Unit 1 Flashcards
Homogenous solutions
Combinations of substances that appear to be one single substance to the naked eye - clean air, drinking water
Heterogenous solutions
Composed of visibly different substances in various phases (solid, liquid, gas)
Differentiating characteristic (intensive properties)
Properties that are unique to the substance in question, and not determined by the amount of it present - melting point, density, conductivity
Extensive properties
Properties that are dependent the amount of substance present - mass, volume
Physical change
A change that does not alter the chemical composition of a substance - phase change
What is the relationship of pressure to phase change points?
Direct relationship - as pressure lowers, PCP lowers - increasing pressure widens the range where substance is stable in one phase
Triple point
A corresponding temperature and pressure where three different phases coexist
Critical point
The point at which the temperature and pressure have both increased to, and the liquid and gas states are indistinguishable
Supercritical fluid
Temperatures and pressures that exceed the critical point create substances that exist in this phase
Vapor pressure curve
The line between liquid and gas on the Temperature-Pressure graphs
Vapor pressure
When a liquid is in a sealed container, some molecules will eventually evaporate, producing a pressure acting on the walls of the container
Increase temp = increase V.P.
What is the boiling point of any given substance?
When the V.P. = ATM - ATM and V.P. are opposing forces. As soon as the temperature is raised high enough (past the B.P), the vapor pressure exceeds the ATM, and the substance evaporates
Can temperature and energy change at the same time?
No - during a phase change, temperature remains steady as the potential energy of the substance increases or decreases. Then temp increases while energy remains the same in all other cases
Filtration
Mechanically separating the components of a substance by running its parts through a filter
Crystallization
Reducing the temperature of a substance to produce crystal solid forms of a component in order to differentiate it
Distillation
Boiling a substance so its most volatile substance evaporates, then putting the remaining liquid into a condenser where parts can continuously be assayed out
Particulate Model of Matter #1
Any macroscopic sample of a substance is made up of an extremely large amount of microscopic particles
Particulate Model of Matter #2
Particles of matter are constantly moving in different directions through empty space, exerting pressure on the walls of its container.
Ideal Gas Constant
Equation that relates pressure P, temperature T, number of particles n, the universal gas constant R, and volume V, as it relates to PMM #2
PV = nRT
What is the purpose of the Particulate Model of Matter?
To predict and explain the physical properties and behavior of substances.
Average Kinetic energy
The energy of motion, expressed as temperature.
<KE> = 1/2 m (<v>^2)
Note: particles of the same substance at 2 coexisting phases at one temperature have the same average kinetic energy
</v></KE>
True or False: At any given temp, individual particles of the same substance can move at different speeds.
True! See figure 1.10 for explanation. In that same graph, you can also infer that the lowest temperature have the lowest average speed (kinetic energy) of the particles.
True or False: Weight and kinetic energy of a substance doesn’t impact velocity.
False! If you throw a baseball and a golf ball exerting the same amount of energy, which is likely to leave your hand faster?
Particulate Model of Matter #3
Particles interact with each other and the strength of the interactions depends on proximity. Repel at short distances, attract at relatively long distances.
Potential Energy
The energy contained by the positions of the atoms (bonds or no bonds)
+ PE: repulsive forces are dominant
- PE: attractive forces are dominant
0 PE: no forces present
(-) PE change: energy must be removed to move atoms
+ PE change: energy must be added to move atoms
How do potential energy and kinetic energy relate during phase changes?
Only kinetic energy changes during ambient time between phase changes. At phase changes, only potential energy changes to rearrange the bonds of the molecules.
How does potential energy change when atoms move in the direction of their attraction/repulsion?
PE lowers, since low PE represents a more stable state, and stability is desirable.
What factors affect volume of a substance?
Direct: Temperature, number of particles
Indirect: pressure
Why is the ideal gas model inconvenient when comparing them to normal gases?
IGM doesn’t account for IMFs, which doesn’t allow for phase changes to occur. The theory only works if there are no IMFs, low pressure, and high temperature.
Emergence
Macroscopic properties emerging from the special distribution and interactions of particles. Ex. solids appear rigid b/c of arrangement, not because the molecules have physically changed.
During a phase transition, what happens to the energy, and what kind is it?
All energy is invested or lost in the form of potential energy.
Are molecules/particles completely stationary?
Particles are constantly moving in random directions, and attractive interactions between particles pull/push them.
Is low PE or high number of configurations more desirable?
It is dependent on temperature and pressure
High pressure = fewer configs
Low pressure = high configs
High temperature = high PE
Low temperature = low PE
Why is gas favorable at higher temperatures?
You need to add energy to overcome the attractions, and high temps favor high potential energy.
Why are gases favored at lower pressures?
Lower pressures means more space for movement of the particles. L.P. also favors the state with larger # of configurations.
Why are liquids more favorable at lower temperatures?
Lower temperatures mean the attractive bonds between molecules over come the forces exerted by the temperature.
Why are liquids more favorable at higher pressures?
The molecules are condensed, and closer together.
What is an elementary substance?
A substance that cannot be broken down into another seperate substance by organic means, since they contain one single type of atom - i.e. elements of the periodic table
What are compounds?
Substances that CAN be split into two or more different substances by organic means - i.e. H2O
Metals
Solid at room temp, good conductors of heat and electricity
Non-metals/semimetals
Gases at room temp, poor conductors
Metalloids
Share properties of both metals and non-metals
Ionic compounds
Solids w/ high melting points that conduct electricity when dissolved in water
Molecular (covalent) compounds
in different states of matter, and are generally poor conductors
If two gases have the same volume, pressure, and temperature, which has more molecules?
They have the same amount
PV/RT, where all of these values are constant. Using this knowledge, you could determine how many times heavier a molecule of one substance is compared to another substance.
Avogadro’s Number
Amount of particles of a substance where the mass in grams is equal to the average atomic mass. 6.022 x 10^23, expressed by 1 mole.
How do we determine number of molecules N in terms of moles n and Avogadro’s Number NA?
N = n (mol) x NA (Avo’s #)
How do we determine number of moles in a substance in terms of mass m and molar mass M?
n = m/M
