Honors Chemistry Chapter 13 (Sister C.)

what is the relationship between evaporation and kinetic energy?

during evaporation, only those molecules with a certain minimum kinetic energy can escape from the surface of the liquid

the ____________ is defined as the boiling point of a liquid at a pressure of 101.3 kPa.

normal boiling point

gases travel in _______________ between collisions

straight-line paths

________ are two or more different molecular forms of the same element in the same physical state

allotropes

how do allotropes of an element differ?

allotropes of an element differ in the way the atoms are structured which results in different properties

As evaporation takes place, the liquid's temperature ________

decreases. evaporation is a cooling process

name the three allotropes of carbon

diamond, graphite, buckminsterfullerene (buckyball)

the change of a substance from a solid to a vapor without passing through the liquid state is called...

sublimation

when can sublimation occur?

sublimation occurs in solids with vapor pressures that exceed atmospheric pressure at or near room temperature

standard temperature and pressure is defined as a...

temperature of 0°C and a pressure of 101.3 kPa, or 1 atm

At any given temperature, the particles of all substances, regardless of physical state, have...

the same average kinetic energy

what determines the shape of a crystal?

the shape of a crystal reflects the arrangement of the particles within the solid

what phases are in equilibrium at a substance's melting point?

the solid and liquid phases are in equilibrium at a substance's melting point

______ atm = ____________ mm Hg = _____________kPa = __________ lbs/in²

1 atm = 760 mm Hg = 101.3 kPa = 14.7 lbs/in²

change 1656 kPa to atm.

16.34 atm

change 190 mm Hg to kPa and atm

25 kPa or 0.25 atm

What pressure, in kilopascals and in atmospheres, does a gas exert at 385 mm Hg?

51.3 kPa or 0.507 atm

using figure 13.18, estimate the boiling point of water at a pressure of 50 kPa.

70°C

would you expect a substance that sublimates at or near room temperature to be a molecular substance or an ionic substance? use what you learned about bonding in chapters 7 and 8 to answer the question.

Molecular substance, because the particles are held together by relatively weak forces and thus become gases more readily.

which of the following results in an increase in temperature? a. increase in kinetic energy b. speed up of the particles c. the stored portion of energy (potential energy)

a

what is the difference between a crystal lattice and a unit cell?

a crystal lattice is the ordered, repeating arrangement of ions, molecules, or atoms in a crystalline solid. a unit cell is the smallest group of particles within this lattice that retains the geometric shape of the crystal.

___________ is a transparent fusion product of inorganic substances that have cooled to a rigid state without cyrstallizing

a glass

Why does the boiling point of a liquid vary with atmospheric pressure?

a liquid boils when the vapor pressure above the liquid equals the external pressure, which is most likely the atmospheric pressure. this happens because liquid molecules at the boiling point have enough kinetic energy to vaporize without being constrained by the external pressure. atmospheric pressure is usually what we understand for external pressure, and it is the total pressure of all the gases in the air. as altitude changes, so does atmospheric pressure. at high altitudes, there are less air molecules, and thus a lower atmospheric pressure. with a lower pressure, liquid molecules need less energy to evaporate, and so the boiling point varies

why does a liquid take the shape but not the volume of its container?

a liquid takes the shape of its container because its molecules can slide past each other, but can not take the volume because inter-molecular forces hold the liquid together

___________ gives the conditions of temperature and pressure at which a substance exists as solid, liquid, or gas (vapor)

a phase diagram

what is an amorphous solid?

a solid not in crystalline form; it lacks an ordered internal structure

refer back to figure 13.9 to answer the following questions: a. what is the normal boiling point of ethanoic acid? b. which liquid has the highest vapor pressure at 40°C? c. at standard atmospheric pressure, which of the substances are in the gaseous state at 70°C? d. water boils at 100°C at standard pressure. how would the pressure on ethanol and on ethanoic acid have to change for these liquids to boil at 100°C? e. mount mckinley in alaska is the tallest peak in north america at 6194 m. the atmospheric pressure at its peak is 44 kPa. what is the boiling point of water at the peak of mount mckinley?

a. 120°C b. chlorofoam c. chlorofoam d. by inspection of the graph in figure 13.9, the pressure for ethanol would have to increase in order for its boiling point to be at 100°C. similarly, the pressure for ethanoic acid would have to decrease in order for its boiling point to be at 100°C e. by inspection of the graph in figure 13.9, at the peak of mt. mckinley with a pressure of 44 kPa, the boiling point of water is at a little under 80°C

convert the following pressures to kilopascals a. 0.95 atm b. 45 mm Hg

a. 96 kPa b. 6 kPa

predict the physical state of each substance at the specified temperature. use the melting point and boiling point data from the table below. a. phenol at 99°C b. ammonia at -25°C c. methanol in an ice-water bath d. methanol in a boiling-water bath e. ammonia at -100°C f. phenol at 25°C

a. liquid b. gas c. liquid d. gas e. solid f. solid

____________ is the temperature at which the motion of particles theoretically ceases

absolute zero which is 0 K or -273.15°C

why does a solid have a definite shape and a definite volume?

any matter that is a solid has a definite shape and a definite volume. the molecules in a solid are in fixed positions and are close together. although the molecules can still vibrate, they cannot move from one part of the solid to another part. as a result, a solid does not easily change its shape or its volume

the collisions of atoms and molecules in air with objects results in

atmospheric pressure

a ______________ is a device that is used to measure atmospheric pressure

barometer

why don't liquids always boil at the same temperature?

because a liquid boils when its vapor pressure is equal to the external pressure

why does a liquid evaporate faster when heated?

because heating a liquid increases the average kinetic energy of its particles. the added energy enables more particles to overcome the attractive forces keeping them in the liquid state

why can sublimation occur?

because solids, like liquids, have a vapor pressure

why does atmospheric pressure decrease as you climb a mountain?

because the density of earth's atmosphere decreases as the elevation increases

the _________ is the temperature at which the vapor pressure of the liquid is just equal to the external pressure on the liquid

boiling point

which elements have allotropes?

carbon, phosphorus, sulfur, oxygen, boron, and antimony

in a _______, the particles are arranged in an orderly, repeating, three-dimensional pattern called a crystal lattice

crystal

a _____________ is a repeating array of any of fourteen kinds of unit cells

crystal lattice

list the 7 crystal systems

cubic, tetragonal, orthorhombic, monoclinic, triclinic, hexagonal, rhombohedral

explain how evaporation lowers the temperature of a liquid

during evaporation, the molecules with the highest kinetic energies are able to escape from the surface of the liquid. this results in a lower average kinetic energy of the remaining molecules, resulting in a lower temperature of the liquid

when vaporization occurs at the surface of a liquid that is not boiling, the process is called...

evaporation

true or false: boiling is not a cooling process

false

true or false: gases are much more dense than liquids

false

substances that can flow are referred to as...

fluids.

the temperature at which a liquid changes into a solid

freezing point

this results from the force exerted by a gas per unit surface area of an object

gas pressure

how does kinetic theory explain gas pressure?

gas pressure is the result of billions of rapidly moving particles in a gas simultaneously colliding with an object

why does a gas take the shape and volume of its container?

gases do not have a definite shape nor a definite volume; the composition of gases causes it to disperse and it takes the shape of the environment it is in if the gas is enough

the pressure at the top of mount everest is 33.7 kPa. Is that pressure greater or less than 0.25 atm?

greater

explain a pressure cooker

in a pressure cooker, the vapor cannot escape and the vapor pressure increases. so water boils at a temperature above 100°C and food can cook more quickly

when can a dynamic equilibrium exist between a liquid and its vapor?

in a system at constant vapor pressure, a dynamic equilibrium exists between the vapor and the liquid. the system is in equilibrium because the rate of evaporation of liquid equals the rate of condensation of vapor

How do the seven crystal systems differ?

in terms of the angles between the faces and in the number of edges of equal length on each face

describe the effect that increasing temperature has on the vapor pressure of a liquid

increasing the temperature of a liquid causes vapor pressure to increase because the particles in the liquid now have a higher kinetic energy and have more ability to escape the surface of the liquid

why do liquids have a definite volume?

intermolecular attractions keep the particles in a liquid close together

explain why liquids and gases differ in density and the ability to be compressed

intermolecular forces reduce the space between particles in a liquid. therefore, the liquid is a condensed state of matter and cannot be compressed with an increase in pressure. gases are able to be compressed because there is empty space in between particles. this explains why liquids have a higher density than gases

_________ solids have high melting points because relatively strong forces hold them together

ionic

how do the melting points of ionic solids generally compare with those of molecular solids?

ionic solids have higher melting points than molecular solids due to the strong electrostatic forces in ionic solids

the energy an object has because of its motion is called

kinetic energy

during an elastic collision...

kinetic energy is transferred without loss from one particle to another, and the total kinetic energy remains constant

according to the ___________, all matter consists of tiny particles that are in constant motion

kinetic theory

_________ are known as condensed states of matter because increasing its pressure doesn't really affect its volume。

liquids and solids

the vapor pressure of a liquid can be determined with a device called a...

manometer

the temperature at which a solid changes into a liquid

melting point

_________ solids have relatively low melting points

molecular

the particles in a gas are usually

molecules or atoms

do gases have a definite shape or volume?

no

do glasses melt at a definite temperature?

no

describe one practical use of sublimation

one useful application of sublimation is the use of dry ice as a coolant in the transportation of frozen goods such as ice cream

the SI unit of pressure is the

pascal

A cylinder of oxygen is cooled from 300 K (27°C) to 150 K (-123°C). By what factor does the average kinetic energy of the oxygen molecules in the cylinder decrease?

recall that the kinetic temperature of a substance is directly proportional to the average kinetic energy of the particles of a substance. if the temperature is decreased by one half, then the average kinetic energy of the oxygen molecules in the cylinder decreases

list 3 kinds of unit cells

simple cubic, body-centered, and face-centered

Do solids flow? why or why not?

solids do not flow because the particles in solids to vibrate about fixed points

use figure 13.9 to determine the boiling point of ethanoic acid at 27 kPa and chlorofoam at 80 kPa

the boiling point of ethanoic acid under this condition is approximately 73°C. the boiling point of chlorofoam under this condition is approximately 53°C

how are the conditions at which phases are in equilibrium represented on a phase diagram?

the conditions of pressure and temperature at which two phases exist in equilibrium are indicated on a phase diagram by a line separating the two regions representing the phases.

what happens when a crystalline solid is shattered?

the fragments have the same surface angles as the original solid

how are the structure and properties of solids related?

the general properties of solids reflect their orderly arrangement of their particles and the fixed locations of their particles.

what factors determine the physical properties of a liquid?

the interplay between the disruptive motions of particles in a liquid and the attractions among the particles determines the physical properties of liquids

what is the relationship between the temperature in kelvins and the average kinetic energy of particles?

the kelvin temperature of a substance is directly proportional to the average kinetic energy of the particles of the substance

describe the behavior of an oxygen molecule in a sealed container of air. include what happens when the molecule collides with another molecule or the container walls

the oxygen molecule will sometimes, very rarely, collide with other gas molecules and create pressure and bounce off with no loss of kinetic energy. also, periodically, it will hit walls of the container and, once again, bounce off with no loss of kinetic energy

what are the three assumptions of the kinetic theory as it applies to gases?

the particles in a gas are considered to be small, hard spheres with an insignificant volume. the motion of the particles in a gas is rapid, constant, and random. all collisions between particles in a gas are perfectly elastic (no kinetic energy is lost)

the height of the mercury column in the tube depends on...

the pressure exerted by particles in air colliding with the surface of the mercury in the dish

What does the triple point on a phase diagram describe?

the triple point describes the only set of conditions at which all three phases of matter can exist in equilibrium with one another

the ________ describes the only set of conditions at which all three phases can exist in equilibrium with one another

triple point

True or false: unlike gases, the particles in a liquid are attracted to each other

true

true or false: an increase in the temperature of a contained liquid increases the vapor pressure

true

true or false: no attractive or repulsive forces exist between the particles in a gas

true

true or false: the melting and freezing points of a substance are at the same temperature

true

true or false: the temperature of the boiling liquid never rises above its boiling point

true

the smallest group of particles within a crystal is known as a _______

unit cell

list the various units used to measure pressure, and identify the si unit

units of pressure include Pa, mm Hg, torr, atm, and bar

an empty space with no particles and no pressure is called a

vacuum

a measure of the force exerted by a gas above a liquid is called...

vapor pressure

the conversion of a liquid to a gas or vapor is called...

vaporization

under what conditions does boiling occur?

when a liquid is heated to a temperature at which particles throughout the liquid have enough kinetic energy to vaporize, the liquid begins to boil

what role does atmospheric pressure play when someone is drinking a liquid through a straw?

when drinking a liquid with the use of a straw, the pressure within the straw has to be less than the atmospheric pressure on the liquid in the cup. this makes it possible for the liquid to be pushed up through the straw

the molecules at the higher temperature have a _____________ of kinetic energies

wider range

your lab partner measures the boiling point of water in an open beaker as 108.2°C. you know that water can be made to boil at this temperature, but you still ask your partner to repeat the measurement. explain

your partner misread the thermometer and needs to recheck the value. since the beaker is an open container, the water should boil at 100°C at or close to sea level