section 2 & 3

Properties of Liquids and the kinetic- molecular theory cont.

• the particles in a liquid are not bound together in fixed positions, instead they move about constantly
• a fluid is a substance that can flow and therefore take the shape of it container

relitively high density

• at normal atmospheric pressurre, most substances are hundreds of times denser in a liquid state than in a gaseos state

relative incompressiblity

• liquids are much less compressible than gasses because liquid particles are more closely packed together

ability to diffuse

• any liquid gradually diffuses throughout any other liquid in which in can dissolve
• the constant, random motion of particles causes diffusion in liquids

diffusion is much slower in liquids than in gasses

• liquid particles are closer together
• the attractive forces between the particles of a liquid slow their movement
• as the temperature of liquid is increased diffusion occurs more rapidly

surface tension

• a property common to all liquids is surface tension, a force that tends to pull adjacent parts of a liquid's surface together, thereby decreasing surface area to the smallest possible size
• the higher the force of attraction between the particles of a liquid, the higher the surface tension
• the molecules at the surface of the water can form hydrogen bonds with the water, but not with the molecules in the air above them
• capillary action is the attraction of the surface of a liquid to the surface of a solid
• this attraction tends to pull the liquid molecules upward along the surface and against the pull of gravity
• the same process is responsible for the concave liquid surface, called a meniscus, that forms in a test tube or graded cylinder

evaporation and boiling

• the process by which a liquid or solid changes to a gas is vaporization
• evaporation is the process by which particles escape from the surface of a non-boiling liquid and enter a gas state
• boiling is the change of a liquid to bubbles of vapor that appear throughout the liquid
• evaporation occurs because the particles of a liquid have different kinetic energies

formation of solids

• when a liquid is cooled, the average energy of its particles decrease
• the physical changes of a liquid to a solid by removal energy as heat is called freezing or solidification

Section 3

• The particles of a solid are more closely packed than those of a liquid or gas
• All interparticle attractions exert stronger affects in solids than in the corresponding liquid or gasses
• attractive forces tend to hold the particles of a solid in relatively fixed positions
• solids are more ordered than liquids and much more ordered than gases
• there are 2 types of solids, crystalline and amorphous solids
• most solids are crystalline solids - they consists of crystals
• a crystal is a substance in which the particles are arranged in an orderly, geometric, repeating pattern
• an amorphous solid is one in which the particles are arranged randomly

Definite shape and volume

• solids can maintain a definite shape without a container
• crystalline solids are geometrically regular
• the volume of a solid changes only slightly with a change in temperature or pressure
• solids have definite volume because their particles are packed closely together