Chemistry Chapter 10: Intermolecular Forces

Questions and Answers

Which of these options is correct regarding surface tension?

Gravitational forces

Adhesive forces

Frictional forces

Cohesive forces (correct)

Which of the following forces is the tendency of liquids to resist separation?

Adhesive forces

Combinatory forces

Cohesive forces (correct)

None of the above

Which of the following would have the higher boiling point?

There is not enough information to determine this

They have the same boiling point

Br2

ICl (correct)

What is produced as a result of rapidly fluctuating induced dipoles and instantaneous dipoles?

Dispersion force Signup and view all the answers

The hydrogen bond occurring between which two molecules would be the strongest?

H2O and HF Signup and view all the answers

The phase of a substance depends on the relative magnitudes of the molecular _________________ and the energy of intermolecular attractions.

kinetic energy Signup and view all the answers

Which of the following has the highest boiling point?

C8H18 Signup and view all the answers

Why does ethanol (C2H6O) have a higher viscosity than octane (C8H18)?

It can make hydrogen bonds Signup and view all the answers

If a bug can walk on water, why can't a human?

A human's weight is much greater than needed to overcome the surface tension of the water. Signup and view all the answers

Intermolecular forces that occur between neutral atoms and molecules are called:

Van der Waals forces Signup and view all the answers

Which of the following will have a higher boiling point?

CBr4 Signup and view all the answers

Droplets are spherical because of:

Cohesive forces Signup and view all the answers

What is the energy required to increase the surface area of a liquid?

Surface tension Signup and view all the answers

Which of the following will have the highest boiling point?

HF Signup and view all the answers

Which molecule will engage in the strongest dispersion forces?

CI4 (carbon tetraiodide) Signup and view all the answers

A liquid does not wet a surface if the adhesive forces are _______ than the cohesive forces.

weaker than Signup and view all the answers

Which molecule will NOT exhibit hydrogen bonding?

NH+4 Signup and view all the answers

Viscosity is defined as the ability of a liquid to:

Resist flow Signup and view all the answers

Which of the following would have the higher boiling point?

CH3CN Signup and view all the answers

At a sufficiently low temperature, a liquid does not have enough kinetic energy to overcome intermolecular attractions, and changes into:

A solid Signup and view all the answers

If water is able to 'wet' a surface, we can say that:

The adhesive forces outweigh the cohesive forces Signup and view all the answers

Intermolecular forces are primarily responsible for:

Holding together molecules in a material Signup and view all the answers

Which of the following gives rise to surface tension?

Cohesive forces Signup and view all the answers

Dispersion forces occur due to:

The temporary asymmetry of electron density Signup and view all the answers

Which molecule would exhibit the strongest dipole-dipole interactions?

CH3Cl Signup and view all the answers

Which molecule would exhibit the strongest dipole-dipole interactions?

HCl Signup and view all the answers

Intermolecular forces are primarily responsible for:

holding together molecules in a material Signup and view all the answers

The hydrogen bond occurring between which two molecules would be the strongest?

H2O and HF Signup and view all the answers

The interactions that molecules of one substance make with the surface of some other substance are called:

adhesive forces Signup and view all the answers

If the surface of a body of water was pierced by an object, the number of hydrogen bonds occurring in the water would:

decrease Signup and view all the answers

Which intermolecular force is present in all condensed phases?

dispersion force Signup and view all the answers

Greater viscosity can typically be due to:

stronger intermolecular forces Signup and view all the answers

The kinetic energies of molecules are responsible for:

increasing the distance between particles Signup and view all the answers

Which molecule can be a hydrogen bond donor?

HOCH2CH2OH Signup and view all the answers

What is surface tension?

the energy required to increase the surface area of a liquid Signup and view all the answers

Which of the following will NOT generate dipole-dipole interactions?

CO2 Signup and view all the answers

Dispersion forces increase with:

increasing molecular mass Signup and view all the answers

The surface of a liquid behaves like a stretched rubber membrane due to:

cohesive forces Signup and view all the answers

Viscosity decreases as:

temperature increases Signup and view all the answers

Which option shows the phases in order of increasing kinetic energy contained within a sample?

solid, liquid, gas Signup and view all the answers

Dispersion forces are specifically the interaction between:

two temporary dipoles Signup and view all the answers

Which substance typically has the greatest viscosity at room temperature?

honey Signup and view all the answers

Which molecule will NOT participate in hydrogen bonding?

CH3OCH3 Signup and view all the answers

A drop of water will retain a spherical shape so as to:

maximize cohesive forces Signup and view all the answers

Which of the following properties allows for surface tension in water?

polarity Signup and view all the answers

Dipole-dipole attractions are:

an intermolecular force of intermediate strength Signup and view all the answers

Which of the following is the best example of a liquid with LOW viscosity?

water Signup and view all the answers

Which of the following exhibits the strongest dispersion force?

molecules that are larger Signup and view all the answers

Water will generate the strongest adhesive forces with a surface that is able to:

generate hydrogen bonds Signup and view all the answers

Three sealed flasks are labeled 'Crystalline solid,' 'Liquid,' and 'Gas' from left to right. Which of the following would have the highest kinetic energy?

gas Signup and view all the answers

Hydrogen bonding is technically a type of:

dipole-dipole attraction Signup and view all the answers

Surface tension will increase with:

increasing intermolecular forces Signup and view all the answers

In order for dispersion forces to attract two different molecules together, the molecules must be:

very close Signup and view all the answers

The molecules are attracted equally in all directions by cohesive forces when:

they are within a liquid Signup and view all the answers

At room temperature, which substance has the lowest viscosity?

gasoline (30 mPas) Signup and view all the answers

Surface tension is due to:

cohesive forces at the surface of a liquid Signup and view all the answers

Dipole-dipole attractions are specifically the interaction between:

two formal dipoles Signup and view all the answers

Hydrogen bonding is responsible for:

DNA base pairing Signup and view all the answers

When water is placed in a glass tube, the meniscus will be:

concave Signup and view all the answers

Intermolecular forces that occur between neutral atoms and molecules are called:

van der Waals forces Signup and view all the answers

Dispersion forces are specifically the interaction between:

two temporary dipoles Signup and view all the answers

Which of the following is the strongest intermolecular force?

hydrogen bonding Signup and view all the answers

A liquid wets a surface if the adhesive forces are ________ than the cohesive forces.

stronger than Signup and view all the answers

Which phase change involves gaining sufficient kinetic energy so as to escape all of the intermolecular forces occurring in a sample?

boiling Signup and view all the answers

The viscosity of a substance is quantified by measuring the rate at which:

a metal ball falls through it Signup and view all the answers

Surface tension depends on the strength of which forces?

cohesive forces Signup and view all the answers

Study Notes

Intermolecular Forces Overview

Intermolecular forces are responsible for interactions between molecules, playing a critical role in the properties of substances.
Key types include dipole-dipole interactions, hydrogen bonding, and dispersion forces.

Dipole-Dipole Interactions

CH3Cl exhibits the strongest dipole-dipole interactions due to its net dipole from tetrahedral geometry.
Among hydrogen halides, HCl demonstrates the strongest dipole-dipole interactions due to its polar bond.

Definitions of Forces

Intermolecular forces hold molecules together in materials, distinguishing them from intramolecular forces that occur within molecules.
Adhesive forces are the attraction between different substances, while cohesive forces refer to attraction between identical molecules.

Hydrogen Bonds

The strongest hydrogen bond interactions occur between H2O and HF because fluorine is highly electronegative, followed by oxygen and nitrogen.
Hydrogen bonds are a specific type of dipole-dipole attraction and significantly influence molecular structure, notably in DNA base pairing.

Viscosity and Temperature

Viscosity refers to a liquid's resistance to flow, which increases with stronger intermolecular forces.
Temperature affects viscosity: higher temperatures reduce viscosity due to increased kinetic energy facilitating easier movement of molecules.

Surface Tension

Surface tension is the energy needed to increase a liquid's surface area, resulting from cohesive forces at the liquid's surface.
Water exhibits a concave meniscus in a glass tube due to its adhesive forces with the glass, maximizing hydrogen bonding.

Dispersion Forces

Dispersion forces, present in all condensed phases, arise from temporary dipoles and increase with molecular size and mass.
They play a significant role in the behavior of nonpolar substances and contribute to the properties of liquids.

Kinetic Energy and States of Matter

Kinetic energy increases from solids to liquids to gases, with gases having the highest kinetic energy due to minimal intermolecular attraction.
The phase change from liquid to gas (boiling) involves overcoming all intermolecular forces.

Measurement of Viscosity

Viscosity can be measured by observing the rate at which a metal ball falls through a liquid, indicating the liquid's flow resistance.

Key Comparisons

Stronger intermolecular forces correlate with higher boiling points. For example, ICl has a higher boiling point than Br2 due to stronger dipole-dipole interactions in ICl compared to dispersion forces in Br2.
In terms of surface tension, cohesive forces are the primary contributors, affecting how a liquid behaves on surfaces.

Summary of Intermolecular Force Types

Hydrogen bonding is the strongest intermolecular force, followed by dipole-dipole attractions and then dispersion forces.
Understanding these forces enables predictions about the physical properties of substances, such as boiling point, viscosity, and surface tension.### Intermolecular Forces and Properties
Dispersion forces are weak electrostatic attractions resulting from rapid fluctuations of dipoles in molecules.
The strongest hydrogen bond occurs between H2O and HF due to fluorine's high electronegativity.
The phase of a substance (solid, liquid, gas) depends on the balance of kinetic energy and intermolecular attractions.
C8H18 has the highest boiling point among the listed hydrocarbons due to larger size and stronger dispersion forces.
Ethanol (C2H6O) has higher viscosity than octane (C8H18) because it can form hydrogen bonds.

Surface Tension and Cohesion

A human cannot walk on water as their weight exceeds the surface tension; insects can due to their lower weight.
Van der Waals forces refer to intermolecular forces between neutral atoms and molecules.
Cohesive forces cause droplets to form spherical shapes, as they attract identical molecules together.
Surface tension is the energy required to increase the surface area of a liquid, reflecting the strength of cohesive forces.

Boiling Points and Molecular Interaction

HF has the highest boiling point among HCl, HBr, and HF due to hydrogen bonding in HF.
CI4 exhibits the strongest dispersion forces as it is the largest molecule among CF4, CCl4, CBr4, and CI4.
The boiling point of CH3CN is higher than that of C3H8 due to dipole-dipole attractions in CH3CN.

Adhesive and Cohesive Forces

Adhesive forces are weaker than cohesive forces when a liquid doesn't wet a surface, leading to a lack of spreading.
Hydrogen bonding is absent in NH+4, making it incapable of engaging in hydrogen bonding unlike NH3 and its derivatives.
Viscosity refers to a liquid's resistance to flow, influenced by intermolecular forces.

State Changes and Molecular Behavior

At low temperatures, liquids can transition into solids when they lack enough kinetic energy to overcome intermolecular attractions.
Water “wets” a surface when adhesive forces surpass cohesive forces, allowing it to spread instead of bead up.
Intermolecular forces hold together molecules in a material, distinct from intramolecular forces that hold atoms within a molecule.

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Explore the concepts of intermolecular forces with flashcards focused on dipole-dipole interactions. This quiz will help you understand which molecules exhibit the strongest interactions based on their geometry and dipole moments.