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PChem 1110 > Unit 1 > Flashcards

Unit 1 Flashcards

1
Q

Homogenous solutions

A

Combinations of substances that appear to be one single substance to the naked eye - clean air, drinking water

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2
Q

Heterogenous solutions

A

Composed of visibly different substances in various phases (solid, liquid, gas)

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3
Q

Differentiating characteristic (intensive properties)

A

Properties that are unique to the substance in question, and not determined by the amount of it present - melting point, density, conductivity

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4
Q

Extensive properties

A

Properties that are dependent the amount of substance present - mass, volume

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5
Q

Physical change

A

A change that does not alter the chemical composition of a substance - phase change

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6
Q

What is the relationship of pressure to phase change points?

A

Direct relationship - as pressure lowers, PCP lowers - increasing pressure widens the range where substance is stable in one phase

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7
Q

Triple point

A

A corresponding temperature and pressure where three different phases coexist

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8
Q

Critical point

A

The point at which the temperature and pressure have both increased to, and the liquid and gas states are indistinguishable

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9
Q

Supercritical fluid

A

Temperatures and pressures that exceed the critical point create substances that exist in this phase

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10
Q

Vapor pressure curve

A

The line between liquid and gas on the Temperature-Pressure graphs

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11
Q

Vapor pressure

A

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.

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12
Q

What is the boiling point of any given substance?

A

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

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13
Q

Can temperature and energy change at the same time?

A

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

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14
Q

Filtration

A

Mechanically separating the components of a substance by running its parts through a filter

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15
Q

Crystallization

A

Reducing the temperature of a substance to produce crystal solid forms of a component in order to differentiate it

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16
Q

Distillation

A

Boiling a substance so its most volatile substance evaporates, then putting the remaining liquid into a condenser where parts can continuously be assayed out

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17
Q

Particulate Model of Matter #1

A

Any macroscopic sample of a substance is made up of an extremely large amount of microscopic particles

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18
Q

Particulate Model of Matter #2

A

Particles of matter are constantly moving in different directions through empty space, exerting pressure on the walls of its container.

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19
Q

Ideal Gas Constant

A

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

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20
Q

What is the purpose of the Particulate Model of Matter?

A

To predict and explain the physical properties and behavior of substances.

21
Q

Average Kinetic energy

A

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>

22
Q

True or False: At any given temp, individual particles of the same substance can move at different speeds.

A

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.

23
Q

True or False: Weight and kinetic energy of a substance doesn’t impact velocity.

A

False! If you throw a baseball and a golf ball exerting the same amount of energy, which is likely to leave your hand faster?

24
Q

Particulate Model of Matter #3

A

Particles interact with each other and the strength of the interactions depends on proximity. Repel at short distances, attract at relatively long distances.

25
Q

Potential Energy

A

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

26
Q

How do potential energy and kinetic energy relate during phase changes?

A

Only kinetic energy changes during ambient time between phase changes. At phase changes, only potential energy changes to rearrange the bonds of the molecules.

27
Q

How does potential energy change when atoms move in the direction of their attraction/repulsion?

A

PE lowers, since low PE represents a more stable state, and stability is desirable.

28
Q

What factors affect volume of a substance?

A

Direct: Temperature, number of particles
Indirect: pressure

29
Q

Why is the ideal gas model inconvenient when comparing them to normal gases?

A

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.

30
Q

Emergence

A

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.

31
Q

During a phase transition, what happens to the energy, and what kind is it?

A

All energy is invested or lost in the form of potential energy.

32
Q

Are molecules/particles completely stationary?

A

Particles are constantly moving in random directions, and attractive interactions between particles pull/push them.

33
Q

Is low PE or high number of configurations more desirable?

A

It is dependent on temperature and pressure
High pressure = fewer configs
Low pressure = high configs
High temperature = high PE
Low temperature = low PE

34
Q

Why is gas favorable at higher temperatures?

A

You need to add energy to overcome the attractions, and high temps favor high potential energy.

35
Q

Why are gases favored at lower pressures?

A

Lower pressures means more space for movement of the particles. L.P. also favors the state with larger # of configurations.

35
Q

Why are liquids more favorable at lower temperatures?

A

Lower temperatures mean the attractive bonds between molecules over come the forces exerted by the temperature.

36
Q

Why are liquids more favorable at higher pressures?

A

The molecules are condensed, and closer together.

36
Q

What is an elementary substance?

A

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

37
Q

What are compounds?

A

Substances that CAN be split into two or more different substances by organic means - i.e. H2O

38
Q

Metals

A

Solid at room temp, good conductors of heat and electricity

39
Q

Non-metals/semimetals

A

Gases at room temp, poor conductors

40
Q

Metalloids

A

Share properties of both metals and non-metals

41
Q

Ionic compounds

A

Solids w/ high melting points that conduct electricity when dissolved in water

42
Q

Molecular (covalent) compounds

A

in different states of matter, and are generally poor conductors

43
Q

If two gases have the same volume, pressure, and temperature, which has more molecules?

A

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.

44
Q

Avogadro’s Number

A

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.

45
Q

How do we determine number of molecules N in terms of moles n and Avogadro’s Number NA?

A

N = n (mol) x NA (Avo’s #)

46
Q

How do we determine number of moles in a substance in terms of mass m and molar mass M?

A

n = m/M

PChem 1110 (4 decks)

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