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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
viscosity
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
26
viscous drag
nonconservative force that is experienced with high viscosity analogous to air resistance
27
laminar flow
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
28
Poiseuille's law
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=(pi*r^4*delta 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
29
turbulent flow
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
30
eddies
swirls of fluid of varying sizes occurring typically on the downstream side of an obstacle caused by turbulent flow
31
critical speed
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
32
calculating critical speed
vc=N(R)n/pD | N(R) is Reynolds number a constant, n is viscosity, p is density, and D is diameter of tube
33
Reynolds number
depends on factors such as size, shape, and surface roughness of any objects within the fluid
34
streamlines
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
35
flow rate
rate of movement of fluids volume per unit time is constant for a closed system and is independent of changes in cross-sectional area
36
linear speed
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
37
continuity equation
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
Bernoulli's equation
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
dynamic pressure
1/pv^2 pressure associated with movement of fluid essentially kinetic energy of the fluid divided by volume
40
static pressure
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
energy density
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
pitot tubes
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
Venturi flow meter
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
Venturi effect
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
circulatory system
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
blood leaving the heart
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
blood returning to the heart
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
pressure gradients
pressure gradients created in the thorax by inhalation and exhalation motivate blood flow
49
heart murmurs
result from structural defects of the heart | heart because of turbulent blood flow
50
respiratory system
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
inspiration
there is a negative pressure gradient that moves air into the lungs breathing air in
52
expiration
there is a positive pressure gradient that moves air out of the lungs opposite of inspiration breathing air out
53
phase
or state different physical forms that matter can exist in gas, liquid, and solid
54
gas phase
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
gas variables
pressure (P) volume (V) temperature (T) number of moles (n)
56
sphygmomanometers
medical devices that measure blood pressure | measure in mmHg
57
standard temperature and pressure (STP)
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
standard state conditions
conditions of 293 K, 1 atm, and 1M concentration | used when measuring standard enthalpy, entropy, free energy changes, and electrochemical cell voltage
59
ideal gas
represents a hypothetical gas with molecules that have no intermolecular forces and occupy no volume
60
real gas
deviate from the ideal gas behavior at high pressures (low volumes) and low temperatures many compressed real gases demonstrate behavior close to ideal
61
ideal gas law
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
ideal gas constant (R)
8.21e-2 L*atm/mol*K | units are based on the units of the variables given in the passage or question
63
density
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
combined gas law
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
Avogadro's principle
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
Boyle's law
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
Charles's law
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
Gay-Lussac's law
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
partial pressure
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
Dalton's law of partial pressures
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
Henry's law
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
vapor pressure
the pressure exerted by evaporated particles above the surface of a liquid
73
evaporation
dynamic process that requires the molecules at the surface of a liquid to gain enough energy to escape into the gas phase
74
kinetic molecular theory
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
kinetic molecular theory assumption 1
gases are made up of particles with volumes that are negligible compared to the container volume
76
kinetic molecular theory assumption 2
gas atoms or molecules exhibit no intermolecular attractions or repulsions
77
kinetic molecular theory assumption 3
gas particles are in continuous, random motion, undergoing collisions with other particles and the container walls
78
kinetic molecular theory assumption 4
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
kinetic molecular theory assumption 5
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
Boltzmann constant
k(B)=1.38e-23 J/K | serves as a bridge b/w the macroscopic and microscopic behaviors of gases
81
root-mean-square speed (u)
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
Maxwell-Boltzmann distribution curve
shows the distribution of gas particle speeds at a given temperature
83
diffusion
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
Graham's law
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
effusion
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
real gas deviations
due to pressure | due to temperature
87
deviations due to pressure
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
deviations due to temperature
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
van der Waals equation of state
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
a and b in van der Waals equation
``` 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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