States of Matter/ Gases
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Transcript States of Matter/ Gases
States of Matter/ Gases
Pg. 91 Foldable
Gases
Kinetic molecular theory:
Small particles separated by empty space
In constant random motion until they collide elastically (no
energy lost)
Can calculate the energy using mass and velocity (KE =1/2mv2)
Behavior of gases
Low density
Can compress and expand
Diffusion and effusion
Diffusion and Effusion
Diffusion- describes movement of one particle through
another
Flows from areas of high concentration to low
Rate depends on mass (lighter diffuse more rapidly)
Effusion- when gases escape through tiny openings
Gas pressure
Pressure- force per unit area
Torr = mm Hg
Atmosphere (atm)= 760 Torr = 101.3 kPa
SI- Pascal (Pa)
psi
Use a barometer to measure (height is usually about 760
Torr)
Forces of attraction (intermolecular forces)
Dispersion forces
Dipole-Dipole
Weak forces
Occur when molecules that have similar charge are forced
together
Slightly stronger
Occur when there is an unequal balance btw. charges of
molecules
Hydrogen bonds
Incredibly strong
Liquids
More dense but less compressibility than gases
Fluidity
Can diffuse
Capillary action
Can be viscous (resistance to flow)
Surface forms a concave miniscus
2 forces at work cohesion (btw. Same molecules) and adhesion (btw.
Molecules that are different
Viscosity decreases with temperature
Surface tension
Measure of the inward pull of particles
Stronger the attraction greater surface tension
Water has high surface tension
Compounds that lower surface tension are called surfactants
Solids
Closely packed particles
Low KE
Very dense
Crystalline solids- solids arragned in orderly geometric way
Crystal lattice- ions arranged in a orderly fashion. Smallest unit
that can be repeated- unit cell
Molecular solids- most liquid at room temp
Covalent network solids- form allotropes (same elements,
different covalent bonds)
Metallic solids- wide range of properties
Amorphous solids- particles not arranged in pattern (glass,
rubber, plastics)