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Transcript of Viscosity Experiment
By: Cherie Lui
What is viscosity?
Viscosity is the resistance of fluids against motion.
It can be considered as the 'thickness' of a fluid, water is relatively thin compared to honey which is thick. You would have to use more force to move an object through a high viscosity liquid compared to a low viscosity liquid. This resistance is caused by the friction of the fluid's molecules against the object moving in the fluid.
Specific devices called viscometers can be utilized to measure a fluid's viscosity. This device achieves this by measuring how long it takes for a fluid to move a particular distance through a tube or the time it takes for a particular object to fall through the liquid. The internationally recognized unit of measurement for viscosity is Pascal-second which means that the it is measured in terms of pressure versus time. A viscous liquid will take a longer time to move a certain distance compared to a less viscous one in a controlled pressure. There are also other ways of expressing viscosity in the SI system including kg m-1 s-1 and Nm-2.
Factors Affecting Viscosity
Various factors are able to affect the viscosity of fluids such as temperature, particle size concentration and attractive force.
Increased temperature in liquids causes the particles to move around more at a faster pace. This allow them to flow more freely therefore creating a lower viscosity. However, in gases, the particles are originally far apart so when heat is applied, it makes the particles to become more compact while they collide with each other, resulting in a higher viscosity.
Concentration of a fluid refers to the amount of substance that is dissolved in a specific volume. In terms of viscosity, a high concentration causes high viscosity as the particles that are compacted together will not flow as freely as a low concentration fluid.
Usually, the attractions between particles are stronger when they are from the same substances. This attraction vary form one to another, but the stronger this attraction, the higher the viscosity.
Small particles are able to move around each other more freely and easily, which means that they can flow faster resulting in a lower viscosity. On the other hand, fluids with larger particles have a higher viscosity as it is harder for them to move around and flow.
Importance of Viscosity
The measure of a fluids' viscosity is extremely important especially in chemistry, industries and many types of manufacturing practices. This is because a fluids' viscosity determines its handling process, storage and method of discard. An example of this would be different pipes built for crude oils around the world under different temperatures with different viscosity. Dues to the differing ground temperatures, some oils will need more pressure in order to keep running along the pipe, which means that the pipe have to designed to hold this viscous fluid while withstanding the pressure of the force that is pushing it along.
In my research experiment, my aim is to explore and compare the viscosity of different household liquids. To conduct this experiment:
A ball will be dropped into a long, clear cylindrical container filled with the same volume of different household fluids such as water, milk and oil.
The time it takes for the ball to reach the bottom of the container will be measured and recorded
By comparing the data in a graph, I will be able to determine the fluid with the highest and lowest viscosity.
Household liquid being tested
Time it takes for the ball to reach the bottom (Viscosity of the liquid)
Ball used in the experiment
Volume of the liquid used
Force applied to the ball initailly
Starting point of the fall of the ball
Drop the ball from the top of an empty cylindrical container
Time how long it takes for the ball to reach the bottom of the container
Repeated several times to ensure that the results are reliable
The glass container may be broken in the process of the experiment, which may lead to hand injuries due to broken glass.
To prevent this, all glass material used in the experiment must be handled carefully to avoid breakage, and if it does break, it must be cleaned carefully with a broom.
Spillage of the liquids may lead to inconvenience as will as increase the risk of slipping over and falling.
To prevent this, the liquids must be handled and cleaned up carefully.
Inappropriate handling of the ball may lead to face injuries, especially around the eyes.
To prevent this, avoid playing with the ball inappropriately during the experiment especially when it is close to the face.
Reliability and Validity
The reliability of the experiment will be achieved through repeating the test several times until the results are reliable, as well as keeping all other variables such as the ball used, controlled. The validity of the experiment will be achieved through the use of correct equipment to measure results such as using a stopwatch to record time.
Formal Experimental Record
To explore and compare the viscosity of different household liquids.
Honey will have the highest viscosity while water will have the lowest viscosity as honey is relatively more 'thick' than water, which is very 'thin'.
1. A mark was made 1.5 cm from the top of the cylindrical container
2. Water was poured into the container until it reached the mark
3. A ball was dropped from the top of the container
4. The time it took for the ball to reach the bottom was timed and recorded
5. Steps 1-4 were repeat ed 3 times to ensure the results were reliable
6. The whole experiment was repeated with milk, detergent, honey and oil.
From the data and the graphs, we can easily conclude that the liquids tested from lowest viscosity to lowest viscosity are water, milk, oil, detergent and honey. The obvious outlier in these results is the honey with the average time of 655.77 seconds, which clearly stands away from the rest of the liquids in the graph, evidently having the highest viscosity. The liquid with the lowest viscosity is water, its average time being 0.37 seconds.
One of the difficulties I encountered during this experiment was the mess that was created from the stickiness of the honey as well as the grease from the oil. It was hard to clean up and have the experiment repeated, but this was overcome by working in the kitchen which allowed quick and convenient access to water and other cleaning tools. Another difficulty was to ensure that my reaction to the start of the fall of the marble and the end of it was accurate. The accuracy was improved through getting more data with trials and taking the average, however it was still not completely accurate.
One way this experiment could be improved is through the use of more accurate ways of timing the fall such as using a sensor, or close analysis of a video of the process. The accuracy/ range of results could also be improved by using a taller container, or using a long type instead of a glass cylinder which would extend the time and reduce human errors and inaccuracy.
After knowing the viscosity of various household liquids, we are able to identify the most appropriate and convenient container to store each of these liquids. For example, liquids with high viscosity such as the honey would need more force to pour out, which meant that a squeezable bottle would be most suitable to ensure that the honey does not take too long to come out. Low viscosity liquids such as water and milk pours out relatively quicker, so an appropriate container would be a bottle or a jug with a narrow opening, spout of a pitcher.
Tricia Ellis-Christensen. 2013. Viscosity.
Dr. Lev Nelick. 2013. The Importance of Viscosity in Different Applications.
Columbia. 2012. The Concept of viscosity.
ChemEd. 2013. Viscosity.