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Kinetic Theory, Gas Laws & Stoichiometry. I. Kinetic (molecular) Theory – explains properties of (s), (l), (g), in terms of forces between particles & the E they possess…..the MOTION of the particles – it says that particles (atoms & molecules) are in constant motion Vid KMT.
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Kinetic Theory, Gas Laws & Stoichiometry • I. Kinetic (molecular) Theory – explains properties of (s), (l), (g), in terms of forces between particles & the E they possess…..the MOTION of the particles – it says that particles (atoms & molecules) are in constant motion • Vid KMT
A. Phases or state of matter • 1. matter composed of tiny particles • 2. particles in constant motion • 3. total E of colliding particles remains constant (some particles lose E & some gain E in collisions ….the collisions are ELASTIC which means they don’t lose any kinetic energy)
B. Kinetic Energy (KE) is the energy due to motion. • 1. KE = ½ mv2 • 2.Units are Joules. kgm2/s2
C. 2nd Law of Motion • 1. The acceleration produced by a net force is directly proportional to the force that caused it & in the same direction. • (if F↑ then a ↑) AND
Force, mass, & acceleration • 2.The acceleration produced by a force is inversely proportional (if m↑ then a↓)to the mass of the object. • 3. a = F/m or F = ma m = F/a
II. Gases & the Kinetic Theory • A. Gas particles are far apart relative to their size • B. Collisions between gas particles & container (cause pressure) are elastic • C. Gas particles are in continuous rapid, random motion (they have lots of KE!)
D. No forces of attraction between gas particles (no IMF’s) • E. Average KE of gas particles depends on the Temperature of the gas … KE = ½ mv2
KE = ½ mv2 • 1 . Since m is the mass of the particle & all the particles of a specific gas have the same mass then the KE is completely dependent on the speed of the particle. • *** so an increase in Temp means an increase in speed & vice versa
2. All gases at the same temp have the same avg KE SO lighter gas particles have higher avg. speeds than heavier gas particles. • Look at your chart that shows the sizes of the atoms
Characteristics of Gases Gases expand to fill any container. • random motion, no attraction • no set shape Gases are fluids (like liquids). • no attraction Gases have very low densities. • no set volume = lots of empty space Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
III. Characteristics of gases • an IDEAL gas is an imaginary gas that perfectly fits all the “rules” of the kinetic theory….. • a REAL gas does not behave completely according to the “rules” of the kinetic theory, but this is usually only noticeable at extreme pressure & low temp
A. Gases are easy to expand (volume)---gas molecules don’t strongly attract each other • B. Gases are easy to compress --- gas molecules don’t strongly repel each other • C. Gases have densities that are about 1/1000 of their solid or liquid densities ---gas molecules are much farther apart in gases than in liquids or solids
Characteristics of Gases • Gases can be compressed. • no set volume = lots of empty space • Gases undergo diffusion & effusion. • random motion Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
D. Gases completely fill their containers --- gas molecules are in constant motion • 1. fluidity – gas particles glide easily past each other or FLOW
E. Hot gases leak through holes faster than cold gases --- the hotter the gas, the faster the molecules are moving • 1. diffusion – random movement of particles from an area of greater concentration to an area of lesser concentration • 2. effusion – process through which gas particles pass through a small opening • Vid review gases
