LECTURE 6.2 – TEMPERATURE SCALES

Today’s Learning Targets• LT 5.3 – I can define what STP is on an exit ticket• LT 5.4 – I can discuss how the kinetic energy of a gas molecules is related to the

temperature of the gas mixture on an exit ticket • LT 5.5 – I can define what absolute zero and relate it to the Kelvin temperature

scale on an exit ticket• LT 5.6 – I can convert between the Kelvin and Celsius temperature scales on an

exit ticket• LT 5.7 – I can explain Boyle’s Law, how it relates pressure and volume, and I can

calculate pressure and volume values for a given problem on an exit ticket

What are the temperature scales?

I. Temperature• The temperature that we

feel is created by the movement of atoms.

• The movement of gas molecules in the air creates our observable temperature

• The temperature is a measurement of the average energy of a sample

II. Temperature Scales• The 2 main

temperature scales in chemistry are the Celsius and Kelvin scales

• The Celsius scale sets the freezing point of water at 0 oC and the boiling point of water at 100 oC

What is STP?

I. STP• When working with gases,

reactions are normally carried out under standard temperature and pressure or STP

• STP is defined as 273 K and 1 atm

What is absolute zero?

I. Kelvin Scale• The other unit of

temperature used in chemistry is the Kelvin scale.

• The Kelvin scale sets 0 K as being absolute zero.

II. Absolute Zero• Absolute zero is the

temperature at which all molecular motion stops.

• Coldest possible temperature

• It is impossible to go below absolute zero (0 K) because molecular motion has stopped at this point.

How do we convert between Celsius and Kelvin

I. Converting Between Kelvin and Celsius • To convert from Celsius to Kelvin:

Kelvin = Co + 273• To convert from Kelvin to Celsius:

Celsius = Kelvin – 273

Class Example

• It is 33 oC outside, what is this temperature in Kelvin?

Table Talk

• If I have something at 298 K, what temperature is it in Celsius?

Stop and Jot

• You measure a reaction at 1250 oC, what is the temperature in Kelvin?