Chemistry Chapter 10: Intermolecular Forces
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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?

    <p>Dispersion force</p> Signup and view all the answers

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

    <p>H2O and HF</p> 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.

    <p>kinetic energy</p> Signup and view all the answers

    Which of the following has the highest boiling point?

    <p>C8H18</p> Signup and view all the answers

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

    <p>It can make hydrogen bonds</p> Signup and view all the answers

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

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

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

    <p>Van der Waals forces</p> Signup and view all the answers

    Which of the following will have a higher boiling point?

    <p>CBr4</p> Signup and view all the answers

    Droplets are spherical because of:

    <p>Cohesive forces</p> Signup and view all the answers

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

    <p>Surface tension</p> Signup and view all the answers

    Which of the following will have the highest boiling point?

    <p>HF</p> Signup and view all the answers

    Which molecule will engage in the strongest dispersion forces?

    <p>CI4 (carbon tetraiodide)</p> Signup and view all the answers

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

    <p>weaker than</p> Signup and view all the answers

    Which molecule will NOT exhibit hydrogen bonding?

    <p>NH+4</p> Signup and view all the answers

    Viscosity is defined as the ability of a liquid to:

    <p>Resist flow</p> Signup and view all the answers

    Which of the following would have the higher boiling point?

    <p>CH3CN</p> 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:

    <p>A solid</p> Signup and view all the answers

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

    <p>The adhesive forces outweigh the cohesive forces</p> Signup and view all the answers

    Intermolecular forces are primarily responsible for:

    <p>Holding together molecules in a material</p> Signup and view all the answers

    Which of the following gives rise to surface tension?

    <p>Cohesive forces</p> Signup and view all the answers

    Dispersion forces occur due to:

    <p>The temporary asymmetry of electron density</p> Signup and view all the answers

    Which molecule would exhibit the strongest dipole-dipole interactions?

    <p>CH3Cl</p> Signup and view all the answers

    Which molecule would exhibit the strongest dipole-dipole interactions?

    <p>HCl</p> Signup and view all the answers

    Intermolecular forces are primarily responsible for:

    <p>holding together molecules in a material</p> Signup and view all the answers

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

    <p>H2O and HF</p> Signup and view all the answers

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

    <p>adhesive forces</p> 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:

    <p>decrease</p> Signup and view all the answers

    Which intermolecular force is present in all condensed phases?

    <p>dispersion force</p> Signup and view all the answers

    Greater viscosity can typically be due to:

    <p>stronger intermolecular forces</p> Signup and view all the answers

    The kinetic energies of molecules are responsible for:

    <p>increasing the distance between particles</p> Signup and view all the answers

    Which molecule can be a hydrogen bond donor?

    <p>HOCH2CH2OH</p> Signup and view all the answers

    What is surface tension?

    <p>the energy required to increase the surface area of a liquid</p> Signup and view all the answers

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

    <p>CO2</p> Signup and view all the answers

    Dispersion forces increase with:

    <p>increasing molecular mass</p> Signup and view all the answers

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

    <p>cohesive forces</p> Signup and view all the answers

    Viscosity decreases as:

    <p>temperature increases</p> Signup and view all the answers

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

    <p>solid, liquid, gas</p> Signup and view all the answers

    Dispersion forces are specifically the interaction between:

    <p>two temporary dipoles</p> Signup and view all the answers

    Which substance typically has the greatest viscosity at room temperature?

    <p>honey</p> Signup and view all the answers

    Which molecule will NOT participate in hydrogen bonding?

    <p>CH3OCH3</p> Signup and view all the answers

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

    <p>maximize cohesive forces</p> Signup and view all the answers

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

    <p>polarity</p> Signup and view all the answers

    Dipole-dipole attractions are:

    <p>an intermolecular force of intermediate strength</p> Signup and view all the answers

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

    <p>water</p> Signup and view all the answers

    Which of the following exhibits the strongest dispersion force?

    <p>molecules that are larger</p> Signup and view all the answers

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

    <p>generate hydrogen bonds</p> 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?

    <p>gas</p> Signup and view all the answers

    Hydrogen bonding is technically a type of:

    <p>dipole-dipole attraction</p> Signup and view all the answers

    Surface tension will increase with:

    <p>increasing intermolecular forces</p> Signup and view all the answers

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

    <p>very close</p> Signup and view all the answers

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

    <p>they are within a liquid</p> Signup and view all the answers

    At room temperature, which substance has the lowest viscosity?

    <p>gasoline (30 mPas)</p> Signup and view all the answers

    Surface tension is due to:

    <p>cohesive forces at the surface of a liquid</p> Signup and view all the answers

    Dipole-dipole attractions are specifically the interaction between:

    <p>two formal dipoles</p> Signup and view all the answers

    Hydrogen bonding is responsible for:

    <p>DNA base pairing</p> Signup and view all the answers

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

    <p>concave</p> Signup and view all the answers

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

    <p>van der Waals forces</p> Signup and view all the answers

    Dispersion forces are specifically the interaction between:

    <p>two temporary dipoles</p> Signup and view all the answers

    Which of the following is the strongest intermolecular force?

    <p>hydrogen bonding</p> Signup and view all the answers

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

    <p>stronger than</p> 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?

    <p>boiling</p> Signup and view all the answers

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

    <p>a metal ball falls through it</p> Signup and view all the answers

    Surface tension depends on the strength of which forces?

    <p>cohesive forces</p> 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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    Description

    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.

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