Liquids Density and Compression More dense than gases

Liquids

Density and Compression • More dense than gases • Intermolecular forces stronger • Incompressible (an enormous amount of pressure must be applied to reduce volume a very small amount)

Fluidity • Can flow and diffuse (less than gases) • Ex) Food coloring in water • Ex) Water vs. Natural Gas in a basement

Viscosity • Resistance of liquid to flow – Honey • Particles in the liquid are close enough for attractive forces to slow their movement • Determined by type of intermolecular forces, size and shape of particles, and temp.

Viscosity & Attractive Forces • Stronger forces= Higher viscosity

Viscosity & Particle Size/Shape • Bigger molecules move slower when compared to smaller molecules that have the same attractive forces • Ex: Oils and motor oil have long chains, less distance between atoms, resulting in a greater chance for attraction between atoms

Viscosity &Temperature • Viscosity decreases with temp • Added energy makes it easier for liquid to overcome attractive forces • Ex. Heating cooking oil

Surface Tension Defined • Middle particles have attractions to particles above, below, • • and on both sides Surface particles have no attractions above them to balance the attractions below them. Net attractive force pulling down on particles at the surface For surface area to increase, middle particles must move up and overcome all the attractions holding them in the interior Surface Tension: Energy required to increase surface area, a measure of the inward pull by particles in the interior

Surface Tension • Stronger attractive forces= Greater surface tension. – Ex. Water • has a high surface tension due to H bonds (allows spiders to walk on water) • Difficult to remove dirt from skin and clothing using only water-detergents and soap decrease surface tension by breaking H bonds. • Water then spreads out allowing dirt to be carried away with the water • Ex) drops of soapy water vs. plain water on a penny

Cohesion & Adhesion • Cohesion= Force of attraction between identical • • molecules Adhesion= Force of attraction between different molecules Water in a graduated cylinder forms a concave meniscus – adhesive forces between glass and water are greater than cohesive forces between water molecules so the water rises along the inner walls of the container