Transcript States of Matter/ Gases

States of Matter/ Gases
Pg. 91 Foldable
Gases
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Kinetic molecular theory:
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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
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Low density
Can compress and expand
Diffusion and effusion
Diffusion and Effusion
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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
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Pressure- force per unit area
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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)
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Dispersion forces
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Dipole-Dipole
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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
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Incredibly strong
Liquids
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More dense but less compressibility than gases
Fluidity
Can diffuse
Capillary action
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Can be viscous (resistance to flow)
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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
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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
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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)