Chemistry Chapter 13
What everyday evidence suggests that all matter is in constant motion?
Possible answers:Odors will travel through a room; ink will move throughout a beaker of water.
As determined by Kinetic Theory, Describe the motion of the particles in a gas.
Rapid, constant and random
Describe the particles in a solid
The general properties of solids and the shapes of crystals reflect the orderly arrangement and the fixed locations of particles within the solids.
What determines the physical properties of liquids?
The interplay between the disruptive motions of the particles and the attractions among the particles (p 390)
A liquid will melt when (choose one) -all the particles have the same kinetic energy. -bonds form between the particles. -disruptive vibrations overcome the attractive forces. -attractions overcome the disruptive vibrations.
disruptive vibrations overcome the attractive forces
Identify the change of state that occurs when solid CO2 changes to CO2 gas as it is heated. (choose one) -condensation -freezing -vaporization -sublimation
sublimation
Identify the change of state that occurs when solid CO2 changes to CO2 gas as it is heated. (choose one) condensation freezing vaporization sublimation
sublimation (Remember this is when it goes from solid to vapor)
What is the significance of the TRIPLE point in a phase diagram? (choose one) -Temperature and pressure are equal. -Two phases are in equilibrium. -Three phases are in equilibrium. -The distinction among three phases disappears.
-THREE phases are in equilibrium (Vs. when TWO PHASES exist in EQUILIBRIUM - this is indicated by the line separating the phases, not by the triple point.)
1 atom =___________mm Hg = ___________kPa
1 atm = 760mm Hg = 101.3 kPa
Why do liquids and gases differ in density and the ability to be compressed?
1. Attractive forces in liquids keep particles together 2. Molecules in liquids are in close contact. Molecules in gases are relatively far apart.
What are the three assumptions of KINETIC THEORY as it applies to gases?
1. Particles in gas are small, hard spheres w/ insignificant volume. 2. Motions of the particles is rapid, constant and random 3. All collisions between particles in a gas are perfectly elastic.
A liquid boils when the vapor pressure of particles within the liquid (choose one) 1. Equals the atmospheric pressure 2. is larger than the atmospheric pressure 3. is smaller than the atmospheric pressure
1. equals the atmospheric pressure Boiling occurs when: Vapor pressure = atmospheric pressure * Know this!
As determined by Kinetic Theory, particles of gas are considered to be: (choose one from each) 1. small or large 2. soft or hard 3. cone shaped or sphere shaped 4. insignificant volume or large volume
1. small 2. hard 3. sphere shaped 4. insignificant volume
Which one of the following statements is INCORRECT? 1.The intermolecular forces are relatively weak in liquids that evaporate easily. 2. Vapor pressure is constant when a dynamic equilibrium exists between a liquid and its vapor. 3. The stronger the intermolecular forces, the higher the vapor pressure is. 4. Vapor pressure increases with temperature.
3. The stronger the intermolecular forces, the higher the vapor pressure is. The correct way to look at it is this: Vapor Pressure increases when the temperature of a contained liquid increases. (Because kinetic energy increases with the heat)
In liquids, the attractive forces are (choose one) 1. very weak compared with the kinetic energies of the particles. 2. strong enough to keep the particles confined to fixed locations in the liquid. 3. very minor compared with the kinetic energies of the particles. 4. strong enough to keep particles relatively close together but not strong enough to keep particles from moving past one another.
4. strong enough to keep particles relatively close together but not strong enough to keep particles from moving past one another.
What is glass?
A transparent fusion product of inorganic substances that have cooled to a rigid state WITHOUT crystallizing.
standard atmosphere (atm)
ATM is the pressure required to support 760 mm of mercury in a mercury barometer at 25 degress C.
kinetic theory
All matter consists of tiny particles that are in constant motion.
allotrope
Allotropes are two or more different molecular forms of the same element in the same physical state. (Although they are composed of atoms of the same element, they have different properties because their STRUCTURES are different.)
Why is the equilibrium that exists between a liquid and its vapor in a closed container called a dynamic equilibrium?
Although the net amounts of vapor and liquid remain constant, some molecules are while an equal number of particles are condensing.
amorphous solid; define and give examples
An amorphous solid lacks an ordered internal structure. Examples include rubber, plastic and asphalt and glasses. (Atoms are randomly arranged.)
vacuum
An empty space with no particles and no pressure
How is the Kelvin temperature of a substance related to the average kinetic energy of its particles?
An increase in kinetic energy causes the temperature to rise. As the substance cools, the particles tend to move more slowly, and their average kinetic energy declines.
Describe "how" a liquid beings to boil. (temperature and energy)
At a temperature at which particles throughout a liquid have enough kinetic energy to vaporize, the liquid begins to boil.
What causes atmospheric pressure and why is it much lower on the top of a mountain than it is at sea level?
Atmospheric pressure results from the collisions of particles in air with objects. There are fewer particles in a given volume of air at the top of a mountain than at sea level
Why do boiling points vary with altitude?
Because a liquid boils when the vapor pressure of particles within the liquid EQUALS the atmospheric pressure. (And atmospheric pressure varies with altitude.) Thus: Liquids boil when VAPOR PRESSURE = ATMOSPHERIC PRESSURE Know this!
How does perspiration help cool your body on a hot day?
Because the evaporation of perspiration is an endothermic process the skin is cooled.
In a system at constant vapor pressure, a DYNAMIC EQUILIBRIUM exists between the vapor and the liquid. Why?
Because the rate of evaporation of liquid EQUALS the rate of condensation of the vapor.
Name at least one physical property that would permit you to distinguish a molecular solid from an ionic solid
Ionic compounds generally have higher melting points than molecular solids.
In a closed container, when the rate of evaporation (of a liquid) equals the rate of condensation, this is called _______.
DYNAMIC EQUILIBRIUM. The particles continue to evaporate and condense, but there is no net change in the number of particles.
What is elastic collision?
Energy is tranferred between particles. It's a collision in which the TOTAL kinetic energy of the colliding bodies or particles is the same AFTER the collision as it was BEFORE (opposed to inelastic collision )
The escape of molecules from the surface of a liquid is known as (choose one) -boiling. -sublimation. -evaporation. -condensation.
Evaporation *Evaporation absorbs energy
What is gas pressure the result of?
Gas pressure is the result of simultaneous collisions of billions of rapidly moving particles in a gas with an object.
How does kinetic theory explain gas pressure?
Gas pressure results from the force exerted by a gas; this force is caused by moving bodies when they collide with other bodies. ( see page 386 for more explanation)
Describe the effect that increasing temperature has on the vapor pressure of a liquid.
It increases the kinetic energy,which increases the vapor pressure.
Is the average kinetic energy of the particles in a block of ice at 0 degrees C the same as or different from the average kinetic energy of the particles in a gas-filled weather balloon at 0 degrees C? Explain
It is the same, because the temperature is the same.
The average kinetic energy of the particles in a substance is directly proportional to the (choose one) -Fahrenheit temperature. -Kelvin temperature. -physical state of the substance. -Celsius temperature.
Kelvin temperature
Which is denser, liquid or gas?
Liquids. Intermolecular ATTRACTIONS reduce the amount of space between particles in liquids, thus liquids are more dense than gases.
Explain why increasing the temperature of a liquid increases its rate of evaporation
More molecules have enough energy to escape attractions within the liquid.
Are perfectly elastic collisions possible between objects that are large enough for you to see?
No. Collisions between objects other than at the atomic level involve some loss of kinetic energy to heat.
Would you expect a dynamic equilibrium in a liquid in an open container? Explain
No. In an open container, most of the particles that escape from the surface of the liquid as vapor do not condense back to liquid.
During evaporation, what molecules can escape?
Only those molecules with a certain minimum kinetic energy can escape from the surface
crystal - How are particles arranged?
Orderly, repeating, three-dimensional patterns called crystal lattice.
Increasing the amount of liquid in a closed container will cause the vapor pressure of the liquid to (choose one) -increase. -decrease. -remain the same. -vary in a way that depends on the liquid.
Remain the same (But if you increased the temperature of the liquid, the vapor pressure would increase.)
What is atmospheric pressure?
Results from the collisions of atoms and molecules in air with objects. Atmospheric pressure DECREASES as you climb a mountain. Why? Because the density of the Earth's atmospher DECREASES as the elevation INCREASES.
An increase in the average kinetic energy of the particles in a substance causes the temperature to (choose one) Rise Fall
Rise
The ______ of a crystal reflects the arrangement of the particles within the solid.
Shape
What is gas pressure a result of?
Simultaneous collisions of billions of rapidly moving particles in a gas with an object.
When Vapor Pressure exceeds Atmospheric Pressure, what happens?
Sublimation Sublimation occurs when: Vapor Pressure> Atmospheric Pressure Examples of a substance that undergoes sublimation is Iodine
When can sublimation occur?
Sublimation occurs in Solids -with VAPOR PRESSURES that exceed ATMOSPHERIC pressure -at or near ROOM TEMPERATURE. *This is Key to know: This occurs when vapor pressures >atmospheric pressure
Describe when sublimation occurs in solids
Sublimation occurs in solids: -that have vapor pressures that exceed atmospheric pressure at or near room temperature In other words: SUBLIMATION: When Vapor Pressures > Atmospheric Pressures @ room temperature.
What is the significance of the triple point in a phase diagram? (Choose one) -Temperature and pressure are equal. -Two phases are in equilibrium. -Three phases are in equilibrium. -The distinction among three phases disappears.
THREE phases are in equilibrium
melting point
Temperature at which a solid changes into a liquid. At this temperature, the disruptive vibrations of the particles are strong enough to overcome the attractions that hold them in fixed positions.
What happens to the temperature of a substance when the average kinetic energy of its particles decreases?
Temperature falls
Why do different liquids have different normal boiling points?
The INTERMOLECULAR ATTRACTIONS in some compounds are stronger than in others
You have two similar sealed jars of water at the same temperature. In the first jar, there is a large amount of water. In the second jar, there is a small amount of water. Explain how the vapor pressure can be the same in both jars, even though many more water molecules are evaporating in the first jar.
The KINETIC energy of the escaping molecules is the same, and so the VAPOR PRESSURE is the same!
Describe the relationship between the Kelvin temperature of a substance and the average kinetic energy of the particles of the substance.
The Kelvin temperature is directly proportional to the average kinetic energy of the particles of the substance
What is the relationship between the temperature in kelvins and the average kinetic energy of particles?
The Kelvin temperature scale reflects the relationship between temperature and average kinetic energy
pascal (Pa)
The SI unit of pressure. It represents a very small amount of pressure.
By what factor does the average kinetic energy of the molecules of gas in an aerosol container increase when the temperature is raised from 27 C (300K) to 627 C (900 K)
The average kinetic energy triples.
What is the difference between boiling point and normal boiling point of a liquid.
The boiling point is the temperature at which the vapor pressure equals the external pressure. At the normal boiling point, the external pressure is 101.3 kPa.
normal boiling point
The boiling point of a liquid at a pressure of 101.3kPa.
Sublimation and Deposition
The change of a substance from a solid to a vapor without passing through the liquid state. The change of a substance from a vapor to a solid without going through the liquid state.
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 phases.
evaporation
The conversation from a liquid to a gas (vaporization) AT THE SURFACE OF A LIQUID that is not boiling
vaporization
The conversion of a liquid to a gas or vapor. (Note the difference between this and evaporation)
What is kinetic energy?
The energy an object has because of its motion is called kinetic energy
Explain why molecular solids usually have lower melting points than ionic solids
The forces between the molecules are weaker than the forces between ions.
What is unique about how glass and how it melts?
The irregular internal structures of glasses are intermediate between those of a crystalline solid and those of a free-flowing liquid. Glasses DO NOT melt at a definite temperature.
vapor pressure
The measure of the force exerted by a gas above a liquid.
What is significant about the temperature absolute zero?
The point where no more heat can be removed from the system. The zero point on the Kelvin temperature scale. No molecular activity occurs at this temperature.
What is happening at the molecular level when a DYNAMIC EQUILIBRIUM occurs?
The rate of evaporation of the liquid equals the rate of condensation of the vapor. Dynamic Equilibrium: When Evaporation rate = Condensation rate
unit cell
The smallest group of particles within a crystal that retains the geometric shape of the crystal
boiling point (bp)
The temperature at which the VAPOR PRESSURE of the liquid is just equal to the EXTERNAL PRESSURE on the liquid.
Explain why a liquid stays at constant temperature while it is boiling.
The temperature is constant while the liquid boils because the added energy is used to vaporize the molecules.
According to Kinetic theory, what is the difference between particles in gas and particles in liquid?
There are no ATTRACTIONS between particles in Gas. BUT the particles in liquid are attracted to each other. These attractions in liquid keep the particles close together, which is why liquids have volume.
In a system at constant vapor pressure, describe the equilibrium relationship between the vapor and the liquid.
There is a dynamic equilibrium relationship between the vapor and the liquid. The rates of evaporation and condensation are EQUAL in a system at constant vapor pressure
phase diagram
This is a graph that shows the relationships among the solid, liquid, and vapor states of a substance in a sealed container. It lets you know the TEMPERATURE and PRESSURE at which substances exist in their various stages. The Line on the diagram shows where TWO phases (such as vapor and liquid) can exist in equilibrium
triple point
This is the point on the phase diagram at which ALL THREE curves meet. It represents the point where ALL THREE PHASES can be in equilibrium with one another. *Don't confuse this with the line on the phase diagram that shows where two phases are in equilibrium.
True or False: The rate of evaporation of a liquid from an open container increases as the liquid is heated
True. Heating allows a greater number of particles at the liquid's surface to overcome the attractive forces that keep them in the liquid state.
What is the significance of a line in a phase diagram? (choose one) -Only one phase is present. -Two phases are in equilibrium. -Three phases are in equilibrium. -The distinction between two phases disappears.
Two phases are in equilibrium (**The triple point is where THREE phases are in equilibrium)
There is liquid-vapor equilibrium in a container. Explain WHY the vapor pressure in the container is not affected when the VOLUME of the container is changed.
Vapor pressure depends ONLY on the KINETIC ENERGY of the escaping molecules.
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 you draw on a straw, the pressure inside the straw is less than the pressure (atmospheric) on the liquid in the container; so liquid is pushed into your mouth.
According to Kinetic theory, do particles in gases and in liquids have kinetic energy?
YES, and this Kinetic energy allows gases and liquids to flow (and conform to the shape of their containers). NOTE that kinetic energy is different from ATTRACTIONS between particles.
Is evaporation a cooling process?
YES, because as evaporation takes place, the liquids temperature decreases.
barometer
a device used to measure atmospheric pressure
Which one of the following is the most disordered? (choose one) -a gas near the temperature at which it condenses -a liquid near its freezing point -a solid near its melting point -a liquid near its boiling point
a gas near the temperature at which it condenses
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.
The pressure a gas exerts on another object is caused by (choose one) -the physical size of the particles. -collisions between particles and an object. -collisions between particles. -the chemical composition of the gas
collisions between particles AND AN OBJECT
A mixture of gases contains oxygen, nitrogen, and water vapor. What physical process could you use to remove the water vapor from the sample?
condensation of the water vapor on a cold surface
In a series of liquids, as the intermolecular forces of attraction strengthen, would you expect the vapor pressure to increase or decrease? Explain.
decrease; As the attractions become stronger, it becomes more difficult for molecules to overcome the attractions and vaporize.
The boiling point of a liquid (choose one) -increases at higher altitudes. -decreases at higher altitudes. -is the same at all altitudes. -is unrelated to altitude.
decreases at higher altitude
Which one of the following is a process that absorbs energy? -freezing -condensation -evaporation -solidifying
evaporation (Know why)
The solid-liquid equilibrium line in the phase diagram of a given substance slants to the right. How is the substance's freezing point affected by increased pressure? Does it increase or decrease?
increases
The vapor pressure of a contained liquid can be measured in _______________.
manometers. **The vapor pressure is equal to the DIFFERENCE in height of the mercury in the two arms of the U-tube.
Crystals are classified into __________ groups (how many?)
seven
List three states of matter in order of INCREASING disorder at the molecular level. (choose one) -gas < liquid < solid -gas < solid < liquid -liquid < solid < gas -solid < liquid < gas
solid < liquid <gas
Allotropes have different properties because (choose one) -their atoms are arranged in different patterns. -they are composed of different elements. -they are in different states. -they consist of different isotopes of the same element.
their atoms are arranged in different patterns