Energy and Temperature Scales

Calculations and Conversions

Are Heat and Temperature the Same?

• Heat----Amount of energy that an object has

• Temperature---measurement of the kinetic energy that an object has

Fahrenheit

• oF is the symbol used for this unit• 32o is the freezing point of water• 212o is the boiling point of water• Not a very easy scale to work with

due to the wide range of numbers between the fixed points.

Converting from Fahrenheit to Celsius

• Use the following equation to convert between units

• F – 32• 1.8

Celsius

• Easier to use for science• 0oC is the freezing point of water• 100oC is the boiling point of water• Uses symbol oC• Easier to use because it goes from 0-

100 so just more practical for science and other fields

Converting from Celsius to Fahrenheit

• Use the following equation to convert from fahrenheit to celsius

• C x 1.8 + 32 = F

The “Absolute Scale” Kelvin

• Named after Lord Kelvin• Scale does not use degree signs• Scale does not have negative

numbers• This makes it an ideal scale for

physics and particle related studies because even at low temperatures it gives the impression that kinetic energy is still present

Kelvin Con’t

• Kelvin calculated the lowest temperature possible by theory

• “Absolute Zero” point where it is believed that all molecular motion stops

• -273.15 Celsius• -454 Fahrenheit • Nobody has ever reached this point

Conversions between Celsius and Kelvin

• To convert from Celsius to Kelvin• C + 273 = Kelvin Temperature• To convert from Kelvin to Celsius• K – 273 = Degrees Celsius• If you start with Fahrenheit you

must convert to Celsius first, and then to Kelvin

What is Thermochemistry?

• The study of the energy of chemical reactions and the changes that it undergoes

• 1. Heat---the amount of energy that an object has

• 2. Energy—the ability to do work or to use the heat

Exothermic Vs Endothermic

•Endothermic—a reaction where energy is absorbed by the system or object

• The temperature of the surroundings will decrease

• The temperature of the object will increase

• Can cause solids to melt, and liquids to boil

Exothermic

• A reaction where energy is released by the system or object

• The temperature of the surroundings will increase

• The temperature of the object will decrease

• Causes gases to condense and liquids to freeze

Specific Heat Capacity

• The amount of heat required to raise the temperature of 1 gram of an object by 1 degree Celsius

• Depends on the mass and composition of the object

• Water has the highest specific heat for any material we will encounter

Specific Heat Equation

Heat of Fusion

• The amount of heat required to melt a substance at its melting point

• Since it is at the melting point, temperature is not part of the equation

The Equation

•Q = mHf

Heat of Vaporization

• The amount of energy it required to boil a substance at its boiling point

• Since it is at the boiling point, temperature is not part of the equation

The Equation

•Q = mHV