Project Number: 2023-1-PL01-KA220-SCH-000164042
UNIT 9: Interactions Between Molecules
Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Education and Culture Executive Agency (EACEA). Neither the European Union nor EACEA can be held responsible for them.
Weak intermolecular bonds &
Strong intramolecular interactions
Source: canva.com
Introduction
In this activity you will explore weak intermolecular bonds and strong intramolecular interactions
Source: canva.com
Learning Outcomes
1- Students express the difference between weak and strong interactions. 2- Students explain the boiling event at the molecular level by associating it with weak and strong interactions.
Source: canva.com
Atoms
We know that all matter in the universe is made of atoms. However, atoms are very rarely found alone in nature. Atoms interact with other atoms to form elements and compounds.
Source: canva.com
Atoms
electron
How this interaction takes place depends on the number and arrangement of electrons atoms have.
Source: canva.com
Atoms
nukleus
In fact, when you try to observe an atom, the only shape you will see in the first place is the nucleus.
Source: canva.com
Atoms
electron
The nucleus is located at the center of the atom and contains the "+" charged particles called "protons" and the uncharged "neutrons" that hold these protons together like glue (because, as you know, like charges repel each other and opposite charges attract each other).
proton
neutron
Source: canva.com
Atoms
Proton
The particle that determines the type of an atom is the proton. So, you can think of the number of protons as the atom's identity card.
Protons are positively charged particles located in the nucleus (center) of the atom
Source: canva.com
Atoms
Electron
In addition to these, there is a third type of particle outside the nucleus, which is inconspicuous at first glance, but which is the protagonist of chemical bonding, which we will discuss in a moment: Electrons.
Electrons are negatively charged particles that orbit around the nucleus.
Source: canva.com
Atoms
We say inconspicuous at first glance because electrons are much smaller particles than protons and neutrons, and they move very fast, far away from the nucleus. However, these "-" charged particles do not move completely randomly.
electron
Source: canva.com
Atoms
In science books you have seen various models of the atom (the Bohr model of the atom), which are likened to the solar system. Although this is not a completely accurate representation, it is still used in many sources because it makes it easier to understand the movement of electrons and the role they play in the bond structure.
Bohr model of the atom
Source: canva.com
Atoms
According to this notation, electrons move in specific orbits around the nucleus, or in more technical terms, in energy levels consisting of several layers of probability states for their position. These layers have different electron capacities. The layer closest to the nucleus can hold up to two electrons.
Source: canva.com
Atoms
The second and third energy levels can hold up to eight electrons. When a layer at one energy level is full, the next electron arrives and settles in the layer at the next higher energy level. Therefore, all the layers before the outermost layer of the atom are completely full of electrons.
Source: canva.com
Atoms
For this reason, electrons in the outermost orbital (valence orbital) are taken into account when talking about chemical bonds. In some elements, the electron capacity in the valence orbital is not completely filled. This causes that atom to be in an unstable state.
Source: canva.com
Atoms
Atoms always tend to fully fill the electron capacity in all orbits and become stable. To do this, they can share electrons with other elements, give electrons to them or accept electrons from them.
Source: canva.com
Atoms
As a result, the balance of positively and negatively charged particles in the atom will change. If the number of "+" charged protons and "-" charged electrons in an atom is equal, it is called a "neutral atom".
Source: canva.com
Atoms
However, if an atom does not contain an equal number of protons and electrons, it is called an "ion".
Source: canva.com
Atoms
Since the number of electrons in such atoms is not equal to the number of protons, each ion has a net charge. They are called "negative ions" if the number of electrons is greater than the number of protons, and "positive ions" if the number of protons is greater than the number of electrons.
Source: iStock.com
Atoms
For example, lithium has a single electron in its outermost layer. It takes less energy for lithium to give up that one electron than to accept seven more electrons to fill its outer layer.
Source: canva.com
Atoms
If lithium loses an electron, it now has three protons and only two electrons, leaving it with a total charge of +1 and the name lithium cation. The lithium ion we are talking about here is a positive ion.
Source: canva.com
Atoms
The tendency of atoms to stabilize and the interactions between the charged ions they transform into form the basis of chemical bonds. We can classify these interactions between chemical species as "strong interactions" and "weak interactions".
Source: canva.com
Atoms
Through these interactions, atoms take the elemental and compound forms they are found in nature. Strong interactions are the forces that hold the atoms that make up molecules together, i.e. chemical bonds. Weak interactions are the forces that arise between positively and negatively charged molecules.
Source: iStock.com
STRONG INTERACTIONS CHEMICAL BONDS
1) Ionic Bonding
Ionic bonding is based on the exchange of electrons between two chemical species. The result is an anion, an ion with a minus charge, and a cation, an ion with a plus charge.
STRONG INTERACTIONS CHEMICAL BONDS
1) Ionic Bonding
The chemical bond formed due to the electrical attraction between the positive and negative charges is called an ionic bond. The neutral sodium atom has 11 electrons and 11 protons. The outermost valence orbital shell has 1 electron. It can become stable by giving up this 1 valence electron. The neutral chlorine atom has 17 electrons and 17 protons.
Source: canva.com
STRONG INTERACTIONS CHEMICAL BONDS
1) Ionic Bonding
The outermost valence orbital has 7 electrons. Chlorine can become stable by taking 1 electron. During the formation of the sodium chloride molecule, sodium atoms give 1 electron to form the plus charged sodium ion (Na+) and chlorine atoms give 1 electron to form the minus charged chlorine ion (Cl-).
Source: canva.com
STRONG INTERACTIONS CHEMICAL BONDS
1) Ionic Bonding
Due to the electrical attraction between the oppositely charged ions, an ionic bond is formed between them. There is a marked difference between the electronegativities of the atoms forming the ionic bond, that is, their capacity to attract electrons participating in the chemical bond. For this reason, ionic bonds are usually formed between metal atoms with low electronegativity and nonmetal atoms with high electronegativity.
Source: canva.com
STRONG INTERACTIONS CHEMICAL BONDS
2) Covalent Bond
When there is no significant difference between the electronegativities of two atoms, they can try to reach a stable state by sharing electrons. The chemical bond formed between atoms with close electronegativities and in which electrons are shared is called a covalent bond.
STRONG INTERACTIONS CHEMICAL BONDS
2) Covalent Bond
A covalent bond between two atoms of the same type is called an apolar covalent bond. For example, in the hydrogen (H2) molecule, two hydrogen atoms share their electrons and try to make their electron arrangement similar to helium, a noble gas.
Source: canva.com
STRONG INTERACTIONS CHEMICAL BONDS
2) Covalent Bond
Since the electronegativities of the atoms are the same in an apolar covalent bond, the electrons involved in the bond formation are equally attracted by the atoms. Therefore, the distribution of electrical charges in the molecule is balanced.
Source: canva.com
STRONG INTERACTIONS CHEMICAL BONDS
2) Covalent Bond
A covalent bond between two atoms with a small difference in electronegativity is called a polar covalent bond.
Source: canva.com
STRONG INTERACTIONS CHEMICAL BONDS
2) Covalent Bond
For example, in the water molecule, the electronegativity of oxygen is greater than that of hydrogen. Since the bonding electrons shared by hydrogen and oxygen in the water molecule are more attracted by oxygen, oxygen atoms are partially charged with a negative charge and hydrogen atoms are partially charged with a positive charge. Therefore, the water molecule is a polar molecule.
Source: canva.com
STRONG INTERACTIONS CHEMICAL BONDS
3) Metallic Bond
A metallic bond is a type of bond formed between metal atoms. Due to the low electronegativity of metals, these atoms weakly attract the electrons involved in bond formation. When metal atoms come together, the valence electrons in the highest- energy electron shell are separated from the atoms and move freely in the valence orbitals of neighbouring metal atoms.
STRONG INTERACTIONS CHEMICAL BONDS
3) Metallic Bond
These free-moving valence electrons form a sea of electrons and, as a result, a metallic bond is formed due to the electrostatic attraction forces between the positively charged metal ions and these free electrons.
Source: canva.com
STRONG INTERACTIONS CHEMICAL BONDS
3) Metallic Bond
Properties of metals such as high melting and boiling temperatures, bright colours, malleability, good conductivity of heat and electricity are due to the freely mobile valence electrons.
Source: Shutterstock.com
WEAK INTERACTIONS
Weak interactions are interactions between positively and negatively charged molecules. Weak interactions do not involve a bond. Although they are a type of interaction that is not as difficult to break as chemical bonds, we can clearly notice the effect of weak interactions in our environment. We can basically categorize weak interactions under two headings: hydrogen bonding and Van der Waals forces.
WEAK INTERACTIONS
1.Hydrogen Bonding
Hydrogen bonding is the strongest type of weak intermolecular interaction. It occurs between molecules formed by hydrogen and elements such as oxygen, nitrogen and fluorine, which are willing to take electrons to stabilize (electronegativity).
WEAK INTERACTIONS
1.Hydrogen Bonding
When hydrogen forms a covalent bond with an element of high electronegativity, the electrons involved in the bond formation are more attracted to the atoms of the element of high electronegativity.
Source: canva.com
WEAK INTERACTIONS
1.Hydrogen Bonding
Therefore, the negative charge density is higher on the atom with high electronegativity than on hydrogen. As a result, the atom with high electronegativity is partially charged with a negative charge (𝛿𝛿-), while hydrogen is partially charged with a positive charge (𝛿𝛿+).
Source: canva.com
WEAK INTERACTIONS
1.Hydrogen Bonding
This causes the molecule to be polar. An electrostatic force of attraction arises between the partially plus charged (𝛿𝛿+) hydrogen atom in the polar molecule and the partially minus charged (𝛿𝛿-) atom in the neighboring molecule.
Source: canva.com
WEAK INTERACTIONS
1.Hydrogen Bonding
This interaction is called hydrogen bonding. Hydrogen bonds play many roles in sustaining life.
- For example, hydrogen bonds hold two DNA strands together. Hydrogen bonding is at the heart of many interesting and unique properties of water.
- For example, its high boiling point, its expansion when it freezes, its high heat capacity - that is, the amount of heat required to raise its temperature by 1 oC - are all due to its ability to form hydrogen bonds.
Source: Shutterstock.com
WEAK INTERACTIONS
1.Hydrogen Bonding
Without hydrogen bonds, water would be a gas instead of a liquid at room temperature. Hydrogen bonding also causes the surface tension of water to be high.
Source: Shutterstock.com
WEAK INTERACTIONS
2. Van der Waals Forces
Van der Waals forces make molecules stick together and stay together. These forces are particularly involved in phase changes of substances such as gases and liquids and in the interactions of molecular surfaces. In short, Van der Waals forces are the general name for the attraction and repulsion interactions between molecules and play an important role in understanding the structure and behavior of substances.
WEAK INTERACTIONS
2. Van der Waals Forces
There are different types of van der Waals forces:
- Between a polar molecule and another polar molecule (dipole- dipole interactions),
- Between a polar molecule and an apolar, i.e. non-polar molecule (Dipole-Induced Dipole Interactions),
- Between partially negatively and partially positively charged molecules (London forces),
Source: Shutterstock.com
LET'S CONSTRUCT WHAT WE HAVE LEARNED
In this activity, we will discuss the boiling event that we frequently encounter in daily life at the molecular level and discuss the effect of strong and weak interactions on boiling. Boiling is the rapid transition from liquid to gaseous state when the vapour pressure of a liquid is equal to atmospheric pressure. Since this event occurs not only on the surface of the liquid, as in evaporation, but all over the liquid, bubbles are observed to form in the liquid during boiling. However, the temperature at which liquids begin to boil under constant pressure, i.e. the boiling point, varies according to the type of liquid.
In other words, boiling point is a distinctive feature for liquids. But why? What changes when the type of liquid changes so that the boiling point changes? To understand this, we need to look closely at liquid molecules. The boiling point depends on the strength of intermolecular interactions. The stronger the force of attraction between molecules, the higher the boiling point. Therefore, when the type of liquid changes, the boiling point changes because the intermolecular attraction force of the liquid also changes. So what do you think the force of attraction between molecules depends on? ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..........
When we compare ethyl alcohol and water, it is seen that there are hydrogen bonds between the molecules of both compounds. What do you think is the reason why the boiling points of ethyl alcohol and water are different? .......................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... What do you think is the reason why the boiling points of ethyl alcohol and methyl alcohol are different? ..........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
A student analysed the table above and made the following argument: “The type of weak interaction between methyl alcohol molecules and ethyl alcohol molecules is the same. Both chemicals have hydrogen bonds between molecules. The number of bonds between methyl alcohol molecules and the number of bonds between ethyl alcohol molecules is the same. However, the boiling points of these two chemicals are different. This is because the number of intramolecular bonds forming these chemicals is different. In both ethyl alcohol and methyl alcohol, the atoms in the molecule are connected to each other by covalent bonds. However, when the formulas of the compounds are examined, it is seen that the number of atoms forming the molecule is different.
This shows that the number of bonds in the molecule is different. Since the number of bonds (thus the amount of strong interaction) is high in molecules with a high number of atoms, the boiling point is high.”
This argument is known to be false. Determine why this argument is wrong. ................................................................................................................................................................................................................................................................................................................ Since this argument is known to be false, what do you think is the reason for the difference between the boiling points of ethyl alcohol and methyl alcohol? ................................................................................................................................................................................................................................................................................................................
UNIT 9: Interactions Between Molecules
Eco-Smart Schools
Created on October 15, 2025
Start designing with a free template
Discover more than 1500 professional designs like these:
View
Urban Illustrated Presentation
View
3D Corporate Reporting
View
Discover Your AI Assistant
View
Vision Board
View
SWOT Challenge: Classify Key Factors
View
Explainer Video: Keys to Effective Communication
View
Explainer Video: AI for Companies
Explore all templates
Transcript
Project Number: 2023-1-PL01-KA220-SCH-000164042
UNIT 9: Interactions Between Molecules
Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Education and Culture Executive Agency (EACEA). Neither the European Union nor EACEA can be held responsible for them.
Weak intermolecular bonds &
Strong intramolecular interactions
Source: canva.com
Introduction
In this activity you will explore weak intermolecular bonds and strong intramolecular interactions
Source: canva.com
Learning Outcomes
1- Students express the difference between weak and strong interactions. 2- Students explain the boiling event at the molecular level by associating it with weak and strong interactions.
Source: canva.com
Atoms
We know that all matter in the universe is made of atoms. However, atoms are very rarely found alone in nature. Atoms interact with other atoms to form elements and compounds.
Source: canva.com
Atoms
electron
How this interaction takes place depends on the number and arrangement of electrons atoms have.
Source: canva.com
Atoms
nukleus
In fact, when you try to observe an atom, the only shape you will see in the first place is the nucleus.
Source: canva.com
Atoms
electron
The nucleus is located at the center of the atom and contains the "+" charged particles called "protons" and the uncharged "neutrons" that hold these protons together like glue (because, as you know, like charges repel each other and opposite charges attract each other).
proton
neutron
Source: canva.com
Atoms
Proton
The particle that determines the type of an atom is the proton. So, you can think of the number of protons as the atom's identity card.
Protons are positively charged particles located in the nucleus (center) of the atom
Source: canva.com
Atoms
Electron
In addition to these, there is a third type of particle outside the nucleus, which is inconspicuous at first glance, but which is the protagonist of chemical bonding, which we will discuss in a moment: Electrons.
Electrons are negatively charged particles that orbit around the nucleus.
Source: canva.com
Atoms
We say inconspicuous at first glance because electrons are much smaller particles than protons and neutrons, and they move very fast, far away from the nucleus. However, these "-" charged particles do not move completely randomly.
electron
Source: canva.com
Atoms
In science books you have seen various models of the atom (the Bohr model of the atom), which are likened to the solar system. Although this is not a completely accurate representation, it is still used in many sources because it makes it easier to understand the movement of electrons and the role they play in the bond structure.
Bohr model of the atom
Source: canva.com
Atoms
According to this notation, electrons move in specific orbits around the nucleus, or in more technical terms, in energy levels consisting of several layers of probability states for their position. These layers have different electron capacities. The layer closest to the nucleus can hold up to two electrons.
Source: canva.com
Atoms
The second and third energy levels can hold up to eight electrons. When a layer at one energy level is full, the next electron arrives and settles in the layer at the next higher energy level. Therefore, all the layers before the outermost layer of the atom are completely full of electrons.
Source: canva.com
Atoms
For this reason, electrons in the outermost orbital (valence orbital) are taken into account when talking about chemical bonds. In some elements, the electron capacity in the valence orbital is not completely filled. This causes that atom to be in an unstable state.
Source: canva.com
Atoms
Atoms always tend to fully fill the electron capacity in all orbits and become stable. To do this, they can share electrons with other elements, give electrons to them or accept electrons from them.
Source: canva.com
Atoms
As a result, the balance of positively and negatively charged particles in the atom will change. If the number of "+" charged protons and "-" charged electrons in an atom is equal, it is called a "neutral atom".
Source: canva.com
Atoms
However, if an atom does not contain an equal number of protons and electrons, it is called an "ion".
Source: canva.com
Atoms
Since the number of electrons in such atoms is not equal to the number of protons, each ion has a net charge. They are called "negative ions" if the number of electrons is greater than the number of protons, and "positive ions" if the number of protons is greater than the number of electrons.
Source: iStock.com
Atoms
For example, lithium has a single electron in its outermost layer. It takes less energy for lithium to give up that one electron than to accept seven more electrons to fill its outer layer.
Source: canva.com
Atoms
If lithium loses an electron, it now has three protons and only two electrons, leaving it with a total charge of +1 and the name lithium cation. The lithium ion we are talking about here is a positive ion.
Source: canva.com
Atoms
The tendency of atoms to stabilize and the interactions between the charged ions they transform into form the basis of chemical bonds. We can classify these interactions between chemical species as "strong interactions" and "weak interactions".
Source: canva.com
Atoms
Through these interactions, atoms take the elemental and compound forms they are found in nature. Strong interactions are the forces that hold the atoms that make up molecules together, i.e. chemical bonds. Weak interactions are the forces that arise between positively and negatively charged molecules.
Source: iStock.com
STRONG INTERACTIONS CHEMICAL BONDS
1) Ionic Bonding
Ionic bonding is based on the exchange of electrons between two chemical species. The result is an anion, an ion with a minus charge, and a cation, an ion with a plus charge.
STRONG INTERACTIONS CHEMICAL BONDS
1) Ionic Bonding
The chemical bond formed due to the electrical attraction between the positive and negative charges is called an ionic bond. The neutral sodium atom has 11 electrons and 11 protons. The outermost valence orbital shell has 1 electron. It can become stable by giving up this 1 valence electron. The neutral chlorine atom has 17 electrons and 17 protons.
Source: canva.com
STRONG INTERACTIONS CHEMICAL BONDS
1) Ionic Bonding
The outermost valence orbital has 7 electrons. Chlorine can become stable by taking 1 electron. During the formation of the sodium chloride molecule, sodium atoms give 1 electron to form the plus charged sodium ion (Na+) and chlorine atoms give 1 electron to form the minus charged chlorine ion (Cl-).
Source: canva.com
STRONG INTERACTIONS CHEMICAL BONDS
1) Ionic Bonding
Due to the electrical attraction between the oppositely charged ions, an ionic bond is formed between them. There is a marked difference between the electronegativities of the atoms forming the ionic bond, that is, their capacity to attract electrons participating in the chemical bond. For this reason, ionic bonds are usually formed between metal atoms with low electronegativity and nonmetal atoms with high electronegativity.
Source: canva.com
STRONG INTERACTIONS CHEMICAL BONDS
2) Covalent Bond
When there is no significant difference between the electronegativities of two atoms, they can try to reach a stable state by sharing electrons. The chemical bond formed between atoms with close electronegativities and in which electrons are shared is called a covalent bond.
STRONG INTERACTIONS CHEMICAL BONDS
2) Covalent Bond
A covalent bond between two atoms of the same type is called an apolar covalent bond. For example, in the hydrogen (H2) molecule, two hydrogen atoms share their electrons and try to make their electron arrangement similar to helium, a noble gas.
Source: canva.com
STRONG INTERACTIONS CHEMICAL BONDS
2) Covalent Bond
Since the electronegativities of the atoms are the same in an apolar covalent bond, the electrons involved in the bond formation are equally attracted by the atoms. Therefore, the distribution of electrical charges in the molecule is balanced.
Source: canva.com
STRONG INTERACTIONS CHEMICAL BONDS
2) Covalent Bond
A covalent bond between two atoms with a small difference in electronegativity is called a polar covalent bond.
Source: canva.com
STRONG INTERACTIONS CHEMICAL BONDS
2) Covalent Bond
For example, in the water molecule, the electronegativity of oxygen is greater than that of hydrogen. Since the bonding electrons shared by hydrogen and oxygen in the water molecule are more attracted by oxygen, oxygen atoms are partially charged with a negative charge and hydrogen atoms are partially charged with a positive charge. Therefore, the water molecule is a polar molecule.
Source: canva.com
STRONG INTERACTIONS CHEMICAL BONDS
3) Metallic Bond
A metallic bond is a type of bond formed between metal atoms. Due to the low electronegativity of metals, these atoms weakly attract the electrons involved in bond formation. When metal atoms come together, the valence electrons in the highest- energy electron shell are separated from the atoms and move freely in the valence orbitals of neighbouring metal atoms.
STRONG INTERACTIONS CHEMICAL BONDS
3) Metallic Bond
These free-moving valence electrons form a sea of electrons and, as a result, a metallic bond is formed due to the electrostatic attraction forces between the positively charged metal ions and these free electrons.
Source: canva.com
STRONG INTERACTIONS CHEMICAL BONDS
3) Metallic Bond
Properties of metals such as high melting and boiling temperatures, bright colours, malleability, good conductivity of heat and electricity are due to the freely mobile valence electrons.
Source: Shutterstock.com
WEAK INTERACTIONS
Weak interactions are interactions between positively and negatively charged molecules. Weak interactions do not involve a bond. Although they are a type of interaction that is not as difficult to break as chemical bonds, we can clearly notice the effect of weak interactions in our environment. We can basically categorize weak interactions under two headings: hydrogen bonding and Van der Waals forces.
WEAK INTERACTIONS
1.Hydrogen Bonding
Hydrogen bonding is the strongest type of weak intermolecular interaction. It occurs between molecules formed by hydrogen and elements such as oxygen, nitrogen and fluorine, which are willing to take electrons to stabilize (electronegativity).
WEAK INTERACTIONS
1.Hydrogen Bonding
When hydrogen forms a covalent bond with an element of high electronegativity, the electrons involved in the bond formation are more attracted to the atoms of the element of high electronegativity.
Source: canva.com
WEAK INTERACTIONS
1.Hydrogen Bonding
Therefore, the negative charge density is higher on the atom with high electronegativity than on hydrogen. As a result, the atom with high electronegativity is partially charged with a negative charge (𝛿𝛿-), while hydrogen is partially charged with a positive charge (𝛿𝛿+).
Source: canva.com
WEAK INTERACTIONS
1.Hydrogen Bonding
This causes the molecule to be polar. An electrostatic force of attraction arises between the partially plus charged (𝛿𝛿+) hydrogen atom in the polar molecule and the partially minus charged (𝛿𝛿-) atom in the neighboring molecule.
Source: canva.com
WEAK INTERACTIONS
1.Hydrogen Bonding
This interaction is called hydrogen bonding. Hydrogen bonds play many roles in sustaining life.
Source: Shutterstock.com
WEAK INTERACTIONS
1.Hydrogen Bonding
Without hydrogen bonds, water would be a gas instead of a liquid at room temperature. Hydrogen bonding also causes the surface tension of water to be high.
Source: Shutterstock.com
WEAK INTERACTIONS
2. Van der Waals Forces
Van der Waals forces make molecules stick together and stay together. These forces are particularly involved in phase changes of substances such as gases and liquids and in the interactions of molecular surfaces. In short, Van der Waals forces are the general name for the attraction and repulsion interactions between molecules and play an important role in understanding the structure and behavior of substances.
WEAK INTERACTIONS
2. Van der Waals Forces
There are different types of van der Waals forces:
Source: Shutterstock.com
LET'S CONSTRUCT WHAT WE HAVE LEARNED
In this activity, we will discuss the boiling event that we frequently encounter in daily life at the molecular level and discuss the effect of strong and weak interactions on boiling. Boiling is the rapid transition from liquid to gaseous state when the vapour pressure of a liquid is equal to atmospheric pressure. Since this event occurs not only on the surface of the liquid, as in evaporation, but all over the liquid, bubbles are observed to form in the liquid during boiling. However, the temperature at which liquids begin to boil under constant pressure, i.e. the boiling point, varies according to the type of liquid.
In other words, boiling point is a distinctive feature for liquids. But why? What changes when the type of liquid changes so that the boiling point changes? To understand this, we need to look closely at liquid molecules. The boiling point depends on the strength of intermolecular interactions. The stronger the force of attraction between molecules, the higher the boiling point. Therefore, when the type of liquid changes, the boiling point changes because the intermolecular attraction force of the liquid also changes. So what do you think the force of attraction between molecules depends on? ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..........
When we compare ethyl alcohol and water, it is seen that there are hydrogen bonds between the molecules of both compounds. What do you think is the reason why the boiling points of ethyl alcohol and water are different? .......................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... What do you think is the reason why the boiling points of ethyl alcohol and methyl alcohol are different? ..........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
A student analysed the table above and made the following argument: “The type of weak interaction between methyl alcohol molecules and ethyl alcohol molecules is the same. Both chemicals have hydrogen bonds between molecules. The number of bonds between methyl alcohol molecules and the number of bonds between ethyl alcohol molecules is the same. However, the boiling points of these two chemicals are different. This is because the number of intramolecular bonds forming these chemicals is different. In both ethyl alcohol and methyl alcohol, the atoms in the molecule are connected to each other by covalent bonds. However, when the formulas of the compounds are examined, it is seen that the number of atoms forming the molecule is different.
This shows that the number of bonds in the molecule is different. Since the number of bonds (thus the amount of strong interaction) is high in molecules with a high number of atoms, the boiling point is high.”
This argument is known to be false. Determine why this argument is wrong. ................................................................................................................................................................................................................................................................................................................ Since this argument is known to be false, what do you think is the reason for the difference between the boiling points of ethyl alcohol and methyl alcohol? ................................................................................................................................................................................................................................................................................................................