The rope ladder of a boat hangs over the side of
the boat and just touches the water. The
ladder rungs are 8 inches apart. How many
rungs will be under the water when the tide
rises 3.5 feet?
A. 1 rung
B. 2 rungs
C. 5 rungs
D. 0 rungs
How much heat would need
to be added to a 2.5 kg
sample of water in order to
increase the temperature
from 35oC to 95oC? (Remember Q
= mcΔT) cwater = 4190 J/kgoC
A. 366.6 kJ
B. 628.5 kJ
C. 995.1 kJ
D. 1361.8 kj
Because the rubber ball’s
temperature increased faster
than the banana dipped in LN2,
that means which had a higher
specific heat.
A. The rubber ball
B. The banana
C. Both have the same
D. Neither are capable for getting heat
Pre-AP Physics Unit 5:
Thermodynamics
“Thermodynamics”
 Is derived from Greek meaning “movement of heat.”
The First Law of Thermodynamics
 Official Definition:
When heat flows in or out of a system, the energy it
gains or loses is equal to the amount of heat transferred.
 Or… Heat = Energy !
 Is analogous to the Law of Conservation of Energy
 We are now dealing with Internal Energy
Temperature:
 What is it?
 How “Hot” or “Cold” a substance is.
 Temperature represents the average
translational kinetic energy of the individual
particles in a system.
 The Temperature Scales
 Fahrenheit – water freezes at 32oF and boils at 212oF
 Celsius – Water freezes at 0oC and boils
at 100oC
 Kelvin – is based off of Absolute Zero
 Absolute Zero
 So cold that all particles stop moving!
 Total energy of the particles is 0.
Temperature:
 Temperature Conversions
 Celsius to Fahrenheit
9
𝑇𝐹 = 𝑇𝐶 + 32
5
 Fahrenheit to Celsius
5
𝑇𝐶 = (𝑇𝐹 − 32)
9
 Celsius to Kelvin
 Examples
𝑇𝐾 = 𝑇𝐶 + 273
A piece of metal is heated to 475 oF,
what is this temperature in Celsius?
A. 887 oC
B. 246 oC
C. 519 oC
D. -27 oC
The melting point of copper is
1073 oC. What is this
temperature in Kelvin?
A. 800 K
B. 1899 K
C. 578 K
D. 1346 K
Specific Heat Capacity
 What is it?
 The resistance to change in temperature of a substance.
 The Equation:
 Q = mcΔT
 Examples:
How much heat energy is
required in order to raise the
temperature of a 0.5 kg iron nail
from a temperature of 25oC to
80oC?
A. 5750 J
B. 18400 J
C. 12650 J
D. 24150 J
A 75 kg piece of a concrete
sidewalk on a sunny day will gain
about 650,000 Joules of heat
energy from the sun. By how
much will its temperature
increase on that day?
A. 25133333 K
B. 3.0 K
C. 16810 K
D. .33 K
An iron pot containing 5 kg of water at
an initial temperature of 23oC is placed
on a stove. If the stove applies 560,000
Joules of heat energy, what is the final
temperature of the water?
A. 49.7 oC
B. 26.7 oC
C. 3.7
oC
D. 76.5 oC
A cup of water (c=4190) and a
piece of metal (c=350) are both
left to sit out on a sunny day. By
the end of the day, which will
have a greater change in
temperature?
A. water
B. metal
C. They will have same temperature
D. I don’t know
The Second Law of
Thermodynamics
 Official Definition:
Heat, of itself, never flows from a colder object to a
warmer object.
 Energy always flows from Hot to Cold
 This law is also called the Law of Entropy
What is Entropy?
 The amount of disorder in a system
 The universe is always moving towards more entropy
 Examples:
 Ice melting
 Liquid water evaporating
 It takes Work (energy) to decrease Entropy
Types of Heat Transfer
 Conduction
 Heat transfer between materials that are in direct contact
with each other.
 Convection
 Transfer in a fluid by movement of the substance itself.
 Radiation
 Energy transmitted by electromagnetic waves.
Phase Changes
 The States of Matter:
Phase Changes
 Types of Phase Changes:
 Melting
Melting
Boiling
Evaporation
 Evaporation
 Condensation
 Boiling
 Sublimation
Condensation
Sublimation
Phase Changes
 How do you change the melting point or boiling point of
a substance?
 Add a solute
 Change the pressure
Phase Changes
 Energy During Phase Changes
 What happens to the temperature of water as heat is
added?
 It Increases.
 What happens to the temperature during a phase change?
 It remains constant.
Phase Changes
 Latent Heat
 Latent Heat of Fusion
 The amount of energy required to change a unit mass of any
substance from a solid to a liquid (and vice versa).
 Abbreviated Lf (or Hf )
 Latent Heat of Vaporization
 The amount of energy required to change a unit mass from
liquid to gas (and vice versa).
 Abbreviated Lv (or Hv)
Lf
Lv
Phase Changes
 Latent Heat
 Equation:
Q = mL
Where:
Q = heat added during phase change
m = mass of sample
L = Latent Heat (of fusion or vaporization)
 Examples:
How much heat is required to boil 3.5
kg of water? (Lv = 2.26x106 J/kg)
A. 7910 J
B. .0001264 J
C. .0000001264 J
D. 7910000J
An experiment is performed and
it is found that it takes 13.0 x 106
Joules of energy to melt 4.8 kg of
iron. What is the Latent Heat of
fusion for Iron?
A. 2.7 x 106 J/kg
B. 2.7 x 103 J/kg
C. 6.2 x 107 J/kg
D. 6.2 x 104 J/kg
Latent Heat of Fusion
Lf