Dr. Maria D. Pastrana National High School
Mauban, Quezon
LIQUIDS’ IMF
Title of the Activity Exploring the Effects of Liquid Type on
Surface Tension and Evaporation
Group Members:
Aloc, Gladys U.
Bernardo, Tyke Caeram M.
Dequilla, Cyenne Patrissia C.
Tampoc, Zlyvanna Eunizse A.
Tipones, Ronjohn A.
EDEN C. SANCHEZ
Subject Teacher
Dr. Maria D. Pastrana National High School
Mauban, Quezon
I.
Objective:
In the end of this experiment, the students are expected to be able to:



II.
Compare the surface tension and evaporation rate of different liquids using a 1-peso
coin.
Investigate the effects of liquid type on these properties.
Understand the molecular mechanisms behind evaporation and surface tension.
Materials:
The materials needed to conduct this experiment are:





III.
1-peso coin
Water, ethanol, acetone, pentane/butane
4 small cups with labels
4 droppers
A stopwatch or timer
Questions to investigate:
1. How many drops of liquid can a 1-peso coin hold?
The experiment shows that water held about 63 drops on the 1 peso coin.
Isopropyl held about 31 drops on the coin. Acetone held about 25 drops on the
coin. Lastly, Butane only held about 1-2 drops on the coin before it quickly
vaporized.
2. How long will it take for one drop of a liquid to evaporate?
The evaporation rates of different liquids can vary significantly due to their
molecular properties. Based on the experiment, water took the longest time to
evaporate, roughly about more than 20 minutes. Water molecules are attracted to
each other by hydrogen bonding, which makes it harder for them to escape into
the vapor phase. Meanwhile a drop of isopropyl alcohol took about 5 minutes to
evaporate which is faster than water. Isopropyl alcohol evaporates faster than water
because its weaker intermolecular forces (hydrogen bonding and dipole-dipole
interactions) allow molecules to escape more easily into the vapor phase. On the
other hand, acetone took a faster evaporation time compared to the two
mentioned liquids, a drop took about 3 minutes to evaporate. Acetone’s weaker
intermolecular forces and lack of hydrogen bonding contribute to its rapid
evaporation compared to isopropyl alcohol and water. Lastly butane's evaporation
rate was the fastest, a drop of butane on a coin took seconds or less to evaporate.
The reason for this is because butane has a relatively low boiling point and weak
intermolecular forces.
IV.
Observation:
Dr. Maria D. Pastrana National High School
Mauban, Quezon
V.
Discussion:
1. Which molecules can hold more drops on the coin?
Based on the experiment we conducted, water held more drops on the coin
compared to the rest of the liquid, specifically, it held 63 drops on the coin. The
reason for this is because water is a polar molecule with strong hydrogen bonding,
leading to high surface tension. Next is isopropyl alcohol, it held 31 drops on the
coin. Its surface tension is high, similar to water, so it can hold more drops on a coin.
Third is acetone, it held 25 drops on the coin. Acetone is a polar molecule with
dipole-dipole interactions. Its surface tension is lower than water’s, so it can hold
fewer drops on a coin. Lastly, butane, it only held 1 or 2 drop on the coin before it
immediately vaporized. Butane is a nonpolar molecule with only London dispersion
forces, which are weaker than the IMFs in polar molecules. Therefore, it has a lower
surface tension and can hold fewer drops on a coin.
2. Which molecules took longer to evaporate?
The rate of evaporation of a molecule is determined by the strength of its
intermolecular forces (IMFs). Molecules with stronger IMFs take longer to evaporate
because more energy is required to break the bonds.
Our experiment showed that water takes longer to evaporate compared to
the rest of the liquids. Water is a polar molecule with strong hydrogen bonding,
which requires a significant amount of energy to break. Isopropyl alcohol is a polar
molecule with both hydrogen bonding and dipole-dipole interactions. Like water, it
also takes longer to evaporate due to the strong IMFs. Meanwhile, acetone is a
polar molecule with dipole-dipole interactions. It has weaker than the hydrogen
bonds in water and isopropyl alcohol. Therefore, acetone evaporates faster than
water and isopropyl alcohol but slower than butane. On the other hand, Butane is a
nonpolar molecule with only London dispersion forces, which are the weakest type
of IMFs. Therefore, butane evaporates the fastest among these four substances.
So, among these substances, water and isopropyl alcohol take longer to
evaporate due to their stronger IMFs, while butane evaporates the fastest due to its
weaker IMFs. Acetone falls in between.
3. Are the molecules that can hold the lesser number of drops the same
as the molecules that took less time to evaporate?
Yes, the molecules that can hold the fewer number of drops are generally the
same as the ones that evaporate more quickly. Water molecules have strong
hydrogen bonds due to their polar nature. These bonds create a cohesive force that
allows water to form larger drops and resist breaking apart. Consequently, water
takes longer to evaporate because breaking these bonds requires more energy.
While butane molecules are nonpolar and have weaker intermolecular forces. They
don’t form strong bonds, so butane evaporates rapidly. The lack of cohesive forces
allows it to break into smaller droplets and disperse easily. Similarly, acetone is also a
Dr. Maria D. Pastrana National High School
Mauban, Quezon
polar molecule, but its intermolecular forces are weaker than water. It can form
smaller drops and evaporates quickly due to weaker hydrogen bonding. Lastly,
alcohol, isopropyl has a hydroxyl group (OH), allowing it to form hydrogen bonds.
These bonds create cohesion, resulting in larger drops. However, isopropyl still
evaporates faster than water due to its lower boiling point.
4. Based on the formula and geometries of the substances, are the
molecules that can hold more drops on the coin polar or nonpolar?
What about those that took longer to evaporate? What is the IMF for
each molecule of liquids?
Molecules that can hold more drops on a coin are typically polar. This is
because polar molecules have stronger intermolecular forces (IMFs) such as
hydrogen bonding and dipole-dipole interactions, which result in higher surface
tension. The higher the surface tension, the more drops a liquid can hold on a coin.
Molecules that take longer to evaporate are typically polar and have stronger
intermolecular forces (IMFs). This is because stronger IMFs, such as hydrogen bonding
and dipole-dipole interactions, require more energy (in the form of heat) to break,
leading to a slower evaporation rate
Water is a polar molecule due to its bent molecular geometry, which results in
a net dipole moment. The primary IMF in water is hydrogen bonding, which is a
special type of dipole-dipole interaction. This strong IMF makes water have a high
surface tension (can hold more drops on a coin) and a relatively slow evaporation
rate.
Butane is a nonpolar molecule. It has a linear molecular geometry, and the
electron cloud is evenly distributed. The primary IMF in butane is London dispersion
forces, which are weaker than hydrogen bonds. Therefore, butane has a lower
surface tension and a faster evaporation rate compared to water.
Acetone is a polar molecule due to the presence of a carbonyl group (C=O),
which creates a dipole. The primary IMF in acetone is dipole-dipole interaction.
Acetone has a lower surface tension than water but higher than butane, and it
evaporates faster than water but slower than butane.
Isopropyl alcohol is a polar molecule because of the -OH (hydroxyl) group,
which creates a dipole. The primary IMF is hydrogen bonding (due to the -OH group)
and dipole-dipole interaction. Isopropyl alcohol has a high surface tension and a
relatively slow evaporation rate, similar to water.
In general, polar molecules with stronger IMFs (like water and isopropyl
alcohol) can hold more drops on a coin and take longer to evaporate compared to
nonpolar molecules with weaker IMFs (like butane).