Unit 2 – Energy Transfer!
• Energy: the capacity to do work (the ability to
move or change matter); energy has no mass and
no volume; it’s intangible; it’s NOT matter.
Three types of energy we talk about
• Kinetic: energy of motion
• Potential: energy due to position; chemical potential
energy is energy stored in bonds and Intermolecular
Forces
• Radiant/Electromagnetic energy (heat and light) 
we are mostly concerned with heat
Heat versus Temperature
Heat
•
•
•
•
•
Def: energy due to molecular motion
Symbol = Q
Units: joules (j) or calories (cal)
Measured only when it is used to do work
Does work by speeding up the motion of
molecules and atoms
• Flows from hot areas to cold areas
• Heat is dependent on mass (the more stuff there
is, the more energy it can have overall)
Heat versus Temperature
Temperature
• Def: a measure of the average Kinetic Energy (KE) of a
substance
• Symbol = T
• Units: Kelvin (K) or degrees Celsius (°C)
• Refers to the intensity of heat in an object
• Change in T = ΔT = Tf - Ti
• Temperature is NOT a form of energy
• Temperature IS a predictor of heat flow from areas of
high T to low T
• Objects can be the same temperature but have
different amounts of heat energy
Temperature Scales
• Sig figs and temperature: because the Celsius
temperature scale is a continuum with both
positive and negative values, a temperature
measurement of 0°C has 1 sig fig (0.1°C = 2 sig
figs; 0.98°C = 3 sig figs)
• 0 K  absolute zero; all molecular motion stops
(all atoms condense into one big fuzzy atom)
• 0 K  theoretical temperature not yet obtained
(within a millionth of a degree)
Conversions
K = °C + 273
These two will be
°C = K – 273
the most important
°F = (9/5*°C) + 32
°C = 5/9* (°F – 32)
Some temperatures you should know
off the top of your head…
°C
K
°F
Water melts/freezes
0
273
32
100
373
212
Water boils/condenses
Especially these!
What is happening
Try a few!
• 450 K
First to Celsius
Equation: °C = K – 273
Calculations: °C = 450 – 273 = 177 °C
Then to Fahrenheit
Equation: °F = (9/5*°C) + 32
Calculations: °F = (9/5 * 177 °C ) + 32 = 318.6 + 32 =
350.6 °F = 351 °F with sig figs
Try a few!
• 98.6 °F
First to Celsius
Equation: °C = 5/9* (°F – 32)
Calculations: °C = 5/9* (98.6 – 32) = 5/9*66.6 = 37°C
Then to Kelvin
Equation: K = °C + 273
Calculations: K = 37 °C + 273 = 310 K
Work together
• Spend about 5 minutes practicing some of the
others on the bottom of p.1 of your notes
Kinetic Molecular Theory *
1. Matter is made up of tiny particles (atoms,
molecules)
2. The particles are in constant, random motion
3. Collisions between particles are elastic (all
energy stays as motion, none is lost to heat)
*the basic principles of KMT are theoretical and begin to break down
under certain circumstances  KMT is better at describing matter
in high energy states (gases, for example)
States/Phases of matter
State
Shape &
volume
Distance
between
molecules
Entropy (disorder)
Motion of
particles
Solid
Definite
shape and
volume
Small
No disorder (particles
stay in the same
position relative to
one another)
No random
motion
(fixed
positions)
Liquid
Indefinite
shape and
definite
volume
Small
Much disorder
(particles move past
each other but
continue touching)
Some
random
motion
(flowing)
Gas
Indefinite
shape,
indefinite
volume
Large
Much disorder
(particles move
randomly, not
touching, only
sometimes colliding)
Completely
random
motion
(diffusion)