Day 17 in SCI110: More Heat and Specific Heat; Gas Laws; Review
- Spring 2005 Schedule
- Last time: Heat and Specific Heat
- Returned group projects and Quiz 2 - looked at answers
- Discussed heat, and specific heat
- What is heat? A measure of the internal energy of an
object.
- Measuring heat:
- Three scales: Celsius, Fahrenheit, Kelvin
- calorie: the amt of energy (or heat) needed to raise the temperature of 1 gram of water 1 degree Celsius.
- British Thermal Unit: the amt of energy (or heat) needed to raise the temperature of 1 pound of water 1 degree Fahrenheit.
- 1 calorie = 4.184 J (Joules - measure of
mechanical energy)
- To heat up an object using heat Q:
- Q is directly proportional to the change in temperature
- Q is directly proportional to the mass of the object
- The constant of proportionality c in
Q=c m DeltaT is the
specific heat of the material (see table 4.2,
p. 73)
- Heat transfer:
- Conduction: transfer of energy from
molecule to molecule
- Convection: transfer of heat by a
displacement of groups of molecules with higher
kinetic energy
- Radiation: "all objects with
temperatures above absolute zero give
off radiant energy" -- this is energy
in the form of light (or other rays
invisible to the human eye --
e.g. infrared)
- Phase changes and heat energy
- Laws of thermodynamics
- First Law: energy cannot be created or
destroyed: merely changed from one form
into another.
- Specific Heat Experiment (pp. 62-63)
- Explore topics in Science News for Final Projects (proposals due today!)
- Today:
- Phase changes and heat energy: Goal: understand figure 4.18, p. 77
- Two tricky things about the plot:
- It's "broken" to jump quickly from 0 to 100
- It's plotting T versus Q, rather than Q versus T!
- Specific heat of water depends on the phase of water
(e.g. solid, liquid, gas)
- Even though there is heat input, there is no change in
temperature while phase is changing.
- Laws of thermodynamics
- First Law: energy cannot be created or
destroyed: merely changed from one form
into another.
- Second Law: natural processes proceed
toward a state of increasing disorder
- Specific Heat Experiment (pp. 62-63) - let's try that experiment one more time!
- Gas Laws:
- Hand in your final presentation topic
- Review for exam
- Sample specific heat calculation
- Exercises, chapter 4
- Overview of topics
- Homework:
- Study for your exam! I'll post some study questions on the website....
Website maintained by Andy Long.
Comments appreciated.