Chapter 13 – States of Matter Enduring understandings: 1. State of matter depends on IMA strength and speed of molecules. 2. Atomic-scale motion can be altered by adding or removing thermal energy (heat), or by altering the air pressure acting on the sample. 3. Graphs and charts are helpful in quantifying state of matter relationships. 4. Temperature is a measure of the average KE of a molecule in a sample. 5. Gases exert a pressure on their containers that can be measured. 6. Kinetic and Potential Energy changes during heating and cooling processes can be measured.

Atomic scale view of matter Particle motion visualization – click here. Changes of state – name them! Kinetic Molecular Theory Constant motion Add or remove energy, affect the KE or the PE Kelvin temperature is proportional to average KE of the sample. Distribution of KE among a sample is best seen graphically.

Question… How fast is an average air molecule moving in this room right now?

Speed of air molecules at 298 K 1150 miles per hour = 500 meters per second! Speed depends on the identity of the molecule, and all O2 molecules don’t all travel the same speed!

Comparing two samples – one warm, one cold. Back to evap. page Kelvin temperature is proportional to the average KE of a molecule in the sample. When we take the temperature of a sample, what are we measuring?

Gas pressure results from 2 actions Tires can go flat without a leak… Pressure is defined as force/area. How can the force that each molecule exerts on the tire wall change? 2 actions: speed of particle and frequency of collisions The force is strong with this molecule

Barometer Measures air pressure Mercury is dense – but a column of it can be held up by the force of air molecules pushing on it! Pressure units: mm Hg, in Hg, kPa, atm, torr

Manometers open and closed types Confined gas exerts a pressure on the surface of Hg(l) Open manometer: difference in heights indicates pressure difference from atmospheric pressure. Open to atmospheric pressure

What am I called? sphygmomanometer

Liquids Evaporation is a surface phenomenon Back to KE curve Evaporation is a surface phenomenon What happens if I cover the container?

Equilibrium vapor pressure You can measure the pressure of the confined vapor. The pressure depends on the temperature of the liquid. Equilibrium condition: Rate of evap = rate of condensation

What happens when vapor pressure equals atmospheric pressure? Locate the normal boiling points of each substance. What happens when vapor pressure equals atmospheric pressure?

Solids Two types: Allotropes of carbon:

What state of matter am I? Interpreting phase diagrams: phase boundaries Critical and triple point Normal mp and bp practice

CO2 phase diagram

Who am I?