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ENERGY
Energy
•Ability to do work
Kinetic Energy
•Energy of motion
Temperature
•Measure of the Average Kinetic
Energy of the particles of a sample
vs.
Heat
•Kinetic energy of the particles
(always flows from hot to cold)
Potential Energy
•Stored energy
Temperature Scales in Science
• Celsius :
– The lowest point on the scale is -273.15 °C
• Absolute Zero
• Kelvin:
– The lowest point on the scale is 0K
• Absolute Zero
NEVER, EVER USE
FAHRENHEIT IN
SCIENCE!!!!! IT IS THE
“F” WORD!!!
What is Absolute Zero?
• The point at which no more heat can be
removed from a system
• Almost no movement of molecules
• Theoretical temperature
Temperature Conversions
Table T
K= °C + 273
°C = K-273
(this is not on the table)
Energy Changes
In a chemical or physical change there may be a
transfer of energy (heat)
Exothermic process:
there is a release of energy (heat)
Endothermic process:
there is absorption of energy (heat)
Energy changes
Exothermic Reactions will feel “hot”
Endothermic Reactions will feel “cold”
What is heat?
• Bill Nye The Science Guy on Heat
Heating and Cooling Curves
• Shows the heating or the cooling of a specific
substance
• Heat is added at a constant rate
• When a substance is undergoing a phase
change THE TEMPERATURE DOES NOT
CHANGE until the phase change is complete
Phase changes (Vocabulary)
•
•
•
•
•
•
Melting (Fusion)
Vaporization (l-g)
Sublimation (solidgas)
Deposition (gas solid)
Freezing (fusion)
Condensation (g-l)
GAS
T
e
m
p
er
at
ur
e
(◦
C
)
Endothermic
Boiling Point
LIQUID
Melting Point
SOLID
Time (minutes)
GAS
T
e
m
p
e
r
a
t
u
re
Exothermic
LIQUID
Freezing Point
(◦C)
SOLID
Time (minutes)
Condensation Point
T
e
m
p
er
at
ur
e
(◦
C
)
Δ Kinetic Energy
Kinetic Energy is
constant
Δ Kinetic Energy
Kinetic Energy is
constant
Δ Kinetic Energy
Time (minutes)
Potential
Energy is
constant
T
e
m
p
er
at
ur
e
(◦
C
)
Potential
Energy is
constant
Δ Potential
Energy
Potential
Energy is
constant
Time (minutes)
Δ Potential
Energy
T
e
m
p
er
at
ur
e
(◦
C
)
q = mCΔT
q = mHv
q = mCΔT
q = mHf
q = mCΔT
Time (minutes)
Law of Conservation of Energy
In any chemical or physical process,
energy is neither created nor
destroyed, it is merely transferred.
How is heat measured?
• Calorimetry
– The precise measurement of heat flow into or out
of a system.
– The heat released by a system is equal to the heat
absorbed by its surroundings
– The heat absorbed by a system is equal to the
heat released by the surroundings
– A calorimeter is an insulated device used to
measure the absorption or release of heat
Constant Pressure Calorimeter
• Most changes in the lab occur at
constant pressure
• The heat of a system is it’s
enthalpy (H)
• The heat released or absorbed by
a system at constant pressure is
equal to the system’s change in
enthalpy (ΔH )
• ΔH = q
• q= mC ΔT
Heat
mass
Change in temperature (Final
Temperature – Initial Temperature)
Specific heat
ΔH
Process
Heat
Positive (Final
Temperature is higher
than the initial
temperature)
Endothermic
Absorbed
Negative(Final
Temperature is lower
than the initial
temperature)
Exothermic
Released
• Calorimetry