Physics Honors
AB –Day
2/8-2/9/2016
Temperature, Heat and Energy
Agenda
• What are you doing in the Summer?
• Homework
• Temperature, Heat, and Energy
• Length Contraction/Expansion
Summer Programs
UT Mites Program
Texas A&M Summer Camps
UTSA Summer Engineering Camps
Rice University Summer Programs
Heat
First, lets look at Temperature
• Temperature is proportional to the average kinetic energy of
particles in substance
Temperature
• Adding or removing energy usually change the
temperature
• This energy is called Thermal Energy
• Sum of both KE and PE
• KE – random motion of particles
• PE – separation and orientation of particles relative to
each other
• A temperature difference causes energy to flow
What is happening when ice cube comes in
contact with an object?
What is happening when ice cube comes in
contact with an object?
Temperature
• Which way does the energy flow?
Thermal Equilibrium
• Energy transfers between two objects in contact
until they reach the same temperature
• Temperature is constant and there is no net
transfer of energy
Zeroth Law of Thermodynamics
• Objects in contact with one another are in thermal
equilibrium if they have the same temperature. Nothing Else
Matters.
The Flow of Thermal Energy
• This Flow is quantified as Heat
• Heat is measured in Joules
𝑄 = 𝑚𝑐𝑝 ∆𝑇
𝑄 − 𝐻𝑒𝑎𝑡 m − mass
𝑐𝑝 − 𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 ℎ𝑒𝑎𝑡 𝑐𝑎𝑝𝑎𝑐𝑖𝑡𝑦
∆𝑇 − 𝐶ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑇𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒
Measuring Temperature
• In order to actually measure heat a
universal scale was needed
• Celsius Scale is used in most of the
world
• Fahrenheit is used in the United
States
Conversion Between ℉ and ℃
• 𝑇𝐹 =
9
𝑇𝐶
5
• 𝑇𝐶 =
5
(𝑇𝐹
9
+ 32
− 32)
Kelvin Scale
• Kelvin Scale based on absolute zero
• Absolute Zero – is point when atoms or molecules
(particles) stop moving
• This violates Quantum Mechanics
• Can be approached but never be attained
• -273.15℃
• 𝑇𝐾 = 𝑇𝐶 + 273.15
Conceptual Questions
• Does a hot drink contain a lot of heat?
• What does temperature measure in terms of the atoms or
molecules in the substance?
• What is energy that is transferred because of a temperature
difference?
Thermal Expansion
• An increase in temperature usually causes expansion
• Linear expansion
∆𝐿 = 𝛼𝐿𝑖 ∆𝑇
𝛼 − 𝑐𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡 𝑜𝑓 𝑡ℎ𝑒𝑟𝑚𝑎𝑙 𝑒𝑥𝑝𝑎𝑛𝑠𝑖𝑜𝑛
Thermal Expansion
• Expansion is not just linear
• Expansion in area and volume
• So what happens when an object decreases in
temperature
So how does this happen?
• Freezing water busting pipes
Water has a special property
• Between 4℃ and 0℃, water no longer contracts in
size and begins to expand
Temperature Minilab – Homework
• Go to Thermo PhET Lab
• Press go to Activity
• Depending on browser directions will be different
• Homework quiz on Fri