MALLARI, REJEAN FAITH P.

4 BSABE-B

ABE 413

Laboratory 2

Introduction

Fluid dynamics play a critical role in material processing, as most industrial

processes involve fluids in some capacity—whether as raw materials, reagents,

or heat transfer media. The efficiency and outcome of these processes are

often influenced by the viscosity of the fluid being used. A fluid with low

viscosity, often described as "thin," flows easily, whereas a fluid with high

viscosity, referred to as "thick," flows more slowly and resists movement.

At the core of this behavior is viscosity, a property that measures a fluid's

resistance to flow. It represents the internal friction between different layers of

fluid as they move relative to one another, whether in liquid or gas form. This

friction becomes particularly important when the fluid interacts with surfaces,

as it dictates how easily the fluid can be moved or manipulated. Understanding

viscosity is essential for predicting how fluids will behave in different conditions,

making it a key factor in optimizing industrial processes, from mixing to

pumping and beyond.

This laboratory employs a straightforward method for measuring viscosity.

The procedure involves releasing a ball into a liquid-filled container and

recording the time it takes to descend a predetermined distance. The viscosity

of the liquid is then calculated using a formula that incorporates several

variables, including the density of both the ball and the liquid, the ball's radius,

and its velocity during descent.

Objectives

1. Understand the concept of viscosity and its impact on a fluid's flow behavior

and resistance to movement.

2. Perform a hands-on experiment by dropping a ball into a liquid to measure

its viscosity, while accurately recording the time taken for the sphere to travel a

specific distance.

3. Utilize the viscosity equation to analyze experimental data and accurately

determine the viscosity of the tested liquid.

4. Develop critical thinking and data analysis skills by interpreting

experimental results.

Brief RRL

Kumar (2019) defines viscosity as a fluid’s resistance to deformation under

shear force, often referred to as flow behavior or pouring resistance. It

represents the internal friction within a fluid that opposes its movement.

Viscosity plays a critical role in processing, particularly for liquids whose

viscosity is influenced only by temperature and pressure, known as Newtonian

fluids. Both liquids and gases possess some degree of viscosity, which can be

likened to the friction between solids, resisting motion while still allowing

acceleration.

Viscosity is influenced by several factors, including temperature, pressure,

and the presence of additional molecules. While pressure has a minimal

impact on liquid viscosity and is often disregarded, the introduction of other

substances, such as sugar in water, can significantly increase viscosity.

However, temperature exerts the most pronounced effect on viscosity. In

liquids, higher temperatures reduce viscosity by providing molecules with

sufficient energy to overcome intermolecular forces. In contrast, for gases,

increasing temperature raises viscosity due to the increased frequency of

molecular collisions, as intermolecular forces play a lesser role in gas behavior

(Helmenstine, 2021)

Several methods are employed to measure the viscosity of fluids, typically

based on one of three principles: a moving surface in contact with a fluid, an

object moving through a fluid, and fluid flow through a resistive component.

These principles are realized through three primary types of viscometers

commonly used in the industry: the rotating viscometer, the falling-ball

viscometer, and the capillary viscometer. Among these, the falling-ball

viscometer is particularly effective for viscosity measurement and is

recognized in international standards. In this method, a ball rolls or slides

through the sample liquid within an inclined cylindrical tube. The viscosity of

the fluid is determined by correlating the time it takes for the ball to fall a

specific distance, with results expressed as dynamic viscosity. The absolute

falling-ball viscometer is notable for its capability to accurately measure a

broad range of viscosities while maintaining low uncertainty levels (Yuan & Lin,

2008).

Methods and Materials

Materials:

 Sphere

 Liquid (water, buko juice, alcohol)

 Graduated cylinder
 Ruler

 Timer

 Calculator

 Marker

 Scale or balance

To accurately measure the viscosity of a liquid, you’ll need to gather

specific materials and follow a systematic procedure. Begin by collecting a

small spherical object, such as a marble or a steel ball, ensuring that it has a

higher density than the liquid you are testing so it doesn’t float. Additionally,

you’ll require a graduated cylinder, a ruler, a timer/stopwatch, a calculator, a

marker, and a scale or balance to measure mass.

The first step is to calculate the density of the sphere. This is done by

measuring its mass using the scale and determining its volume, which can be

calculated based on the sphere's dimensions. Afterward, you’ll need to find the

density of the liquid by similarly measuring its mass and volume. Once both

densities are determined, fill the graduated cylinder with the liquid. Using the

grease pencil, mark two distinct positions—one near the top and one near the

bottom of the cylinder—at fixed distances to track the sphere's movement.

Next, gently drop the sphere into the liquid and start the stopwatch as soon

as the bottom of the sphere reaches the upper mark. Stop the stopwatch when

the sphere passes the lower mark. To ensure accuracy, repeat this process at

least three times and then calculate the average time it takes for the sphere to

fall between the two marks.

 Once you have the average time, calculate the velocity of the sphere using
�
the formula � = � where � represents the distance between the marks, and �

is the average time. With the velocity calculated, you can now compute the

viscosity of the liquid using the formula:

2(�� − ��)��2
��������� =
9�
In this equation:
​
�� is the density of the sphere,

�� is the density of the liquid,

� is the acceleration due to gravity (9.8 m/s²),

� is the radius of the sphere, and

� is the velocity you previously calculated.

Results and Discussions

� (mass of the cylinder) = 306g

� (sphere circumference) = diameter of the used sphere is 0.5 in or 1.27 cm
������������� = π�
= 3.14 (1.27)
= 3.99 cm
= 0.0399 m or 1.57 in or 39.9 mm

Sphere density (�� )

� = 5g
4 4
�= (��3 ) = (�(6.35)3 = 1072.53��3
3 3
� 5� � �
�� = = 3 = 4.66187426 × 10−3 3 = �. ��� ��
� 1072.53�� ��

Water Density (�� )

� = 454� − 306� = 148�

� = 150 ��
 � 148� �
�� = = = �. �� ��
� 150��

Alcohol Density (�� )

� = 435� − 306� = 129�

� = 150 ��
� 129� �
�� = = = �. �� ��
� 150��

Buko Juice Density (��)

� = 452� − 306� = 146�

� = 150 ��
� 146� �
�� = = = �. �� ��
� 150��

Table 1. Data Gathered

Water
Time (s) Distance (m)
Trial 1 0.22 0.095
Trial 2 0.30 0.095
Trial 3 0.26 0.095
Average 0.26 0.095
Velocity (m/s) 0.365
Viscosity (Pa. s) 0.000788

� 0.095
�������� = = = �. ��� �/�
� 0.26
2(4.662−0.99)(9.8)(0.006)2
��������� = = 0.000788 Pa. s
9(0.365)

Buko Juice
Time (s) Distance (m)
Trial 1 0.40 0.095
Trial 2 0.19 0.095
Trial 3 0.19 0.095
Average 0.26 0.095
Velocity (m/s) 0.365
Viscosity (Pa. s) 0.000882
 � 0.095
�������� = = = �. ��� �/�
� 0.26
2(4.662−0.97)(9.8)(0.006)2
��������� = = 0.000882 Pa. s
9(0.365)

Alcohol
Time (s) Distance (m)
Trial 1 0.37 0.095
Trial 2 0.28 0.095
Trial 3 0.22 0.095
Average 0.29 0.095
Velocity (m/s) 0.328
Viscosity (Pa. s) 0.000909

� 0.095
�������� = = = �. ��� �/�
� 0.29
2(4.662−0.86)(9.8)(0.006)2
��������� = 9(0.328)
= 0.000909 Pa. s

The experimental results indicate that alcohol exhibits the highest viscosity

among the tested liquids, with a measured value of 0.000909 Pa.s. This is

followed by buko juice, which has a viscosity of 0.000882 Pa.s, and water,

which is the least viscous at 0.000788 Pa.s. The slower descent of the marble

in the alcohol-filled cylinder, compared to its faster drop in buko juice and water,

provides a clear visual confirmation of alcohol's higher viscosity.

Viscosity, however, is not a fixed property and can be influenced by

several external factors. Variables such as temperature, pressure, and the

presence of impurities can significantly alter the internal friction of a fluid,

thereby affecting its viscosity. For instance, higher temperatures generally

reduce viscosity, while impurities may increase it. Understanding these factors

is essential for explaining the mechanics behind viscosity and its behavior.
Summary and Conclusion

The falling sphere method is a straightforward technique for measuring the

viscosity of various liquids, showcasing the differences in fluid resistance. In a

recent experiment, alcohol was identified as having the highest viscosity at

0.000909 Pa.s, followed by buko juice at 0.000882 Pa.s, while water had the

lowest viscosity at 0.000788 Pa.s. This was visually confirmed by the slower

descent of the marble in alcohol compared to its faster fall in buko juice and

water.

The results underscore the significant impact of viscosity on fluid behavior.

It is essential to recognize that viscosity is not constant; it varies with external

factors such as temperature, pressure, and impurities. Generally, increasing

temperature decreases viscosity, allowing for easier fluid flow, while impurities

can increase viscosity by enhancing resistance.

Understanding these factors is crucial for grasping the practical

implications of viscosity, especially in industrial applications where fluid

management is key to efficiency. Overall, the falling sphere method not only

accurately measures viscosity but also provides insights into the complex

relationship between fluid properties and external conditions, enriching our

understanding of fluid dynamics in real-world contexts.

References

Kumar, A. (2019). An Analysis of Viscosity Measurement. JETIR, 6(1). https://ww

w.jetir.org/papers/JETIRFT06073.pdf

Helmenstine, A. (2021). Viscosity Definition and Examples. Science Notes and

Projects. https://sciencenotes.org/viscosity-definition-and-examples/
Yuan, P. & Lin B. (2008). Measurement of viscosity in a vertical falling ball

viscometer. https://www.americanlaboratory.com/913-Technical-Articles/778-M

easurement-of-Viscosity-in-a-Vertical-Falling-Ball-Viscometer/#:~:text=The%20

rolling%20and%20sliding%20movement,are%20given%20as%20dynamic%20vi

scosity