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concept 4b Flashcards

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1
Q

fluids

A

characterized by their ability to flow and conform to the shapes of their containers
both liquids and gases are fluids
can impose large perpendicular forces, falling water from significant height is painful

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2
Q

solids

A

do not flow and are rigid enough to retain a shape independent of their container
can also exert forces perpendicular to their surfaces
but solids are able to withstand shear (tangential) forces

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3
Q

density

A 
ratio of their mass to their volume 
scalar quantity, has no direction 
p=m/V 
p is rho and represents density 
units are kg/m^3 or g/mL or g/cm^3
1g/cm^3=1000kg/m^3
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4
Q

finding weight using density

A

with known density at any volume you can calculate weight
Fg=pVg
this is the calculation that appears when working through buoyancy problems

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5
Q

specific gravity

A

ratio of an object’s density to the density of water
comparing the density of a fluid to pure water at 1 atm and 4 deg C (which is 1 g/cm^3 or 1000 kg/m^3)
SG=p/(1 g/cm^3)
this is unitless and expressed as a decimal
can be used to determine if an object will sing or float in water

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6
Q

pressure

A

ratio of force to the area over which it is applied
scalar quantity
measured in pascals (Pa), millimeters of mercury (mmHg) or torr, or atmospheres (atm)
P=F/A
1 Pa= 1 N/m^2

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7
Q

units of pressure

A 
1.013e5 Pa 
760 mmHg
760 torr
1 atm 
these are the equivalent measures of pressure
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8
Q

atmospheric pressure

A

pressure of the atmosphere
changes with altitude
impacts a number of processes, including hemoglobin’s affinity for oxygen and boiling of liquids

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9
Q

absolute pressure

A

the actual pressure at a given depth in a fluid
including both ambient pressure at the surface and the pressure associated with increased depth in the fluid
aka hydrostatic pressure
total pressure exerted on an object that is submerged in a fluid
P=Po+pgz
P is absolute pressure, Po is the incident or ambient pressure, p is density of fluid, g is accel due to gravity, z is depth of object

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10
Q

ambient pressure

A

the pressure at the surface

aka incident

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11
Q

gauge pressure

A

the difference b/w the absolute pressure inside a tire and the atmospheric pressure outside the tire
amount of pressure in a closed space above and beyond atmospheric pressure
Pg=P-Patm=(Po+pgz)-Patm

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12
Q

hydrostatics

A

study of fluids at rest and the forces and pressures associated with standing fluids

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13
Q

Pascal’s principle

A

states that pressure applied to a non compressible fluid is distributed equally to all points within that fluid and the walls of the container
P=F1/A1=F2/A2

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14
Q

hydraulic system

A

a simple machine that exerts mechanical advantage using an incompressible fluid
based on Pascal’s principle and conservation of energy

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15
Q

Archimedes’ principle

A

states that a body immersed in a volume of fluid experiences a buoyant force equal to the weight of the displaced fluid
F(buoy)=p(fluid)V(fluid displaced)g
=p(fluid)V(submerged)g
remember to always use the density of the fluid itself not the density of the object

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16
Q

buoyancy

A

the upward force that results from immersion in a fluid

described by Archimedes’ principle

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17
Q

will an object float or sink?

A

an object will FLOAT if its average density is less than the average density of the fluid it is immersed in
an object will SINK if its average density is greater than that of the fluid

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18
Q

molecular forces in liquids

A

surface tension
cohesion
adhesion

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19
Q

surface tension

A

the result of the cohesive forces in a liquid creating a barrier at the interface b/w a liquid and the environment
causes the liquid to form a thin but strong layer like a “skin” at the liquid’s surface
exp. dome the forms on top of penny

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20
Q

cohesion

A

the attractive force that a molecule of liquid feels toward other molecules of the same liquid
liquids will stick together
intermolecular force b/w molecules of liquid

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21
Q

adhesion

A

the attractive force that a molecule of liquid feels toward molecules of some other substance
intermolecular force b/w molecules of a liquid and molecules of another substance
liquids will stick to other substances
exp. water climbing up a paper towel

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22
Q

meniscus

A

curved surface in which liquid “crawls” up the side of the container a small amount
will form when the adhesive forces are greater than the cohesive forces

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23
Q

backwards (convex) meniscus

A

the liquid level is higher in the middle than at the edges
occurs when the cohesive forces are greater than the adhesive forces
Mercury (only metal that is liquid at room temp) forms one when placed in a container

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24
Q

fluid dynamics

A

the study of fluids in motion

in many aspects of life, delivery of water to our homes and blood flow thorough our arteries and veins

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25
Q

viscosity

A

the resistance of fluid flow
increased viscosity of a fluid increases its viscous drag
thin fluids, gases, water, dilute aqueous solutions, have low viscosity and flow easily
whole blood, vegetable oil, honey, cream, molasses are thick fluids and flow slowly

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26
Q

viscous drag

A

nonconservative force that is experienced with high viscosity
analogous to air resistance

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27
Q

laminar flow

A

smooth and orderly movement of fluids
often modeled as layers of fluid that flow parallel to each other
low viscosity fluids have low internal resistance and have laminar flow

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28
Q

Poiseuille’s law

A

relates viscosity, tube dimensions, and pressure differentials to the rate of flow b/w 2 points in a system
allows to calculate laminar flow
Q=(pir^4delta P)/8nL
Q is flow rate, r is radius of the tube, delta P is the pressure gradient, n (eta) is viscosity, and L is length of pipe
even small change in radius has significant effect on pressure gradient, assuming constant flow rate

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29
Q

turbulent flow

A

rough and disorderly movement of fluids
causes the formation of eddies
also can arise in unobstructed flow if speed of fluid exceeds a critical speed

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30
Q

eddies

A

swirls of fluid of varying sizes occurring typically on the downstream side of an obstacle
caused by turbulent flow

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31
Q

critical speed

A

depends on the physical properties of the fluid, viscosity and diameter of tube
when speed of fluid exceeds critical speed fluid demonstrates complex flow patterns and laminar flow occurs only in thin layer of fluid adjacent to the wall, boundary layer

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32
Q

calculating critical speed

A

vc=N(R)n/pD

N(R) is Reynolds number a constant, n is viscosity, p is density, and D is diameter of tube

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33
Q

Reynolds number

A

depends on factors such as size, shape, and surface roughness of any objects within the fluid

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34
Q

streamlines

A

representation of molecular movement
indicate the pathways followed by tiny fluid elements (fluid particles) as they move
never cross each other
velocity vector of fluid particles will alway be tangential to the streamline

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35
Q

flow rate

A

rate of movement of fluids
volume per unit time
is constant for a closed system and is independent of changes in cross-sectional area

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36
Q

linear speed

A

measure of the linear displacement of fluid particles in a given amount of time
the product of linear speed and area are equal to flow rate
Q=v1A1=v2A2
Q is flow rate, v is linear speed of fluid at points and A is area at points
linear speed will increase with decreasing cross-sectional area

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37
Q

continuity equation

A

Q=v1A1=v2A2
it tells us that fluids will flow more quickly through narrow passages and more slowly though wider ones
and flow rate is constant

38
Q

Bernoulli’s equation

A

an equation that relates static and dynamic pressure for a fluid to the pressure exerted on the walls of the tube and the speed of the fluid
P1+1/2pv1^2+pgh1=P2+1/2pv2^2+pgh2
P is absolute pressure of fluid, p is density of fluid, v is linear speed, g is accel due to gravity, and h is height of fluid

39
Q

dynamic pressure

A

1/pv^2
pressure associated with movement of fluid
essentially kinetic energy of the fluid divided by volume

40
Q

static pressure

A

P+pgh
same equation for absolute pressure
pgh is similar to gravitational potential energy and is pressure associated with the mass of fluid sitting above some position

41
Q

energy density

A

ratio of energy per cubic meter
pressure can be thought of as this
systems at higher pressure have a higher energy density than systems at lower pressure

42
Q

pitot tubes

A

specialized measurement devices that determine the speed of fluid flow by determining the difference b/w the static and dynamic pressure of the fluid at given points along the tube

43
Q

Venturi flow meter

A

application of Bernoulli’s equation
tube that starts wide and becomes narrow with tubes connected
as tube narrows the linear speed increases
thus the pressure exerted on the walls decreases causing the column about the tube to have a lower height

44
Q

Venturi effect

A

describes the relationship b/w the continuity equation and Bernoulli’s equation
as cross-sectional area of the tube decreases, the speed of fluid increases, and the pressure exerted on the walls of the tube decreases

45
Q

circulatory system

A

is a closed loop that has a non constant flow
this flow is a result of valves, gravity, physical properties of our vessels (elasticity), and mechanics of the heart
measured and felt as a pulse
there is a loss of volume from circulation as result of osmotic and hydrostatic pressure
blood volume entering the heart always equals blood volume leaving the heart during single cycle

46
Q

blood leaving the heart

A

each vessel has a progressively higher resistance, but total resistance of the system decreases bc increased number of vessels in parallel with each other
similar to parallel resistors in circuits, equivalent resistance is lower for capillaries in parallel than in the aorta

47
Q

blood returning to the heart

A

facilitated by mechanical squeezing of skeletal muscles which increase pressure in the limbs and pushes blood to the heart
expansion of the heart decreases pressure in the heart and pulls blood in
venous circulation holds approximately 3 times as much blood as arterial circulation

48
Q

pressure gradients

A

pressure gradients created in the thorax by inhalation and exhalation motivate blood flow

49
Q

heart murmurs

A

result from structural defects of the heart

heart because of turbulent blood flow

50
Q

respiratory system

A

mediated by changes in pressure
follows the same resistance relationship as the circulatory system
when air reaches the alveoli it has essentially no speed

51
Q

inspiration

A

there is a negative pressure gradient that moves air into the lungs
breathing air in

52
Q

expiration

A

there is a positive pressure gradient that moves air out of the lungs
opposite of inspiration
breathing air out

53
Q

phase

A

or state
different physical forms that matter can exist in
gas, liquid, and solid

54
Q

gas phase

A

display similar behavior and follow similar law regardless of their particular chemical identities
classified as fluids bc can flow and take on the shapes of their containers
atoms move rapidly and are far apart from each other
only weak intermolecular forces exist b/w gas particles
ability to expand to fill any volume
easily compressible, distinguishes them from liquids

55
Q

gas variables

A

pressure (P)
volume (V)
temperature (T)
number of moles (n)

56
Q

sphygmomanometers

A

medical devices that measure blood pressure

measure in mmHg

57
Q

standard temperature and pressure (STP)

A

conditions of 273 K (0 deg. C) and 1 atm
many processes involving gases take place under these conditions
are not identical to standard state conditions
usually used for gas law calculations

58
Q

standard state conditions

A

conditions of 293 K, 1 atm, and 1M concentration

used when measuring standard enthalpy, entropy, free energy changes, and electrochemical cell voltage

59
Q

ideal gas

A

represents a hypothetical gas with molecules that have no intermolecular forces and occupy no volume

60
Q

real gas

A

deviate from the ideal gas behavior at high pressures (low volumes) and low temperatures
many compressed real gases demonstrate behavior close to ideal

61
Q

ideal gas law

A

PV=nRT
P is pressure, V is volume, n is number of moles, T is temperature, and R is the ideal gas constant
can be used to describe the behavior of many real gases at moderate pressures and temperatures significantly about absolute zero

62
Q

ideal gas constant (R)

A

8.21e-2 Latm/molK

units are based on the units of the variables given in the passage or question

63
Q

density

A

p=m/V=PM/RT

m is mass, V is volume, P is pressure, M is molar mass, R is gas constant, T is temp

64
Q

combined gas law

A

gas law that combines Boyle’s law, Charles’s law, and Gay-Lussac’s law
states that pressure and volume are inversely proportional to each other and each is directly proportional to temperature
P1V1/T1=P2V2/T2

65
Q

Avogadro’s principle

A

states that all gases at a constant temperature and pressure occupy volumes that are directly proportional to the number of moles of gas present
n/V=k
n1/V1=n2/V2
k is a constant, n is number of moles, V is volume
*as the number of moles of gas increases, the volume increases in direct proportion

66
Q

Boyle’s law

A

states that at constant temperature, the volume of a gaseous sample is inversely proportional to its pressure
PV=k
P1V1=P2V2
pressure and volume are inversely related
when one increases the other decreases

67
Q

Charles’s law

A

states that the volume of a gas at constant pressure is directly proportional to its absolute (kelvin) temperature
V/T=k
V1/T1=V2/T2
volume and temperature at directly proportional
when one increases, the other increases

68
Q

Gay-Lussac’s law

A

states that the pressure of a gaseous sample at constant volume is directly proportional to its absolute temperature
P/T=k
P1/T1=P2/T2
pressure and temperature at directly proportional
when one increase, the other increases

69
Q

partial pressure

A

the pressure that one component of a gaseous mixture would exert if it were alone in the container
Pa=XaPt
Xa=(moles of gas A)/(total moles of gas)
Pa is partial pressure of gas a, Xa is mole fraction, Pt is total pressure in container

70
Q

Dalton’s law of partial pressures

A

states that the total pressure of a gaseous mixture is equal to the same of the partial pressures of the individual components
Pt=Pa+Pb+Pc+…

71
Q

Henry’s law

A

states that the mass of gas that dissolves in a solution is directly proportional to the partial pressure of the gas about the solution
[A]=k(h)*Pa
[A1]/P1=[A2]/P2=k(h)
[A] conc. of A in solution, k(h) is Henry’s constant, Pa is partial pressure of A
Henry’s constant depends on identity of gas
solubility of a gas will increase with increasing partial pressure of gas

72
Q

vapor pressure

A

the pressure exerted by evaporated particles above the surface of a liquid

73
Q

evaporation

A

dynamic process that requires the molecules at the surface of a liquid to gain enough energy to escape into the gas phase

74
Q

kinetic molecular theory

A

theory proposed to account for the observed behavior of gases
considers gas molecules to be point like, volume-less particles exhibiting no intermolecular forces that are in constant random motion and undergo completely elastic collisions with the container or other gas particles
used to explain the behavior of gases

75
Q

kinetic molecular theory assumption 1

A

gases are made up of particles with volumes that are negligible compared to the container volume

76
Q

kinetic molecular theory assumption 2

A

gas atoms or molecules exhibit no intermolecular attractions or repulsions

77
Q

kinetic molecular theory assumption 3

A

gas particles are in continuous, random motion, undergoing collisions with other particles and the container walls

78
Q

kinetic molecular theory assumption 4

A

collisions b/w any 2 gas particles (or b/w particles and the container walls) are elastic, meaning that there is conservation of both momentum and kinetic energy

79
Q

kinetic molecular theory assumption 5

A

the average kinetic energy of gas particles is proportional to the absolute temperature (in kelvin) of the gas, and it is the same for all gases at a given temperature, irrespective of chemical identity or atomic mass
KE=1/2mv^2=2/3k(B)T
k(B) is Boltzmann constant

80
Q

Boltzmann constant

A

k(B)=1.38e-23 J/K

serves as a bridge b/w the macroscopic and microscopic behaviors of gases

81
Q

root-mean-square speed (u)

A

u=sqrt[3RT/M]
R is ideal gas constant, T is temp, M is molar mass
used to find the average speed of a gas particle
the higher the temp, the faster the molecules move
the large the molecules, the slower they move

82
Q

Maxwell-Boltzmann distribution curve

A

shows the distribution of gas particle speeds at a given temperature

83
Q

diffusion

A

movement of molecules from high concentration to low concentration through a medium (air or water)
heavier gases diffuse more slowly than lighter ones bc of differing average speed
when gases mix with one another

84
Q

Graham’s law

A

states that the rate of effusion or diffusion for a gas is inversely proportional to the square root of the gas’s molar mass
r1/r2=sqrt[M2/M1]
r are the diffusion rates, M are the molar masses

85
Q

effusion

A

the flow of gas particles under pressure from one compartment to another thought a small opening
when a gas moves through a small hole under pressure
slower for larger molecules

86
Q

real gas deviations

A

due to pressure

due to temperature

87
Q

deviations due to pressure

A

at moderately high pressure a gas’s volume is less than would be predicted by the ideal gas law due to intermolecular attraction
at extremely high pressures the size of particles become relatively large compared to the distance b/w them, this causes the gas to take up a larger volume than would be predicted by the ideal gas law

88
Q

deviations due to temperature

A

as temp is reduced toward its condensation point (bp), intermolecular attraction causes the gas to have a smaller volume than that which would be predicted by ideal gas law
the closer a gas is to bp the less ideally it acts
at extremely low temps gases will occupy more space than predicted by ideal gas law

89
Q

van der Waals equation of state

A

one of several real gas laws
corrects for attractive forces and the volumes of gas particles, which are assumed to be negligible in the ideal gas law
(P+n^2a/V^2)(V-nb)=nRT
a and b are physical constants experimentally determined

90
Q

a and b in van der Waals equation

A 
a is the term for attractive forces 
b is the term for big particles 
smaller gases have smaller a 
larger molecules have large b
if a and b are zero it is the ideal gas law

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