Chapter 10: States of Matter• Kinetic Molecular Theory: the idea that particles of matter are always in motion; this applies to all states of matter• Used to explain properties of matter in terms of energy
Ideal Gas= hypothetical gas that perfectly fits all 5 assumptions of the Kinetic Molecular Theory: 1) Gases consist of a large # of particles that occupy a larger space with respect to their relative sizes thus gases can be easily compressed 2) Collisions b/t particles and walls are perfectly elastic ( = no loss of KE) 3) Gas particles are in rapid, random, constant motion 4) There are no forces of attraction b/t gas particles 5) Temperature of a gas depends on the average KE of the particles; directly proportional A gas that is always a gas - Doesn’t exist!
Characteristics of Gases• Expansion: no definite shape or volume; fill any container, regardless of shape• Fluidity: particles slide easily over one another; act like liquids, thus they are both fluids• Low Density and Compressibility: volume can be decreased greatly• Diffusion: since gases are always randomly moving, freely mix together with other gases• Effusion: process by which gases move out of a small opening; molecules with low mass effuse more quickly than those with larger masses KE= ½ mv2
Liquids• Least common state of matter in universe; not so on Earth• Operate at slim range of temps/pressures• Volume, shape, density?• Particles in constant motion, and closer than those of a gas (d/t intermolecular forces
Other Characteristics of liquids:• Have a very high density when compared to gases; depends on temperature lower temp…except for water• Not easily compressed• Easily diffuse in other liquids it can dissolve in d/t… much slower than it is in gases – why?
Surface Tension• All liquids exhibit surface tension = a force that tends to pull adjacent particles at a liquids surface together, decreasing its surface area to the smallest possible size; meniscus• Results from… water shows high surface tension• Capillary action = attraction of a liquid to a solid; rises in a small tube against gravity
Surface TensionLook at the picture below. The milk forms small droplets that resemble a crown. But why does this happen? Because of the surface tension of water, which keeps the droplets spherical.
Some terms: melting/freezing point boiling/condensation point 0ºC 100ºCsolid liquid gas MELTING BOILING(ice) FREEZING CONDENSATION (water) (steam) SUBLIMATION
More info on Liquids• Vaporization – liquid to gas• Evaporation – escape from a non-boiling liquid at its surface• Boiling – vaporization through the entire liquid• Freezing – physical change from liquid to solid through the loss of HEAT. Evaporation- a beautiful process.
Solids• Particles in a solid are tightly- packed together due to attractive forces. Highly-ordered.• Atomic/molecular motion is restricted, but it occurs. Sodium Chloride crystals• 2 types: 1) Crystalline: consists of crystals (orderly, geometric, repeating pattern) 2) Amorphous: particles are Amorphous solid randomly arranged
Properties of solids• Definite shape and volume• Definite melting point (d/t addition of heat)• High density and incompressible• Low rates of diffusion
Crystals• Arranged in a lattice structure• Smallest unit of a crystal that shows the 3- D pattern of the lattice = UNIT CELL
Changes of State• Phase = any part of a system that has a uniform composition and properties• Condensation = process by which a gas turns into a liquid• Vapor = a gas in contact with its liquid or solid phase
Vapor Pressure• The pressure exerted by a vapor that is in equilibrium with its corresponding liquid• Develops in a closed system• Increase AKE, increase particles leaving liquid, increased pressure• Volatile liquids evaporate easily d/t weak IMF
Notes on Boiling Point• BP = when vapor pressure equals atmospheric pressure• Increase pressure, increase BP = pressure cooker• Molar Enthalpy of Vaporization = amount of heat needed to vaporize 1 mole of a liquid at the liquid’s BP at a constant pressure; the stronger the attraction….• Vapor pressure is directly proportional to temperature• Vacuum evaporator – how does it work?
Freezing and Melting• Definitions?• What is the difference b/t freezing water and ice? Boiling water and steam?
Do Now• Explain the importance and significance of this graph…
More Vocab• Molar Enthalpy of Fusion = the amount of heat required to melt one mole of a solid (40.79 kJ/mol for water)• Sublimation vs. deposition
Phase Diagramsgraph of pressure vs. temperature that shows the conditions under which the phases of a substance would exist
Water• Most abundant liquid on Earth; essential to life; most reactions take place in it IMPORTANT!!!• Review its structure and properties…