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Viscosity is a material property which describes the resistance of a fluid to shearing flows. It corresponds roughly to the intuitive notion of a fluid's 'thickness'. For instance, honey has a much higher viscosity than water.

Viscosity is measured using a viscometer. Measured values span several orders of magnitude. Of all fluids, gases have the lowest viscosities, and thick liquids have the highest.

Viscosities at or near standard conditionsEdit

Here "standard conditions" refers to temperatures of 25 °C and pressures of 1 atmosphere. Where data points are unavailable for 25 °C or 1 atmosphere, values are given at a nearby temperature/pressure.

The temperatures corresponding to each data point are stated explicitly. By contrast, pressure is omitted since gaseous viscosity depends only weakly on it.

GasesEdit

Noble gasesEdit

The simple structure of noble gas molecules makes them amenable to accurate theoretical treatment. For this reason, measured viscosities of the noble gases serve as important tests of the kinetic-molecular theory of transport processes in gases (see Chapman–Enskog theory). One of the key predictions of the theory is the following relationship between viscosity  , thermal conductivity  , and specific heat  :

 

where   is a constant which in general depends on the details of intermolecular interactions, but for spherically symmetric molecules is very close to  .[1]

This prediction is reasonably well verified by experiment, as the following table shows. Indeed, the relation provides a viable means for obtaining thermal conductivities of gases since these are more difficult to measure directly than viscosity.[1][2]

Substance Molecular
formula
Viscosity
(μPa·s)
Thermal conductivity
(W m-1K-1)
Specific heat
(J K-1kg-1)
  Notes Refs.
Helium He 19.85 0.153 3116 2.47 [2][3]
Neon Ne 31.75 0.0492 618 2.51 [2][3]
Argon Ar 22.61 0.0178 313 2.52 [2][3]
Krypton Kr 25.38 0.0094 149 2.49 [2][3]
Xenon Xe 23.08 0.0056 95.0 2.55 [2][3]
Radon Rn ≈26 ≈0.00364 56.2 T = 26.85 °C;
  calculated theoretically;
  estimated assuming  
[4]

Diatomic elementsEdit

Substance Molecular formula Viscosity (μPa·s) Notes Ref.
Hydrogen H2 8.90 [5]
Nitrogen N2 17.76 [5]
Oxygen O2 20.64 [6]
Fluorine F2 23.16 [7]
Chlorine Cl2 13.40 [7]

HydrocarbonsEdit

Substance Molecular formula Viscosity (μPa·s) Notes Ref.
Methane CH4 11.13 [8]
Acetylene C2H2 10.2 T = 20 °C [9]
Ethylene C2H4 10.28 [8]
Ethane C2H6 9.27 [8]
Propyne C3H4 8.67 T = 20 °C [9]
Propene C3H6 8.39 [10]
Propane C3H8 8.18 [8]
Butane C4H10 7.49 [8]

OrganohalidesEdit

Substance Molecular formula Viscosity (μPa·s) Notes Ref.
Carbon tetrafluoride CF4 17.32 [11]
Fluoromethane CH3F 11.79 [12]
Difluoromethane CH2F2 12.36 [12]
Fluoroform CHF3 14.62 [12]
Pentafluoroethane C2HF5 12.94 [12]
Hexafluoroethane C2F6 14.00 [12]
Octafluoropropane C3F8 12.44 [12]

Other gasesEdit

Substance Molecular formula Viscosity (μPa·s) Notes Ref.
Air 18.46 [6]
Ammonia NH3 10.07 [13]
Nitrogen trifluoride NF3 17.11 T = 26.85 °C [14]
Boron trichloride BCl3 12.3 Theoretical estimate at T = 26.85 °C;
estimated uncertainty of 10%
[14]
Carbon dioxide CO2 14.90 [15]
Carbon monoxide CO 17.79 [16]
Hydrogen sulfide H2S 12.34 [17]
Nitric oxide NO 18.90 [7]
Nitrous oxide N2O 14.90 [18]
Sulfur dioxide SO2 12.82 [10]
Sulfur hexafluoride SF6 15.23 [5]
Molybdenum hexafluoride MoF6 14.5 Theoretical estimates at T = 26.85 °C [19]
Tungsten hexafluoride WF6 17.1
Uranium hexafluoride UF6 17.4

LiquidsEdit

n-AlkanesEdit

Substances composed of longer molecules tend to have larger viscosities due to the increased contact of molecules across layers of flow.[20] This effect can be observed for the n-alkanes and 1-chloroalkanes tabulated below. More dramatically, a long-chain hydrocarbon like squalene (C30H62) has a viscosity an order of magnitude larger than the shorter n-alkanes (roughly 31 mPa·s at 25 °C). This is also the reason oils tend to be highly viscous, since they are usually composed of long-chain hydrocarbons.

Substance Molecular formula Viscosity (mPa·s) Notes Ref.
Pentane C5H12 0.224 [21]
Hexane C6H14 0.295 [22]
Heptane C7H16 0.389 [22]
Octane C8H18 0.509 [22]
Nonane C9H20 0.665 [21]
Decane C10H22 0.850 [22]
Undecane C11H24 1.098 [21]
Dodecane C12H26 1.359 [22]
Tridecane C13H28 1.724 [21]
Tetradecane C14H30 2.078 [22]
Pentadecane C15H32 2.82 T = 20 °C [23]
Hexadecane C16H34 3.03 [21]
Heptadecane C17H36 4.21 T = 20 °C [24]

1-ChloroalkanesEdit

Substance Molecular formula Viscosity (mPa·s) Notes Ref.
Chlorobutane C4H9Cl 0.4261 [25]
Chlorohexane C6H11Cl 0.6945
Chlorooctane C8H17Cl 1.128
Chlorodecane C10H21Cl 1.772
Chlorododecane C12H25Cl 2.668
Chlorotetradecane C14H29Cl 3.875
Chlorohexadecane C16H33Cl 5.421
Chlorooctadecane C18H37Cl 7.385 Supercooled liquid

Other halocarbonsEdit

Substance Molecular formula Viscosity (mPa·s) Notes Ref.
Dichloromethane CH2Cl2 0.401 [26]
Trichloromethane
(chloroform)
CHCl3 0.52 [10]
Tribromomethane
(bromoform)
CHBr3 1.89 [27]
Carbon tetrachloride CCl4 0.86 [27]
Trichloroethylene C2HCl3 0.532 [28]
Tetrachloroethylene C2Cl4 0.798 T = 30 °C [28]
Chlorobenzene C6H5Cl 0.773 [29]
Bromobenzene C6H5Br 1.080 [29]
1-Bromodecane C10H21Br 3.373 [30]

AlkenesEdit

Substance Molecular formula Viscosity (mPa·s) Notes Ref.
2-Pentene C5H10 0.201 [31]
1-Hexene C6H12 0.271 [32]
1-Heptene C7H14 0.362 [32]
1-Octene C8H16 0.506 T = 20 °C [31]
2-Octene C8H16 0.506 T = 20 °C [31]
n-Decene C10H20 0.828 T = 20 °C [31]

Other liquidsEdit

Substance Molecular formula Viscosity (mPa·s) Notes Ref.
Acetic acid C2H4O2 1.056 [21]
Acetone C3H6O 0.302 [33]
Benzene C6H6 0.604 [21]
Bromine Br2 0.944 [21]
Ethanol C2H6O 1.074 [21]
Glycerol C3H8O3 934 [34]
Hydrazine H4N2 0.876 [21]
Iodine pentafluoride IF5 2.111 [35]
Mercury Hg 1.526 [21]
Methanol CH4O 0.553 [36]
1-Propanol (propyl alcohol) C3H8O 1.945 [37]
2-Propanol (isopropyl alcohol) C3H8O 2.052 [37]
Squalane C30H62 31.123 [38]
Water H2O 0.890 [21]

Aqueous solutionsEdit

The viscosity of an aqueous solution can either increase or decrease with concentration depending on the solute and the range of concentration. For instance, the table below shows that viscosity increases monotonically with concentration for sodium chloride and calcium chloride, but decreases for potassium iodide and cesium chloride (the latter up to 30% mass percentage, after which viscosity increases).

The increase in viscosity for sucrose solutions is particularly dramatic, and explains in part the common experience of sugar water being "sticky".

Table: Viscosities (in mPa·s) of aqueous solutions at T = 20 °C for various solutes and mass percentages[21]
Solute mass percentage = 1% 2% 3% 4% 5% 10% 15% 20% 30% 40% 50% 60% 70%
Sodium chloride (NaCl) 1.020 1.036 1.052 1.068 1.085 1.193 1.352 1.557
Calcium chloride (CaCl2) 1.028 1.050 1.078 1.110 1.143 1.319 1.564 1.930 3.467 8.997
Potassium iodide (KI) 0.997 0.991 0.986 0.981 0.976 0.946 0.925 0.910 0.892 0.897
Cesium chloride (CsCl) 0.997 0.992 0.988 0.984 0.980 0.966 0.953 0.939 0.922 0.934 0.981 1.120
Sucrose (C12H22O11) 1.028 1.055 1.084 1.114 1.146 1.336 1.592 1.945 3.187 6.162 15.431 58.487 481.561

Substances of variable compositionEdit

Substance Viscosity (mPa·s) Temperature (°C) Reference
Whole milk 2.12 20 [39]
Olive oil 56.2 26 [39]
Canola oil 46.2 30 [39]
Sunflower oil 48.8 26 [39]
Honey   2000-10000 20 [40]
Ketchup[a]   5000-20000 25 [41]
Peanut butter[a]   104-106 [42]
Pitch 2.3×1011 10-30 (variable) [43]
  1. ^ a b These materials are highly non-Newtonian.

Viscosities under nonstandard conditionsEdit

GasesEdit

 
Pressure dependence of the viscosity of dry air at 300, 400 and 500 kelvins

All values are given at 1 bar (approximately equal to atmospheric pressure).

Substance Chemical formula Temperature (K) Viscosity (μPa·s)
Air 100 7.1
200 13.3
300 18.5
400 23.1
500 27.1
600 30.8
Ammonia NH3 300 10.2
400 14.0
500 17.9
600 21.7
Carbon dioxide CO2 200 10.1
300 15.0
400 19.7
500 24.0
600 28.0
Helium He 100 9.6
200 15.1
300 19.9
400 24.3
500 28.3
600 32.2
Water vapor H2O 380 12.498
400 13.278
450 15.267
500 17.299
550 19.356
600 21.425
650 23.496
700 25.562
750 27.617
800 29.657
900 33.680
1000 37.615
1100 41.453
1200 45.192

Liquids (including liquid metals)Edit

 
Viscosity of water as a function of temperature
Substance Chemical formula Temperature (°C) Viscosity (mPa·s)
Mercury[44][45] Hg -30 1.958
-20 1.856
-10 1.766
0 1.686
10 1.615
20 1.552
25 1.526
30 1.495
50 1.402
75 1.312
100 1.245
126.85 1.187
226.85 1.020
326.85 0.921
Ethanol C2H6O -25 3.26
0 1.786
25 1.074
50 0.694
75 0.476
Bromine Br2 0 1.252
25 0.944
50 0.746
Water H2O 0.01 1.7911
10 1.3059
20 1.0016
25 0.89002
30 0.79722
40 0.65273
50 0.54652
60 0.46603
70 0.40355
80 0.35405
90 0.31417
99.606 0.28275
Glycerol C3H8O3 25 934
50 152
75 39.8
100 14.76
Aluminum Al 700 1.24
800 1.04
900 0.90
Gold Au 1100 5.130
1200 4.640
1300 4.240
Copper Cu 1100 3.92
1200 3.34
1300 2.91
1400 2.58
1500 2.31
1600 2.10
1700 1.92
Silver Ag 1300 3.75
1400 3.27
1500 2.91
Iron Fe 1600 5.22
1700 4.41
1800 3.79
1900 3.31
2000 2.92
2100 2.60

In the following table, temperature is given in kelvins.

Substance Chemical formula Temperature (K) Viscosity (mPa·s)
Gallium[45] Ga 400 1.158
500 0.915
600 0.783
700 0.700
800 0.643
Zinc[45] Zn 700 3.737
800 2.883
900 2.356
1000 2.005
1100 1.756
Cadmium[45] Cd 600 2.708
700 2.043
800 1.654
900 1.403

SolidsEdit

Substance Viscosity (Pa·s) Temperature (°C)
granite[46] 3×1019 - 6×1019 25
asthenosphere[47] 7.0×1019 900
upper mantle[47] 7×10201×1021 1300–3000
lower mantle[citation needed] 1×10212×1021 3000–4000

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