Flashcards in Chemistry - Chapter 13 Deck (51):
the energy an object has because of its motion
all matter consists of tiny particles that are in constant motion
what are the three assumptions of the kinetic theory as it applies to gases? (3)
1. the particles in a gas are considered to be small, hard spheres with an insignificant volume
2. the motion of the particles in a gas is rapid, constant, and random
3. all collisions between particles in a gas are perfectly elastic
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
results from the force exerted by a gas per unit surface area of an object
an empty space with no particles and no pressure
the collisions of atoms and molecules in air with objects
what happens to the atmospheric pressure if elevation went up? down? (2)
up = atmospheric pressure decreases b/c the density of Earth's atmosphere decreases as the elevation increases
down = atmospheric pressure increases b/c the density of Earth's atmosphere increases as the elevation decreases
device used to measure atmospheric pressure
what does atmospheric pressure depend on?
weather and altitude
what does it represent?
SI unit of pressure
represents a very small amount of pressure
what are the 3 mathematical conversions?
1 atm = 760mm Hg = 101.3kPa
standard atmosphere (atm)
the pressure required to support 760mm of mercury in a mercury barometer at 25 degrees Celcius
what is the standard temperature and pressure (STp) are defined as...?
a temp. of 0 degrees Celcius and a pressure of 101.3kPa, or 1 atm
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
Relationship between the average kinetic energy of the particles and the substance's temperature?
they are directly related to each other
* increase in average kinetic energy of the particles cause the temp. of a substance to rise
what is absolute zero? (3)
(0 K, or -273.15 degrees Celsius)
the temp at which the motion of particles theoretically ceases
no temp. can be lower than absolute zero
what states of matter are known as condensed states of matter? (2)
liquids and solids
b/c increasing pressure on either of them will have little to no effect on them
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 conversion of a liquid to a gas or vapor
vaporization that occurs at the surface of a liquid that is not boiling
a measure of the force exerted by a gas above a 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 of vapor
what happens to the particles in equilibrium?
the particles in the system continue to evaporate and condense, but no net charge occurs in the number of particles in the liquid or vapor.
what will happen when there is a rise in the temperature of a contained liquid?
an increase in vapor pressure, b/c the particles in the warmed liquid have increased kinetic energy
how easy it will melt
what liquid is the most / least volatile?
most = diethyl
least = water
what is used to measure vapor pressure?
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
the temp. at which the vapor pressure of the liquid is just equal to the external pressure on the liquid
what happens to a liquid in an open container? (3)
the rate of evaporation increased as heat is applied
heating allows a greater number of particles to overcome the attractive forces that keep them in the liquid state
average kinetic energy increases and the temp. rises
b/c atmospheric pressure is lower at high altitudes...?
boiling points decrease at higher altitudes
at a lower external pressure...?
the boiling point decreases
at a higher external pressure...?
the boiling point increases
what kind of a process is boiling?
a cooling process
normal boiling point
the boiling point of a liquid at a pressure of 101.3kPa
Difference b/t crystalline structure of diamond and graphite? (2)
Diamond = each carbon atom in the interior of the diamond is strongly bonded to 4 others and the array is rigid and compact
Graphite = has carbon atoms that are linked in widely spaced layers of hexagonal arrays
the temp. at which a solid changes into a liquid
the temp. at which a liquid changes into a solid
the melting and freezing points of a substance are... (2)
at the same room temp. At that temp., the liquid and solid phases are in equilibrium
the particles are arranged in an orderly, repeating, 3-D pattern called a lattice
the smallest group of particles within a crystal that retains the geometric shape of the crystal
two or more molecular forms of the same element in the same physical state
composed of atoms of the same element but we have different properties b/c of diff. structures
lacks an ordered internal structure
atoms are randomly arranged
a transparent fusion product of inorganic substances that have cooled to a rigid state without crystallizing
* doesn't melt, it gradually heats up and softens.
when can sublimation occur?
in solids with vapor pressures that exceed atmospheric pressure at or near room temperature
the change of a substance from a solid to a vapor without passing through the liquid state
which type of solid is likely to have the lowest melting point -- an ionic solid or a molecular solid? Explain.
a molecular solid b/c the attractive forces holding them together are weak
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
gives the conditions of temperature and pressure at which a substances exists as a solid, liquid, or gas (vapor)