Solved: Explain why rubbing alcohol feels cold when applied to the skin

What are intermolecular forces? Why are intermolecular forces important?

Explain why rubbing alcohol feels cold when applied to the skin.

What determines whether a substance is a solid, liquid, or gas?

What are the properties of liquids? Explain the properties of liquids in terms of the molecules or atoms that compose them.

Why are water droplets spherical?

What are the properties of solids? Explain the properties of solids in terms of the molecules or atoms that compose them.

What is the difference between a crystalline solid and an amorphous solid?

What is surface tension? How does it depend on intermolecular forces?

What is viscosity? How does it depend on intermolecular forces?

What is evaporation? Condensation?

Why does a glass of water evaporate more slowly in the glass than if you spilled the same amount of water on a table?

Explain the difference between evaporation below the boiling point of a liquid and evaporation at the boiling point of a liquid.

What is the boiling point of a liquid? What is the normal boiling point?

Acetone evaporates more quickly than water at room temperature. What can you say about the relative strength of the intermolecular forces in the two compounds? Which substance is more volatile?

PROBLEM 14Q Explain condensation and dynamic equilibrium.

What is the vapor pressure of a substance? How does it depend on the temperature and strength of intermolecular forces?

PROBLEM 16Q Explain how sweat cools the body.

Explain why a steam burn from gaseous water at \(100^{\circ} \mathrm{C}\) is worse than a water burn involving the same amount of liquid water at \(100^{\circ} \mathrm{C}\). Equation Transcription: Text Transcription: 100 degrees C

Explain what happens when a liquid boils.

Explain why the water in a cup placed in a small ice chest (without a refrigeration mechanism) initially at \(-5^{\circ} C\) does not freeze. Equation Transcription: Text Transcription: -5 degrees C

Explain how ice cubes cool down beverages.

Is the melting of ice endothermic or exothermic? What is the sign of \(\Delta H\) for the melting of ice? For the freezing of water? Equation Transcription: Text Transcription: delta H

Is the boiling of water endothermic or exothermic? What is the sign of \(\Delta H\) for the boiling of water? For the condensation of steam? Equation Transcription: Text Transcription: delta H

What are dispersion forces? How does the strength of dispersion forces relate to molar mass?

What are dipole–dipole forces? How can you tell whether a compound has dipole–dipole forces?

What is hydrogen bonding? How can you tell whether a compound has hydrogen bonding?

What is a molecular solid? What kinds of forces hold molecular solids together?

How do the melting points of molecular solids relate to those of other types of solids?

What is an ionic solid? What kinds of forces hold ionic solids together?

How do the melting points of ionic solids relate to those of other types of solids?

What is an atomic solid? What are the properties of atomic solids?

In what ways is water unique?

PROBLEM 34Q How would ice be different if it were denser than water? How would that affect aquatic life in cold-climate lakes?

PROBLEM 35P Which evaporates more quickly: 55 mL of water in a beaker with a diameter of 4.5 cm or 55 mL of water in a dish with a diameter of 12 cm? Why?

Two samples of pure water of equal volume are put into separate dishes and kept at room temperature for several days. The water in the first dish is completely vaporized after 2.8 days, while the water in the second dish takes 8.3 days to completely evaporate. What can you conclude about the two dishes?

One milliliter of water is poured onto one hand, and one milliliter of acetone (fingernail-polish remover) is poured onto the other. As they evaporate, they both feel cool. Which one feels cooler and why? (Hint: Which substance is more volatile?)

Spilling water over your skin on a hot day will cool you down. Spilling vegetable oil over your skin on a hot day will not. Explain the difference.

Several ice cubes are placed in a beaker on a lab bench, and their temperature, initially at \(-5.0^{\circ} \mathrm{C}\), is monitored. Explain what happens to the temperature as a function of time. Make a sketch of how the temperature might change with time. (Assume that the lab is at \(25^{\circ} \mathrm{C}\).) Equation Transcription: Text Transcription: -5.0 degrees C 25 degrees C

Water is put into a beaker and heated with a Bunsen burner. The temperature of the water, initially at \(25^{\circ} \mathrm{C}\), is monitored. Explain what happens to the temperature as a function of time. Make a sketch of how the temperature might change with time. (Assume that the Bunsen burner is hot enough to heat the water to its boiling point.) Equation Transcription: Text Transcription: 25 degrees C

Which causes a more severe burn: spilling 0.50 g of \(100^{\circ} \mathrm{C}\) water on your hand or allowing 0.50 g of \(100^{\circ} \mathrm{C}\) steam to condense on your hand? Why? Equation Transcription: Text Transcription: 100 degrees C

The nightly winter temperature drop in a seaside town is usually less than that in nearby towns that are farther inland. Explain.

When a plastic bag containing a water and ice mixture is placed in an ice chest initially at \(-8^\circ \mathrm{C}\), the temperature of the ice chest goes up. Why?

The refrigeration mechanism in a freezer with an automatic ice maker runs extensively each time ice forms from liquid water in the freezer. Why?

An ice chest is filled with 3.5 kg of ice at \(0^{\circ} \mathrm{C}\). A second ice chest is filled with 3.5 kg of water at \(0^{\circ} \mathrm{C}\). After several hours, which ice chest is colder? Why? Equation Transcription: Text Transcription: 0 degrees C

Why does 50 g of water initially at \(0^{\circ} \mathrm{C}\) warm more quickly than 50 g of an ice/water mixture initially at \(0^{\circ} \mathrm{C}\)?

In Denver, Colorado, water boils at \(95^{\circ} \mathrm{C}\). Explain. Equation Transcription: Text Transcription: 95 degrees C

At the top of Mount Everest, water boils at \(70^{\circ} \mathrm{C}\). Explain. Equation Transcription: Text Transcription: 70 degrees C

How much heat is required to vaporize 33.8 g of water at \(100^{\circ} \mathrm{C}\)? Equation Transcription: Text Transcription: 100 degrees C

How much heat is required to vaporize 43.9 g of acetone at its boiling point?

How much heat does your body lose when 2.8 g of sweat evaporates from your skin at \(25^{\circ} \mathrm{C}\)? (Assume that the sweat is only water.) Equation Transcription: Text Transcription: 25 degrees C

PROBLEM 52P How much heat does your body lose when 4.86 g of sweat evaporates from your skin at 25 °C? (Assume that the sweat is only water.)

PROBLEM 53P How much heat is emitted when 4.25 g of water condenses at 25 °C?

PROBLEM 54P How much heat is emitted when 65.6 g of isopropyl alcohol condenses at 25 °C?

The human body obtains 835 kJ of energy from a chocolate chip cookie. If this energy were used to vaporize water at \(100^{\circ} \mathrm{C}\), how many grams of water could be vaporized? (Assume that the density of water is 1.0 g/mL.) Equation Transcription: Text Transcription: 100 degrees C

The human body obtains 1078 kJ from a candy bar. If this energy were used to vaporize water at \(100^{\circ} \mathrm{C}\), how much water in liters could be vaporized? (Assume that the density of water is 1.0 g/mL.) Equation Transcription: Text Transcription: 100 degrees C

How much heat is required to melt 37.4 g of ice at \(0^{\circ} \mathrm{C}\)? Equation Transcription: Text Transcription: 0 degrees C

How much heat is required to melt 23.9 g of solid diethyl ether (at its melting point)?

How much energy is released when 34.2 g of water freezes?

How much energy is released when 2.55 kg of diethyl ether freezes?

What kinds of intermolecular forces are present in each substance? (a) \(\mathrm{Kr}\) (b) \(\mathrm{N}_2\) (c) \(\mathrm{CO}\) (d) \(\mathrm{HF}\)

What kinds of intermolecular forces are present in each substance? (a) \(H C l\) (b) \(\mathrm{H}_{2} \mathrm{O}\) (c) \(B r_{2}\) (d) \(H e\) Equation Transcription: Text Transcription: HCl H_2 O Br_2 He

What kinds of intermolecular forces are present in each substance? (a) \(\mathrm{NCl}_{3}\) (trigonal pyramidal) (b) \(\mathrm{NH}_{3}\) (trigonal pyramidal) (c) \(\mathrm{SiH}_{4}\) (tetrahedral) (d) \(\mathrm{CCl}_{4}\) (tetrahedral) Equation Transcription: Text Transcription: NCl_3 NH_3 SiH_4 CCl_4

What kinds of intermolecular forces are present in each substance? (a) \(O_{3}\) (b) \(H B r\) (c) \(\mathrm{CH}_{3} \mathrm{OH}\) (d) \(I_{2}\) Equation Transcription: Text Transcription: O_3 HBr CH_3 OH I_2

Which substance has the highest boiling point? Why? Hint: They are all nonpolar. (a) \(\mathrm{CH}_{4}\) (b) \(\mathrm{CH}_{3} \mathrm{CH}_{3}\) (c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{3}\) (d) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}\) Equation Transcription: Text Transcription: CH_4 CH_3 CH_3 CH_3 CH_2 CH_3 CH_3 CH_2 CH_2 CH_3

Which noble gas has the highest boiling point? Why? (a) Kr (b) Xe (c) Rn

One of these two substances is a liquid at room temperature and the other one is a gas. Which one is the liquid and why? \(\mathrm{CH}_{3} \mathrm{OH} \quad\ \ \ \ \ \ \ \ \ \ \ \mathrm{CH}_{5} \mathrm{SH}\) Equation Transcription: Text Transcription: CH_3 OH CH_4 SH

One of these two substances is a liquid at room temperature and the other one is a gas. Which one is the liquid and why? \(\mathrm{CH}_{3} \mathrm{OCH}_{3} \quad\ \ \ \ \ \ \ \ \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\) Equation Transcription: Text Transcription: CH_3 OCH_3 CH_3 CH_2 OH

A flask containing a mixture of \(\mathrm{NH}_{3}(g)\) and \(\mathrm{CH}_{4}(g)\) is cooled. At \(-33.3^{\circ} \mathrm{C}\) a liquid begins to form in the flask. What is the liquid? Equation Transcription: Text Transcription: NH_3 (g) CH_4 (g) -33.3 degrees C

PROBLEM 74P Explain why CS2 is a liquid at room temperature while CO2 is a gas.

PROBLEM 75P Are CH3CH2CH2CH2CH3 and H2O miscible?

Are \(\mathrm{CH}_{3} \mathrm{OH}\) and \(\mathrm{H}_{2} \mathrm{O}\) miscible? Equation Transcription: Text Transcription: CH_3 OH H_2 O

Determine whether a homogeneous solution forms when each pair of substances is mixed. (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3} \text { and } \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}\) (b) \(\mathrm{CBr}_{4} \text { and } \mathrm{H}_{2} \mathrm{O}\) (c) \(\mathrm{Cl}_{2} \text { and } \mathrm{H}_{2} \mathrm{O}\) Equation Transcription: Text Transcription: CH_3 CH_2 CH_2 CH_2 CH_3 and CH_3 CH_2 CH_2 CH_2 CH_2 CH_3 CBr_4 and H_2 O Cl_2 and H_2 O

Identify each solid as molecular, ionic, or atomic. (a) \(A r(s)\) (b) \(\mathrm{H}_{2} \mathrm{O}(\mathrm{s})\) (c) \(K_{2} O(s)\) (d) \(F e(s)\) Equation Transcription: Text Transcription: Ar(s) H_2 O(s) K_2 O(s) Fe(s)

Identify each solid as molecular, ionic, or atomic. (a) \(\mathrm{CaCl}_{2}(\mathrm{~s})\) (b) \(\mathrm{CO}_{2}(s)\) (c) \(N i(s)\) (d) \(I_{2}(s)\) Equation Transcription: Text Transcription: CaCl_2 (s) CO_2 (s) Ni(s) I_2 (s)

Identify each solid as molecular, ionic, or atomic. (a) \(H_{2} S(s)\) (b) \(\mathrm{KCl}(\mathrm{s})\) (c) \(N_{2}(s)\) (d) \(N I_{3}(s)\) Equation Transcription: Text Transcription: H_2 S(s) KCl(s) N_2 (s) NI_3 (s)

Identify each solid as molecular, ionic, or atomic. (a) \(S F_{6}(s)\) (b) \(C(s)\) (c) \(\mathrm{MgCl}_{2}(\mathrm{~s})\) (d) \(\operatorname{Ti}(s)\) Equation Transcription: Text Transcription: SF_6 (s) C(s) MgCl_2 (s) Ti(s)

Which solid has the highest melting point? Why? (a) \(A r(s)\) (b) \(C C l_{4}(s)\) (c) \(\mathrm{LiCl}(s)\) (d) \(\mathrm{CH}_{3} \mathrm{OH}(\mathrm{s})\) Equation Transcription: Text Transcription: Ar(s) CCl_4 (s) LiCl(s) CH_3 OH(s)

Which solid has the highest melting point? Why? (a) \(C(s, \text { diamond })\) (b) \(K r(s)\) (c) \(\mathrm{NaCl}(\mathrm{s})\) (d) \(\mathrm{H}_{2} \mathrm{O}(\mathrm{s})\) Equation Transcription: Text Transcription: C(s, diamond) Kr(s) NaCl(s) H_2 O(s)

For each pair of solids, determine which solid has the higher melting point and explain why. (a) \(T i(s) \text { and } N e(s)\) (b) \(\mathrm{H}_{2} \mathrm{O}(\mathrm{s}) \text { and } \mathrm{H}_{2} \mathrm{~S}(\mathrm{~s})\) (c) \(K r(s) \text { and } X e(s)\) (d) \(\mathrm{NaCl}(\mathrm{s}) \text { and } \mathrm{CH}_{4}(\mathrm{~s})\) Equation Transcription: Text Transcription: Ti(s) and Ne(s) H_2 O(s) and H_2 S(s) Kr(s) and Xe(s) NaCl(s) and CH_4 (s)

For each pair of solids, determine which solid has the higher melting point and explain why. (a) \(\mathrm{Fe}(\mathrm{s}) \text { and } \mathrm{CCl}_{4}(\mathrm{~s})\) (b) \(\mathrm{KCl}(\mathrm{s}) \text { or } \mathrm{HCl}(\mathrm{s})\) (c) \(\mathrm{TiO}_{2}(\mathrm{~s}) \mathrm\ {Or\ HOOH}(\mathrm{s})\) Equation Transcription: Text Transcription: Fe(s) and CCl_4 (s) KCl(s) or HCl(s) TiO_2 (s) or HOOH(s)

List these substances in order of increasing boiling point: \(\mathrm{H}_{2} \mathrm{O},\ \mathrm{Ne},\ \mathrm{NH}_{3},\ \mathrm{NaF},\ \mathrm{SO}_{2}\) Equation Transcription: Text Transcription: H_2 O, Ne, NH_3 , NaF, SO_2

List these substances in order of decreasing boiling point: \(\mathrm{CO}_{2},\ \mathrm{Ne},\ \mathrm{CH}_{3} \mathrm{OH},\ \mathrm{KF}\) Equation Transcription: Text Transcription: CO_2 , Ne, CH_3 OH, KF

Ice actually has negative caloric content. How much energy, in each of the following units, does your body lose from eating (and therefore melting) 78 g of ice? (a) joules (b) kilojoules (c) calories (1 cal = 4.18 J) (d) nutritional Calories or capital “C” Calories (1000 cal = 1 Cal)

Ice has negative caloric content. How much energy, in each of the following units, does your body lose from eating (and therefore melting) 145 g of ice? (a) joules (b) kilojoules (c) calories (1 cal = 4.18 J) (d) nutritional Calories or capital “C” calories (1000 cal = 1 Cal)

An 8.5-g ice cube is placed into 255 g of water. Calculate the temperature change in the water upon the complete melting of the ice. Hint: Determine how much heat is absorbed by the melting ice and then use \(q=m C \Delta T\) to calculate the temperature change of the 255 g of water. Equation Transcription: Text Transcription: q = mC delta T

A 14.7-g ice cube is placed into 324 g of water. Calculate the temperature change in the water upon complete melting of the ice. Hint: Determine how much heat is absorbed by the melting ice and then use \(q=m C \Delta T\) to calculate the temperature change of the 324 g of water. Equation Transcription: Text Transcription: q = mC delta T

PROBLEM 93P How much ice in grams would have to melt to lower the temperature of 352 mL of water from 25 °C to 0 °C? (Assume that the density of water is 1.0 g/mL.)

PROBLEM 94P How much ice in grams would have to melt to lower the temperature of 55.8 g of water from 55.0 °C to 0 °C? (Assume that the density of water is 1.0 g/mL.)

How much heat in kilojoules is evolved in converting 1.00 mol of steam at \(145^{\circ} \mathrm{C}\) to ice at \(-50.0^{\circ} \mathrm{C}\)? The heat capacity of steam is \(1.84 \mathrm{~J} / \mathrm{g}^{\circ} \mathrm{C}\) and that of ice is \(2.09 \mathrm{~J} / \mathrm{g}^{\circ} \mathrm{C}\). Equation Transcription: Text Transcription: 145 degrees C -50.0 degrees C 1.84 J/g degrees C 2.09 J/g degrees C

How much heat in kilojoules is required to warm 10.0 g of ice, initially at \(-10.0^{\circ} \mathrm{C}\), to steam at \(110.0^{\circ} \mathrm{C}\). The heat capacity of ice is \(2.09 \mathrm{~J} / \mathrm{g}^{\circ} \mathrm{C}\) and that of steam is \(1.84 \mathrm{~J} / \mathrm{g}^{\circ} \mathrm{C}\). Equation Transcription: Text Transcription: -10.0 degrees C 110.0 degrees C 2.09 J/g degrees C 1.84 J/g degrees C

Draw a Lewis structure for each molecule and determine its molecular geometry. What kind of intermolecular forces are present in each substance? (a) \(\mathrm{H}_{2} \mathrm{Se}\) (b) \(\mathrm{SO}_{2}\) (c) \(\mathrm{CHCl}_{3}\) (d) \(\mathrm{CO}_{2}\)

Draw a Lewis structure for each molecule and determine its molecular geometry. What kind of intermolecular forces are present in each substance? (a) \(\mathrm{BCl}_{3}\) (remember that B is a frequent exception to the octet rule) (b) \(\mathrm{HCOH}\) (carbon is central; each H and O bonded directly to C) (c) \(C S_{2}\) (d) \(\mathrm{NCl}_{3}\) Equation Transcription: Text Transcription: BCl_3 HCOH CS_2 NCl_3

The melting point of ionic solids depends on the magnitude of the electrostatic attractions that hold the solid together. Draw ionic Lewis structures for NaF and MgO. Which do you think has the higher melting point?

Draw ionic Lewis structures for KF and CaO. Use the information and the method in the previous problem to predict which of these two ionic solids has the higher melting point.

Explain the observed trend in the melting points of the alkyl halides. Why is HF atypical?

Explain the observed trend in the boiling points of the compounds listed. Why is \(\mathrm{H}_{2} \mathrm{O}\) atypical? Equation Transcription: Text Transcription: H_2 O

An ice cube at \(0.00^{\circ} \mathrm{C}\) with a mass of 23.5 g is placed into 550.0 g of water, initially at \(28.0^{\circ} \mathrm{C}\), in an insulated container. Assuming that no heat is lost to the surroundings, what is the temperature of the entire water sample after all of the ice has melted? Equation Transcription: Text Transcription: 0.00 degrees C 28.0 degrees C

If 1.10 g of steam at 100.0 °C condenses into 38.5 g of water, initially at 27.0 °C, in an insulated container, what is the final temperature of the entire water sample? Assume no loss of heat into the surroundings. Equation Transcription: Text Transcription: 100 degrees C 27.0 degrees C

Consider the molecular view of water shown here. Pick a molecule in the interior and draw a line to each of its direct neighbors. Pick a molecule near the edge (analogous to a molecule on the surface in three dimensions) and do the same. Which molecule has the most neighbors? Which molecule is more likely to evaporate?

Water does not easily remove grease from dirty hands because grease is nonpolar and water is polar; therefore they are immiscible. The addition of soap, however, results in the removal of the grease. Examine the structure of soap shown here and explain how soap works.

PROBLEM 107P One prediction of global warming is the melting of global ice, which may result in coastal flooding. A criticism of this prediction is that the melting of icebergs does not increase ocean levels any more than the melting of ice in a glass of water increases the level of liquid in the glass. (a) Is this a valid criticism? Does the melting of an ice cube in a cup of water raise the level of the liquid in the cup? Why or why not? A response to this criticism is that scientists are not worried about rising ocean levels due to melting icebergs; rather, scientists are worried about rising ocean levels due to melting ice sheets that sit on the continent of Antarctica. ________________ (b) Would the melting of the ice sheets increase ocean levels? Why or why not?

Determine whether a homogeneous solution forms when each pair of substances is mixed. (a) \(\mathrm{CCl}_{4} \text { and } \mathrm{H}_{2} \mathrm{O}\) (b) \(\mathrm{Br}_{2} \text { and } \mathrm{CCl}_{4}\) (c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH} \text { and } \mathrm{H}_{2} \mathrm{O}\) Equation Transcription: Text Transcription: CCl_4 and H_2 O Br_2 and CCl_4 CH_3 CH_2 OH and H_2 O