A MAGNET IS BROUGHT NEAR TO THE CURRENT CARRYING CONDUCTOR THEN

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PHYSICS FORMULAS AND PRACTICE PROBLEMS

REFLECTION AT CURVED SURFACES & REFRACTION AT CURVED SURFACES:

1. Magnification : m = -v/u  or m=hi/ho

2. Mirror formula, 1/f = 1/u + 1/v

3. focal length f = R/2

4. Lens formula 1/f = 1/v - 1/u

5. Lens makers fomula :  1/f = (n-1) (1/R1 - 1/R2)

6. The relation between refractive indices of media, object distance, image distance, and radius of curvature is given by :

                                       n2/v - n1/u = (n2-n1)/R

7. In case of plane mirrors, R, F are infinity, then the power is equal to zero.

                                        n2/v  = n1/u

8. The refractive index of prism is 

                 n = sin{[A+D]/2}/SIN [A/2]

9. Speed of wave is , v = Frequency x wavelength

10. snell's law is n1sini = n2sinr

11. A + d = i1 + i2

PROBLEMS IN PHYSICS - REFLECTION AT CURVED SURFACES

PROBLEM 1: 

Where is the image formed when 8 cm tall object is placed at 20 cm. in front of a concave mirror with focal length 5 cm.  Find out the size of the image also.

PROBLEM 2:

A 10 cm tall object is placed in front of a convex mirror of focal length 15 cm, Find out the image distance and write its characteristics .

b>PROBLEM 3:

10 cm focal length concave mirror is placed at 40 cm, from a wall.  Calculate the object distance such that its image is formed on the wall.

PROBLEM 4:

In front of 15 cm focal length concave mirror, an object is placed at 30 cm, if the object is displaced through 10 cm towards mirror, calculate by how much distance the image is displaced?

PROBLEM 5:

The image is formed behind the mirror, at a distance of 10 cm, when an object is placed at 20 cm in front of it.  Identify the type of mirror used and also calculate the focal length.  

ELECTRICITY:

1. Electric current i = Q/t

2. Potential difference,  V =  W/Q

3. Resistance R = (Resistivity * length)/Area  

4. Resistance R=V/I

5. Electric power P = V * I

6. P=V2/R

7. CONDUCTIVITY = 1/Resistivity

8. Resistors connected in series, R = R1 + R2 + R3 +.....

9. Resistors connected in parallel  1/R = 1/R1 + 1/R2 + 1/R3.......

MODEL PROBLEMS :


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1. If you are using an electric lamp and it lights for 6 hours and the current drawn by it is 0.24 A. Then calculate the amount of charge flowing through the lamp.  

2. A circuit consists of five resistors, 10 ohm, 20 ohm, 30 ohm, 40 ohm, 50 ohm, your aim is to decrease the effective resistance using the given resistors, then how do you connect them and calculate the resultant resistance.

3. Suppose that you are using a water heater to heat the water having resistance of 90 ohm, and connected to 240 v. p.d. Determine the current flowing through the water heater.

4. Calculate the number of units when 50w, 60w, 80w electrical appliances are being used daily for 2 hours for 30 days. 



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A QUICK REVISION - PHYSICAL SCIENCES

Are you ready? ...........

I : REFLECTION and REFRACTION AT CURVED SURFACES 

1. Predict, Which mirror is used as rear view mirror ? 

2. What is the unit of the power of the lens? Define one dioptre.

3. Suppose that a person is using a concave mirror for shaving, Where should he place his face in front of the mirror?

4. Explain the refraction of light at plane surface and curved surface? When a ray of light passes from a denser medium to rarer medium which angle is greater ? Explain.

5. Guess to get always an erect and diminished image, which mirror should be used whether convex mirror or concave mirror ? Why?

6. Suppose your friend is using a lens with power is -1D, What does it denote?

7. When you are using a spherical mirror, the magnification produced by a mirror is -2, +2, Explain the characteristics of the mirror.

8. Predict, the path of the reflected ray, when a ray of light is incident on a concave mirror along its principal axis and find the angle of reflection.

. 9.Which mirror and lens makes the  paper to catch fire when focused to sunlight?

ACIDS AND BASES

1. Give a few examples for acids and bases.

2. Write the properties of acids and bases

3. What are the indicators used to test whether a substance is acid 

or a base?

4. What are the materials required to understand the reaction between acids,bases and metals?

5. Write the observations from the experiment - reaction of acids with carbonates?

6. List out the salts and their formulas

7. How many types of salts are there

8. What do you understand from the reactions between metal oxides and acids ? 

9. Predict the result when non-metal oxides reacted with bases.

10. Write the importance of pH value in your daily life

11. When do you say a process is chloro-alkali process?

12. How can you say that a wet blue litmus paper is used to test the acidic property instead of a dry litmus paper?

CHEMICAL EQUATIONS

1. What is the difference between skeltal chemical equation and balanced chemical equation?

2. Give an example for precipitation reaction and double displacement reaction.

3. Understand the following chemical equation and identify X and Y.

                  X + Barium Chloride -----> Y + Sodium Chloride

4. If the products in a chemical equaion are Mn and Al2O3, then predict the reactants in that equation.

5. If the reactants are Carbon dioxide and Water, then guess the products and balance the chemical equation.

6. Balance the chemical equation when Pb(NO3)2 (aq) reacted with KI (aq).

HUMAN EYE AND COLOURFUL WORLD

1. Name the defect of vision in person ....whose far point is less than infinity?

2. Define spectrum?

3. Give reason why the sky look blue?

4. Predict why the sky appear black for an astronaut?

5. Write the nature of eye lens?

6. What are the conditions to occur dispersion of light?

7. Predict the defect when a person can see only objects beyond      2m. from his eyes.

8. Suppose your friend's far point of the eye gets reduced,  name     his eye defect.

9. Why does ray of light splits when passed through prism?

10. Calculate the Angle of prism, whose refractive index is 1.5 and angle of minimum deviation is equal to angle of prism.

11. Draw the emergent ray, incident ray, refracted ray when a light ray passes through a prism.

ATOMIC STRUCTURE

 

1. Explain electromagnetic spectrum.

2. What is the relation between E, h, frequency

3. Write the units of planck's constant.

4. Explain the progress of explanation on structure of atom

5. What is the importance of Quantum numbers and write the quantum numbers for an electron which is in 4th orbit's s orbital.

6. Where and when do you apply different principles used while writing electronic configuration.

7. Write the energy levels of different orbitals in ascending order and give the reason why the electron does not enter into 3d instead of 4s

PERIODIC CLASSIFICATION OF THE ELEMENTS

1. Define atomic mass and atomic number.

2. How the atomic mass was used earlier for scientists to classify the elements.  Do all these laws valid or not?

3. Which is said to be modern law classification of elements. Explain

4. How can you identify the group and period of a given element.

5. What are the properties of atom.  Explain the variations and factors affecting the properties.

6. How can you say a block is s-block, p-block, d-block, f-block?

7. Describe the metallic and non-metallic property of the elements.

8. List out the Lanthanides and actinides.

CURRENT ELECTRICITY & ELECTROMAGNETISM

1. Write the units for electric current, charge, emf, potential difference, work done, magnetic flux, magnetic induction.

2. How electricity and magnetism are related.

3. Explain the working of a battery and when do you say a battery is able to convert chemical energy into electric energy.

4. Describe in your own words about a conductor when it is in open and closed circuit.

5. What are the differences between emf and potential difference.  When emf will be potential difference? Do they equal or not?

6. Draw a circuit diagram consists of three resistors, one battery, a plug key.

7. Solve the net current using Kirchoff's laws. 

8. Apply Kirchoff's voltage or loop law to find out unknown resistance or unknown current flowing through the circuit.

9. Write all the factors affecting the resistance of a conductor, write the ohm's law and how do you verify experimentally?

10. What is electromagnetic induction? How Lenz's law related to it.

11. Explain Faraday's law of electromagnetic induction.

12. Write the differences among when the current is flowing through a straight conductor, circular coil and a solenoid.

13. What are the parts present in an electric motor and dynamo.

14. Can you produce electricity from a motor?

15. Write the differences between a.c. dynamo and d.c. dynamo.

16. How oersted's experiment is helpful to understand the relation between electricity and magnetism.

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EXPERIMENTS IN PHYSICS AND CHEMISTRY

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EXPERIMENT 1: 

AIM:

DEMONSTRATING CONVERGENT RAYS AND DIVERGENT RAYS




Materials required: Rubber foam piece, slipper sole, Pins

Procedure: To understand convergent rays and divergent rays from mirror, we need to take a small piece of rubber foam and draw a straight line. Put the pins along the line drawn, and appears as straight lines coming out from the foam, now bend the piece of rubber foam inwards, and then we can observe that the pins meet at a point, and now bend the rubber foam, outwards then the pins appear that they are moving away from each other.



Conclusions:  Convergent rays meet to a point and divergent rays move away from each other.  The experiment also help us to understand the concept of normals to the curved surfaces, in the first case, the pins act as normals to the concave mirror and in the second case, the pins move away from a point.  The distance between converged or diverged point to surface is called Radius of curvature and the line is called normal.   

EXPERIMENT 2:

AIM: To find the focal length of a given concave mirror.

Materials required : Concave mirror, Screen, V-Stand (holder),                                          meter scale

Procedure: Collect the required materials from your laboratory, take V-stand and place the concave mirror in V-Stand, and to find the focal length of the concave mirror, we can use sun or tree or a person at a distance can be chosen as an object.  If you suppose sun as the object, then face the reflecting surface towards sun, and observe the clear image of the sun as a smallest bright spot on the screen or white paper, if you suppose tree as an object, then face the reflecting surface of the mirror towards the tree and observe an inverted image of the tree on the screen or a white paper.  

                 The distance from the image to the pole of the mirror is known as focal length of the mirror.  This distance is the distance between image and mirror as observed practically.

                We can observe the variation in size of the image when we move the screen towards or away from the Focus.

Precautions: Measure the distance accurately, look at the size of the screen or white paper which should not obstruct incoming sun rays.

EXPERIMENT 3:

AIM: To find the focal length of the given convex lens

Materials required: Convex lens, V-stand, screen, candle,                                              meter scale

Procedure: 

                       Collect apparatus or materials required from laboratory, place the convex lens in v-stand, and place the screen on one side of the lens, and allow the light rays coming from distant object such as a tree.  Adjust the distance from the screen to the lens such that the image of the tree should be clear.  The distance from the image to the optic center of the lens is called the focal length of the lens.  

Precautions: screen, lens should be on the same line.

Result:

Focal length can be also called as minimum limiting object distance. 

EXPERIMENT 4:

AIM: To understand the change in focal length of lens with surrounding medium

Materials required: Convex lens, Circular lens holder, glass tumbler, Black stone

Procedure: 

Before doing the experiment, find out the focal length of the given convex lens using distant object method, and note down the value.  Use the same lens and place in a lens holder.  Place a black stone at the bottom in glass tumbler which is filled with water.  Now slowly, place the lens holder with lens into the water, to see the clear image of the black stone.  The distance from the black stone to the lens will become the focal length of the lens.  

Precautions: Place the lens holder slowly into the water, the length of the tumbler should be at least 5 times than that of the focal length of the lens.  

Result & Observations:

We observe that the focal length of the convex lens is increased when it is placed in water.  We understand that the focal length depends on surrounding medium of the lens also.

  

EXPERIMENT 5

AIM: To calculate/find the Least distance of distinct vision of eye

Materials required: 30 cm scale, Any printed material(news paper, textbook), observer

Procedure:

To identify the least distance of distinct vision of eye, read a text book or news paper, at certain distance from your eye.  Now you are able to read the contents from the book or paper, now you try to move the book or paper towards your eye till the contents are unable to read by you.  Then you try to increase the distance from your eyes till you get clear/clarity of the letters.  Ask your friend to measure the distance between your eyes and the book, this distance will be the least distance of the distinct vision of your eyes. Check the distance frequently, you can understand that whether there is any eye defect or not.

Precautions:

Hold the book properly, measure the distances accurately.

Conclusion: 

Least distance of distinct vision can be varied with age.


EXPERIMENT 6



AIM: To understand dispersion of light - splitting of white light ray into seven colours

Materials required: Prism, Source of white light, [a dark room], a screen

Procedure .....The splitting of white light ray into its constituent colours is known as dispersion.  To do this activity, take a prism and white light source and allow the white light to pass through the prism, then we get seven colours called VIBGYOR.

Precautions: To get a narrow beam of light, white light should be allowed to pass through a small hole of paper or wooden plank.


Observations: When white light passes through a prism, dispersion takes place and refraction can be observed.  

The angle of deviation is different for different colours.  Violet is deviated maximum and red is deviated least. 




EXPERIMENT 7:

AIM: To prove white light is constituent of seven colors.

MATERIALS REQUIRED: Plane mirror, sunlight from sun, small tub with water

PROCEDURE:

Take small tub and fill it with water, place the plane mirror in water such that it makes some angle with water surface and make it in the presence of sunlight, the water droplets act as prism and makes the white light into seven colors and these are reflected from the mirror and arrange the reflected light to fall on to the white wall.  One can observe the formation of rainbow.  

precautions to be taken:

1. arrange the demonstration under the presence of sun light.

2. the mirror should be at certain angle to the surface of water

Observations:

-white light is constituent of seven colors (VIBGYOR).

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