Honors Chemistry Chapter 15 Kinetic Theory

15.1 Molecules in Motion Robt Hooke – explanation of gas behavior ◦ Kinetic Theory – explains the effects of temp & press on matter 3 Basic Assumptions of Kinetic Theory: 1.All matter is composed of small particles 2.The particles are in constant motion 3.All collisions are perfectly elastic  There is no change in total kinetic energy of the 2 particles before & after their collision

15.1 Molecules in Motion Many properties of matter are the result of the motion of the particles Mean Free Path – the avg distance a molec travels before it collides w/ another molec Speed, distance of travel, & # of collisions in a gas vary w/ temp. & mass of the gas particles

15.2 Pressure Gas molecs collide w/ the walls of their container as well as other molecs ◦ Exert a force on the container Pressure – caused by force & # of collisions w/ the walls of the container ◦ Meas in terms of force per unit area

15.2 Pressure Everything is subject to a certain press from molecs of gas in the air ◦ Air press varies from place to place and from time to time in a particular place Standard atmospheric press – avg air sea level ◦ kPa (kilopascals)  1 Pa (pascal) = press of 1 Newton / m 2  Very small press – usually use kPa

15.3 Measuring Pressure Manometer – instrument used in measuring gas press ◦ 2 types of manometers:  Open Type – atmos exerts pressure on the column of liquid in open arm  Studied gas exerts press in other arm  Difference I liquid level betw the 2 arms is a meas of diff in press betw atomos & contained gas  If density of liquid is known, press diff can be calculated

15.3 Measuring Pressure Closed type manometer has a vacuum above liquid in one arm ◦ No press from atmos acting on liquid  Independent of atmos press Barometer – closed manometer used to measure atmos press ◦ Most have a scale to read height of Hg in mm

15.3 Measuring Pressure Standard atmos press – kPa will support a column of Hg 760mm high ◦ kPa = 760 mm Hg or ◦ 1kPa = 7.5 mmHg  We will use for std press Closed manometer can meas actual or absolute press ◦ Can calc absolute press w/ open manometer if atmos press is know ◦ Leave room for examples

15.3 Measuring Pressure Types of manometers:

15.3 Measuring Pressure Mercury Barometer:

15.4 KINETIC ENERGY AND TEMPERATURE Avg. speed of particles depends on: ◦ 1. Temp. ◦ 2. mass of particles KINETIC ENERGY - energy possess by an obj. bec. of its motion ◦ K.E. = 1/2 m v 2 ◦ avg K.E. of particles in a gas is same for all a certain temp  2 same temp., particles have = K.E.

15.4 KINETIC ENERGY AND given temp. particle w/ small mass will mover faster than particle w/ large mass Decr. in temp. of subst. means particles move slower ◦ incr. in temp. - particles move faster

15.4 KINETIC ENERGY AND TEMPERATURE ABSOLUTE ZERO - which all molec. motion ceases ◦ o C (rounded to -273 o C) KELVIN SCALE - (absolute scale) - zero pt. is absolute zero ◦ K = o C + 273

15.4 KINETIC ENERGY AND TEMPERATURE Temp. can be used to determine direction of flow of energy. ◦ flows from high temp. to low temp  explained by kinetic theory HEAT - amt. of energy transferred bec. of difference in temp. ◦ meas. in joules

15.5 STATES OF MATTER 4 states of matter ◦ kinetic theory used to explain behavior of all 1. Gas - particles are independent of ea. other ◦ move in straight lines until collision, then change direction ◦ travel in randon manner ◦ assume shape & vol. of container

15.5 STATES OF MATTER 2. Liquid - particles appear to vibrate around moving point ◦ actually move in straight line betw. near neighbors ◦ particles can pass over one another ◦ have definite vol. & assume shape of their container

15.5 STATES OF MATTER 3. Solid - particles appear to vibrate around fixed point ◦ actually move in straight line betw. very near neighbors ◦ particles arranged in definite patterns ◦ have definite vol. & def. shape

15.5 STATES OF MATTER Physical state of room temp & std press depend on the bonding in the substs ◦ Ionic substs – very strong bonds – solids ◦ Molec substs – held together by van der Waals forces  Weaker than ionic bonds

15.5 STATES OF MATTER Polar molec w/ high molec mass tend to be solids Nonpolar molecs w/ low melec mass tend to be gases The greater the molec mass & greater polarity tend to make substs form condensed states ◦ Solids or liquids

15.6 Plasma 4 th state of matter ◦ State of matter composed of e-’s & + ions ◦ Most of the universe is made of plasma  Stars ◦ Nuclear rxns (fusion) occur only in plasmas ◦ Since it’s made up of charged particles, it is affected by electric & magnetic fields ◦ Magnetohydrodynamics – (MDH) – the study of plasma