Viscosity of Liquids

CBC Demo lab at OSU

3 Apr 202001:03

Summary

TLDRThis video explores the impact of intermolecular forces on viscosity using tubes filled with hexane, ethanol, water, and glycerin. Hexane, a non-polar substance, exhibits only dispersion forces, while ethanol shows mild hydrogen bonding. Water and glycerin, with multiple hydroxyl groups, demonstrate strong hydrogen bonding. A ball bearing's descent rate in each tube illustrates viscosity differences, with hexane allowing the fastest fall, followed by ethanol, water, and finally glycerin, highlighting the significant role of hydrogen bonding in increasing viscosity.

Takeaways

🧪 The experiment compares the viscosity of hexane, ethanol, water, and glycerin.
🌀 Hexane is a non-polar substance with only dispersion intermolecular forces.
🍺 Ethanol exhibits mild hydrogen bonding in addition to dispersion forces.
💧 Water has strong hydrogen bonding, which affects its viscosity.
🧪 Glycerin, with three hydroxyl groups, has a high capacity for hydrogen bonding.
🏎️ The ball bearing in hexane falls the fastest, indicating the lowest viscosity.
🚗 Ethanol's ball bearing falls next, showing moderate viscosity due to mild hydrogen bonding.
🚕 Water's ball bearing falls slower, reflecting the stronger intermolecular forces from hydrogen bonding.
🚢 Glycerin's ball bearing falls the slowest, demonstrating the highest viscosity due to extensive hydrogen bonding.
🔬 The rate of the ball bearing's fall correlates with the strength of intermolecular forces.
📉 Stronger intermolecular forces, such as hydrogen bonding, increase a substance's viscosity.
📈 Weaker intermolecular forces, like those in non-polar substances, result in lower viscosity.
📚 The demonstration illustrates the relationship between intermolecular forces and viscosity.

Q & A

What is the main topic discussed in the video script?
-The main topic discussed in the video script is the effect of intermolecular forces on viscosity.
What are the substances used in the experiment to demonstrate intermolecular forces?
-The substances used in the experiment are hexane, ethanol, water, and glycerin.
What type of intermolecular forces does hexane have?
-Hexane, being a non-polar substance, has only dispersion (also known as London dispersion forces) as its intermolecular forces.
How does ethanol differ from hexane in terms of intermolecular forces?
-Ethanol has mild hydrogen bonding in addition to dispersion forces, unlike hexane which only has dispersion forces.
Why does water have a higher viscosity than hexane and ethanol?
-Water has a lot of hydrogen bonding, which is stronger than the dispersion forces in hexane and the mild hydrogen bonding in ethanol, resulting in higher viscosity.
What is the role of the ball bearings in the tubes?
-The ball bearings in the tubes are used to demonstrate the effect of intermolecular forces on the flow rate, with the rate of fall indicating the viscosity of the substance.
How does the presence of hydrogen bonding in glycerin affect its viscosity compared to the other substances?
-Glycerin has multiple hydroxyl groups, leading to a lot of hydrogen bonding, which makes it very viscous and causes the ball bearing to fall very slowly.
What can be inferred about the relationship between the type of intermolecular forces and the flow rate of the substances?
-The stronger the intermolecular forces, such as hydrogen bonding, the slower the flow rate of the substance, as seen with glycerin compared to hexane.
What is the significance of the experiment in understanding the concept of viscosity?
-The experiment visually demonstrates how different types and strengths of intermolecular forces directly affect the viscosity of a substance, making the concept more tangible and understandable.
How does the script suggest that the strength of intermolecular forces can be compared?
-The script suggests that the strength of intermolecular forces can be compared by observing the rate at which the ball bearings fall through the different substances.
What additional factors might affect the viscosity of a substance besides intermolecular forces?
-Factors such as temperature, pressure, and the presence of impurities can also affect the viscosity of a substance, although the script primarily focuses on intermolecular forces.

Outlines

00:00

🌡️ Intermolecular Forces and Viscosity

This paragraph explores the relationship between intermolecular forces and viscosity through an experiment. Tubes filled with hexane, ethanol, water, and glycerin demonstrate varying degrees of intermolecular forces, from non-polar dispersion in hexane to strong hydrogen bonding in water and glycerin. A ball bearing is placed inside each tube to visually compare their flow rates when the tubes are flipped. The results show hexane allowing the ball bearing to fall the fastest due to its weak intermolecular forces, followed by ethanol with mild hydrogen bonding. Water, with significant hydrogen bonding, slows the ball bearing's descent, and glycerin, with its multiple hydroxyl groups, takes the longest due to its strong hydrogen bonding, illustrating how stronger intermolecular forces increase viscosity.

Mindmap

Keywords

💡Intermolecular forces

Intermolecular forces are the forces of attraction or repulsion that act between neighboring particles, such as atoms, molecules, or ions. In the context of the video, these forces are crucial in determining the viscosity of different substances. For example, the script mentions that hexane, a non-polar substance, only has dispersion forces, while ethanol, water, and glycerin exhibit varying degrees of hydrogen bonding, which is a type of intermolecular force.

💡Viscosity

Viscosity refers to the measure of a fluid's resistance to flow. It is directly related to the intermolecular forces within the fluid. In the video, the script demonstrates how different substances with varying intermolecular forces exhibit different viscosities, with hexane having the lowest viscosity and glycerin the highest, as shown by the rate at which the ball bearings fall through the tubes.

💡Hexane

Hexane is a non-polar hydrocarbon and a common solvent. In the video, it is used to illustrate a substance with only dispersion forces, which are the weakest of the intermolecular forces. The script shows that the ball bearing falls fastest in hexane, indicating its low viscosity due to the lack of strong intermolecular forces.

💡Ethanol

Ethanol is an organic compound with the ability to form hydrogen bonds due to the presence of a hydroxyl group. The script mentions that ethanol has 'some mild hydrogen bonding,' which contributes to its viscosity. The ball bearing falls slower in ethanol than in hexane, demonstrating the effect of hydrogen bonding on viscosity.

💡Water

Water is a polar molecule known for its strong hydrogen bonding capabilities. The script emphasizes that water has 'a lot of hydrogen bonding,' which significantly increases its viscosity compared to non-polar substances like hexane. The ball bearing falls slower in water than in ethanol, illustrating the impact of strong intermolecular forces on a fluid's resistance to flow.

💡Glycerin

Glycerin, also known as glycerol, is a粘稠 substance with multiple hydroxyl groups capable of forming extensive hydrogen bonds. The video script points out that glycerin 'with 308 groups has tons of hydrogen bonding,' making it the most viscous of the substances presented. The ball bearing takes the longest time to fall in glycerin, showcasing the high resistance to flow due to strong intermolecular forces.

💡Hydrogen bonding

Hydrogen bonding is a type of dipole-dipole attraction between a hydrogen atom covalently bonded to a highly electronegative atom and another electronegative atom. In the video, hydrogen bonding is a key concept, as it is the primary intermolecular force that increases the viscosity of substances like ethanol, water, and glycerin. The script demonstrates this by showing the varying speeds of the ball bearings falling through tubes of different substances.

💡Ball bearing

A ball bearing is a spherical object used in the video to demonstrate the effect of intermolecular forces on viscosity. The script describes an experiment where ball bearings are placed in tubes filled with different substances, and their rate of fall is observed. The speed at which the ball bearings move through the tubes is directly related to the viscosity of the substances, with hexane allowing the fastest fall and glycerin the slowest.

💡Dispersion forces

Dispersion forces, also known as London dispersion forces or van der Waals forces, are the weakest of the intermolecular forces and occur between all molecules, including non-polar ones like hexane. The script explains that hexane only has dispersion forces, which is why the ball bearing falls the fastest in this substance, indicating its low viscosity.

💡Polar substance

A polar substance is a molecule that has an uneven distribution of electron density, resulting in a molecule with a positive and a negative end, or pole. In the video, water is described as a polar substance, which is capable of forming strong hydrogen bonds. This is why water has a higher viscosity than non-polar substances like hexane.

💡Non-polar substance

A non-polar substance is a molecule in which the electron distribution is even, resulting in no distinct positive or negative ends. The script uses hexane as an example of a non-polar substance, which only exhibits dispersion forces and has a low viscosity, as shown by the rapid fall of the ball bearing in the hexane-filled tube.

Highlights

Intermolecular forces significantly affect viscosity.

Demonstration involves tubes filled with hexane, ethanol, water, and glycerin.

Hexane, a non-polar substance, exhibits dispersion intermolecular forces.

Ethanol has mild hydrogen bonding in addition to dispersion forces.

Water is characterized by strong hydrogen bonding.

Glycerin, with 308 hydroxyl groups, has extensive hydrogen bonding.

A ball bearing is placed inside each tube to demonstrate the effect on movement.

Hexane allows the ball bearing to fall the fastest due to weak intermolecular forces.

Ethanol's mild hydrogen bonding slows the ball bearing's descent compared to hexane.

Water's strong hydrogen bonding significantly slows the ball bearing's movement.

Glycerin's extensive hydrogen bonding causes the slowest descent of the ball bearing.

The experiment visually demonstrates the relationship between intermolecular forces and viscosity.

The rate of the ball bearing's fall correlates with the strength of intermolecular forces.

Hexane's non-polar nature results in the least resistance to the ball bearing's movement.

Ethanol's hydrogen bonding provides moderate resistance, slowing the ball bearing.

Water's robust hydrogen bonding creates a high resistance environment for the ball bearing.

Glycerin's numerous hydroxyl groups result in the highest resistance, impeding the ball bearing's fall.

The experiment provides a practical application of understanding viscosity in different substances.

The demonstration effectively illustrates the impact of molecular structure on physical properties.

The varying descent rates of the ball bearing highlight the differences in intermolecular forces.