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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 =1/2mv 2 ) Behavior of gases Low density

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States of Matter/ Gases

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  1. States of Matter/ Gases Pg. 91 Foldable

  2. 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

  3. 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

  4. 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)

  5. Forces of attraction (intermolecular forces) • Dispersion forces • Weak forces • Occur when molecules that have similar charge are forced together • Dipole-Dipole • Slightly stronger • Occur when there is an unequal balance btw. charges of molecules • Hydrogen bonds • Incredibly strong

  6. Liquids • More dense but less compressibility than gases • Fluidity • Can diffuse • Capillary action • Surface forms a concave miniscus • 2 forces at work cohesion (btw. Same molecules) and adhesion (btw. Molecules that are different • Can be viscous (resistance to flow) • 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

  7. 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)

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