Physics Honors C *Day 09/12/13

Physics Honors
AB –Day
Temperature, Heat and Energy
• 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
First, lets look at Temperature
• Temperature is proportional to the average kinetic energy of
particles in substance
• Adding or removing energy usually change the
• 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?
• 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
The Flow of Thermal Energy
• This Flow is quantified as Heat
• Heat is measured in Joules
𝑄 = π‘šπ‘π‘ βˆ†π‘‡
𝑄 − π»π‘’π‘Žπ‘‘ m − mass
𝑐𝑝 − 𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 β„Žπ‘’π‘Žπ‘‘ π‘π‘Žπ‘π‘Žπ‘π‘–π‘‘π‘¦
βˆ†π‘‡ − πΆβ„Žπ‘Žπ‘›π‘”π‘’ 𝑖𝑛 π‘‡π‘’π‘šπ‘π‘’π‘Ÿπ‘Žπ‘‘π‘’π‘Ÿπ‘’
Measuring Temperature
• In order to actually measure heat a
universal scale was needed
• Celsius Scale is used in most of the
• Fahrenheit is used in the United
Conversion Between ℉ and ℃
• 𝑇𝐹 =
• 𝑇𝐢 =
+ 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 = 𝑇𝐢 + 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
Thermal Expansion
• An increase in temperature usually causes expansion
• Linear expansion
βˆ†πΏ = 𝛼𝐿𝑖 βˆ†π‘‡
𝛼 − π‘π‘œπ‘’π‘“π‘“π‘–π‘π‘–π‘’π‘›π‘‘ π‘œπ‘“ π‘‘β„Žπ‘’π‘Ÿπ‘šπ‘Žπ‘™ 𝑒π‘₯π‘π‘Žπ‘›π‘ π‘–π‘œπ‘›
Thermal Expansion
• Expansion is not just linear
• Expansion in area and volume
• So what happens when an object decreases in
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