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11.3 Properties of Liquids

11.3 Properties of Liquids. By: Mira Amin, Katie Blackburn, Neil Marfatia. Viscosity. Viscosity – the resistance of a liquid to flow Stronger the intermolecular forces,  greater the viscosity  slower it flows Common unit = poise (P) = 1 g/cm-s

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11.3 Properties of Liquids

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  1. 11.3 Properties of Liquids By: Mira Amin, Katie Blackburn, Neil Marfatia

  2. Viscosity • Viscosity – the resistance of a liquid to flow • Stronger the intermolecular forces,  greater the viscosity  slower it flows • Common unit = poise (P) = 1 g/cm-s • Usually reported in centipoise (cP) = .01 P • Depends on attractive forces b/w molecules • Viscosity increases with molecular weight • Viscosity decreases with temperature

  3. Surface Tension • Molecules at the surface experience net inward force • Pulls molecules from surface into interior  lowers surface area • Packs molecules closer together • Surface Tension – energy required to increase the surface area of a liquid by a unit amount (units: J/m^2) • Stronger the intermolecular forces, higher the surface tension • Water has high surface tension b/c of strong hydrogen bonds

  4. Allows water striders to “walk” on water Dew forming on a leaf A soap bubble balances surface tension forces against internal pneumatic pressure. Coin floats on water

  5. Surface Tension • Cohesive forces– intermolecular forces that bind similar molecules to one another • Ex: hydrogen bonding in water • Adhesive forces – intermolecular forces that bind a substance to a surface • Ex: formation of a meniscus • Capillary action – rise of liquids up very narrow tubes • Helps water and dissolved nutrients travel upward through plants

  6. Capillary Action

  7. Chapter Questions • 1) How do viscosity and surface tension of liquids change as intermolecular forces become stronger? • b) as temperature increases? • 2) Distinguish between adhesive forces and cohesive forces • b) explain the cause for the U-shaped meniscus formed when water is in a glass tube • c) how is the capacity of paper towels to absorb water related to capillary action?

  8. Chapter Answers • Higher viscosity and surface tension • As temp. increases, viscosity and surface tension decrease • Cohesive forces bind similar molecules together, while adhesive forces bind a substance to a surface • Meniscus forms b/c adhesive forces b/w H2O and glass are greater than cohesive forces b/w H2O molecules • Liquid adheres to the paper towel

  9. Bibliography • http://www.metacafe.com • http://www.science.uwaterloo.ca/~cchieh/cact/c123/liquid.html • http://ga.water.usgs.gov/edu/capillaryaction.htm l • http://palimpsest.stanford.edu/don/dt/dt3713.html • http://www.fas.harvard.edu/~scdiroff/lds/NewtonianMechanics/CapillaryAction/CapillaryAction.html

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