Chapter 13: States of Matter

Explain why the boiling point of a liquid varies with atmospheric pressure

Boiling occurs when the vapor pressure of a liquid equals the external pressure. If the atmospheric pressure changes, the boiling point will change

Freezing point

temp at which a liquid changes into a solid

Absolute zero

temp. at which the motion of particles theoretically ceases

Amorphous solid

lacks an ordered internal structure. Ex: rubber, plastic, glass, and asphalt -atoms randomly arranged glasses

Greater number of molecules equals

more pressure because more collisions

Kinetic refers to...

motion

vapor pressure

measure of the force exerted by a gas above a liquid

Glass

a transparent fusion product of inorganic substances that have cooled to a rigid state without crystallizing.

Explain the second assumption of the kinetic theory as it applies to gases "The motion of the particles in a gas are rapid, constant, and random."

-As a result, gases fill their containers regardless of shape and volume of the containers -Uncontained gas can spread out into space without limit -particles travel in straight line paths until they collide with another particle or another object such as the wall of the container -particles change direction only when they rebound from collisions with one another or with other objects -their path of uninterrupted travel in a straight line is very short

Explain the second assumption of the kinetic theory as it applies to gases "All collisions between particles in a gas are perfectly elastic"

-During elastic collision: kinetic energy is transferred without loss from one particle to another --total kinetic energy remains constant

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 are rapid, constant, and random. -All collisions between particles in a gas are perfectly elastic

Explain the first assumption 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. "

-Within a gas, the particles of a gas are relatively far apart compared with the distance between particles in a liquid or a solid. -Between particles, there's just empty space. --No attractive or repulsive forces exist between the particles

Atmospheric pressure

-air exerts pressure on Earth b/c gravity holds the particles in air within Earth's atmosphere -collisions of atoms and molc. in air with objects results in...

An increase in the temperature of a contained liquid increases the vapor pressure...why?

-because the particles in the warmed liquid have increased kinetic energy --> more the particles with reach the minimum kinetic energy necessary to escape the surface of the liquid -the particles escape the liquid and collide with the walls of the container with a greater frequency

Crystal systems

-crystal has sides or faces with angles at which the faces of a crystal intersect (always the same for a given subst. and are characteristic of that subst.) -classified into seven groups, or crystal systems, with characteristic shapes -edges are labeled a,b,c -Angles are labeled alpha, beta, y -differ in terms of angles bet. faces, and the number of edges of equal length on each face

Shape of crystal

-depends on arrangement of the particles within it

How is boiling a cooling process?

-during boiling, the particles with the highest kinetic energy escape first when the liquid is at its boiling pt -supplying more heat allows more particles to acquire enough kinetic energy to escape -but the temp of the boiling liquid never goes above its boiling pt --heat supplied at greater rate, the liquid only boils faster

Why does liquid evaporate faster when heated?

-heating the liquid increases average kinetic energy of its particles -added energy enables more particles to overcome the attractive forces keeping them in a liquid state -as evap. occurs, the particles with the highest kinetic energy tend to escape first -particles left in liquid have a lower av. kinetic energy than the particles that have escaped

What happens when you heat a solid?

-its particles vibrate more rapidly as their kinetic energy increases -organizations of particles within the solid breaks down and eventually the solid melts

What cause this force in gas pressure?

-moving bodies exert a force when they collide with other bodies -although a single particle in a gas is a moving body, the force it exerts is extremely small -yet simultaneous collisions involving many particles would produce a measurable force on an object

Key difference between gases and liquids

-no attractions between particles of a gas -particles in liquid attracted to one another -intermolecular attractions keep the particles in a liquid close together: why liquid has definite volume

SI unit for pressure

-pascal (Pa) -rep. small amount of pressure -normal atmospheric pressure is 100,000 Pa or 100 kPa

One standard atmospheric pressure

-pressure required to support 760 mm of mercury in a mercury barometer oat 25 degrees Celsius - 1 atm= 760 mm Hg= 101.3 kPa

Average kinetic energy

-the particles in any collection of atoms or molc. at a given temp. have a wide range of kinetic energies -most of the particles have kinetic energies somewhere in the middle of this range -use average kinetic energy when discussing kinetic energy of a collection of particles in a subst.

Constrast between Crystalline solid and Amorphous solid

-when crystalline solid shatters, the fragments have the same surface angles as the original solid -glass or amorphous solid shattered would have fragments with irregular angles and jagged edges

Why is atmospheric pressure much lower on the top of the mountain than it is at sea level?

Atmospheric pressure results from the collisions of particles in air with objects -fewer particles in a given volume at the top of the mountain than at sea level

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

Because gas particles do not attract nor repel one another and are in constant motion with a large amount of space between them, they expand to their container's size and shape.

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.

Because molecules are spaced very far apart from one another and do not attract or repel one another, they collide less frequently with each other than with the container walls. When a molecule collides with another molecule or the container, no energy is lost (elastic). It will bounce off the side of the container with the same amount of energy it hit the container with.

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

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

Strong IMF

LESS -VP MORE BOILING PT

Weak IMF

MORE - VP LESS- BP

A fully inflated raft is left outside overnight. The next morning the raft is not fully inflated. As the air temperature rises during the day, the raft expands to the size it was the night before. Assuming that the amt of air inside the raft did not change, use kinetic theory to explain why the size of the raft changes

The Kelvin temperature is directly proportional to the average kinetic energy -as the temp rises the air particles speed up and increase in kinetic energy which cause the raft to expand -as the temperature drops the air particles slow down resulting in a decrease in kinetic energy, causing the raft to deflate to its original

Explain why molecular solids usually have lower melting points than ionic solids

The intermolecular attractions between molecules are weaker than attractions between ions

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

Explain how evaporation lowers the temperature of a liquid

When the molecules with the highest kinetic energy escape from the liquid, the average kinetic energy of the remaining particles is lower and the temperature decreases

Rhombohedral

a =b=c alpha = beta= y doesn't = 90

Monoclinic

a doesnt = b doesn't = c Beta= y = 90 doesn't equal alpha

Orthorhombic

a doesnt equal b doesn't equal c alpha = beta = y =90

Triclinic

a doesnt equal b doesn't equal c alpha doesn't = beta doesn't = y doesn't =90

Heating allows

a greater number of particles at the liquids surface to overcome the attractive forces that keep them in the liquid state -remaining particles in the liquid move faster and faster as they absorb the added energy -thus, average kinetic energy of the particles in the liquid increases and the temperature of the liquids rises

In terms of kinetic energy, explain how a molecule in a liquid evaporates.

a molecule with a certain minimum kinetic energy can escape from the surface of the liquid and vaporize

Hexagonal

a=b doesn't = c alpha = beta = 90 y= 120

Tetragonal

a=b doesn't = c alpha=beta=y=90

Cubic

a=b=c=90 degrees alpha=beta=y

random walk

aimless path the molecules take

Kinetic theory

all matter consists of tiny particles that are constantly in motion

The increase in kinetic energy results in

an increase in temperature -remaining absorbed energy does speed up particles that increases kinetic energy

The interplay between the disruptive motions of particles in a liquid

and the attractions among the particles determines the physical properties of liquids

barometer

device used to measure atmospheric pressure

Gas pressure is the result of...

billions of rapidly moving particles in a gas simultaneously colliding with an object --no particles moving, no collisions occur --therefore, no pressure

Because atmospheric pressure is lower at higher altitudes,

boiling pts decrease at higher altitudes

vaporization

conversion of a liquid to a gas or vapor

normal boiling point

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

Vacuum

empty space with no particles and no pressure

Kinetic energy

energy object has b/c of its motion

Kinetic energy allows the particles in gases and liquids

flow past one another -referred as fluids -allows them to conform to the shape of their containers

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

have the same average kinetic energy

HIGHER ALTITUDE --> LESS ATMOSPHERIC PRESSURE --> DECREASING BOILING PT

impt.

HIGHER VP HIGHER TEMP

impt.

Less mass.. greater velocity Greater mass less velocity

impt.

The melting and freezing pts of a subst. are at the same temp. At that temp, the liquid and solid phases are

in equilibrium

crystal lattice

repeating array of any one of the fourteen kinds of unit cells

Gas pressure

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

Intermolecular attractions reduce

the amount of space between the particles in a liquid -thus liquids are more dense than gases -increasing the pressure on liquid has hardly an effect on its volume -known as condensed state of matter

At a lower external pressure,

the boiling pt decreases the particles in the liquid need less kinetic energy to escape from the liquid

At a higher external pressure

the boiling pt increases -the particles in the liquid need more kinetic energy to escape from the liquid

Atmospheric pressure decreases as you climb up a mountain because...

the density of Earth's atmosphere decreases as elevation increases. -the higher up you go---> less pressure -ball pit analogy

How are the structure and properties of solids related?

the general properties of solids reflect the orderly arrangement of their particles and the fixed locations of their particles. -atoms, ions, or molecules are packed tightly together -solids are dense and no easy to compress -because particles tend to vibrate around fixed points, solids do not flow

As evaporation increases...

the liquid's temperature decreases -hence, cooling process

Crystal

the particles are arranged in an orderly, repeating, three-dimensional pattern called a crystal lattice. -The shape of the crystal reflects the arrangement of the particles within the solid

Describe what happens when a solid is heated to its melting point

the particles have sufficient kinetic energy to overcome the attractive forces holding them in place

unit cell

the smallest group of particles within a crystal that retains the geometric shape of the crystal.

Melting pt

the temperature at which a solid changes into a liquid. -disruptive vibrations of the particles are strong enough to overcome the attractions that hold them in fixed positions

boiling pt

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

The Kelvin temp of a substance is directly proportional

to the average kinetic energy of the particles of a substance -ex. particles of a helium gas at 200 K have twice the average kinetic energy as the particles in helium gas at 100K

Allotropes

two or more different molecular forms of the same element in the same physical state. -composed of the same element but they have different properties because structures are different

evaporation

vaporization that occurs at the surface of a liquid that is not boiling

Atmospheric pressure depends on

weather and altitude -height of mercury column in the tube depends on pressure exerted by particles in the air colliding with the surface of the mercury in the dish -sea level: mercury column760 mm Hg