Leacture 4 Flashcards
What is surface tension?
Surface tension is the force that causes the molecules at the surface of a liquid to be pulled together, resulting in the liquid contracting to its smallest surface area, often forming a spherical shape.
What causes capillary action?
Capillary action occurs due to the attraction between liquid molecules and a solid surface; a strong attraction results in an upward concave meniscus, while a weak attraction results in a downward meniscus.
Define viscosity.
Viscosity is the resistance of a liquid to flow, where higher viscosity means the liquid flows more slowly (e.g., honey), and lower viscosity means it flows more easily (e.g., water).
How does vapour pressure (VP) of a liquid depend on temperature?
Vapour pressure increases with temperature because more molecules have enough kinetic energy to escape into the gas phase.
Explain vapour pressure of solids.
Like liquids, solids can have a vapour pressure in a closed container, which increases rapidly with temperature until reaching a point where solid, liquid, and vapour phases coexist (triple point).
What is the triple point of water?
The triple point of water is the temperature and pressure where water exists simultaneously in solid, liquid, and vapour forms, occurring at 0.0098°C and 4.579 mmHg.
What is sublimation?
Sublimation is the process where a solid changes directly into a gas without passing through the liquid phase, like CO₂ at -78.1°C under 1 atm pressure.
What is the relationship between vapour pressure and boiling point?
The boiling point of a liquid is the temperature at which its vapour pressure equals the atmospheric pressure.
What is the formula for absorbance in spectroscopy?
A=ε⋅c⋅l, where A is absorbance, ε is the molar absorptivity, c is concentration, and l is the path length.
Why does carbon dioxide not exist as a liquid at 1 atm pressure?
CO₂ sublimes directly from solid to gas at 1 atm, only forming a liquid at higher pressures (e.g., above 5.1 atm at -56.6°C).
