1. Unit 7 -Absolute Temperature  The kinetic theory of gases relates the absolute temperature of a gas to the average kinetic energy of its molecules or atoms. KE = ½ (mass)(velocity) 2  The faster the molecules move, the more the kinetic energy they have, and thus the higher temperature the substance has.  Absolute temperature is based on the idea that at some temperature, all kinetic motion will stop. This is known as absolute zero

2. Kelvin Temperature Scale  The Kelvin temperature scale was created to eliminate negative temperature values.  0 degrees Kelvin is considered absolute zero, or where there is no molecular motion.  There is no temperature lower than 0 Kelvin, and we can never get to 0 Kelvin. 0 Kelvin = - 273 o C Kelvin = o C + 273 ***All temperatures must be in the Kelvin temperature scale when using the gas laws!

3.  Absolute Zero video clip Absolute Zero video clip Absolute Zero video clip P Temperature, o C -273 o C

4. Charles’ Law Volume and Temperature  The volume and the temperature of a gas are directly proportional when the pressure and number of moles remain constant. V 1 = V 2 T 1 T 2 T 1 T 2  Temperature is in Kelvin. K = o C + 273 V T (K)

5. Charles’ Law

6. Sample Problem The volume of a bubble is 1.5 liters. If its temperature increases from 20 to 50 o C, what is its final volume? V 1 = V 2 V 1 = 1.5 L T 1 = 20 o C T 1 T 2 V 2 = ? T 2 = 50 o C First convert Temperatures to Kelvin!!!! T 1 = 20 + 273 = 293 K T 2 = 50 + 273 = 323 K 1.5 L= V 2 293K 323K (293K)V 2 = (1.5L)(323K) V 2 = 1.65 L

7. Guy – Lussac’s Law Pressure and Temperature  The pressure of a gas is directly proportional to its temperature (when volume and the number of moles remain constant).  P 1 = P 2 T 1 T 2 T 1 T 2  Temperature in Kelvin K = o C + 273 P T (K)

8. Sample Problem  If a child has a rigid ball with 25 atm of pressure at 22 o C, what will the pressure be at 0 o C? P 1 = P 2 P 1 = 25atm T 1 = 22 o C T 1 T 2 P 2 = ? T 2 = 0 o C First Convert Temperature to Kelvin! T 1 = 22 o C + 273 = 295K T 2 = 0 o C + 273 = 273K 25 atm = P 2 295K 273K P 2 (295K) = (25atm)(273K) P 2 = 23.1 atm

9. Why we can’t get to Absolute Zero