Lecture 31 Flashcards
Explain how LDF affects bp
The stronger the LDF the harder it is to distrust forces so the mp & bp will be higher
-an increase in size = a stronger LDF
What does surface tension refer to
The resistance of a liquid to increase its surface area; the energy required to increase surface area by a given amount
Why do liquids tend to form spherical droplets
A surface molecule is only attracted by below and to the sides, so it experiences a net attraction downward
What does high surface tension imply
Strong intermolecular forces; the stronger the intermolecular forces between particles, the more energy it takes to increase the surface area, so the greater the surface tension
How does temperature affect surface tension
Increasing temperature: decreasing surface tension
-higher temps mean the liquid molecules have higher KE to disrupt attractions to molecules
Decreasing temperature: increasing surface tension
What is capillarity
The rising of a liquid in a tube
If the meniscus is concave: the adhesive forces are stronger than the cohesive forces
If the meniscus is convex: the cohesive forces are stronger than the adhesive forces
What is wetting
The spreading of a liquid across a surface
If the cohesive forces are stronger than the adhesive forces the water will retain shape
If the adhesive forces are stronger than the cohesive forces the liquid will spread out
What is viscosity
The resistance of liquid to flow. High viscosity implies strong IM forces
How does temperature affect viscosity
Increasing temperature: viscosity decreases because faster moving molecules overcome IM forces more easily so the resistance to flow decreases
How is viscosity affected by molecular shape
- smaller spherical molecules make little contact so they flow easily (low viscosity)
- larger molecules make more contact and flow slowly (high viscosity)
What is solubility
A homogeneous mixture in which the solute is dissolved in the solvent
“Like dissolves like”
