Surface Tension

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INTRODUCTION

Surface tension is a property of the surface of a liquid that allows it to resist an Surface tension is a property of the surface of a liquid that allows it to resist an external force. It causes liquid surfaces to behave as stretched elastic membranes. This external force. It causes liquid surfaces to behave as stretched elastic membranes. This property is caused by cohesion of like molecules, and is responsible for many of the behaviors property is caused by cohesion of like molecules, and is responsible for many of the behaviors of liquids. Its strength depends on the forces of attraction among the particles of the liquid of liquids. Its strength depends on the forces of attraction among the particles of the liquid itself and with the particles of the gas, solid, or liquid with which it comes in contact. The itself and with the particles of the gas, solid, or liquid with which it comes in contact. The surface tension is very much visible to us in our everyday life, for instance in floating of some surface tension is very much visible to us in our everyday life, for instance in floating of some objects on the surface of water, even though they are denser than water, and in the ability of objects on the surface of water, even though they are denser than water, and in the ability of some insects (e.g. water striders) and even reptiles (basilisk) to run on the water surface. The some insects (e.g. water striders) and even reptiles (basilisk) to run on the water surface. The spherical shape of the liquid drops is also due to surface tension. Quantitatively, surface tension spherical shape of the liquid drops is also due to surface tension. Quantitatively, surface tension is defined as the force acting normally per unit length of a line drawn on the surface of the is defined as the force acting normally per unit length of a line drawn on the surface of the liquid. Surface tension has the

liquid. Surface tension has the dimensiondimension of of forceforce per unitper unit lengthlength or of or of energyenergy per unitper unit areaarea. The. The two are equivalentbut when referring to energy per unit of area the term

two are equivalentbut when referring to energy per unit of area the term surface energysurface energy isis used which is a more general term in the sense that it applies also to

used which is a more general term in the sense that it applies also to solidssolids and not just liquids.and not just liquids. In materials scien

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CAUSE OF SURFACE TENSION

The cohesive forces among the liquid molecules are responsible for this The cohesive forces among the liquid molecules are responsible for this phenomenon of surface tension. In the bulk of the liquid, each molecule is pulled equally in phenomenon of surface tension. In the bulk of the liquid, each molecule is pulled equally in every direction by neighbouring liquid molecules, resulting in a net force of zero. The molecules every direction by neighbouring liquid molecules, resulting in a net force of zero. The molecules at the surface do not have other molecules on all sides of them and therefore are pulled at the surface do not have other molecules on all sides of them and therefore are pulled inwards. This creates some internal pressure and forces liquid surfaces to contract to the inwards. This creates some internal pressure and forces liquid surfaces to contract to the minimal area.

minimal area.

Surface tension is responsible for the shape of liquid droplets. Although easily Surface tension is responsible for the shape of liquid droplets. Although easily deformed, droplets of water tend to be pulled into a spherical shape by the cohesive forces of deformed, droplets of water tend to be pulled into a spherical shape by the cohesive forces of the surface layer. In the absence of other forces, including gravity, drops of virtually all liquids the surface layer. In the absence of other forces, including gravity, drops of virtually all liquids would be perfectly spherical. The spherical shape minimizes the necessary "wall tension" of the would be perfectly spherical. The spherical shape minimizes the necessary "wall tension" of the surface layer according to Laplace's law.

surface layer according to Laplace's law.

Another way to view it is in terms of energy. A molecule in contact with a Another way to view it is in terms of energy. A molecule in contact with a neighbour is in a lower state of energy than if it were alone (not in contact with a neighbour). neighbour is in a lower state of energy than if it were alone (not in contact with a neighbour). The interior molecules have as many neighbours as they can possibly have, but the boundary The interior molecules have as many neighbours as they can possibly have, but the boundary molecule

molecules are ms are missing neighbourissing neighbours (compared to s (compared to interior moleculinterior molecules) and therefore es) and therefore have a have a higherhigher energy. For the liquid to minimize its energy state, the number of higher energy boundary energy. For the liquid to minimize its energy state, the number of higher energy boundary molecules must be minimized. The minimized quantity of boundary molecules results in a molecules must be minimized. The minimized quantity of boundary molecules results in a minimized surface area.

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The principle behind the phenomenon can be explained using the basic The principle behind the phenomenon can be explained using the basic molecula

molecular theory r theory as follows.as follows.

Liquids, according to the Molecular theory, are made up of molecules. Let KLMN Liquids, according to the Molecular theory, are made up of molecules. Let KLMN represent a surface film of thickness LM, which is same as the molecular range. Consider three represent a surface film of thickness LM, which is same as the molecular range. Consider three molecules A, B, C at different positions. The molecule A experiences force of attraction equally molecules A, B, C at different positions. The molecule A experiences force of attraction equally in all directions, due to its neighbouring molecules. The solid circle represents its sphere of in all directions, due to its neighbouring molecules. The solid circle represents its sphere of influence (whose radius is equal to the molecular range). Therefore, the net force acting on A is influence (whose radius is equal to the molecular range). Therefore, the net force acting on A is zero. Consider the molecule at B (till below the surface). Like A, even B experiences a force of zero. Consider the molecule at B (till below the surface). Like A, even B experiences a force of attraction due to its neighbouring molecules. But unlike A, B is not pulled equally on all sides attraction due to its neighbouring molecules. But unlike A, B is not pulled equally on all sides and experiences a net pull downward. This is because it experiences more attraction due to and experiences a net pull downward. This is because it experiences more attraction due to number of molecules inside the liquid. Coming to molecule 'C', we find that it experiences a number of molecules inside the liquid. Coming to molecule 'C', we find that it experiences a greater downward pull because it is attracted by even lesser numbers of molecules. The greater downward pull because it is attracted by even lesser numbers of molecules. The downward force or pull experienced by molecules B and C is called the force of cohesion. In downward force or pull experienced by molecules B and C is called the force of cohesion. In other words, the force of cohesion represents t

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If one has to bring a molecule like A to the surface KL, then work has to be done If one has to bring a molecule like A to the surface KL, then work has to be done against this force of cohesion. Therefore, this work done is stored as potential energy of the against this force of cohesion. Therefore, this work done is stored as potential energy of the molecule. This means that the sur

molecule. This means that the surface film has potential energy. Greater the number face film has potential energy. Greater the number of moleculesof molecules on the surface, greater is the potential energy of the film. We know that every system in the on the surface, greater is the potential energy of the film. We know that every system in the universe tends to acquire a minimum potential energy. In order to attain stable equilibrium, the universe tends to acquire a minimum potential energy. In order to attain stable equilibrium, the surface film also tends to have minimum P.E. and so, the number of molecules in the surface surface film also tends to have minimum P.E. and so, the number of molecules in the surface film is minimum. Since the thickness of the film (LM or KN) is fixed, the surface area has to film is minimum. Since the thickness of the film (LM or KN) is fixed, the surface area has to minimum in order to acquire minimum volume. In an attempt to minimize the surface area, the minimum in order to acquire minimum volume. In an attempt to minimize the surface area, the film contracts and acts like a stretched

film contracts and acts like a stretched membrane.membrane.

Fig.3 Direction of Surface Tension Fig.3 Direction of Surface Tension

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FACTORS AFFECTING SURFACE TENSION

Surface tension varies from liquid to liquid and also with the change in the Surface tension varies from liquid to liquid and also with the change in the conditions available. Primarily surface tension of a liquid is governed by the strength of conditions available. Primarily surface tension of a liquid is governed by the strength of intermolecular attractive forces. Therefore, the magnitude of surface tension is a measure of intermolecular attractive forces. Therefore, the magnitude of surface tension is a measure of intermole

intermolecular attractive forces. The ccular attractive forces. The conditions affecting surface tension are onditions affecting surface tension are as follows:as follows:

y

y TemperatureTemperature y

y Solute concentrationSolute concentration y

y Presence of ContaminantsPresence of Contaminants

Effect of Temperature: Effect of Temperature:

Surface tension is dependent on temperature. For that reason, when a value is Surface tension is dependent on temperature. For that reason, when a value is given for the surface tension of an interface, temperature must be explicitly stated.

given for the surface tension of an interface, temperature must be explicitly stated. SurfaceSurface tension decreases with rise in temperature, almost linearly. The decrease of surface tension tension decreases with rise in temperature, almost linearly. The decrease of surface tension with increase in temperature results because the kinetic energy (or speeds) of the molecules with increase in temperature results because the kinetic energy (or speeds) of the molecules increases. Thus, the strength of intermolecular forces decreases resulting in the decrease of increases. Thus, the strength of intermolecular forces decreases resulting in the decrease of surface tension also. For example, clothes are washed more efficiently in hot water than in cold surface tension also. For example, clothes are washed more efficiently in hot water than in cold water due to decreased surface tension in hot water.

water due to decreased surface tension in hot water.

The surface tension of all

The surface tension of all substances reduces to zero at substances reduces to zero at a particular temperature knowna particular temperature known as the critical temperature which is intrinsic to

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There are only empirical relations connecting surface tension and temperature. There are only empirical relations connecting surface tension and temperature. The most accurate among them is the Eotvas equation. According to Eotvas the effect of The most accurate among them is the Eotvas equation. According to Eotvas the effect of temperature on surface tension is given by the equation.

temperature on surface tension is given by the equation.

Where,  = s

Where,  = surface tension, k = constant, V=Murface tension, k = constant, V=Molar volume of olar volume of the substance, the substance, Tc =Tc = critical temperature and T= temperature

critical temperature and T= temperature

As 'T' approaches critical temperature, the surface tension becomes zero. At this As 'T' approaches critical temperature, the surface tension becomes zero. At this stage the meniscus between the liquid and vapour disappears.

stage the meniscus between the liquid and vapour disappears.

Variation of surface tension with temperature Variation of surface tension with temperature

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Effects of Solute

Effects of Solute ConcentratioConcentration:n:

Solutes can have different effects on surface tension depending on their Solutes can have different effects on surface tension depending on their structure:

structure:

y

y Little or no effect, for example sugarLittle or no effect, for example sugar y

y Increase surface tension, inorganic saltsIncrease surface tension, inorganic salts y

y Decrease surface tension progressively. Alcohols, phenol etc.Decrease surface tension progressively. Alcohols, phenol etc. y

y Decrease surface tension and, once a minimum is reached, no more effect: surfactantsDecrease surface tension and, once a minimum is reached, no more effect: surfactants

like detergents like detergents

What complicates the effect is that a solute can exist in a different concentration at the surface What complicates the effect is that a solute can exist in a different concentration at the surface of a solvent than in

of a solvent than in its bulk. This difference varies from one solute/solvent combination to another.its bulk. This difference varies from one solute/solvent combination to another.

Effect of

Effect of Contamination:Contamination:

The presence of dust, oil or grease on the surface of water, reduces the surface The presence of dust, oil or grease on the surface of water, reduces the surface tension of water. Impurities affect surface tension appreciably. It is observed that impurities, tension of water. Impurities affect surface tension appreciably. It is observed that impurities, which tend to concentrate on the surface of liquids, compared to its bulk lower the surface which tend to concentrate on the surface of liquids, compared to its bulk lower the surface tension.

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EFFECTS OF SURFACE TENSION

Capillary Rise in a Vertical Tube

Capillary action is the result of adhesion and surface tension. Adhesion of water Capillary action is the result of adhesion and surface tension. Adhesion of water to the walls of a vessel will cause an upward force on the liquid at the edges and result in a to the walls of a vessel will cause an upward force on the liquid at the edges and result in a meniscus whic

meniscus which turns upward. The surface tension acts to h turns upward. The surface tension acts to hold the surface intact, so instead of hold the surface intact, so instead of just the edges moving upward, the whole liquid surface is dragged upward. The height to which just the edges moving upward, the whole liquid surface is dragged upward. The height to which

water rises decreases with increase in the radius of the capillary tube. water rises decreases with increase in the radius of the capillary tube.

Capillary action occurs when the adhesion to the walls is stronger than the Capillary action occurs when the adhesion to the walls is stronger than the cohesive forces between the liquid molecules. The height to which capillary action will take cohesive forces between the liquid molecules. The height to which capillary action will take water in a uniform circular tube is limited by surface tension. Acting around the circumference, water in a uniform circular tube is limited by surface tension. Acting around the circumference, the upward force is:

the upward force is:



  





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      

The height h to which capillary action will lift water depends upon the weight of The height h to which capillary action will lift water depends upon the weight of water which the surface tension will lift:

water which the surface tension will lift:



The height to which the liquid can be lifted is given by The height to which the liquid can be lifted is given by

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P

_{ressure inside a Bubble}

The surface tension of water provides the necessary wall tension for the The surface tension of water provides the necessary wall tension for the formation of bubbles with water and for the shape of liquid droplets. Although easily deformed, formation of bubbles with water and for the shape of liquid droplets. Although easily deformed, droplets of water tend to be pulled into a spherical shape by the

droplets of water tend to be pulled into a spherical shape by the cohesivecohesive forces of the surfaceforces of the surface layer. The spherical shape minimizes then necessary "wall tension" of the surface layer layer. The spherical shape minimizes then necessary "wall tension" of the surface layer according to

according to Laplace¶s lawLaplace¶s law..

The pressure difference between the inside and outside of a bubble depends The pressure difference between the inside and outside of a bubble depends upon the surface tension and the radius of the bubble. The relationship can be obtained by upon the surface tension and the radius of the bubble. The relationship can be obtained by visualizing the bubble as two hemispheres and noting that the internal pressure which tends to visualizing the bubble as two hemispheres and noting that the internal pressure which tends to push the hemispheres apart is counteracted by the surface tension acting around the push the hemispheres apart is counteracted by the surface tension acting around the circumference of the circle. For a bubble with two surfaces providing tension, the pressure circumference of the circle. For a bubble with two surfaces providing tension, the pressure relationship is:

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The net upward force on the top hemisphere of the bubble is just the pressure The net upward force on the top hemisphere of the bubble is just the pressure difference times the area of the equatorial circle:

difference times the area of the equatorial circle:

The surface tension force downward around circle is twice the surface tension The surface tension force downward around circle is twice the surface tension times the circumference, since two surfaces contribute to the f

times the circumference, since two surfaces contribute to the force:orce:

This gives This gives

This latter case also applies to the case of a bubble surrounded by a liquid, such This latter case also applies to the case of a bubble surrounded by a liquid, such

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SURFACE TENSION OF WATER

Water is one of the liquids exhibiting great surface tension. The surface tension Water is one of the liquids exhibiting great surface tension. The surface tension of water is 71.97 dynes/cm at 25°C. It would take a force of 72 dynes to break a surface film of of water is 71.97 dynes/cm at 25°C. It would take a force of 72 dynes to break a surface film of water 1 cm long. The surface tension of water decreases significantly with temperature as water 1 cm long. The surface tension of water decreases significantly with temperature as shown in the graph. The surface tension arises from the polar nature of the water molecule. shown in the graph. The surface tension arises from the polar nature of the water molecule. Soaps and detergents further lower the surface tension. Critical temperature of water is 374 °C Soaps and detergents further lower the surface tension. Critical temperature of water is 374 °C or 647K.

or 647K.

Temperature

Temperature Surface Surface TensionTension

0 75.64 0 75.64 25 71.97 25 71.97 50 67.91 50 67.91 100 58.85 100 58.85

Graph Showing variation of Surface Tension with Temperature Graph Showing variation of Surface Tension with Temperature

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COMMON EXAMPLES OF SURFACE TENSION

Cleansing Action of Detergents

Detergents and soaps are used for cleaning because pure water can't remove Detergents and soaps are used for cleaning because pure water can't remove oily, organic soiling. Soap cleans by acting as an emulsifier. Basically, soap allows oil and water oily, organic soiling. Soap cleans by acting as an emulsifier. Basically, soap allows oil and water to mix so that oily grime can be removed during rinsing. Detergents are primarily surfactants, to mix so that oily grime can be removed during rinsing. Detergents are primarily surfactants, which could be produced easily from petrochemicals. Surfactants lower the surface tension of which could be produced easily from petrochemicals. Surfactants lower the surface tension of water, essentially making it 'wetter' so that it is less likely to stick to itself and more likely to water, essentially making it 'wetter' so that it is less likely to stick to itself and more likely to interact with oil and grease.

interact with oil and grease.

Washing with cold water

The major reason for using hot water for washing is that its surface tension is The major reason for using hot water for washing is that its surface tension is lower and it is a better wetting agent. But if the detergent lowers the surface tension, the lower and it is a better wetting agent. But if the detergent lowers the surface tension, the heating may be unnecessary.

heating may be unnecessary.

Surface tension disinfectants

Disinfectants are usually solutions of low surface tension. This allows them to Disinfectants are usually solutions of low surface tension. This allows them to spread out on the cell walls of bacteria and disrupt them. One such disinfectant, S.T.37, has a spread out on the cell walls of bacteria and disrupt them. One such disinfectant, S.T.37, has a name which points to its low surface tension compared to the 72.8

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Clinical test for jaundice

Normal urine has a surface tension of about 66 dynes/cm but if bile is present (a Normal urine has a surface tension of about 66 dynes/cm but if bile is present (a test for jaundice), it drops to about 55. In the Hay test, powdered sulfur is sprinkled on the test for jaundice), it drops to about 55. In the Hay test, powdered sulfur is sprinkled on the urine surface. It will float on normal urine, but sink if the S.T. is lowered by the bile.

urine surface. It will float on normal urine, but sink if the S.T. is lowered by the bile.

Shape of Liquid Droplets

Surface tension is responsible for the shape of liquid droplets. Although easily Surface tension is responsible for the shape of liquid droplets. Although easily deformed, droplets of water tend to be pulled into a spherical shape by the cohesive forces of deformed, droplets of water tend to be pulled into a spherical shape by the cohesive forces of the surface layer. A water droplet can act as lens and form an image as a simple magnifier. The the surface layer. A water droplet can act as lens and form an image as a simple magnifier. The relativel

relatively high surface tension y high surface tension of water accounts for the of water accounts for the ease with which it ease with which it can be can be nebulinebulized, orzed, or placed into aerosol form.

placed into aerosol form.

Floating of needle on water

If carefully placed on the surface, a small needle can be made to float on the If carefully placed on the surface, a small needle can be made to float on the surface of water even though it is several times as dense as water. If the surface is agitated to surface of water even though it is several times as dense as water. If the surface is agitated to break up the surface tension, then needle will quickly sink.

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METHODS OF MEASURING SURFACE TENSION

Because surface tension manifests itself in various effects, it offers a number of Because surface tension manifests itself in various effects, it offers a number of paths to its measurement. Which method is optimal depends upon the nature of the liquid paths to its measurement. Which method is optimal depends upon the nature of the liquid being measured, the conditions under which its tension is to be measured, and the stability of being measured, the conditions under which its tension is to be measured, and the stability of its surface when it is deformed

its surface when it is deformed

y

y Capillary rise method: The end of a capillary is immersed into the solution. The height atCapillary rise method: The end of a capillary is immersed into the solution. The height at

which the solution reaches inside the capillary is related to the surface tension by the which the solution reaches inside the capillary is related to the surface tension by the equation discussed below.

equation discussed below.

y

y StalagmometriStalagmometric method: A c method: A method of weighting and reading a method of weighting and reading a drop of drop of liquidliquid..

y

y Wilhelmy plate method: A universal method especially suited to check surface tensionWilhelmy plate method: A universal method especially suited to check surface tension

over long time intervals. A vertical plate of known perimeter is attached to a balance, over long time intervals. A vertical plate of known perimeter is attached to a balance, and the force due to wetting is measured.

and the force due to wetting is measured.

y

y Spinning drop method: This technique is ideal for measuring low interfacial tensions.Spinning drop method: This technique is ideal for measuring low interfacial tensions.

The diameter of a drop within a heavy phase is measured while both are rotated. The diameter of a drop within a heavy phase is measured while both are rotated.

y

y Pendant drop method: Surface and interfacial tension can be measured by thisPendant drop method: Surface and interfacial tension can be measured by this

technique, even at elevated temperatures and pressures. Geometry of a drop is technique, even at elevated temperatures and pressures. Geometry of a drop is analyzed optically. For details, see Drop.

analyzed optically. For details, see Drop.

y

y Sessile drop method: A method for determining surface tension and density by placing aSessile drop method: A method for determining surface tension and density by placing a

drop on a

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EXPERIMENT TO DETERMINE THE SURFACE

TENSION OF WATER BY CAPILLARY RISE METHOD

Aim:

Aim: To determine the surface tension of water by capillary rise methodTo determine the surface tension of water by capillary rise method

Apparatus:

Apparatus: Capillary tube, needle, a beaker of clean water, travelling microscope.Capillary tube, needle, a beaker of clean water, travelling microscope.

Theory: Theory:

A capillary tube, open at both ends when dipped vertically in a liquid the liquid A capillary tube, open at both ends when dipped vertically in a liquid the liquid level rises in the tube due to surface tension. Let h be the capillary ascent of liquid in the tube level rises in the tube due to surface tension. Let h be the capillary ascent of liquid in the tube and  the density of the

and  the density of the liquid. The surface tension is given by the formula:liquid. The surface tension is given by the formula:



 



   

 

Where, r is the radius of capillary tube, Where, r is the radius of capillary tube,

h the capillary ascent h the capillary ascent  the density of water,  the density of water,

g the acceleration due to gravity and g the acceleration due to gravity and 

 is the angle of contactis the angle of contact

P

P_rocedure:_rocedure:

Place the adjustable height stand on the table and make its base horizontal by Place the adjustable height stand on the table and make its base horizontal by leveling screws. Place a beaker containing clean water on the stand. Find the least count of the leveling screws. Place a beaker containing clean water on the stand. Find the least count of the travelling microscope for the horizontal and vertical scale. Raise the microscope to a suitable travelling microscope for the horizontal and vertical scale. Raise the microscope to a suitable height, keeping its axis horizontal and pointed towards the capillary tube. Make the horizontal height, keeping its axis horizontal and pointed towards the capillary tube. Make the horizontal

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cross wire just touch the central part of the central part of the concave meniscus (seen convex cross wire just touch the central part of the central part of the concave meniscus (seen convex through the microscope as in Fig. 1). Note the reading of the microscope on the vertical scale. through the microscope as in Fig. 1). Note the reading of the microscope on the vertical scale. Now lower the travelling microscope so that the horizontal cross-wire coincides with the tip of Now lower the travelling microscope so that the horizontal cross-wire coincides with the tip of the pointer. Note down the reading. The difference in their readings gives the capillary rise in the pointer. Note down the reading. The difference in their readings gives the capillary rise in the tube.

the tube.

Fig.1 Water Meniscus through microscope

Fig.1 Water Meniscus through microscope Fig.2 Measurement of inner diameterFig.2 Measurement of inner diameter

To measure the inner diameter of the capillary tube, place the tube horizontally To measure the inner diameter of the capillary tube, place the tube horizontally on the stand. Focus the microscope on the end of the tube which was earlier dipped in water. A on the stand. Focus the microscope on the end of the tube which was earlier dipped in water. A white circle (the inner bore) surrounded by a green strip (glass cross-section) will be seen as white circle (the inner bore) surrounded by a green strip (glass cross-section) will be seen as shown in Fig.2. Make the horizontal cross wire touch the inner circle at A. Note the microscopic shown in Fig.2. Make the horizontal cross wire touch the inner circle at A. Note the microscopic reading on the vertical scale. Now lower the microscope so that the horizontal crosswire reading on the vertical scale. Now lower the microscope so that the horizontal crosswire touches the inner circle at B. Again note down the reading. The difference of these values gives touches the inner circle at B. Again note down the reading. The difference of these values gives the vertical inner diameter of the capillary tube. Now move the microscope on the horizontal the vertical inner diameter of the capillary tube. Now move the microscope on the horizontal scale and make the vertical cross wire touch the inner circle at C. Move it to the right to make scale and make the vertical cross wire touch the inner circle at C. Move it to the right to make

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the vertical crosswire touch the circle at D. Note the reading. The difference of the readings the vertical crosswire touch the circle at D. Note the reading. The difference of the readings gives the horizontal inner diameter of the capillary tube.

gives the horizontal inner diameter of the capillary tube.

The angle of contact of water in glass

The angle of contact of water in glass is 8. Thereforeis 8. Therefore =0.99027  1=0.99027  1

The following Observations are recorded: The following Observations are recorded:

P

P_{reliminary Observations for the Travelling Microscope}_{reliminary Observations for the Travelling Microscope}

Value of one division on the main scale = 0.5 mm Value of one division on the main scale = 0.5 mm

No: of divisions on the Vernier Scale = 50 No: of divisions on the Vernier Scale = 50

Least Count = Least Count =   _{}_{}____{}_{}

=

 __   = 0.01mm= 0.01mm

Table for Capillary Rise Table for Capillary Rise

Sl Sl No. No.

Position of the cross Position of the cross wire

wire

Microscope

Microscope Reading Reading Capillary Capillary RiseRise (Difference between (Difference between the readings) the readings) (mm) (mm) MSR MSR (mm) (mm) VSR Total=MSR+VSRXLC VSR Total=MSR+VSRXLC (mm) (mm) 1

1 At At the the MeniscuMeniscus s 43.5 43.5 14 14 43.6443.64

33.54 33.54 2

2 At At the the tip tip of of thethe Pointer

Pointer

10.0

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Table for the inner diameter of the

Table for the inner diameter of the capillary tubecapillary tube

Sl Sl No.

No. Measurement Measurement Position Position of of the cross wire the cross wire

Microscop

Microscope e Reading Reading Capillary Capillary RiseRise (Difference (Difference between the between the readings) readings) (mm) (mm) MSR MSR (mm) (mm) VSR Total=MSR+VSRXLC VSR Total=MSR+VSRXLC (mm) (mm) 1

1 Vertical Vertical InnerInner Diameter Diameter (i)Upper edge (i)Upper edge of the tube of the tube 119 119 39 39 119.39119.39 1.01 1.01 (ii)At the tip

(ii)At the tip of the Pointer of the Pointer 120 120 40 40 120.40120.40 2 Horizontal 2 Horizontal inner inner Diameter Diameter

(i)Left Edge of (i)Left Edge of the tube the tube 1 1 15 15 1.151.15 0.85 0.85 (ii)Right Edge (ii)Right Edge of the tube of the tube 0 0 30 30 0.300.30 Mean Diameter = 0.93mm = 0.93x10 Mean Diameter = 0.93mm = 0.93x10-3-3mm Result: Result: 1.

1. Capillary Rise (h) = 30.4 mm = 30.4x10Capillary Rise (h) = 30.4 mm = 30.4x10-3-3mm 2.

2. Radius of Capillary Tube (r)=d/2= Radius of Capillary Tube (r)=d/2= 0.47mm=0.470.47mm=0.47x10x10-3-3mm

3.

3. Surface Tension of Water =Surface Tension of Water =     



=

7.18x107.18x10

-2 -2_N/m_N/m

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CONCLUSION

Physics, the science of matter and its motion, space-time and energy is relevant Physics, the science of matter and its motion, space-time and energy is relevant in each of our activities. Everything surrounding to us is made of matter and Physics explains in each of our activities. Everything surrounding to us is made of matter and Physics explains matter as combinations of fundamental particles which are interacting through fundamental matter as combinations of fundamental particles which are interacting through fundamental forces. It will not be an exaggeration if it is said that Nature is almost Physics (in fact the word forces. It will not be an exaggeration if it is said that Nature is almost Physics (in fact the word Physics itself is derived from the Greek word

Physics itself is derived from the Greek word physis physis meaning nature). Physics is all around us.meaning nature). Physics is all around us. The importance of physics to society today is most easily represented by our reliance on The importance of physics to society today is most easily represented by our reliance on technology. Surface tension is just one of the innumerous physical phenomena that influence technology. Surface tension is just one of the innumerous physical phenomena that influence our day to day life. Even a concept wise small effect like it influences our life to an unimaginable our day to day life. Even a concept wise small effect like it influences our life to an unimaginable extent. The application of it ranges widely from the washing action of detergents to surface extent. The application of it ranges widely from the washing action of detergents to surface travel of water striders. The phenomenon is also evident in the spherical shape of liquid travel of water striders. The phenomenon is also evident in the spherical shape of liquid droplets, bubbl

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BIBLIOGRAPHY

Books

y

y Concepts of Physics 1 by H.C.VermaConcepts of Physics 1 by H.C.Verma

y

y Mechanics 2 by D.C.PandeyMechanics 2 by D.C.Pandey

y

y NOOTAN ISC Physics for class XINOOTAN ISC Physics for class XI

y

y ISC Physics PractiISC Physics Practical for class Xcal for class XI I by K.K.Mohindro Pitambarby K.K.Mohindro Pitambar

Websites

y y en.wikipedia.orgen.wikipedia.org y y www.britannica.comwww.britannica.com y y www.tutornext.comwww.tutornext.com y y hyperphysics.gsu.eduhyperphysics.gsu.edu y y www.tutorvista.comwww.tutorvista.com